plenary lectures - Xishuangbanna Tropical Botanical Garden,CAS

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PLENARY LECTURES
Note: these are in order of presentation during the week.
PL01: The 'abominable mystery' solved –
the origin of flowering plants
Friis, E1
1
Department of Palaeobotany, Swedish Museum of
Natural History, Stockholm, Sweden
A multitude of small, charcoalified flowers, fruits, seeds
and other reproductive structures have been retrieved
from sediments of Cretaceous age. The fossils are highly
informative, in some cases preserving astonishing
morphological and anatomical details. Excellent
preservation, together with the application of advanced
techniques
such
as
synchrotron-based
X-ray
microtomography, has resulted in unexpected insights
into the diversification and reproductive biology of early
angiosperms. Documentation of extinct lineages with
character combinations unknown in extant angiosperms
are particularly interesting for analyses of character
evolution and may help bridge some of the gaps in the
phylogenetic tree of extant angiosperms. The fossil
flowers of the newly described Canrightia resinifera
provide an example of an Early Cretaceous angiosperm
with intriguing floral structure that combines features of
several extant magnoliid lineages and it is suggested that
Canrightia may be a link between Chloranthaceae and
Piperales close to the root of the eumagnoliid tree.
Phylogenetic and structural signals from the fossil record
also shed new light on Darwin's mystery: 'The rapid
development as far as we can judge of all the higher
plants within recent geological times is an abominable
mystery'. The fossils indicate that the major
diversification of angiosperms was preceded by a longer,
more gradual radiation. Great changes in floristic
diversity and distribution from the Early to Late
Cretaceous and between Cretaceous and Cenozoic are
evident. Most significant is the high diversity of Early
Cretaceous fossils related to ANITA-grade angiosperms,
Chloranthaceae and alismatalean monocots indicating
predominance of herbs, small shrubs and aquatic plants
in the early history of angiosperms. These probably had
restricted ecological ranges, which may explain the
paucity of angiosperm leaves and pollen in strata
representing the earliest phases of angiosperm evolution.
Eumagnoliids and eudicots were also established early,
but both groups are rare at this level of angiosperm
evolution, and it is significant that no core eudicots have
yet been encountered among Early Cretaceous
angiosperms. However, around the mid-Cretaceous
eudicot diversity increased rapidly, particularly through a
considerable radiation of various rosid lineages (e.g.,
Fagales) and basal lineages of asterid angiosperms (e.g.,
Cornales and Ericales). Eumagnoliids also show marked
diversification at this time with particular development of
many taxa related to Laurales. These phylogenetic
changes greatly affected vegetation structure resulting in
a predominance of woody angiosperms in the Late
Cretaceous floras.
PL02: Technological
tomorrow's crops
innovations
for
Fischhoff, DA1
1
Monsanto Company, St Louis, Missouri, USA
Genetic improvement of crop plants in the past two
decades primarily focused on the implementation of
DNA marker technologies in plant breeding programs
and on the first generation of crop biotechnology traits
that provided weed control via herbicide tolerance and
systems for insect resistance. Traits developed through
both biotechnology and plant breeding efforts that protect
yield potential against pests and disease will continue to
be important, especially when considering possible
climate-related changes in geographical range and
reproductive capabilities of weeds and insects. Future
generations of pest control traits are being developed
through the application of new technologies including
protein engineering and RNAi to offer growers products
with additional modes of action and ever-improving
efficacy against pests. In addition, significant research
efforts in crop biotechnology now focus on
enhancements to complex traits such as intrinsic yield
potential, nutrient utilization and abiotic stress
mitigation, which when coupled with similar efforts to
improve these traits via advanced plant breeding
techniques and agronomic practices, could represent a
step-change in crop yield performance. Increasing yields
while at the same time significantly decreasing the key
resources (water, land and energy) required to produce
each unit of output is one of the most important
challenges facing agriculture. Leveraging advanced
enabling technologies such as high-throughput genome
sequencing, functional genomics, and systems biology in
both plant breeding and biotechnology disciplines will be
required to help deliver the next generation of traits in
agricultural crops.
PL03: Integrating genetic and ecological
data in plant conservation
Oostermeijer, G1
1
Institute for Biodiversity and Ecosystem Dynamics,
University of Amsterdam, The Netherlands
Already in the 1980s, pioneer conservation biologists
discussed the possibly important role of genetics in the
viability of small and isolated populations. Since then, an
enormous amount of research has shown that such
populations are experiencing loss of genetic variation
through drift and inbreeding, and that gene flow is often
insufficient to compensate for that. However, when it
comes to the question how detrimental this is to their
viability, we are still not able to present very many
empirical studies that clearly demonstrate this. This is
largely due to our failure to effectively integrate genetics
with other important components of plant population
viability, such as demography and reproductive biology.
Nevertheless, the studies performed on each of these
components separately suggest that there are major
changes in each of them. The still painfully scarce studies
that have attempted to integrate them into single PVA's
1
show that demography, reproduction and genetics act
synergistically, and cause the often mentioned but rarely
demonstrated extinction vortex. As a result of habitat
destruction and fragmentation, many plant populations
are genetically depauperate, and show reduced viability
that cannot be alleviated by habitat management and
restoration alone and requires additional genetic rescue
measures. Our knowledge of the implications of
outbreeding depression after genetic rescue is still
insufficient to provide conservation managers with
scientifically sound advice. The rapid developments in
ecogenomics will provide exciting new avenues of
implementing genetics into plant conservation.
Nevertheless, we still need to combine these new
approaches with appropriate field experiments in order to
obtain the best answers to still urgent questions. To better
implement genetics into practical conservation,
researchers need to (i) pay more attention to translating
their scientific results, and (ii) focus on the specific
questions of conservation managers.
PL04: Plant modelling
Prusinkiewicz, P1
1
University of Calgary, Calgary, Canada
Branching architecture is a conspicuous feature of most
plants. It is also difficult to conceptualize, as it is not
coded directly in the plant genotype, but emerges from a
hierarchy of morphogenetic processes in an indirect and
often non-intuitive way. As early as the 1960s and 1970s,
computer models were introduced to investigate the
relations between local control of development and the
global branching form of plants. Over the last decade,
models rooted in molecular-level data and hypotheses
have offered further insights. At the basis of these models
lies a postulated feedback between the concentrations
and flow of auxin, and the distribution of auxin
transporters, in particular PIN1 proteins. Operating in the
shoot apical meristems, this feedback can explain the
spatial arrangement of buds around their supporting axes
(phyllotaxis). Operating along the plant axes, a related
feedback mechanism explains which buds will eventually
develop into branches, and at which points of time (bud
activation). Of particular interest are strategies that plants
employ to avoid overcrowding if the branching processes
repeat and several orders of branches are formed. One
strategy, employed by herbaceous plants and
inflorescences, is to gradually reduce the size of
branches, producing fractal patterns. Another strategy,
widely employed by trees, is to avoid overcrowding
through competition between buds and branches for light
and space. Recent models show that a wide variety of
temperate-climate tree architectures results from different
biases in this competition. Although many gaps in our
knowledge remain, the link between molecular-level
processes and the branching architecture of herbaceous
plants and trees begins to appear.
PL05: Live cell analysis of plant fertilization
Higashiyama, T1
1
Nagoya University, ERATO Higashiyama Live-Holonics
Project, Japan
In the fertilization process of flowering plants,
gametophytic interactions between the pollen tube and
the embryo sac occur deeply inside the pistil of the
flower. Due to the inaccessibility, it still remains unclear
how gametophytic cells communicate to achieve double
fertilization. We developed the in vitro Torenia system,
whereby pollen tubes growing through a cut style are
attracted to a protruding embryo sac and cause double
fertilization. By using this system, the synergid cell was
shown to emit some diffusible attractant(s) (Higashiyama
et al., Science, 2001), which had been sought for more
than 140 years. We investigated genes expressed in the
synergid cell of Torenia, by collecting isolated synergid
cells. We found that cysteine-rich peptides (CRPs) were
abundantly expressed in the synergid cell. Among the
CRPs, at least two defensin-like polypeptides, named as
LUREs, showed strong activity to attract pollen tubes.
By developing a laser-assisted thermal-expansion
microinjector, LUREs were finally identified as
attractants derived from the synergid cell (Okuda et al.,
Nature, 2009). One of our goals is to clarify the
mechanism of directional control of pollen-tube growth
by LUREs. In this talk, I will show our recent progress,
including results based on visualization of LURE
molecules as well as pollen tube guidance of Arabidopsis
in vivo. On the other hand, we developed a method for
live cell imaging of fertilization in Arabidopsis. I will
also discuss the mechanism of double fertilization based
on the direct observation of fertilization processes
(Hamamura et al., in press).
PL06: The Eucalyptus grandis genome
sequence
Myburg, AA1, Grattapaglia, D2, Tuskan, GA4, Jenkins,
J5, Schmutz, J5, Hefer, CA1, Pappas Jr, GA2,3, Sterck,
L6, Rouzé, P6, Van De Peer, Y6, Hayes, R7,8, Hellsten,
U7,8, Goodstein, D7,8, Rokshar, DS7,8, Barry, K8,
Bristow, J8, The Eucalyptus Genome Network9
1
Dept of Genetics, Forestry and Agricultural
Biotechnology Institute (FABI), University of Pretoria,
Pretoria, South Africa; 2Plant Genetics Laboratory,
EMBRAPA Genetic Resources and Biotechnology EPqB, Brasilia, Brazil; 3Genomic Sciences Program,
Universidade Católica de Brasília - SGAN, Brasília,
Brazil; 4Environmental Sciences Division, Oak Ridge
National Laboratory, Oak Ridge, USA; 5HudsonAlpha
Genome Sequencing Center, Huntsville, USA; 6Dept of
Plant Systems Biology, Ghent University, Gent, Belgium;
7
Center For Integrative Genomics, Dept of Molecular
and Cell Biology, University of California, Berkeley,
USA; 8DOE Joint Genome Institute, Walnut Creek, USA;
9
www.eucagen.org
Almost all of the more than 700 known species of
Eucalyptus L'Hér. (Myrtaceae) are endemic to Australia.
They are a dominant component of the flora of
2
Australasia occupying 79% of the native forest estate.
Worldwide, eucalypt species and hybrids constitute the
largest hardwood fibre crop with over 20 million hectares
of plantations grown primarily for timber, pulp and
paper. Fast-growing eucalypts are also a promising
source of lignocellulosic biomass for energy production.
The Eucalyptus genome sequence, the first for an
Australian plant, will offer important benefits for
ecological and evolutionary biology studies, as well as
for tree breeding and biotechnology. Over the past three
years, the Department of Energy (DOE) Joint Genome
Institute (JGI) has performed whole-genome (8X)
shotgun sequencing for Eucalyptus grandis (est. genome
size 640 Mbp, n = 11), combining 7.7 million Sanger
reads from plasmid, fosmid and BAC libraries of a
partially inbred (S1), but fully viable 17-year-old tree,
BRASUZ1. Due to high residual heterozygosity, initial
genome assembly resulted in approximately 25% of the
assembly occurring in two haplotypes of 3–4X coverage,
while the remainder of the genome assembled into a
single haplotype of 6–7X coverage. High-density linkage
maps with >2000 DArT and microsatellite markers
guided the subsequent assembly of 11 large chromosome
(pseudomolecule) scaffolds containing 88% (605 Mbp)
of the draft assembly. Similarity searches with 1.6
million E. grandis ESTs suggested that a large proportion
(96%) of expressed gene loci are located in the mapped
chromosome assemblies. Ab initio and homology-based
annotation performed in parallel efforts at the JGI and the
University of Ghent was further supported by over 4
million 454-FLX-Titanium ESTs produced by JGI, as
well as Sanger and Illumina EST data provided by
collaborators. The annotations produced by the two
groups revealed that the 11 chromosome scaffolds
contain more than 90% (41,201 – JGI, 43,219 – UGent)
of the predicted protein-coding loci, of which more than
70% have EST support. A preliminary analysis of
genome duplication performed at UGent suggested that,
in addition to the ancient hexaploidization event shared
by Rosids and Asterids, the Eucalyptus genome most
likely contains one more recent duplication event. The
two genome annotations were released in public
databases
(www.phytozome.net,
http://bioinformatics.psb.ugent.be/webtools/bogas/)
in
Jan 2011. The E. grandis genome sequence will be the
first reference for the Rosid order Myrtales and will
therefore be informative for comparative genomic studies
within the Eudicots.
PL07: Phytochrome photosensory signaling
and transcriptional networks
Quail, P
1
1
Plant and Microbial Biology, UC Berkeley, and Plant
Gene Expression Center, Albany, USA
A central goal of current phytochrome (phy) research is
to define the cellular, molecular and biochemical
mechanisms involved in the primary steps of the lighttriggered, intra-cellular transduction process utilized by
this photoreceptor family (phyA to phyE). The present
paradigm charting this signaling pathway asserts that
transduction involves rapid translocation of the lightactivated photoreceptor molecule from the cytoplasm to
the nucleus, where it interacts physically with a subset of
members of the bHLH transcription factor family, termed
Phytochrome-Interacting Factors (PIFs), inducing
transcriptional responses in target genes. We have shown
that a quadruple pif mutant (pif1pif3pif4pif5 abbreviated
pifq) exhibits a constitutively photomorphogenic (cop)like phenotype in completely dark-grown seedlings,
indicating that these transcription factors collectively
repress photomorphogenesis in post-germinative
darkness, and that photoactivated phy reverses this
repression by inducing rapid degradation of the PIF
molecules upon initial exposure to light. This process
involves rapid, phy-induced phosphorylation of the
interacting bHLH protein, followed by degradation via
the ubiquitin proteasome system. Using random
mutagenesis, we have identified a surface-exposed
binding site for the PIFs in the light-sensing knot region
of the photoreceptor, that is necessary for normal phy
signaling in inducing seedling deetiolation, suggesting
that this site is integral to the biochemical signal transfer
process from the activated photoreceptor to target
proteins in the cell. Microscopic examination of the pifq
mutant indicates accelerated oil body mobilization and
chloroplast differentiation in dark-grown seedlings,
phenocopying the normal light-induced deetiolation
process in the wild-type. Genome-wide expression
profiling of the pifq seedlings shows robust derepression
of a broad array of nuclear genes encoding chloroplasttargeted proteins in sustained darkness, consistent with
the visible and cellular cop-like phenotypes. Collectively,
the data support the notion that the PIF subfamily of
bHLH transcription factors function constitutively to
promote skotomorphogenic development in seedlings
emerging from buried seed, repressing premature
photomorphogenic
development
in
subterranean
darkness, until this repression is relieved by proteolytic
degradation of the PIFs upon photoactivation of the phy
system by initial exposure to light at the soil surface. The
transcriptome analysis has identified a subset of genes
that both are regulated by the PIFs in darkness in the pifq
mutant, and are rapidly responsive to light in the wildtype. These genes are thus potential direct targets of phy
regulation via the PIF transcription factors. Recent
evidence indicates that the PIFs may have a role in
multiple signaling pathways in addition to light, thereby
suggesting that they function as components of a central
cellular signaling hub.
PL08: Genes, jeans, and genomes: exploring
the mysteries of polyploidy in cotton
Wendel, JF1
1
Dept of Ecology, Evolution, & Organismal Biology,
Iowa State University, USA
Increasingly powerful technologies arebeingused to study
the ecology and evolution of polyploids in many plant
groups, resulting in dramatic discoveriesof novel
genomic interactions and processes. Gossypium includes
classic allopolyploids arising from a biological reunion12 MYAof divergent diploids from different hemispheres.
This serendipitous merger generated a spectrum of
genomic
responses, including gene
silencing,
intergenomic gene conversion, and genome-wide
3
disruption and reconciliation of ancestral gene expression
patterns. Using several microarray platformsand other
technologies, we are studying transcriptional changes in
synthetic and natural Gossypium allopolyploids and
reconstructed F1 and polyploid hybrids, using differing
tissues and genetic backgrounds. Allopolyploid
formation induces massive alteration in gene expression
and complex transcriptomicresponses, including genomic
dominance and novel (transgressive) expression patterns.
Using microarrays and sequencing protocols that
distinguish transcript levels for each member
(homoeolog) of each duplicated gene,we show that
allopolyploidization entails significant homoeolog
expression modulation that is temporally partitioned into
alterations arising immediately as a consequence of
genomic merger and secondarily as a result of long-term
evolutionary transformations in duplicate gene
expression.About one fourth of homoeolog expression
biases occur instantaneously with hybridization, with the
remaining arising from long-term evolutionary forces
such as duplicate gene neofunctionalization and
subfunctionalization. Expression is biased toward the
paternal D-genome, demonstrating an overall unequal
contribution of two genomes to the transcriptome. We
are exploring gene expression during cotton fiber
development and evolution, taking advantage of a wellestablished phylogenetic framework and the unique
opportunity offered by the existence of multiple, parallel
domestications of different wild progenitors by
aboriginal peoples in both Africa–Asia and
Mesoamerica. The fibertranscriptome is extraordinarily
complex, with homoeolog expression varying widely
even at the level of development and maturation of a
single cell. Most homoeolog expression bias reflects
polyploidy rather than domestication, but domestication
has increased expression bias in fibers towards the Dgenome.We are exploring the functional consequences of
gene duplicationin cotton and the possibility of novel
gene recruitment following genome doubling.This work
provides insights into the genetic architecture underlying
the evolution of morphology, as well as the potential
evolutionary significance of genome doubling.
PL09: Evolution of the Australian flora
through the last 65 million years
Crisp, M2
1
This is the 2011 Nancy Burbidge Memorial Lecture of
the Australasian Systematic Botany Society
2
The Australian National University, Canberra, Australia
Australia has changed from a rainforest-covered
Gondwanan landscape to an arid island-continent
dominated by sclerophyll plants such as eucalypts and
acacias. What were the key evolutionary and ecological
drivers of this transformation? By integrating the fossil
record with molecular phylogenetics, we can help
reconstruct the time line of evolutionary history and
environmental changes can be identified by their
historical signatures in phylogenies. Not surprisingly,
most lineages can be traced to ancestors in wet habitats.
However, reconstructions of fire-adaptive traits in
Myrtaceae and Proteaceae suggest that flammable
4
sclerophyll communities might have existed in the early
Palaeocene, 60 Myr ago. After Australia separated from
Gondwana 30 Myr ago, the climate became more
seasonal and the monsoon tropical flora was assembled
both by in situ adaptation of Gondwanan lineages and
from immigrants from the north as Australia drifted
towards southeast Asia. Comparisons of divergence
times among multiple pairs of lineages on either side of
the arid Nullarbor Plain barrier support the hypothesis
that mid-Miocene aridification (15 Myr ago) isolated the
temperate sclerophyll floras of southwestern and
southeastern Australia. The largest and youngest biome,
the arid zone, is thought to contain a mix of young taxa
adapted from the mesic near-coastal regions, Asian
immigrants and relicts of the ancestral rainforest,
clinging to aquifers in the central Australian ranges.
Surprisingly, one 'relict' group, the Livistona fan palms,
have turned out to be very recent immigrants. These
findings have raised more questions than they have
answered and I will discuss some of these new
challenges.
PL10: Cellulose synthesis
Somerville, C1, Gu, Y2, Chen, S1, Wallace, I1, Carroll,
A1, Anderson, C1, Sorek, N1, Paredez, A1
1
University of California, Berkeley, USA; 2Pennsylvania
State University, USA
Cellulose is thought to be the most abundant component
of terrestrial biomass because of its role as the major
structural element of plant cell walls. Cellulose is also a
component of many commodities such as lumber, paper,
textiles and animal fodder. Thus, it is surprising that
relatively little is known about how the properties of
cellulose are controlled during synthesis. In 2006 we
reported that it was possible to observe what appeared to
be individual cellulose synthase complexes synthesizing
cellulose in live cells using GFP-labeled complexes and
spinning disc confocal microscopy. This method of
observing the process has been used by us and others to
observe the effects of genetic and environmental
perturbations of the process and to infer some aspects of
the molecular details of the process. This general
approach has shown that cellulose synthase is staged in
the Golgi from where it is secreted in vesicles to the
plasma membrane. At the plasma membrane the complex
is activated and associates with the cortical cytoskeleton
which plays a role in orienting the deposition of cellulose
fibrils in a pattern that is regulated dynamically in
response to developmental and environmental cues.
Recent results indicate that phosphorylation of the
cellulose synthase complex participates in some aspect of
the interaction between the cellulose synthase complex
and cortical microtubules in primary cell walls. Several
of the kinases that act on cellulose synthase have recently
been discovered and may open up new opportunities to
identify the signal transduction pathways that link the
process to cellular functions. Additionally, a number of
other proteins that have been implicated in cellulose
synthesis by mutant studies have been shown to alter the
kinetics of the process and several appear to colocalize
with the cellulose synthase complex. The complexity
revealed by the study of the many factors that affect the
overall process suggest that cellulose synthesis is a much
more complex process than merely polymerizing
glucose. We have come to think of it as a molecular
process that is similar in complexity to transcription or
translation; resolving the details of the process will
require a similar level of ingenuity as was required to
elucidate those processes
KEYNOTE SYMPOSIA
KNS01: Epigenomics and small RNA
Asymmetries of DNA methyltransferases activity
between male and female gametes cause imprinting
Arabidopsis
Berger, F1, Thiet, VM1, Jullien, PE1
1
Temasek Lifescience Laboratory, Singapore
Imprinted genes are expressed predominantly by one
parental allele. In plants, most imprinted genes are
expressed in endosperm, the tissue that nurtures embryo
development inside the seed. The endosperm derives
from the fertilized central cell. Imprinted expression
relies on DNA demethylation occurring in the central cell
but not in sperm cells. After fertilization, the asymmetry
of DNA methylation acquired at imprinted loci during
gametogenesis is inherited to endosperm where a
transcriptionally active maternal allele coexists with a
silenced paternal allele, resulting in an imprinted status.
Demethylation in the central cell relies both on the
inactivation of MET1 transcription and the expression of
the DNA demethylase DEMETER. Hence imprinting has
so far been linked exclusively to cytosine methylation on
CG contexts, which depends on MET1 activity. The
RNA dependent DNA methylation (RdDM) pathway
causes de novo methylation of cytosine residues in any
context and is involved in silencing transposons,
participates to the maintenance of constitutive
heterochromatin around centromeres, as well as the
silencing of transgenes. We report that the RdDM
pathway is active only in male gametes but not in the
central cell. The inactivation of the RdDM pathway in
the central cell relies on specific transcriptional
activation of the major player of this pathway by the
retinoblastoma pathway in a manner similar to that
reported for MET1. The asymmetry of RdDM activity is
sufficient to cause imprinting of several loci. We present
the case of an imprinted gene controlled by the RdDM
pathway and extrapolate further generalization of the
mechanism.
A credible molecular framework for small RNAbased transgenerational effects in plants
Brosnan, C1, Dunoyer, P1, Voinnet, O1
1
Swiss Federal
Switzerland
Institute
of
Technology,
Zurich,
We have recently demonstrated that endogenous and
exogenous small RNAs move from cell–to–cell and over
long distances in plants. Hundreds of small RNAgenerating loci are found in the Arabidopsis genome, and
we have shown that their expression, processing and
activity may be influenced by specific stresses and may
also vary extensively from one plant ecotype to another.
Because a significant fraction of mobile small RNAs has
the potential to induce DNA methylation and chromatin
modification at homologous loci, a model emerges
whereby somatic integration of environmental cues might
be converted into large bulks of mobile genetic
information that could ultimately pattern gene expression
into the meristems, the new growth and, possibly, the
gametophytes. This process may not only adapt
dynamically the new growth to the changing
environment, but may also have long-term transgenerational consequences owing to the action of plant
maintenance DNA methylases and the absence of
resetting in these organisms. It may also explain the
formation of ‘spontaneous epialleles’ arising under
specific environmental conditions. I will present a series
of molecular data and striking observations, which,
collectively, constitute a credible framework for this
proposed transgenerational small RNA-based memory in
plants.
Heterochromatin reprogramming by small RNA
regulates germ cell fate and transposon silencing in
polyploid hybrids
Martienssen, R1, Tanurdzic, M1, Finigan, P1, Creasey,
K1, VanEx, F1, Auer, P3, Vaughn, M1, Slotkin, K1,2,
Ernst, E1, Vielle-Calzada, J4, Doerge, R3
1
Cold Spring Harbor Laboratory, Cold Spring Harbor,
NY, USA; 2Ohio State University, Columbus, OH, USA;
3
Dept of Statistics, Purdue University, West Lafayette,
IN, USA; 4CINVESTAV, Irapuato, Mexico
In many plants, including Arabidopsis, hybrids between
species and subspecies encounter post-fertilization
barriers in which hybrid seed fail to develop, or else give
rise to infertile progeny. In Arabidopsis, some of these
barriers are sensitive to ploidy and to the epigenetic
status of donor and recipient genomes. Recently, a role
has been proposed for heterochromatin in reprogramming
events that occur in reproductive cells, as well as in the
embryo and endosperm after fertilization. 21nt
epigenetically activated small interfering RNA
(easiRNA) from transposable elements accumulate in
cultured cells and in pollen, and are translocated from the
surrounding pollen grain into the sperm, while in the
maturing seed 24nt siRNA are primarily maternal in
origin. Thus maternal and paternal genomes likely
contribute differing small RNA to the zygote and to the
endosperm. As heterochromatic sequences also differ
radically between and within species, small RNA
sequences will diverge in hybrids. If transposable
elements in the seed are not targeted by small RNA from
the pollen, or vice versa, this could lead to hybrid seed
failure, in a mechanism reminiscent of hybrid dysgenesis.
Unexpectedly, mutants in the easiRNA pathway lead to
specification of diploid functional megaspores from
somatic cells in the ovule, reminiscent of apospory in
other species, as well as meiotic defects. Thus
heterochromatin reprogramming may play a role in
apomixis, and may utilize a similar mechanism.
5
KNS02: Plant speciation
The nature of species boundaries in plants
Rieseberg, L1, Kane, N1, Andrew, R1, Renaut, S1,
Scasitelli, M1, Strasburg, J2
1
University of British Columbia, Canada;
University, Bloomington, USA
2
Indiana
Despite numerous reports of hybridization in natural
populations of plants and animals, hybridizing species
typically remain morphologically distinct due to the
action of multiple reproductive barriers. Less is known
about pattern of molecular genetic differences between
hybridizing taxa. In a recent monograph on speciation,
Jerry Coyne and Allen Orr argue 'much of the genome
cannot move between species because it is linked to
divergently selected alleles'. However, recent population
genomic studies suggest that reproductive barriers may
be more porous than conventionally believed, but most
such studies lack sufficient resolution to determine the
number and sizes of regions of low migration or to
identify the factors responsible for them. Here we report
on
high
resolution
genomic
scans
of
migration/differentiation across several pairs of
sunflower (Helianthus) taxa that vary in divergence time,
strength of reproductive isolation, and degree of
geographic separation. We show that genomic regions of
differentiation are small, except in areas of low
recombination, such as near the breakpoints of
chromosomal rearrangements. We also demonstrate that
the degree of geographical isolation is a better predictor
of patterns of introgression than the strength of biological
isolation. On a more general level, our results add to a
growing body of evidence indicating that the extent of
introgression is far greater (and the effects of 'speciation
genes' far smaller) than implied by speciation texts. Thus,
the genomes of hybridizing plant species are complex
mosaics that exhibit fine-scale variation in ancestry.
of traits and species. Altogether, recent results on plant
speciation provide strong evidence for the role of natural
selection in creating reproductive barriers between plant
populations, and suggest that their genetic basis could
lead to rapid speciation.
From genes to GIS: the origin of diversity in Solanum
Moyle, L1
1
Indiana University, Bloomington, USA
Adaptation and reproductive isolation both contribute to
the formation of new species and therefore the generation
of biodiversity. Nonetheless, surprisingly little is known
about the specific mechanisms that underpin these two
fundamental evolutionary processes. Working with tools
that range from species distribution modelling to finescale genetic mapping, we are using the plant group
Solanum section Lycopersicon (the wild tomatoes) to
dissect the genetics and evolution of adaptive trait
differences and reproductive isolating barriers among
species. Tomatoes are separated by a range of pre- and
postzygotic isolating barriers; our Quantitative Trait
Locus (QTL) mapping indicates that the genetic
architecture of these barriers is oligogenic and strongly
epistatic. Species also differ markedly in phenotypic,
physiological, and biochemical traits; our modeling and
quantitative genetic analyses indicate that much of this
variation is due to adaptive responses to natural variation
in abiotic and biotic environments. Using ecological,
evolutionary, and genomic approaches, our goal is to
integrate our investigations of both adaptation and
isolation, to understand mechanisms of evolutionary
diversification in this charismatic and biologically
diverse group.
KNS03: New signalling molecules
Divergent natural selection and plant speciation
Strigolactones: their roles as endogenous hormones
and rhizosphere signals
Ortiz-Barrientos, D1
Yamaguchi, S1
1
1
The University of Queensland, Brisbane, Australia
Natural selection sometimes drives the evolution of new
species as traits favoured within populations may
incidentally create reproductive isolation between
populations. Here, I synthesize the various mechanisms
by which natural selection can lead to the evolution of
reproductive isolation, and discuss its impact during the
early stages of divergence. I discuss recent data on the
origin of Senecio pinnatifolius parapatric ecotypes and
the various forms of reproductive isolation emerging
between them. I combine ecological and population
genomics approaches to demonstrate how both biotic and
abiotic selective agents maintain morphological
differences in the face of gene flow, and discuss the role
of coadapted gene complexes and genetic architecture in
the initiation of reproductive isolation between
populations. Finally, I show how drift and natural
selection interact to produce striking patterns of genomic
differentiation across large expanses of land, possibly
leading to adaptive radiations and the parallel evolution
6
RIKEN Plant Science Center, Yokohama, Japan
Shoot branching is a major determinant of plant
architecture and is highly regulated by endogenous and
environmental signals. Previous studies using a group of
enhanced shoot branching mutants suggested the
involvement of a novel carotenoid-derived hormone in
inhibiting the outgrowth of axillary buds. We have
recently shown that strigolactones (SL), a group of
terpenoid lactones, act as this new hormone or its
biosynthetic precursor. SLs were first discovered in root
exudates in the 1960s, as seed germination stimulants of
root parasitic plants, such as Striga and Orobanche
species. Later, they were shown to have a function in
symbiotic interaction with arbuscular mycorrhizal fungi,
which facilitate the uptake of inorganic nutrients by
plants in the rhizosphere. Thus, SLs act as an endogenous
hormone as well as being released from roots as an
allelochemical in symbiosis and parasitism with
neighboring
organisms.
Earlier
studies
have
demonstrated that SL production is highly elevated by
phosphate and/or nitrate starvation in several plant
species, which is thought to contribute to successful
symbiosis with arbuscular mycorrhizal fungi. Our recent
experiments using rice mutants suggested that the
elevated SL production under phosphate-deficient
conditions also plays a role in minimizing shoot
branching for efficient utilization of the limiting
phosphorus resource. These findings support the idea that
the dual role of SL as an endogenous hormone and a
rhizosphere signal might be closely related to adaptive
responses to inorganic nutrient availability.
Secreted peptide signals required for maintenance of
root stem cell niche in Arabidopsis
Matsubayashi, Y1
1
Graduate School of Bio-Agricultural Sciences, Nagoya
University, Japan
Secreted peptides are now recognized as important
members of intercellular signals that coordinate and
specify cellular functions in plants. Some of the secreted
peptide hormones undergo complex post-translational
modifications that are mediated by specific enzymes
which recognize multiple target peptides. Because such
modifications are generally critical for the functions of
individual peptide hormones, the presence of novel
peptide hormones should be revealed through phenotypic
analysis of the mutants of post-translational modification
enzymes. Tyrosine sulfation is a post-translational
modification that has been found in several peptide
hormones in plants. This modification is mediated by
tyrosylprotein sulfotransferase (TPST). In loss-offunction mutant of TPST (tpst-1), root meristematic
activity is considerably decreased and root stem cells are
not maintained. Because known tyrosine sulfated peptide
hormones did not recover these defects of tpst-1, we
speculated that an as-yet undiscovered tyrosine-sulfated
peptide(s) regulates root meristematic activity and
maintenance of the stem cell niche in Arabidopsis. To
identify this peptide signal, we searched the Arabidopsis
genome for genes likely to encode sulfated peptide(s),
determined their mature peptide structures and tested
their activities to recover defects of tpst-1 mutant. We
identified a novel family of functionally redundant
sulfated peptides that restore root stem cell and transit
amplifying cell proliferation in tpst-1. We named these
peptides root meristem growth factors (RGF). RGFs are
expressed mainly in the stem cell area and the innermost
layer of central columella cells. We also found that RGF1
defines expression levels and patterns of the root stem
cell transcription factor PLETHORA mainly at the posttranscriptional level. The RGFs function independently
of the auxin pathway. Our results reveal that secreted
peptide signals play a crucial role in root meristem
development. Reference: Matsuzaki Y. et al. 2010.
The quest for florigen: are we there yet?
Schmid, M1
1
Max Planck Institute for Developmental Biology,
Tübingen, Germany
The induction of flowering is a central event in the life
cycle of plants. When timed correctly, it helps ensure
reproductive success, and therefore has adaptive value.
Because of its importance, flowering is under the control
of a complex genetic circuitry that integrates
environmental and endogenous signals, such as
photoperiod, temperature and hormonal status. Based on
grafting experiments, it has been long proposed that
photoperiod is perceived in leaves where it leads to the
induction of a flower-forming substance, or 'florigen'.
The florigen is then thought to be transmitted to the shoot
apex where it induces the transition to flowering. The
molecular nature of florigen has eluded characterization
for 70 years. Genetic analyses in Arabidopsis thaliana
have identified mutations in a number of genes such as
CONSTANS (CO) and FLOWERING LOCUS T (FT)
that control flowering in response to inductive
photoperiod. Whereas accumulation of the CO protein
appears to be at the core of measuring photoperiod,
recent data suggested that the FLOWERING LOCUS T
(FT) protein constitutes a mobile signal that transduces
the information to induced flowering from the leaves to
the shoot apex. Interestingly, the function of the CO/FT
module seems to be evolutionary conserved, as mutations
in homologous genes in other species also disrupt
flowering in response to inductive day length. The
regulation of FT expression, the relative contribution of
FT mRNA and protein movement to the floral transition
and finally the role of FT in orchestrating the floral
transition at the shoot apex will be discussed.
KNS04: Reproductive biology
(eco-physiology)
Female gametophyte patterning and function in
grasses
Dresselhaus, T1, Krohn, N1, Srilunchang, K1, Marton,
ML1, Amien, S1, Juranic, M1, Leljac-Levanic, D1,
Sprunck, S1
1
Cell Biology and Plant Biochemistry, University of
Regensburg, Germany
After three rounds of mitotic nuclei divisions, the female
gametophyte of flowering plants (angiosperms) develops
from a megaspore into a multicellular haploid structure
harbouring two female gametes, egg and central cell,
respectively. These gametes produce embryo and
endosperm after the angiosperm-specific process of
double fertilization has been executed. In addition to
gametes, the female gametophyte contains accessory
cells, namely two synergid cells representing glandularlike cells involved in pollen tube attraction and
perception as well as up to 40 antipodal cells in grasses.
During the past few years, the female gametophyte
emerged as an exciting system to study fundamental
biological question in plant cell and developmental
biology such as nuclei migration and karyogamy,
cellularization, establishment and maintenance of cell
specification and polarity as well as cell recognition and
activation mechanisms. We are studying maize as a
model as it generates a typical grass female gametophyte
containing large cells allowing their manual dissection.
Using transcript profiling of isolated female gametes and
accessory cells, we found a number of genes being
specifically up-regulated in either of the female
7
gametophyte cell types. Among these especially
transcripts encoding predicted small secreted proteins
and those for proteins involved in post-translational
protein modification are highly abundant and have been
selected for functional studies. We will report here about
the role of a MATH-BTB protein homologous to animal
MEL-26 being known for its role in cytokinesis and as a
component of an E3-ligase for meiosis-mitosis
progression. A gene encoding a grass-specific diSUMOlike protein was identified as a regulator of nuclei
positioning and cell viability of the female gametophyte.
Other genes for small secreted proteins being involved in
cell specification include an EA1-box protein or small
cysteine-rich proteins (CRPs), which play major roles for
pollen tube guidance, burst and sperm delivery. Although
plant hormone biosynthesis genes seem to be lowly
expressed inside the immature female gametophyte,
exogenous hormones, especially auxin, seem to play an
important role to polarize the female gametophyte also in
grasses.
Recognition of 'self': conversations that commit 'self'
pollen to suicide
Franklin-Tong, N (VE)1
1
University of Birmingham, UK
Cellular responses rely on signalling. Selfincompatibility (SI) is an important geneticallycontrolled mechanism used by many angiosperms to
prevent self-fertilization and inbreeding. A multi-allelic S
locus allows discrimination between ‘self’ (incompatible)
pollen from ‘non-self’ (compatible) pollen when it lands
on the stigma. Interaction of matching S-determinants
from the pistil and pollen to allow ‘self’ recognition,
which triggers rejection of incompatible pollen. In
Papaver rhoeas (poppy) the S-determinants are PrsS
(Papaver rhoeas stigma S) and PrpS (Papaver rhoeas
pollen S). PrsS is a small novel cysteine-rich protein that
acts as a signalling ligand that interacts with its cognate
pollen S-determinant PrpS, and represents one of the few
examples of plant ligands whose interactors are known.
PrpS is a small novel transmembrane protein, so is
interestingly, not a ‘classic’ receptor. Interaction of PrsS
with incompatible pollen stimulates SI-specific Ca2+
influx.
We
recently
identified
SI-activated
conductance(s) that is not voltage activated, but is
voltage sensitive. Evidence suggests that it may represent
a Non-Specific Cation Channel (NSCC). Recent data also
implicate ROS and NO signalling. Downstream targets
include the actin and microtubule cytoskeletons, a
soluble inorganic pyrophosphatase, Pr-p26.1, and
activation of a MAP kinase, PrMPK9-1. Ultimately, and
probably the major target for SI signals is initiation of
programmed cell death (PCD) involving several caspaselike activities in incompatible pollen. This provides a
very neat way to get rid of unwanted ‘self’ pollen and
prevent self-fertilization. I will describe recent progress
in identifying the signaling components and downstream
targets of SI signals, and will attempt to provide an
overview integrating our knowledge of how this SI
system operates. We have recently transformed
Arabidopsis thaliana, which is a self-compatible, with
PrpS, and I will present data showing that when
transgenic pollen expressing PrpS interacts with
recombinant PrsS protein, it elicits a remarkably similar
8
response to that triggered in incompatible Papaver
pollen. This demonstrates that Papaver PrpS is
functional when transferred to an unrelated species and
suggests that Arabidopsis has all the cellular machinery
required to elicit the downstream events triggered by
interaction of PrsS and PrpS. These preliminary data
suggest that the poppy SI system may be potentially
useful for manipulating crop plants to produce F1
hybrids more easily.
Pollen allergens – molecules with impact beyond plant
reproduction
Singh, MB1
1
ARC Centre of Excellence for Integrative Legume
Research, Melbourne School of Land and Environment,
The University of Melbourne, Parkville, Australia
Pollen allergy is the most common elicitor of seasonal
respiratory allergic diseases such as hay fever and
seasonal asthma. The prevalence of both hay fever and
allergic asthma has increased significantly in recent
decades. Recent research has pointed towards the
possible stimulatory effects of global environmental
change on pollen allergen production and thus the
potential for pollen-related allergic symptoms to
increase. These allergic symptoms that are based on
immunoglobulin E (IgE) recognition of specific allergen
molecules affect almost 20% of the population
worldwide. After landing on the moist human respiratory
epithelial surfaces, individual pollen grains release
copious amounts of soluble proteins that are potential
triggers of immediate immunological hypersensitivity
symptoms. This presentation will focus on grass pollen
allergens; their structural properties, biological roles and
allergic potential, and current efforts to generate vaccines
for immunotherapy of pollen induced allergic diseases.
KNS05: Perspectives on climate change and
adaptation
Improving projections of plant species and ecosystem
responses to climate and atmospheric change
Midgley, G1
1
SANBI, South Africa
Current projections of species and ecosystem responses
to anticipated climate change have well known
limitations, but advances are being made that will
improve our understanding of the risk of these changes to
plant biodiversity. In this paper I will outline how greater
integration and coordination between modeling,
experimentation and monitoring efforts are required to
develop our ability to make more credible projections of
species and ecosystem shifts as climate and atmosphere
continue to change. It is particularly important to
recognize that the environmental changes to which we
are committed over the next decade or two provide an
opportunity to test our predictive capabilities, but only if
we are able to coordinate efforts to make the required
observations.
Environmental change and the rise of flowering
plants in evolutionary time
Bond, W1
1
Botany Dept, University of Cape Town, South Africa
As we face a period of rapid projected climate and
environmental change, it is useful to explore how the
world’s modern flora came to be over evolutionary time
scales. Flowering plants are now the dominant
component of the world’s flora, but the ways in which
angiosperms achieved this dominance are still being
elucidated. Adaptive responses to key environmental
changes, including climate, fire regime and atmospheric
CO2 concentration, seem all to have been critical in the
rise of the angiosperms. This deep time perspective
provides an important context for appreciating the
magnitude of ongoing and projected anthropogenic
changes to the world’s disturbance regimes, climate and
atmosphere, and for understanding the adaptive potential
of modern floras in the face of these changes.
Climate change susceptibility and adaptability: how
much is too much change for global species?
Foden, W1
1
IUCN, Cambridge, UK
There is growing evidence that climate change will
become one of the major drivers of shifts in species
dominance and geographic range, and even species
extinctions, in the 21st century. How might we begin to
predict which species will be more vulnerable to climate
change effects than others? The prediction of these
relative vulnerabilities has most commonly been carried
out using models of geographic range change, which
have many well-known limitations. I present a
collaborative IUCN-led study that introduces an
alternative approach based on species' traits, which
provides an opportunity to take into account species
biology (e.g. demographic, physiological and ecological
traits) and expert knowledge that may be derived from
species' evolutionary history (e.g. fire damage
susceptibility and ecological plasticity). Based on
assessments of individual species' biological sensitivity,
their predicted climate change exposure (derived from
General Circulation Model projections), as well as their
anticipated adaptability to climatic change, the study has
assessed relative climate change susceptibility of global
birds, amphibians and corals, as well as various plant
groups from Southern and East Africa. I will highlight
some of the species groups predicted to be at greatest risk
from climate change and identify the regions of their
greatest concentrations. Exploring the relationship
between pilot species' predicted climate change
vulnerability and existing Red List status allows an
assessment of future threats in terms of this measure.
These results present a new kind of assessment for
climate change impacts on species dominance shifts and
potential extinctions. I will discuss implications of the
findings for global plant conservation, including on the
development of strategies for assisted colonisation and
management of possibly novel communities of the
future.
KNS06: Food security in a world with
biophysical limits
Megatrends and ecological intensification of major
cropping systems
Cassman, K1
1
University of Nebraska, Lincoln, USA
Achieving climax human population of about 9.5 billion
and then an orderly decline can occur this century if
economic development can alleviate poverty and support
universal education. Adequate food supply at reasonable
cost is a prerequisite because high food costs reduce
economic growth rates and undermine political stability.
Unfortunately, yield growth rates of our major food crops
are not sufficient to meet expected food demand without
massive expansion of crop production at expense of
remaining carbon-rich and biodiverse rain forests,
wetlands, and savannah. Avoiding this scenario requires
accelerating yield growth rates while concomitantly
reducing the environmental footprint of agriculture
through a process of ecological intensification. Regions
will suitable soils and climate to support high yields must
produce near the yield potential ceiling (Yp)determinedby biophysical limits set by temperature,
water supply, and solar radiation. In some cropproducing regions, however, yields are already
plateauing because average farm yields are 80-85% of
Yp. In other regions, current cropping systems are
degrading soil and water quality because climate and
soils cannot support intensive agriculture. A global atlas
that estimates the difference between yields and Yp on
all currently farmed land can identify where crop yields
are likely to plateau and where large exploitable yield
gaps justify investments in ecological intensification.
Ensuring food security also requires continued
breakthroughs in crop genetic improvementand in
management of soil, water, and nutrients to increase
resource capture and the efficiency with which resources
are used.
Integrated approaches to accelerate crop genetic
improvement
Richards, R1
1
CSIRO, Canberra, Australia
The rate of genetic improvement in our major crops
threateningly lags behind the anticipated future food
requirements of our growing global population. We must
accelerate the rate of grain yield improvement if we are
to avoid future food catastrophes. Where will genetic
increases come from? Empirical plant breeding will
remain the cornerstone of genetic improvement as this
effectively integrates yield improvement with
tolerance/resistances to pests and diseases and with grain
marketability. However, alone this is not going to be
enough. Genetic engineering in the next 20 years will
make major contributions to pest and disease resistance
and will result in improved management practices but it
is unlikely to result in significant genetic advances in
yield potential or tolerance to abiotic stress. The main
advances in the next 20 years are likely to be achieved
9
from (i) smarter, faster and cheaper phenotyping and
genotyping methods and (ii) identifying key traits
responsible for the improved capture of the resources
required for crop growth (light, water, nutrients) and then
convert this to grain. These traits will be required to
design and breed crops for target environments and for
management practices. A challenge is that the most
important traits contributing to increased yield under
both favourable and unfavourable conditions are
multigenic and can be difficult to select in breeding
programs. Beyond 20 years is difficult to predict.
Hopefully photosynthesis will then be more amenable to
improvement than it is now.
Can we increase net primary productivity of major
food crops?
Amthor, J1
1
University of Sydney, Australia
In the face of our growing population, finite arable land
area, and desire for globally increased standards of
living, the need for further crop yield increase is
inevitable. Enhanced crop net primary production (NPP)
is one mechanism, among others, to increase yield.
Extending crop growth duration could increase NPP and
so too might 'improvements' to primary metabolism–
specifically,
faster
photosynthesis,
slower
photorespiration, and/or more efficient growth and
respiration. These improvements to primary metabolism
are considered herein. In principle, faster photosynthesis
might be achieved by improved kinetics of
photosynthetic enzymes, particularly that of rubisco.
Some possibilities are reviewed, but past successes are
limited. Conversely, the demonstrated ability to shortcircuit the photorespiratory pathway in intact plants, and
to release the resulting CO2 directly within the
chloroplast, could be the foundation for significantly
increased crop NPP. Also, revived interest in converting
rice from a C3 to a C4 crop (with attendant increase in
NPP) is intriguing, even if yet unproven. Slowing crop
respiration might increase NPP, but caution is warranted
because rapid growth requires rapid respiration and some
'maintenance respiration' is essential. A knowledge gap
remains concerning the possibility of otiose respiration,
and how it would be eliminated if found. Speculation
about time frame for improving primary metabolism on a
farmer's field is just that –speculation. Some advances
perhaps might be seen within 10 years, but I expect
several decades will pass before significantly improved
crop-plant primary metabolism becomes an on-farm
reality.
KNS07: Plant diversity and
ecology/invasion ecology
The dream of the biodiversity informatics community is
to provide a virtual laboratory equipped with electronic
tools and datasets with which to study the global biota.
BiodiversityWorld and the Catalogue of Life provide
pointers to two themes that will come together with
powerful outcome. Significant progress with the
Catalogue of Life, alongside partners including ITIS,
WoRMS, FADA, and The Plant List, means that we are
close to having an electronic catalogue of the world's
known species, including Plants, Animals, Fungi and
Micro-organisms. This taxonomic backbone provides a
framework for species-based global datasets. Initiatives
to assemble ecological and functional traits across taxa
on a global scale are now feasible, as are the possibilities
for Taxa of the World and Biota of the World services
for access to comparable species lists for each area of the
world and potentially for each biome and ecosystem.
Converging with this growth of datasets is the idea
behind the BiodiversityWorld pilot-project. A suitably
empowered distributed computing environment could
provide the platform, both for access to global
biodiversity datasets, and for libraries of analytical
routines, a toolbox of agreed and experimental
workflows,
and
workspace
for
wide-ranging
experimental, analytical and modelling investigations: a
true virtual laboratory or cyber-infrastructure. This
convergence of platform and data sets will enable the
start of the interesting part: the elucidation of models,
processes and even rules for the behaviour of biodiversity
at the large scale – a space we need to occupy, and the
start of a truly evidence-based global biodiversity
science.
Intelligence systems for emerging plant pests and
diseases
Burgman, M1, Nunn, M1, Lyon, A1
1
The University of Melbourne, Melbourne, Australia
Plant pests and diseases are dealt with most efficiently
when they are identified early, and ideally, before they
arrive in a susceptible area. Biosecurity intelligence
encompasses a range of methods for gathering, filtering
and communicating information on emerging threats, so
that decisions can be made early to mitigate risks. This
presentation outlines three strategies for biosecurity
intelligence: web-based intelligence software, informal
social networks, and foresighting. Web-based systems for
animal diseases are relatively well developed. Our
research shows they have a range of features that may be
useful for plant biosecurity. Foresight activities are
extremely useful for assisting users to tune filters to
identify critical pieces of information. Professional
networks may be supported and developed to disseminate
biosecurity information so that it contributes effectively
to decision making.
A risk assessment protocol for managed relocation
BiodiversityWorld and the Catalogue of Life: tools for
studying the ecology and behaviour of the entire
global biota in a virtual laboratory
Possingham, H1, Rout, T1, McDonald-Madden, E1,
Martin, T1, Armstrong, D1
Bisby, FA1
1
1
University of Reading, UK
10
The University of Queensland, Brisbane, Australia
Managed relocation (sometimes called assisted
colonisation) is the deliberate movement of a species to a
location outside its known range in response to unabatable threats. The threat might be climate change, but
it could equally well be any other human-induced change
that society is unwilling to halt (e.g. land-clearing). We
present a quantitative framework for assessing the
relative costs and benefits of such an action that accounts
for factors like: the chance the translocation is successful;
the chance, and amount, of negative impact; and the
negative effect on the source population. If this benefit is
positive we show how that, using information about
costs, such moves can be prioritised in a rational fashion.
Finally I note, that, despite the resistance to managed
relocation, we seem to have done it an awful lot.
KNS08: The role of modern biology in
reducing pest and pathogen threats to
global food security
Developing durable resistance to potato late blight
disease using an understanding of how the pathogen
infects its host
Birch, PRJ1
1
Division of Plant Sciences, University of Dundee (at
JHI), Invergowrie, Dundee, UK
The oomycete Phytophthora infestans is the cause of late
blight, the most significant global disease of potato.
Notoriously, it precipitated the Irish Potato Famine in the
mid-19th century – seldom can a plant disease have had
such a dramatic effect on the social, political and
demographic structure of a country. More than a century
of breeding for late blight resistant potatoes has met little
success, as most deployed resistances are overcome in a
few growing seasons. Late blight control has thus relied
heavily on application of prophylactic chemicals. In
Europe, new legislation is set to reduce the range and
levels of chemical application, driving an urgent need to
better understand the molecular basis of late blight
disease, in order to seek new approaches to combat
infection.
Over recent years we have learned that, during infection,
P. infestans delivers proteins called RXLR effectors
inside living potato cells. One clear role of these effectors
is to suppress the plant immune system, creating an
environment in which the pathogen can colonize its host.
The genome sequence of P. infestans has revealed
hundreds of candidate RXLR effector genes, residing in
regions rich in transposons where they are likely to
evolve rapidly. We have learned also that these effectors
are the ‘targets’ of resistance receptor genes that are also
evolving rapidly in natural populations of wild potato
species. I will describe how we have been studying
RXLR effectors, finding those that are critical to late
blight disease and are prevalent across the pathogen
population. Such effectors have sparked a search, in wild
potato collections, for resistance genes that recognise
them. I will argue that the careful combination of such
resistances in potato cultivars will provide late blight
disease resistance that is more durable.
Reducing the threat of wheat rusts to global food
security
Park, RF1
1
The University of Sydney, Plant Breeding Institute,
Narellan, Australia
Wheat is the most important cereal crop, and the three
rust diseases that infect it are among the most important
biotic impediments to stable wheat production in many
regions. The development of our understanding of the
wheat rust pathogens, their hosts, and the interactions
between these two organisms, is a remarkable chapter in
the history of the plant sciences. The work began in
earnest in the latter part of the 1880s in Australia with a
series of Rust-in-Wheat conferences, which followed a
stem rust epidemic in 1889 that was estimated to have
caused some £2–3 million in losses. While advances in
our understanding of this host : pathogen system have
permitted considerable success in developing and
deploying rust resistant wheat cultivars, these diseases
continue to impact on global wheat production
principally because of their abilities to overcome the
resistance genes incorporated by breeders. The two most
significant wheat rust challenges to emerge over the past
10 years have been the intercontinental spread of two
pathotypes of the stripe rust pathogen with increased
aggressiveness in the early 2000s, and the detection of
stem rust pathotype 'Ug99' in 1999 Uganda and its
subsequent spread to Kenya, Ethiopia, Yemen, Iran and
South Africa. In both cases, regional epidemics have
reduced production and increased costs to growers due to
the need for fungicide intervention. These challenges
have refocused international rust control efforts,
providing a strong impetus to develop and implement
new tools to monitor rust pathogens and accelerate the
development and adoption of rust resistant wheat
cultivars.
The genome of the wheat and barley crown rot
pathogen Fusarium pseudograminearum reveals
horizontally transferred virulence functions
Gardiner, DM1, Solomon, P2, McDonald, M4, Marshall,
M3, Kazan, K1, Chakraborty, S1, McDonald, B4,
Manners, JM1
1
CSIRO Plant Industry, Queensland Biosciences
Precinct, Brisbane, Australia; 2Research School of
Biology, College of Medicine, Biology and Environment,
The Australian National University, Canberra, Australia;
3
Queensland Facility for Advanced Bioinformatics, The
University of Queensland, Brisbane, Australia; 4Plant
Pathology, Institute of Integrative Biology, Zürich,
Switzerland
Fusarium crown rot disease is a chronic problem in
wheat and barley in arid environments such as Australia
and there are currently no fully resistant wheat cultivars.
In Australia, F. pseudograminearum is the pathogen
predominantly associated with crown rot although related
Fusarium species such as F. graminearum and F.
culmorum have the ability to cause crown rot in some
regions. These three Fusarium species can also cause
globally important head blight disease of wheat. To
increase our understanding of factors affecting pathogen
11
virulence, we have sequenced the genome of an F.
pseudograminearum isolate and compared it to the
publically available genome sequence of F.
graminearum. Despite overall sequence conservations,
striking differences have also been observed between the
genomes of these two Fusaria. Most strikingly we also
identified a gene encoding an amidohydrolase that
appears to have been acquired by horizontal gene
transfer. This gene has a clear orthologue in the genome
of the wheat pathogen Stagonospora nodorum but not in
any other fungal genome and the next closest sequence
matches are from bacteria. Deletion of this gene from F.
pseudograminearum resulted in a reduction in virulence
on barley but not wheat. Population studies suggest this
acquisition of this gene in both species may have been
independent. Its presence in these two unrelated
pathogens but not in any other fungal species suggests a
role for this gene in a common pathogenesis mechanism
that targets an important defence pathway in cereals.
KNS09: Plant taxonomy in the 21st century
Coalescent global communities for species-level plant
taxonomy
Knapp, S1, Baker, W2
1
Dept of Botany, The Natural History Museum, London ,
UK; 2Royal Botanic Gardens Kew, Richmond, Surrey,
UK
Plant taxonomists have in recent years embraced a
number of new initiatives and technologies in attempts to
meet global targets and accelerate species discovery and
delimitation. It is often assumed that the community of
taxonomists describing species is small and fragmented,
but recent work suggests this is not the entire picture.
Despite this, the imperative to both increase and
accelerate our acquisition of knowledge about the species
of plants is great – much attention has been focused on
the so-called 'taxonomic impediment'; taxonomic
capacity and research itself not keeping up with demand
for taxonomic information. Many solutions to this
problem have been proposed, ranging from the purely
technological (for example, bar-coding and automatic
identification) to largely people-centred (for example,
EU and UK-funded projects using the web and NSF's
PBI Initiative). Taxonomy, like physics or astronomy, is
most definitely big science and can learn a lot from these
other disciplines. Can taxonomists come together as
coalescent communities to speak with one voice while
retaining the differences and debate characteristic of a
vibrant scientific discipline? Does the development of
national strategies make sense in a globalised scientific
enterprise? Some of the social issues associated with
working in large distributed groups of researchers have
been explored by a variety of projects over the last few
years; the human factors involved in the science of plant
taxonomy - both in terms of research partnerships and
audiences and how individuals function within
institutions are critical to achieving our goals. These
issues relate to the use of new technologies as well as to
interactions between people themselves. People are often
perceived as the problem, but they must be the solution
12
as well if plant taxonomy is to truly take advantage of the
21st century.
Beyond the Plant List: plant systematics in the 21st
century
Raven, PH1, Hopper, S2
1
Missouri Botanical Garden, St Louis, USA; 2Royal
Botanic Gardens Kew, UK
Gaining an adequate knowledge of the approximately
380,000 valid named and described species of plants and
finding the perhaps 75,000 or more awaiting recognition
poses a significant challenge for the science of plant
systematics. We know very little about the great majority
of even the named species, many of which are known
from only one or a few specimens. Of great use will be
The Plant List, an integrated synonymized list of vascular
plants that was produced by the common efforts of the
Royal Botanic Gardens, Kew, and the Missouri Botanical
Garden and put on line at the end of 2010. Continually
upgraded over the years, and with many other institutions
and individuals – virtually the entire plant taxonomic
community – involved, TPL, by indicating directly such
details of authorship and bibliographical citation and
providing a standard reference to what has already been
established, will relieve botanists of much of the routine
that currently occupies a great deal of their time.In
addition, all of the literature of systematic botany, rapidly
being accumulated in the Biodiversity Heritage Library
and Botanicus, will soon be instantly available for
consultation, and images of type and other specimens
will be fully available on line soon. With this substantial
mass of information available, systematists should be
able to devote themselves to the study of plants in nature,
the determination of their characteristics, their role in
ecosystems, and their conservation status, using
molecular tools, automated character recognition and
identification software, rapid imaging, space technology,
and many other novel means of understanding them.
Because of the rapid destruction of habitats; spread of
alien invasives, pest, and diseases; and especially global
climate change, conservation should become the primary
object of our efforts in this century, with as many as half
of all species at risk of extinction over the coming
decades.
Plant DNA barcoding: the future of taxonomy,
ecology, and species discovery
Kress, J1
1
Dept of Botany, United States National Herbarium,
National Museum of Natural History, Smithsonian
Institution, Washington, DC, USA
How many plant species remain to be discovered and
described? As taxonomists, how and where will we find
them? As ecologists, how will we investigate their life
histories and
community interactions?
As
conservationists, how will we protect and preserve them?
Natural habitats continue to be degraded around the
world and the deadline for finding and describing
biodiversity approaches at an ever-increasing rate. Now
more than in the past we need new scientific tools to
supplement our time-tested methods for species
discovery and understanding. DNA barcodes provide one
such tool. Based on short stretches of DNA that are
easily sequenced and variable enough to distinguish
among species, barcodes provide a rapid assessment of
taxonomic similarity and genetic distinctness. As a first
pass in identifying new taxa, DNA barcodes alert us to
the existence of unknown species and may lead us to test
the validity of previously described taxa. In addition the
assembly of DNA barcode libraries for species-rich
natural communities greatly enables ecological studies
where accurate species identifications are required.
Finally, well-resolved molecular phylogenies of naturally
co-occurring species derived from DNA barcode
sequences have the potential to improve investigations of
the mechanisms that underlie the assembly of plant
communities and the evolution of plant functional traits.
DNA barcodes, if applied appropriately, will enhance
future research focused on the interface between species
discovery, taxonomy, ecology, and evolution.
KNS10: The past, present and future of
plant diversity
Patterns in the history of plant diversity: testing,
reconciliation and accounting for missing data
Crane, PR1
1
Yale School of Forestry and Environmental Studies,
New Haven, USA
Evidence of the structure, biology and diversity of extinct
plants derived from paleobotanical research over the past
200 years has greatly expanded our view of the history of
plant life and provided insights into key events in plant
evolution that would have been inaccessible from studies
of living plants alone. In general, there is remarkable
consistency between the large-scale patterns of plant
evolution inferred from studies of living plants and those
obtained from studies of fossils. However, two areas
have emerged since the last botanical congress where this
reassuring consistency seems to have broken down, and
where paleobotanical and neobotanical evidence appear
to conflict significantly: the pattern of phylogenetic
relationships among seed plants, and the antiquity of
certain lineages of angiosperms (with the associated
implications for the antiquity of certain kinds of biomes).
In both instances questions of missing data seem to be at
the heart of the problem. As a paleobotanist I worry
about the impact of extinct taxa on inferences of seed
plant relationships based on living plants alone. While
acknowledging the inadequacies of current phylogenetic
analyses based on structural data I am unwilling to
abandon those results entirely in favor of other patterns
of relationship that while based on vast amount of
molecular data are likely to be from an inadequate
sample of taxa. At the same time, those who use
molecular dating techniques to determine the age of
clades acknowledge the limitations of current models of
molecular evolution from which such ages are derived.
Nevertheless, they seem more comfortable with their
own results than trusting to the completeness of the fossil
record. In this talk I will argue that neither neobotanists
nor paleobotanists will ever have the data that they would
ideally want to address these questions, but combined
efforts and opportunities for partial reconciliation offer
the promise of more robust hypotheses. Fresh
perspectives on key questions of plant evolution are
possible, but are less likely to come from approaches that
fail to account for all of the available data.
The future of plant diversity
Coates, D1
1
Dept of Environment and Conservation, Western
Australia, Australia
A recent assessment by the Sampled Red List Index
indicates that as many as one fifth of the world’s
estimated 380,000 plant species are under threat. This
suggests that some 76,000 plant species are in danger of
extinction from a broad range of threats including habitat
loss, habitat transformation, over-exploitation, alien
invasive species, pollution and rapid environmental
change. Although the disappearance of such a critical
component of biodiversity poses one of the greatest
challenges for the future it is encouraging that there are
now key strategies being developed and implemented
which are directed towards addressing and recovering
this potential loss. For example, the Global Strategy for
Plant Conservation set 16 outcome-oriented global
targets for 2010 that provided an important starting point
for improving world plant diversity conservation. One
such target Target Eight of The Global Strategy for Plant
Conservation recommends that ‘60% of threatened plant
species’ should be ‘in accessible ex situ collections,
preferably in the country of origin and 10% of them’
should be ‘included in recovery and restoration
programs’ by 2010. Based on current estimates by the
end of 2010 some 4,560 plant species worldwide should
be in reintroduction programs. Such goals may be
ambitious and considered unrealistic by some. However,
as shown in Western Australia, with a flora of 12,200
species, they can be achieved and even exceeded with
70% of the threatened flora in ex situ conservation and
13% used in reintroductions. Equally the goals for
ecological restoration can set very high benchmarks but a
bold and proactive approach where actions are
implemented now, perhaps without full knowledge, but
in an adaptive management framework will need to
considered if successful plant diversity conservation is to
be achieved. Loss of some plant diversity is inevitable
but the magnitude of that loss will depend on our ability
to implement strategies already in place, develop new
strategies and integrate current knowledge in plant
conservation science with on ground actions. For
example, the introduction of plant species outside their
natural range in response to the threat of climate change
has been raised recently as a key tool in plant
translocations. While achieving long term persistence
particularly in the face of rapid environmental change
may require a reassessment of how we manage genetic
diversity, maximise evolutionary potential and deal with
local adaptation. Also recent strategic approaches to
combining ex situ and in situ conservation that involve
the creation of artificial populations of plants that can be
subsequently used for reintroductions and restoration
have considerable potential for enhancing plant diversity
conservation. These approaches will be discussed in the
context of future goals and actions that will be needed to
halt and even reverse the global loss of plant diversity.
13
Plant diversity today: how well do we know what we
have now?
Nic Lughadha, E1, Allkin, R1, Rivers, M2, Saltmarsh, A1
1
2
Royal Botanic Gardens, Kew, Richmond,
University of St Andrews, St Andrews, Scotland
UK;
The volume of plant diversity data available on our
desktops has increased by orders of magnitude over
recent years. New technologies and reductions in the
costs of digital storage have greatly facilitated the capture
of new information and the conversion of existing
information to digital form. Most of us now have at our
fingertips more data on plant diversity than we could
hope to explore in lifetime. But how effective have our
efforts been to analyse, synthesize and apply this
information? How good an overview of plant diversity
do we have currently? Estimates of the number of known
plant species have varied widely, though the creation of
consolidated checklists of accepted species with
synonymy has reduced the range of likely values. Full
species lists have been published for several megadiverse
countries but most still lack a basic inventory of what is
known. Species considered new to science continue to be
described at a steady rate but inventory effort is
taxonomically and geographically patchy. Current data
provide limited support for reliable estimates of how
many species remain to be discovered. Distribution data
at country level or below are readily available for well
over half of all known species, but most of the point data
for most species remains locked up in our herbaria. Thus
we can identify hotspots of diversity and endemism on a
broad scale but generally lack the data required for
detailed analysis and conservation planning more locally.
The vast majority of online records relate to widespread,
temperate plant species and though we can find at least
one image for most plant species these images are often
far from ideal for identification purposes. As systematic
botanists we recognize that any failure to synthesize and
to present the results of such synthesis more effectively
has consequences not only for related disciplines such as
conservation and ecology but also, more broadly for
human health and welfare. . In this review we attempt a
score-card for our knowledge of plant diversity in 2011
and consider how targeted efforts over the next decade
might address deficiencies in our current overview and
our ability to organize current knowledge.
LUNCHTIME
PRESENTATIONS
Making a botanical institute (nearly) from scratch
Sohmer, S1
1
Botanical Research Institute of Texas, Fort Worth, USA
The Botanical Research Institute of Texas (BRIT) was
formed on paper in 1987. Based on the collections
accumulated at Southern Methodist University, BRIT
moved into warehouse space in downtown Fort Worth in
1991, has grown its herbarium from about 400,000
specimens to the nearly 1,100,000 today, and its
14
horticultural and botanical library from about 50,000
books and journals to about 125,000 during the same
period. The budget has grown from about $175,000 per
annum in 1993 to nearly $3,000,000 today, and its staff
from three to over 30. All of its operating costs are
obtained as donations from the private sector and most of
its projects are funded by grants from private foundations
and state and government agencies, such as the National
Science Foundation. BRIT has established leading
programs in horticulture, taxonomy, ecology and
database management in the Peruvian Amazon, major
collection activities in Papua New Guinea and the
Philippines, and is producing the definitive volumes on
the flora of Texas through the Illustrated Flora of Texas
Project. It maintains a leading press publishing a
respected scientific journal and a number of significant
books each year. It has nearly completed a $48 million
capital campaign, the first in its history, that has resulted
in a spectacular facility that will be only the 8th LEED
platinum level building in the entire state of Texas. There
are 168 geothermal wells, solar panels on top of the
collection wing, a piece of the Fort Worth Prairie
growing on top of the research wing, and all manner of
sustainable and material in the building. Dr Sohmer will
focus on the means by which this institute arose from
nearly nothing but a dream and has thus far prospered
almost entirely on private philanthropy.
Sing of Botany
Silk, WK1, 2
1
Dept of Land, Air, and Water Resources, University of
California at Davis, Davis, CA, USA
One in five plant species – the basis of life on earth – are
estimated to be under threat of extinction; sickness of
pollinators is threatening food production; and pollution
is threatening human health. More than ever in human
history there is need for new access to scientific
knowledge and new paradigms for collaboration. At the
University of California at Davis, biologist Diane Ullman
has established an ArtScience fusion program in the hope
that artists will better access scientific literacy, while
scientists will better access art as a means of expression.
In 2009 the course 'Earth, Water, Science, Song' was
introduced to the curriculum. Students write and perform
songs to communicate their understanding of the lectures
and readings in environmental science. Instruction
features conventional science lectures, participation of
guest artists from the community, and studio sessions on
music theory, lyric writing, and performance skills. The
hope is that the act of translating from science lectures to
an art form will foster understanding of the science.
Assigned topics for songwriting include the hydrologic
cycle, the carbon cycle, the nitrogen cycle, spatial and
temporal variation, soil formation, eutrophication, and
fundamental processes such as photosynthesis and
transpiration. Instead of writing a final exam the students
perform in a university lecture hall and in a local art
gallery. A spirit of intense collaboration developed with
the collaborative work among musicians and music
neophytes, science majors and nonmajors. The repetition
of rehearsals fostered retention of course content.
Student energy was high. Students became teachers, as
their performances attracted a large audience from the
community. In this lecture-demonstration we will see
some videos of botanical songs and hear songs designed
to inform, motivate, and celebrate research progress in
botany.
PU02: The world of plants
Raven, PH1
1
Missouri Botanical Garden, St Louis, USA
2
Work supported by the US National Science Foundation
under Grant No. RCN-UBE 0956196. Any opinions,
findings, and conclusions or recommendations expressed
in this material are those of the author and do not
necessarily reflect the views of the National Science
Foundation.
PUBLIC PRESENTATIONS
PU01: Fruits of the vine – future climates and wine
Barlow, S1
1
The University of Melbourne, Melbourne, Australia
Wine produced from the grapevine, Vitis vinifera, has
been consumed for more than 10,000 years, evolving
alongside cereals as essential part of early civilizations in
the Middle East. Since those times many of our great
civilizations have evolved and developed the
sophistication of both viticulture and winemaking to
provide wines of distinction and consistency. A key part
of this development has been the matching of particular
wine varieties, such as Shiraz and Chardonnay ,to special
combinations of soils and climate allowing them to fully
express their characteristic flavor and aroma profiles.
This French concept of terroir encompasses the
combination of climate, soils, geology and topography,
that determines the characteristics of the grapes and
ultimately the wines. Wine regions have effectively
'patented' and trademarked the successful combinations
of terroirs and grape varieties that produce great wines
such as Bordeaux and Burgundy in the form of French
appellation system. Climate change challenges these
established terroir relationships by changing the climate
component thereby altering ripening temperatures and
the resulting wines. Rising temperatures in wine regions
around the world are resulting in earlier ripening and
earlier vintages. In some areas of Australia and Europe
vintages have moved forward by as much as a day per
year over the past 30–40 years. While some of these
vintage temperatures are within the range of season to
season variation many are not and certainly will not be in
the future. How has climate change altered the climate in
well known terroirs and how will the global wine
industry respond to these challenges to established
terroirs particularly if we ,as consumers, wish to continue
to savior the 'grassiness' of Malborough Sauvignon Blanc
or the 'white pepper' of cool climate Shiraz ? What sort of
wines can we look forward to in the future ?
We depend for all fundamental aspects of our lives on
plants. The dominant angiosperms evolved at least 120
million years ago, diversified in the face of climate
evolution and change, coevolved with insects and other
herbivores, and adapted to diverse habitats. Angiosperms
provide our food, most of our medicines, building
materials, cloth, chemical feedstocks, and many other
products and possibilities for the future. In addition they
provide an enormous array of ecosystem services and add
meaning and beauty to our lives. At least 400,000 species
of angiosperms exist, the great majority of them poorly
known, with perhaps 20% of the species and a much
higher proportion of the genetic diversity threatened with
extinction over the next decade or two and probably
more than half by the end of the century. In the face of
human pressures on the environment, already estimated
to be using a rapidly growing 150% of the world’s
sustainable productivity on an ongoing basis, we must
find effective ways of conserving the plants on which we
depend and which offer so much promise for the future.
Learning about them and disseminating the information
efficiently, conserving natural areas in the face of
growing adverse changes, building seed banks, and
educating people to know and love what they are losing –
these are elements of the strategy now so badly needed to
ensure a future that begins to match the present.
PU03: Brave New World: can we solve tomorrow’s
environmental and energy problems by using life
itself? – Public discussion panel1
1
Supported by Royal Botanic Gardens and Domain
Trust, Sydney, Australia; coordinated by Janelle
Hatherly, Manager Public Programs.
Studying life in all its forms is exciting at this time of
great technological change. Computers and modern
scientific techniques have provided us with an
understanding of life processes at the molecular level in a
way never before possible. Yet we know little about the
unicellular organisms that make up most of the Tree of
Life. Much of our scientific research efforts and
investments go into the study and conservation of
relatively few multicellular creatures and ecosystems.
Research on the rest of life focuses mostly on controlling
harmful microorganisms rather than looking for useful
ones.
Is the time right to prioritise research into useful
microbes, harnessing them to convert significant amounts
of CO2 into biomass and biofuels and to capture and
store significant amounts of carbon to slow climate
change? Plants feed us and nature sustains us, but could
microorganisms give us the ‘biggest bang for our buck’?
These questions will be discussed and debated by a
distinguished panel, moderated by Robyn Williams,
eminent Australian Broadcasting Commission science
journalist. The format is conversational with Robyn
setting the scene and then each speaker presenting a point
15
of view for 5–10 minutes. Then Robyn will ask/take
questions – from the floor or via live links.
Speaking for the plants:
* Prof. David Mabberley, Royal Botanic Gardens, Kew,
UK; soon to be Executive Director of Sydney’s Royal
Botanic Gardens and Domain Trust
* Dr Kevin Thiele, Curator Western Australia
Herbarium, Perth, Australia
Speaking for the microbes:
*Dr Jeff Powell, Microbial ecologist and lecturer,
University of Western Sydney, Australia
*Assoc. Prof. Kirsten Heimann, Cell biologist and
biofuels expert, James Cook University, Townsville,
Australia
Sister Water Lily meets the Big Bad Banksia Man
Bernhardt, P1, Meier, R1
1
Saint Louis University, St Louis, USA
Can a whimsical and largely discarded branch of
illustration be used to reinvigorate botanical education?
We review the works of C.M. Barker (England), W.
Crane (England), May Gibbs (Australia), J.J. Grandville
(France) and M.T. Ross (America). All produced detailed
illustrations featuring anthropomorphic flowers, stems
and edible plants. The tragic J.I.I. Gerad (a.k.a.
Grandville, 1803–1847) began this trend in floral fantasy
to amuse a mature audience of sophisticated Parisians but
his techniques were assimilated by later author/artists of
children’s books. Within little more than a century
(1847–1952) their combined oeuvre reminded or taught
viewers simple, amusing and often visually accurate
lessons in plant morphology/identification, phenology,
economic botany, plant-animal mutualisms and
phytogeography. These drawings, often reinforced
botanical information by employing visual puns and
satirizing the old, European, ‘language of flowers’. We
could certainly use a little of this style today with the
fundamentals of plant biology taught so infrequently in
many countries. In particular, author/illustrator, May
Gibbs (1879–1969) developed the art of ‘people plants’
to introduce generations of Australian children to plant
diversity common to southeastern and southwestern
Australia.
The Atlas of Living Australia: infrastructure for
biodiversity research
Hobern, D1
1
Atlas of Living Australia,
Canberra, Australia
CSIRO
Entomology,
The Atlas of Living Australia is a national initiative
focused on making Australia's biodiversity information
more accessible and useable online. In short, 'an online
encyclopedia of all living things in Australia'. The Atlas
website already holds more than 23 million distribution
records for Australia's fauna and flora, integrated with
over 300 environmental layers for mapping and analysis.
In addition the site brings together photos, maps,
identification tools, reference lists of species names and
classifications, databases on biological collections and
literature. All of these resources are freely available at
http://www.ala.org.au/. Ultimately, the Atlas aims to
enable anyone to find, analyse and map information on
all aspects of Australian biodiversity online. Researchers,
managers and others can use the Atlas in their efforts to
protect, manage and monitor Australia's biodiversity and
biosecurity, from conserving species to tracking invasive
pests. As a research tool, the Atlas can help to create
species distribution models, predict areas that could be
suitable for a species, or work out how a species will be
affected by a change in climate, among other things. The
Atlas enables researchers to provide policy and decision
makers with targeted and useful information, presented in
accessible ways. Members of the public can contribute
sightings and photos of species and help to build a more
complete picture of Australia's biodiversity. Funded by
the Australian Government, the Atlas is a collaboration
between CSIRO, Australia's national science research
agency, and more than 60 biological collections from
Museums and Herbaria, Federal and State Departments,
universities and microbial collections.
GENERAL SYMPOSIA
Note: abstracts are arranged by theme and then by symposium number and then by speaker order within each symposium.
Where a symposium is divided into two sessions (A and B), the abstracts are in chronological order under the one
symposium number.
Theme
01: Ecology, environmental change and conservation
02: Economic botany including biotechnology, agriculture
and plant breeding
03: Genetics, genomics and bioinformatics
04: Physiology and biochemistry
05: Structure, development and cellular biology
06: Systematics, evolution, biogeography and biodiversity
informatics
07: Plants in society
16
Symposium numbers
1, 2, 9–27, 126, 127, 149, 150, 158, 163–167
28–36, 152, 159–163
37–42, 45–48, 123, 157
49–55, 124, 145, 151, 153, 156
56-71
4–8, 72–122, 128–144, 155, 168–172
3, 177
THEME 01:
ECOLOGY, ENVIRONMENTAL
CHANGE AND
CONSERVATION
Sym001: Mistletoes: diversity, distribution
and ecological interactions – 25 July
Mistletoe specialist frugivores: diligent dispersers or
self-serving free-loaders
Watson, DM1, Rawsthorne, J1120
1
Environmental Sciences, Charles Sturt University,
Wagga Wagga, Australia
Parasitic plants necessarily depend on host plants for
their water and mineral nutrition, and therefore differ
from most plants in the specificity of safe sites needed
for germination and establishment. Most groups of
parasitic plants use animal-mediated directed dispersal to
increase the likelihood of seeds landing on or near
suitable host plants. This is exemplified by mistletoes,
which attach to single hosts above ground, unlike rootparasites which typically attach to multiple hosts below
ground. These specific dispersal requirements have
encouraged reciprocal adaptation of mistletoes and birds,
and mistletoe specialist frugivores have evolved
independently in seven avian lineages. Most of the
research conducted on mistletoe dispersal has been
restricted to these taxa, their nutritional reliance on
mistletoe fruit presumed to confer the status of principal
seed dispersers. Recent research has called this into
question, however, and the role of mistletoe specialist
frugivores as principal dispersers warrants critical reappraisal. In this contribution, we demonstrate that
mistletoe specialist frugivores move from infected hosts
to other infected hosts, thereby intensifying existing
infections far more frequently than initiating new
infections (by dispersing fruit to uninfected host). So,
even though these birds may remove most seeds, they
may reduce individual and population-level fitness of
mistletoes by loading hosts with increasing numbers of
parasites, lowering overall levels of recruitment. In
addition to reviewing recent research on these specialists,
we summarise several studies of more generalist foragers
that include mistletoe in their diet, demonstrating that
they are far more likely to disperse seeds to uninfected
hosts and stands. Finally, we compare continental regions
with mistletoe-specialist frugivores with other regions
(including Madagascar, New Guinea, New Caledonia,
New Zealand and Europe) where all dispersal is
performed by dietary generalists, evaluating the
ecological and evolutionary consequences for the plants
themselves. Although these coevolved specialists may
have been instrumental in the evolution of dispersal
syndromes and diversification of mistletoes, we suggest
that their dietary specialization has diminished their
importance as seed dispersers and determinants of
mistletoe distribution, and they may not be the helpful
mutualists which they are frequently considered.
Bird–mistletoe interactions with a depleted avifauna:
what determines mutualism failure?
Kelly, D1, Ladley, J1, Robertson, A2
1
Biological Sciences, University of Canterbury,
Christchurh, New Zealand; 2Ecology, INR, Massey
University, New Zealand
The Loranthaceae worldwide have some of the most
apparently-specialised bird-plant mutualisms both for
pollination (such as 'explosive' flowers that cannot open
without a pollinator) and for dispersal (with directed
dispersal to particular sized host branches). However, the
actual level of plant dependence on the mutualism for
successful reproduction varies widely among species.
Here we use the New Zealand Loranthaceae to explore
the factors which predict sensitivity to mutualism failure.
The question is important in New Zealand because both
the mistletoes and their bird mutualists have declined in
abundance and some are of conservation concern. For
pollination, both Peraxilla spp. and Alepis flavida have
ornithophilous flowers, but A. flavida routinely
autonomously self-pollinates so is immune to mutualist
failure unless there is inbreeding depression (which is
known absent in Peraxilla spp., but impossible to test in
A. flavida). In contrast Peraxilla spp. have explosive
flowers and are widely pollen-limited due to a shortage
of pollinating birds. However, many flowers are also lost
to a native florivorous moth Zelleria maculata, so the
relative impacts of pollinaton failure versus flower
predation are complex and both vary with habitat
fragmentation. For dispersal, all tested loranths have an
absolute requirement for passage through a bird gut to
allow adhesion to new host branches. However, levels of
mutualist service for dispersal seem to be much more
adequate than for pollination, even though the same bird
species are providing both services. This may reflect a
general rule that dispersal is 'easier' than pollination
when both are done by vertebrates. There is no evidence
for directed dispersal to small branches in the NZ
species, so seed losses at the defecation stage are
probably very high. Overall the greatest threats to New
Zealand Loranthaceae are introduced herbivores and
pollination failure, with dispersal less at risk.
Studies on the biodiversity and host-specific
interaction of some parasitic angiosperms (mistletoes)
in the Himalayan terrain of Uttaranchal, India
Mondal, AK1, Mondal (Parui), S2
1
Vidyasagar University, Midnapore,
Brabourne College, Kolkata, India
India;
2
Lady
An extensive survey of the Himalayan terrain of Nainital,
Almora, Ranikhet, Kausani and adjoining areas of the
state of Uttaranchal, India was done to record the
parasitic angiosperms growing in this area. Parasitic
angiosperms have been found to have significant
ecological effects on the plant community structures by
altering the competitive balance between host and nonhost species. Six species of parasitic plants or commonly
called mistletoes were recorded from this zone. Among
these, five were hemi-parasites, which included Cassytha
17
filiformis, Dendrophthoe falcate, Loranthus longiflorus,
Phoradendron serotinum, Viscum album, while the sixth
member Cuscuta reflexa was a holo-parasite. The present
paper reports the distribution, dominance and the host
specific interaction of this parasitic species. Viscum
album was found to be the most dominating species
seriously parasitizing the host Pyrus pashia (Rosaceae),
which is an economically important plant. Key words:
Biodiversity,
host-specific
interaction,
parasitic
angiosperms.
Soil nutrient accumulation under two species of
mistletoe produce different soil patchiness in a semiarid open woodland
Facelli, JM1, Watling, J1, Binney, A1
1
The University of Adelaide, Australia
Mistletoes accumulate higher concentrations of nutrients
in their foliage than their hosts. Because of their
abundance in nutrient-poor systems they may play
important functional roles in nutrient cycling. In arid
lands they grow on long-lived plants that frequently
create patches of high nutrient availability, and may
therefore affect the patchiness in nutrient distribution
typical of these systems. Here we report a study of
patterns of nutrient accumulation under two mistletoes,
Amyema quandang and Lysiana exocarpii, growing on
different hosts (Acacia papyrocarpa and Alectryon
oleifolius respectively), in chenopod shrublands of South
Australia. We quantified litter production and litter
nutrient concentrations of the four species. We also
compared soil nitrogen (N), phosphorus (P), and organic
carbon (OC) content in the soils beneath both hosts and
mistletoes, and conducted a growth bio-assay using these
soils and a co-occurring perennial shrub, Enchylaena
tomentosa, that grows almost exclusively under canopies
and is known to require high levels of nutrients.
Mistletoes produced up to 6 times more litter than either
host, regardless of infection status of the latter. Litter N
concentration was similar in A. quandang and its host A.
papyrocarpa, but L. exocarpii had slightly higher litter N
content than A. oleifolius. In contrast, both parasites had
significantly higher litter P concentrations than their
hosts. The soil beneath the hosts had higher nutrient
contents than soil from adjacent, open spaces, and the
soil directly beneath mistletoes had significantly higher
N and P concentrations than soil beneath parts of the host
canopies without mistletoes. While there was no
difference between the soils underneath the two hosts
when they had no mistletoes, the patches underneath the
two species of mistletoe were different. The soil
underneath A. quandang had less organic carbon and
phosphorus, but more nitrogen than the soil underneath
L. exocarpii. These differences were biologically
important since biomass of E. tomentosa was higher
when grown in soil from beneath L. exocarpii than in soil
from underneath A. quandang. Biomass was also higher
in soil from under mistletoes than from under canopies of
the hosts of from open spaces. Mistletoes contributed
both more litter and more nutrients to soil than either tree
species, resulting in significant heterogeneity in nutrient
availability across this nutrient poor ecosystem.
Enrichment of soils beneath mistletoes resulted in higher
growth of a perennial shrub, suggesting that mistletoes
18
could play a significant functional role in nutrient cycling
within this semi-arid woodland.
Cytotoxic activity of Mexican Mistletoe (Cladocolea
loniceroides)
Serrano Maldonado, MJ1, De la Paz Perez Olvera, C1,
Guerrero Legarreta, I1, Soriano Santos, J1
1
Universidad
Mexico
Autónoma
Metropolitana,
Itzapalata,
Mistletoe, as a parasitic plant, grows attached to and
within the branches of trees and shrubs. Cladocolea
loniceroides seed, a Mexican endemic mistletoe, can be
spread through the feces of birds moving from tree to tree
throughout the country. It significantly infests them and
can be a serious pest in forest landscapes and cities’
gardens. Its impact is rather negative causing great tree
mortality. The most effective way to control it is to prune
out infected branches, but mistletoe is useless. Thus, the
aim of the study was to investigate both in vitro and in
vivo antioxidant activity of C. loniceroides extract, as
obtained of leaves, stems or fruits (L, S, F), so as to
observe the in vitro cytotoxic activity against breast
cancer cells with the purpose of using this plant to obtain
an added-value product. Extracts from L, S or F were
obtained by using methanol, water or saponification
reaction. Then each extraction was assayed to assess total
polyphenolics by means of the Folin-Ciocalteu reagent
(fruit>leave>stem: 189.5 ± 4.9; 93.33± 0.94 and 74.53 ±
0.95 mg gallic acid (GA)/g, respectively). Antioxidant
activity (AOxA) was evaluated by DPPH•;
ABTS/laccase; metal ions chelating activity and reducing
power methods. L, S or F extracts showed up to 90.27 ±
0.13 % DPPH inhibition; similar results were observed
when AOxA was evaluated by ABTS/laccase system.
The reducing power of all extracts was higher than that
of reduced glutathione, which was used as control. On
the other hand they exhibited a lower Fe2+ chelating
activity than that of EDTA. Lipoperoxidation induced in
rats was inhibited when those animals were fed with a
fruit aqueous extract (FAE) and there was not significant
differences (p<0.05) when compared to the rat control
group. Later on, FAE showed a citotoxic activity on
ZR75 breast cancer cell line (LD50= 0.1 mg GA/mL).
Therefore C. loniceroides may be processed to obtain an
antioxidant standardized extract which might be useful in
treating breast cancer.
Diversity and host-specificity of invertebrates
inhabiting an Australian mistletoe and its host
eucalypts
Burns, AE1,2, Watson, DM2, Cunningham, SA3
1
Monash University, Clayton, Australia; 2Charles Sturt
University, Australia; 3CSIRO Ecosystem Sciences,
Canberra, Australia
Parasitic plants, such as mistletoes, are important
components of tree canopies, providing an alternative
habitat and resources for a range of animals. However,
the diversity and host-specificity of invertebrates on
mistletoes and their host-plants has received little
attention; thus over-looking the contribution of these
component communities to the biodiversity of tree
canopies. This study investigated the species composition
and host-specificity of invertebrates inhabiting hemiparasitic box mistletoe, Amyema miquelii (Lehm. ex
Miq.) Tiegh. in Eucalyptus trees. Insects, spiders and
mites (i.e. arthropods) were sampled from box mistletoe
and its host eucalypt trees in remnant woodlands in
temperate Australia. The same orders of arthropods were
found on box mistletoe and the host eucalypts but the
density of arthropods was greater on the eucalypts than
the mistletoe plants. Two groups of arthropods in
different trophic groups were investigated in more detail.
The species composition of the herbivorous psyllid
(Hemiptera: Psylloidea) insect assemblages (21 species
total) differed significantly between the plant species, but
the spider (Araneae) assemblages, which consisted of 42
species in total, were similar in species composition
between the mistletoes and eucalypts. Elucidation of
tourist species revealed less than 1% similarity in
community composition between the psyllid assemblages
on the mistletoes and eucalypt trees. In comparison, the
spider assemblages displayed 40% similarity in
community composition between the mistletoes and
eucalypts. Therefore, the greatest contribution of
mistletoe plants to canopy arthropod diversity was at the
lower rather than higher trophic levels of arthropods.
Mistletoe plants in general are likely to support different
herbivorous insect assemblages compared to their hostplants due to differences in plant physiology. By
comparison, predatory arthropod assemblages are likely
to be similar in species composition between mistletoes
and their host-plants due to similarities in habitat
structure, but differ in abundance due to variation in prey
densities on the plants.
Sym002: Plants on rock outcrops: insights
into phylogeny, biogeography and ecology –
26 July
A fresh look on desiccation-tolerant vascular plants
from an anatomical perspective
Korte, N1, Porembski, S1
1
University
Germany
of
Rostock,
Mecklenburg–Vorpommern,
Rock outcrops such as inselbergs can be found in all
climate zones but are especially abundant in the tropics.
They form a center of diversity for desiccation-tolerant
plants which is a very rare trait among higher plants
(1.500 spp.), especially angiosperms (300 spp.). The
physiological mechanisms of desiccation tolerance have
been the subject of many research efforts but
comparative anatomical and morphological studies under
the aspect of poikilohydry are lacking. Therefore,
desiccation-tolerant Cyperaceae (Afrotrilepis pilosa,
Microdracoides
squamosus),
Velloziaceae
(Barbaceniopsis castillonii, Vellozia andina, Xerophyta
sp.,), Borya nitida (Boryaceae), Tripogon spicatus
(Poaceae) and the dicotyledonous Myrothamnus
flabellifolius and M. moschatus (Myrothamnaceae) were
chosen to compare leaf anatomical traits (turgescent and
dry). Main objectives included the determination of
important anatomical structures, which facilitate the
survival of complete desiccation, and the question
whether an ‘anatomical desiccation-tolerant plant
syndrome’ exists. It could not be confirmed that
desiccation tolerance, leaf anatomy and morphology are
necessarily related, but differences among and between
monocotyledonous and dicotyledonous species were
abundant: leaves of Cyperaceae and Velloziaceae folded
symmetrically due to the existence of bulliform cells
above the midrib, which collapse during desiccation and
facilitate the folding of the leaf. All monocotyledonous
leaves showed a high amount of vascular, sometimes
marginal, sclerenchyma and single sclerenchymatic
islands in the mesophyll as stabilizing elements. The
leaves of M. flabellifolius and M. moschatus had less to
no
xeromorphic
characteristics,
were
mainly
parenchymatic, and folded accordion-like. Summarizing,
it can be stated that (leaf) anatomical traits are a piece in
the puzzle of desiccation tolerance but cannot be
generalized across species or species groups; similar
traits can also be detected in other xeromorphic species.
The adaption of desiccation-tolerant plants to subsequent
de- and rehydration is not only to be found in their
anatomy and morphology but naturally on the
physiological level as well.
Hybridization and interespecific gene flow in
Pitcairnia (Bromeliaceae): the maintenance of species
cohesion among isolated populations adapted to rock
outcrops in southeastern Brazil
Palma-Silva, C1, Wendt, T2, Pinheiro, F1, Fay, M3,
Cozzolino, S4, Lexer, C5, Barbarà, T6
1
Instituto de Botânica, São Paulo, Brazil; 2Departamento
de Botânica, CCS/IB/UFRJ, Rio de Janeiro, Brazil;
3
Jodrell Laboratory, Royal Botanic Gardens Kew,
Richmond, Surrey, UK; 4Dipartimento di Biologia
Strutturale e Funzionale, Complesso Universitario di
Monte S. Ângelo, Università degli Studi di Napoli
Federico II, Napoli, Italy; 5Unit of Ecology and
Evolution, Dept of Biology, University of Fribourg,
Switzerland; 6University of Fribourg, Switzerland
The reasons for high rates of speciation promoting
species richness and endemism of rock outcrops are not
entirely understood. The isolation among rock outcrops
together with their long persistence have contributed to
high levels of differentiation of endemic species, that
were crucial in speciation processes in these habitats.
High population differentiation among rock outcrops
indicates that they could be comparable to oceanic
islands on studies of evolutionary processes.
Bromeliaceae has several genera adapted to Neotropical
rock outcrops. Recently bromeliads attracted research
interest in population connectivity and its consequences
for speciation and species cohesion in isolated
environments. Rock outcrops insular features allow us to
use them as models systems for testing the role of low
intra-specific gene flow and high and continuous interspecific gene flow during plant speciation. Here we
studied several populations four sympatric Pitcairnia
species adapted to rock outcrops using plastidial and
nuclear microsatellite loci. Our aim was to understand
the relative role of the gene flow (intra- vs. inter-specific)
and the reproductive barriers (prezygotic vs. postzygotic)
during speciation processes in rock outcrop bromeliads
species. Extensive haplotype sharing and nuclear
admixture analyses indicated inter-specific gene flow
19
among species (hybridization and introgression). Nuclear
migration rates and highly geographically structured
haplotype sharing support that intra-specific gene flow is
low among populations (< 1 Nem per generation), likely
due to restricted seed dispersal and long term interspecific gene flow during bromeliad adaptive radiation
on rock outcrops. Patterns of nuclear genomic diversity
and admixture indicate that both pre and postzygotic
barriers, although incomplete, can potentially contribute
to the reproductive isolation, limiting gene flow between
species. Traits that contribute to assortative mating such
as differences in flowering time, pollinator specificity,
and mating systems (selfing vs. outcrossing rates) are
important pre-zygotic barriers. Post-zygotic barriers,
such
as
nuclear-nuclear
and
cyto-nuclear
incompatibilities are also of great importance in shaping
reproductive isolation among species. Hybridisation and
introgression could contributes to bromeliad biodiversity
by enriching local gene pools on rock outcrops. Thus,
inter-specific gene flow should be important for these
plants, especially because intra-specific gene flow is low.
Consequently, rock outcrops with multiple sympatric
bromeliads deserve special attention in conservation
programs. Finantial support: FAPESP; CNPq; CAPES
Evolution of rock outcrop endemics in eastern Brazil:
a phylogenetic case study in the saxicolous bromeliad
genus Orthophytum Beer
Louzada, R1, Schulte, K2, Silvestro, D3, Wanderley, M4,
Zizka, G5
1
Dept of Botany, Biosciences Institute, University of São
Paulo & Núcleo de Pesquisa Curadoria do Herbário,
Instituto de Botânica, São Paulo, Brazil; 2Australian
Tropical Herbarium, James Cook Unversity, Cairns,
Australia; 3Dept of Botany and Molecular Evolution,
Senckenberg Research Institute & Biodiversity and
Climate Research Centre, Frankfurt, Germany; 4Núcleo
de Pesquisa Curadoria do Herbário, Instituto de
Botânica, São Paulo, Brazil; 5Dept of Botany and
Molecular Evolution, Research Institute Senckenberg &
Dept of Diversity and Evolution of Higher Plants,
Institute of Ecology, Evolution and Diversity, GoetheUniversity, Frankfurt/Main, Germany
Eastern Brazil harbors a great variety of rock outcrop
formations, most notably the inselbergs within the
Atlantic Rainforest domain and the campos rupestres of
the Espinhaço Range. These rock outcrops are
characterized by a highly specialized flora adapted to
high insolation, periods of severe drought, and different
substrates, and are rich in endemics and microendemics.
Molecular phylogenetic studies of Brazilian rock outcrop
plants elucidating the factors contributing to their species
diversity and to the evolution of endemism are still
scarce. Here we present an AFLP study of the saxicolous
bromeliad genus Orthophytum (60 spp.) that diversified
extensively along rock outcrops of eastern Brazil and
which comprises a high proportion of species endemic to
inselbergs and campos rupestres. More than 50% of the
species were described in the last two decades and
assigned to the two major morphological complexes and
six sub-complexes that are discerned within the genus
based on morphological characters, however no
molecular phylogenetic study has been conducted so far
to infer relationships. In the AFLP study 48 species and
20
101 samples were included, covering the entire
geographical range of the genus, and investigated with 12
AFLP primer pairs yielding 4679 characters. The
resulting binary matrix was analyzed using Neighbor
Joining, Maximum Parsimony, and Bayesian methods to
infer phylogeny. A NeighborNet analysis as implemented
in the program SplitsTrees was conducted to detect
possible conflicting signals within the data set as can be
caused by phenomena like hybridization and
introgression. A Bayesian clustering algorithm as
implemented in the software Structure was used to assess
the main genetic structure within Orthophytum and
possible admixture between main clusters. Detailed
distribution data was collected from herbarium specimen
at 26 herbaria (ALCB, ASE, B, BHCB, CEPEC, ESA,
HAL, HB, HEID, HUEFS, IPA, K, MAC, MBM,
MBML, NY, P, R, RB, SP, SPF, UEC, UFP, VIC, W,
WU) to assess ecological niche parameters of the taxa via
the WorldClim database. The data were used to model
the potential distribution of the taxa and to infer
phylogenetic shifts in ecological niches. The
phylogenetic reconstructions obtained are well resolved
showing six monophyletic groups within Orthophytum
sensu stricto: the foliosum, mello-barretoi, magalhaesii,
glabrum, estevesii and saxicola clades. The two
traditionally recognized major sub-complexes, the
pedunculate and the sessile inflorescence group, are
clearly paraphyletic. Based on the phylogenetic evidence,
different
hypotheses
regarding
the
historical
biogeography of Orthophytum (migration routes, past
refugia) are tested and the importance of past range
expansions and contractions during Cenozoic climatic
oscillations for the diversification of the genus along the
rock outcrops of eastern Brazil are discussed.
Endemism and speciation on rocky outcrops of
Western Ghats, India
Janarthanam, Malapati1
1
Goa University, Goa, India
The Western Ghats of India along with Sri Lanka is one
of the 34 biodiversity hotspots of the World. The
Northern Western Ghats and narrow plains between West
Coast and Central & Northern Western Ghats are
characterized by the occurrence of lateritic outcrops that
form plateaus and table lands. They provide unique
habitat to monsoon flora between the months of June and
October. Several hundred herbaceous species show
temporal succession and complete their life cycle during
this period. A good proportion of these species are
endemic to W. Ghats – some very narrow in their
distribution and some others known only from their type
localities. Most of these endemics are habitat specific, i.e.
they are seen only on lateritic outcrops. The major and
prominent groups with high proportion of endemics are
Andropogoneae (Poaceae), Ceropegia (Apocynaceae),
Utricularia (Lentibulariaceae), Smithia (Fabaceae),
Impatiens
(Balsaminaceae)
and
Eriocaulon
(Eriocaulaceae). Among grasses, endemic species-rich C4
genera such as Ischaemum and Glyphochloa are
extensively distributed. Interestingly all these endemic
species rich taxa belong to the terminal higher level taxa
of respective clades. Close relatives of these endemic
taxa extend their distribution to Africa and Australia.
Most of their relatives also show high degree of
endemism in these distant lands. Recent sporadic floristic
studies on lateritic outcrops brought forth several new
species to the fore during the past two decades. Most of
these endemic taxa show sympatric distribution.
Occasionally some populations show intermediate or
overlapping characters. These facts suggest that endemic
taxa are fast evolving and speciation is taking place at a
rapid rate. The driving force behind the speciation on
these rocky outcrops seem to be hybridization and
polyploidy. Heterogeneity in the habitat at finer level
appears to be another factor. This heterogeneity is seen in
the form of patchy distribution of some species even in
small areas though others are dominant throughout the
area. The heterogeneity is also evidenced from the
physical parameters such as the exposed hard lateritic
rocks, amount of lateritic gravel, thickness of soil (if any)
covering the rocks, size and depth of puddles (rock
pools) on lateritic rocks and ultimately precipitation
pattern. These factors ultimately decide the moisture
regime and water availability, especially during interprecipitation events. These combined factors appear to be
responsible for high endemism and speciation. However,
these rocky outcrops have not attracted sufficient
attention from the botanists thus leaving lot of gaps in
understanding of the flora and the processes that drive
the speciation and endemism. On the other hand, these
habitats with rich endemic species and fast evolving flora
are under threat due to habitat degradation warranting
urgent attention of botanists and conservationists.
Sym009: The reintroduction of rare and
endangered plants – 26 July
The challenges of determining success
reintroductions of threatened long-lived plants
1
1
for
1
Monks, L , Dillon, R , Coates, D
1
Dept of Environment and Conservation, Bentley,
Australia
Reintroduction to new, current or extinct locations is
increasingly becoming an important action to recover
some of our most threatened plant species. The challenge
is to devise appropriate criteria which allow us to assess
the success of the reintroduction program. Many
reintroduction programs monitor establishment, growth,
reproduction and recruitment over multiple generations
before attempting to determine whether the population is
viable and self sustaining. Only when a reintroduced
population is shown to be viable and self-sustaining
should it be taken into consideration when determining
the conservation ranking of the taxon. However for
reintroductions programs of long lived woody shrubs
determining success is particularly challenging given the
timeframes over which these taxa reproduce and recruit
new generations. Since 1993 the Department of
Environment and Conservation, the government agency
responsible for managing all flora in Western Australia,
has commenced reintroduction programs for 52 longlived woody plant taxa. Just five of these reintroduced
taxa have recruited a second generation. In determining
success long-term monitoring of survival, growth and
reproduction is being undertaken on reintroduced
populations and compared to natural populations.
However, clearly there needs to be some surrogate
method by which long term success can be predicted in
the timeframes in which a management agency is
required to operate. Population viability analysis models
and mating system analysis are likely to be useful tools
in predicting long term population trends.
Community
ecology
and
reintroduction
of
Tigridiopalma magnifica, a rare and endangered herb
Ren, H1, Zeng, S1
1
South China Botanical Garden, Chinese Academy of
Sciences, Guanghzhou, China
Tigridiopalma magnifica, a perennial herb and the only
species in the genus Tigridiopalma (family
Melastomataceae), is rare and endemic to China. Twelve
sites with populations of T. magnifica have been
identified (1 extinct, 11 extant). T. magnifica only grows
on the surface soil of stone walls or rocks under the
canopy of secondary forests and plantations and has no
specific associated plant. Canopy closure, soil water
content, and the distance to the closest stream are major
factors affecting T. magnifica distribution. We
reintroduced T. magnifica tissue-culture plantlets into
three field sites; one site was near an original distribution
area, one was 11.5 km away, and one was 400 km away.
After 11 months, the survival rate ranged from 40 to
58%, but survival was higher and plantlet crowns were
larger at the site near the original distribution area than at
the other two sites. The combination of advanced
propagation techniques and ecological restoration could
enable successful reintroduction and conservation of T.
magnifica and other rare and endangered plants.
Conservation strategies for rare and endangered
medicinal and aromatic plants
Jamzad, Z1, Charkhchian, MM2, Hatami, A3,
Pourmirzaii, A4, Hasani-Nejad, M1, Araghi, MK1,
Mohebi, J1, Maroofi, H5, Safikhani, K6, Ahmadi, S7
1
Research Institute of Forests & Rangelands, Tehran,
Iran; 2Research Centre of Agriculture and Natural
Resourses, Ghazvin, Iran; 3Research Centre of
Agriculture and Natural Resourses, Shiraz, Iran;
4
Research Centre of Agriculture and Natural Resourses
Krman Iran; 5Research Centre of Agriculture and
Natural Resourses, Kordestan, Iran; 6Research Centre of
Agriculture and Natural Resourses, Hamadan, Iran;
7
Research Centre of Agriculture and Natural Resourses,
Lorestan, Iran
The increasing uses of medicinal and aromatic plants
which in most cases are harvested directly from the
nature has caused sever damages to this important plant
groups in Iran. The country supports around 8000 species
of spermatophytes belonging to 150 families and is one
of the major centers of endemism in Irano-Turanian
phytogeographical region. Twenty two percent of these
species are categorized as endemics. There are narrow
endemics among some of the currently used medicinal
and aromatic plants. In this project we screened 20
perennial species of medicinal and aromatic plants with
an emphasis on endemic species. Their natural habitats,
reproduction and soil seed banks were studied. The
21
project was designed with the following objectives: (1)
Propagation and cultivation of them in National
Botanical Garden of Iran; (2) keeping them as a
germplasm and conserving them in a controlled
environment; (3) reintroducing them to their natural
habitats and recreating their natural populations. These
studies revealed that the seeds of some of them are scant
in soil seed banks of their habitats and living stands are
few with little or no regeneration. Factors that have
caused this situation include harvesting the plants before
seed setting, lack of seed production as a result of
physiological disorders, pest infestation, and habitat
disturbance or draught. Among the aforementioned
factors, inaccurate harvesting and draught were the most
important ones in our study group. We thus collected the
seeds of selected species from their natural habitats,
germinated them in the greenhouse under controlled
conditions providing them with sufficient moisture
through mist propagation units. The seedlings were then
transferred outdoors in the garden and their phenological
behaviors were recorded. The seeds of cultivated
specimens were then collected and saved for replanting
in the garden and in their original habitats. The seedlings
of new grown specimens will be transferred to their
original habitats to give them a chance to produce new
populations.
The
cultivation
experience
of
Dracocephalum kotschyi, Gontscharovia popovi; Nepeta
pogonosperma; N. rvularis; N. assurgens; Origanum
vulgare; Thymus daenensis; T. kotschyanus; T. persicus;
T.
pubescens;
Salvia
oligophylla;
Ziziphora
clinopodioides showed their remarkable adaptability to
new ecological conditions different from their own.
Park). Currently, no young seeding exists around and
within those populations. Typically, they grow in dry
forest on lava fields. Because of its rarity and small
population sizes, it may go extinct or become more
severely depressed quickly in few decades if no proper
preservation actions are taken. In the past ten years, the
US government tried to recover this species by artificial
planting in the conservation areas in Hawai’i. My
research goal is to perform a molecular genetic analysis
of the DNA polymorphism in populations of Pleomele
hawaiiensis aiming to determine the level of their genetic
structure within this species. RAPDs and ISSR results
indicate the remaining wild population has lower genetic
diversity than the artificial planted population, and shows
this species faces severe genetic bottleneck. This species
may have no longer long distance seed dispersal and lack
efficient pollinators. The data supports other researches
that genetic deterioration may result from decreasing
population size and populations tend to have lower
genetic variation, especially in rare plant species. This
study points out the reintroduced plants can have better
genetic diversity for form a more healthy population in
the endangered plant species if the seeds resource are
collected from different populations. That will help the
endangered species recovery in reality. A better
understanding of population genetic structure will benefit
the conservation work and explain the species’
evolutionary history. Selecting seeds from the most
different genetically diverse individuals from the genetic
data of population structure is important to preventing the
endangered plant species toward towards extinction from
the wild.
The study of population genetics in the endangered
species Pleomele hawaiiensis in Hawaii
Experimental establishment in situ of Dactylanthus
taylorii
(Balanophoraceae),
an
endangered
holoparasitic flowering plant in New Zealand
Lu, P-L1
1
Botany Dept, University of Hawaii at Manoa, USA
The Hawaiian Archipelago includes various endemic
species that are the result of speciation subsequent to
isolation from source populations. Pleomele hawaiiensis
Degener & Degener is an USA federally listed
endangered species by the US Fish and Wildlife Service
(USFWS) since 1996 and listed in the International
Union for the Conservation of Nature and Natural
Resources (IUCN)’¦s Red List of threatened species since
1997. The main reasons for its rarity might be due to
habitat loss by development encroachments and the
introduction and spread of invasive animals. There is no
previous research about its ecological, genetic, and
physiological biology. Based on the flower and seed
structure and morphology, bees are potential pollinators
and birds are the possible seed dispersal candidate.
According to Wagner’s classification, there are six
endemic Pleomele species in Hawaii Islands. The other
species (P. aurea (H.Mann) N.E.Brown, P. auwahiensis
St John, P. fernaldii St John, P. forbesii Degener, and P.
halapepe St John) are distributed throughout the other
high islands of the Hawaiian archipelago. Only the single
species P. hawaiiensis is recognized as occurring on the
Big Island. P. hawaiiensis is endemic to Hawai’i in the
state of Hawaii in six to eight subpopulations totaling
approximately 300 individuals in Puuwaawaa, the
Kaloko/Kaloao area, the Kapua/Kahuku area, and on
Holei Pali (located in the Hawai¡¦i Volcanoes National
22
Holzapfel, S1, Dodgson, J2
1
2
Dept of Conservation,
Kawhia, New Zealand
Hamilton,
New
Zealand;
Holoparasitic flowering plants provide considerable
challenges for conservation management due to their
absolute dependency on a host plant, and because many
aspects such as germination, host attachment and growth
are often not well understood. We present results from
the first successful, quantified field trial to establish from
seed populations of dactylanthus (Dactylanthus taylorii),
the southern-most member of a family of rootholoparasitic
angiosperms
(Balanophoraceae).
Dactylanthus is an acutely threatened species endemic to
New Zealand, growing underground as a perennial tuber
attached to the root of native host trees and shrubs.
Nectar-rich inflorescences break through the forest floor,
where they are pollinated by a ground-foraging endemic
bat. The resulting copious small seeds form long-lived,
dense local seed banks and germinate independent of
host presence. Browsing of inflorescences by introduced
mammals is limiting the species’ recruitment and has led
to its disappearance over 96% of its pre-human
distribution range. Being able to establish new
populations by sowing would provide an important tool
for the recovery of the species. A known quantity of
Dactylanthus seed was sown into twenty-four field plots
at four sites differing in host species dominance, host age
and canopy closure. Two sowing methods were used at
each site, replicating individually dispersed seeds and an
entire buried infructescence, respectively. Over ten years
plots were monitored annually at the peak of flowering
time. Successful establishment was first confirmed in
two plots four years after sowing; six years later
Dactylanthus was present in twenty-two plots. Plants
generally appeared healthy and were still growing in
number and size at the conclusion of the trial. Average
and maximum inflorescence numbers per plot were high
compared to protected wild populations, though
successively smaller increases each year indicated that
the population was approaching its maximum flowering
capacity. The two sowing methods resulted in similar
number of successful plots overall, while broad sowing
resulted in a greater number of inflorescences and, by
proxy, individual plants per plot. Establishment and
inflorescence numbers were similar at sites with different
host species and host ages, but were lower for the open
canopy site. Female inflorescences strongly outnumbered
males at all four sites and in every flowering year, though
the proportion of male inflorescences increased each
season. This is in stark contrast to wild populations,
which are usually characterised by an over-abundance of
plants producing male inflorescences. These results, and
the rare occurrence of hermaphroditic inflorescences in a
species usually regarded as dioecious, are explored as
possible evidence of previously undetected monoecy,
subdioecy, or sex-switching of individuals. While the
success of this study has direct applications for the
conservation management of Dactylanthus, results also
provide important new insights into the biology and
ecology of the species and holoparasitic flowering plants
in general.
Conservation and reintroduction of four threatened
trees in southwest China
Sun, W1
1
Kunming Botanical Garden, Kunming Institute of
Botany, Chinese Academy of Sciences, China
Magnolia sinica (Manglietiastrum sinicum), M.
phanerophlebia
and
Michelia
coriacea
from
Magnoliaceae are critically endangered endemics to
southwest China’s Yunnan Province. Among the three
extant species from genus Trigonobalanus (Fagaceae), T.
doichangensis is a globally endangered plant native to
North Thailand and South Yunnan of China (firstly
recorded in 1981). M. sinica, M. phanerophlebia,
Michelia coriacea and T. doichangensis are scientifically
important and ornamentally valuable, and they are facing
an extremely high risk of extinction in the wild.
Kunming Botanical Garden (KMBG) under Kunming
Institute of Botany, CAS, has carried out comprehensive
studies on the population/community ecology,
reproductive biology/ecology, and cytological and
genetic variations of the four threatened tree species
since 2001. Based on good understanding of the threats,
scientifically sampled seed collections and propagation
from seeds, a great number of seedlings/saplings of M.
sinica, M. phanerophlebia, Michelia coriacea and T.
doichangensis have been well conserved ex situ at
KMBG. Meanwhile, actions of reintroduction /
reinforcement for the four trees to the semi-natural areas
which they formerly occurred or to the individually
scattered current habitats have been undertaken since
2007, in cooperated with Botanic Gardens Conservation
International (BGCI), Fauna & Flora International (FFI),
the Forestry Department of Yunnan Province (FDY) and
the local forestry bureaus or nature reserves. The
presentation is trying to summarize all the scientific
achievements and conservation activities on M. sinica,
M. phanerophlebia, Michelia coriacea and T.
doichangensis, and is aiming to document these valuable
cases for globally threatened trees conservation.
Sym010: Trace gas and volatile analysis in
the study of plant interactions with the
abiotic and biotic environment – 26 July
Laser-based trace gas detection with applications in
biology and agriculture
Harren, FJM1
1
Radboud University, Nijmegen, The Netherlands
There is a strong growing interest to develop laser
systems (quantum cascade lasers, optical parametric
oscillators) in the mid-infrared wavelength region for
trace gas detection with applications in environmental
sciences, biology, agriculture and medical sciences.
Nowadays, such lasers provide output at relatively high
power and narrow linewidth and emit at any desired
wavelength within the infrared wavelength range 2.5 to
12 micrometer. Accurate detection of specific gases
becomes into reach thanks to the infrared fingerprint
absorption spectrum of molecular gases in this
wavelength region and the exact tuning capabilities of
lasers. When the lasers are combined with sensitive
spectroscopic techniques, such as photoacoustic
spectroscopy or optical cavity enhanced spectroscopy,
gases can be determined extremely sensitive under
atmospheric conditions. Examples will be given on the
detection of the important plant hormone ethylene,
detection of fermentation products of fruit (acetaldehyde
and ethanol) and the detection of NO under pathogen
attack. In addition, we will discuss whether plants do
produce methane, using C-13 enriched plants and
detecting carbon-13 methane via infrared spectroscopy.
In contrast to our expectations we could detect no
significant methane emissions.
Comprehensive GCxGC-TOFMS analysis of plant
volatiles: a newcomer in the plant signaling toolbox?
Gaquerel, E1
1
Max Planck Institute for Chemical Ecology, Jena,
Germany
Metabolomic tools provide novel opportunities for
system-wide analysis of complex functions involving
single chemical compounds or structure groups. Volatile
compounds emitted by plants mediate important ecophysiological functions such as attraction of pollinators
to flowers or the recruitment of natural enemies of
herbivores. Plant volatiles are products of a complex
network of biochemical pathways, which, although well
mapped from a biochemical point of view, remains only
partly understood with regard to its physiological and
23
genetic regulation. Our group uses comprehensive twodimensional gas chromatography coupled to time of
flight mass spectrometry (GCxGC-TOFMS) to track
herbivory-induced reconfigurations of the volatile
metabolome of Nicotiana attenuata, a wild tobacco
species. Changes in volatile components must be
extracted from the thousands of molecular fragments that
constitute a typical GCxGC map. To that end, data-sets
are first filtered and aligned by similarity matching with
a synthetic sample reference and compared using
univariate and multivariate techniques. The use of this
exploratory technique to elucidate the interactive control
exerted by herbivore salivary components and plant
signaling transduction pathways on volatile emissions
will be discussed.
Ethylene and cell death signaling in plant and algal
cells
Woltering, EJ1, Iakimova, ET
1
2
Wageningen University, Wageningen, The Netherlands;
Institute of Ornamental Plants, Sofia, Bulgaria
Programmed cell death (PCD) is a process where cells or
tissues are broken down in an orderly and predictable
manner, whereby nutrients may be re-used by other cells,
tissues or plant parts. Currently two main types of PCD
are recognised in plants: autophagic and non-lysosomal
PCD; the latter is often referred to as apoptotic-like PCD.
True apoptosis, which is accompanied by digestion of
(parts of) the dying cells in the lysosome of other cells,
has not (yet) been observed in plants. Dying cells of
either type of PCD show characteristic features such as
shrinkage of the cytoplasm and compaction and/or
fragmentation of the nucleus. In plants PCD is involved
in many developmental and formative processes
including xylogenesis, reproductive events, formation of
leaf perforations and in the senescence of flowers and
leaves. PCD is involved in the response to adverse
environmental conditions such as chilling and heat stress,
exposure to toxic chemicals or UV radiation and as a
result of oxygen depletion. In addition, PCD is involved
in the (resistance) reaction to pathogens such as bacteria
and fungi. In many systems ethylene plays a role in PCD,
although it may not be the primary inducer of cell death.
The involvement of ethylene in cell death in plant and
algal cells will be discussed.
Nitric oxide and ethylene interactions in plant disease
development and resistance
Mur, LAJ1, Sivakuruman, A1, Hall, MA1, Cristescu, S2,
Harren, F2
1
Abersytwyth University, Wales, UK;
Univerisity, Nijmegen, The Netherlands
2
Radboud
The gaseous hormones nitric oxide and ethylene have
been shown to play important roles in responses to plant
disease development and in disease tolerance. To gain
further insights into the roles of these hormones trace gas
detection methods were employed based on
Photoacoustic and Quantum Cascade lasers (PA and
QCL, respectively) were used for on on-line, in planta
measurements. To strengthen the power of these
analyses, they included transgenic and mutated plant
24
lines which were altered in either the perception of
generation of NO or C2H4. Initially focusing on tobacco
(Nicotiana tabacum) and Arabidopsis NO and ethylene
production during attack by Pseudomonas syringae were
assessed. Gaseous hormone production during
interactions leading to disease and resistance linked to
the formation of a localised cell death known as the
Hypersensitive Response (HR) were compared. Through
the use of lines with modulated nitrate reductase (NIA)
activity, this was confirmed that nitrate reductase to be
the major source of NO during responses to pathogens.
By far the highest rates of NO production were to be
observed during HR and this was shown to be essential
for full plant resistance to disease. Equally, detoxification
of NO by plant-encoded flavohaemoglobins influenced
the speed and extent of HR formation. Examination of
C2H4 production during the HR indicated that the
biphasic generation pattern was greatly influenced by
NO. Perturbation of the ethylene biphasic wave
compromised HR-mediated resistance against pathogens.
The role of NO and C2H4 was examined in tobacco
(Solanum esculentum) following challenge by the
economically important pathogen Botrytis cinerea. This
is a necrotrophic pathogen, causing plant cell death as
part of its pathogenic process. With this interaction
considerable rates of NO and ethylene production were
observed, greater than were previously observed with the
Pseudomonas syringae elicited HR. This undoubtedly
reflects the infection strategy of Botrytis and
demonstrated that NO/ C2H4 production in this case is
disease associated and thus, are not invariably associated
with resistance. Examination of NO- or C2H4 insensitive
tomato mutants showed that disease development was
reduced, confirming their roles in disease development.
The regulation of and effects of these NO /C2H4
interactions are currently being investigated but these
studies demonstrate how novel insights can be gained
when genetic approaches are integrated with careful – in
this case, gaseous, hormone measurements.
Airborne signaling between undamaged plants –
effects on plants and insects
Glinwood, R1, Ninkovic, V1, Pettersson, J1
1
Swedish Univ. Agricultural Sciences, Uppsala, Sweden
Plants damaged by herbivores or pathogens release
volatiles active in defense signaling between or within
plants, but undamaged plants may also engage in
chemical interactions. We present results that contribute
new perspectives on allelopathy and use of volatile cues
by plants and insects. In a system consisting of different
plant species and different barley genotypes we show that
airborne signaling affects plant biomass allocation (1),
reduces attractiveness to an insect herbivore (2, 3) and
affects interactions with the herbivore’s predators (4). In
barley, the inducing and responding capacity is shown to
be genotype-related. Volatile profiling shows differences
in the volatile blends released by different barley
genotypes. Increased understanding of chemical
interaction between undamaged plants may give a new
outlook on the ecology of mixed genotype cropping and
weed-crop interactions and their role in sustainable crop
production (5). (1) Ninkovic 2003. (2) Glinwood et al.
2007. (3) Glinwood et al. 2004. (4) Glinwood et al. 2009.
(5) Ninkovicet al. 2009.
Tracing hidden herbivores by analyzing plant volatile
emissions
Van Dam, NM1, Crespo, E2, Laska, A2, Hordijk, CA3,
Harren, FJM2, Cristescu, SM2
1
Radboud University/IWWR, Nijmegen, The Netherlands;
2
Radboud University/Trace Gas Lab, Nijmegen, The
Netherlands; 3Netherlands Institute for Ecology,
Wageningen, The Netherlands
Plants are attacked by many different herbivores, both
above and below the ground. It is relatively easy to see
whether, when and how much plants have been damaged
by above ground herbivores. Even when the herbivores
have left the plant, the remaining damage can be used to
identify the insect species that has been feeding. This is
more difficult to assess in the case of belowground
feeding root herbivores. Here we illustrate how trace gas
analyses can be used to trace infestations by the cabbage
root fly (Delia radicum). The larvae of this fly species
are a serious pest damaging roots of many different
crucifer species. Their feeding activities reduce the yield
and market value of rape seed, broccoli, Brussels sprouts
and other cruciferous crops. Previous studies have shown
that the headspace of root fly infested Brassica nigra
plants contains specific volatiles. One of these
compounds, dimethyldisulfide (DMDS), attracts natural
enemies of D. radicum in the field and repels
aboveground biocontrol organisms. On-line ProtonTransfer Mass-Spectrometry (PTR–MS) analysis showed
that DMDS emissions, and those of the structurally
related methanethiol and dimethylsulfide (DMS) from
the roots indeed increased significantly 12–16 hours after
root fly infestation. Additionally, infested plants showed
markedly increased emission rates of m/z 60. The
increased emission of m/z 60 was much faster than the
induction of sulfides, starting within 4 h after infestation.
Interestingly, m/z 60 emissions ceased when larvae
pupated, thus making it a marker for actively feeding
larvae. Artificial wounding of the roots briefly increased
the emission rates of m/z 60 as well, whereas root fly
larvae alone did not produce an m/z 60 signal. This
suggests that m/z 60 is produced by the plant and likely
is a product of glucosinolate conversion by myrosinase
and other enzymes involved in this process. Analyses of
pure (iso)thiocyanates revealed that ethyl and allyl
(iso)thiocyanates both yield m/z 60 as a main fragment in
the PTR-MS. Eventually we identified m/z 60 as
thiocyanic acid using a pure reference in the PTR-MS.
Our results show that trace gas analyses of root emitted
volatiles can be used to assess which plants are infested
with actively feeding root fly larvae. Trace gas analyses
thus may be applied in quarantine procedures aiming to
assess whether imported plants or produce is infested
with cryptically feeding pests. Additionally, these results
are valuable for plant breeders aiming to select crops
with enhanced attractiveness to natural enemies of D.
radicum.
Sym011: The Global Strategy For Plant
Conservation: an opportunity and challenge
for the international community – 28 July
Progress in implementing the Global Strategy for
Plant Conservation
Wyse Jackson, P1
1
Missouri Botanical Garden, St Louis, USA
In 2002 the international community adopted the Global
Strategy for Plant Conservation through the United
National Convention on Biological Diversity (CBD). The
Strategy and its different elements quickly became well
known worldwide and highly influential in helping to
shape the programmes and policies of many plantorientated institutions and organisations. Its objectives
and the 16 outcome-oriented targets it incorporated, to be
achieved by 2010, became major drivers for many
national and international plant conservation initiatives
too. However, after eight years of its operation, when the
GSPC has being renewed by the CBD, with a set of 16
updated targets, it is time to review progress in its
implementation to help evaluate what new steps are need
in order to achieve its objectives for the second period of
the GSPC up to 2020. This paper will provide an
overview and evaluation on whether the Strategy is
achieving what it set out to do. It will also consider the
following questions. Are countries fully engaged in its
implementation? What new measures will be needed to
ensure that the targets are met by 2020? Issues that are
hindering progress in its implementation will also be
reviewed, including lack of data, tools and technologies;
limited funding; poor sectoral coordination and limited
institutional capacity and capabilities, as well as lack of
appropriate policies and legal frameworks at the national
level. The ways in which individual botanical institutions
can seek to address these shortcomings will be discussed.
The existing and future roles of the Global Partnership
for Plant Conservation (GPPC) in supporting the GSPC
will be highlighted.
A working list of known plant species – progress and
lessons learned for the GSPC
Paton, A1, Nic Lughadha, E1
1
Royal Botanic Gardens, Kew, UK
Target 1 of the GSPC was, ‘A widely accessible working
list of known plant species, as a step towards a complete
world flora’, prior to revision at COP10 in Nagoya in
October 2010. Good progress has been made towards
that Target with The Plant List launched at the end of
2010, pulling together available resources to produce a
‘working list’ of known species. One of the major
reasons for this success was that organisations such as
Kew and Missouri existed with business aims which
closely matched the Target. GSPC Targets where
facilitating organisations with business aims relevant to
the Target were not identified, were generally less
successful. Perhaps the greatest criticism of work done at
the global level on Target 1 was the relatively weak
integration between national and global level processes.
Strengthening these links will be increasingly important
25
post 2010 as we seek to improve the quality of the
working list and build towards the post 2010 Target of
‘An online Flora of all known plants’. One of the barriers
frequently identified is the lack of national level
taxonomic capacity. However, capacity building needs to
be focused on key capabilities and linked to potential
outputs. What lessons can be learned from progress on
GSPC Targets to date which can help us achieve the post
2010 Targets? A key element will be to ensure that ‘the
World Flora’ and supporting activities relate to national
policies and make the most of existing expertise.
Furthering the GSPC goals by building capacity for
plant conservation in Latin America
Montiel, OM1
1
Missouri Botanical Garden, St Louis, USA
The Global Strategy for Plant Conservation, approved by
the Conference of the Parties to the Convention on
Biological Diversity in 2002, called for building capacity
for the conservation of plant diversity. The Strategy
stressed the need for development of cadres of trained
biologists and conservation practitioners with access to
adequate resources and facilities who would be equipped
to address the challenges of understanding and
conserving plants. The Missouri Botanical Garden has
incorporated the Strategy into its programs by engaging
in capacity building through tiered training designed for
people at different levels of educational background,
including professional botanists and conservationists,
university students, and representatives of rural
communities. Together, these various programs aim to
provide all levels of formal and informal training. The
Global Strategy’s recently revised and approved targets
for 2020 call once more for capacity building and public
engagement in accordance with national needs. The
Missouri Botanical Garden will continue to work with
partners towards the fulfillment of these new goals. A
particular challenge for implementation of the Strategy in
Latin America will be its incorporation into national
plans and initiatives and the development of national
targets to guide these efforts. We are committed to
encouraging and supporting these plans and initiatives
and to continuing to implement training programs that
respond to national needs.
Assessing conservation status of crop genetic
diversity: Oxalis tuberosa as a test case for new
methodologies for clonally propagated crops
Emshwiller, E1, Epperson, BK2, Theim, T1, Tay, D3,
Medina, T4, Girón, RC5, Nina, V6, Ángeles, JE7,
Catacora, P8, Tineo, J9, Cruz, W3, Vivanco, K3, Pérez, I10
1
University of Wisconsin – Madison, Madison, USA;
Michigan State University, East Lansing, USA;
3
International Potato Center, La Molina, USA; 4Instituto
Nacional de Innovación Agraria, Sede Central, La
Molina, USA; 5Instituto Nacional de Innovación Agraria,
EE Santa Ana; 6Instituto Nacional de Innovación
Agraria, EE Andenes, Peru; 7Instituto Nacional de
Innovación Agraria, EE Baños del Inca, Peru; 8Instituto
Nacional de Innovación Agraria, EE Illpa, Peru;
9
Instituto Nacional de Innovación Agraria, EE Canaan,
2
26
Peru; 10 Universidad Nacional de San Antonio Abad del
Cusco, Peru
One target of the Global Strategy for Plant Conservation
involves conserving genetic diversity of crops. In
addition, the UN-FAO's 2nd State of the World's Plant
Genetic Resources for Food and Agriculture
(SoWPGRFA) report recommends that more attention be
given to 'minor crops,' recognizing that even those crops
that are not among the most important ones worldwide
are nonetheless crucial components of the food systems
of particular world regions. The ex-situ conservation of
vegetatively-propagated crops faces particular challenges
compared to seed-propagated crops that can be
maintained as frozen seed. Thus, complementary in-situ
conservation strategies are even more needed to maintain
local diversity as a vital resource for food security in
rural communities. One goal of the SoWPGRFA report is
to 'develop better indicators and methodologies to assess
conservation status and threats.' Because conservation of
crop diversity requires information about how that
diversity is distributed geographically, the use of GIS
techniques for the study of crop diversity is increasing.
However, this does not usually include the use of
methods from geographical genetics and spatial statistics.
We conducted spatial statistical analyses of the Andean
tuber crop 'oca' Oxalis tuberosa, as a model to study the
evolution of clonally-propagated crops under human
influence. Because clonal crops differ from seedpropagated crops in their conservation needs, we used
oca as an example to study how human-mediated
dispersal affects the genetic structure of clonal crop
populations, i.e., how the exchange of planting material
among farmers determines the distribution of oca's clonal
genotypes in traditional Andean agriculture. Cultivated
oca was sampled randomly in carefully distributed
localities throughout the Peruvian Andes, and samples
were subsequently cultivated in a highland experiment
station of INIA (Instituto Nacional de Innovación
Agraria) for morphological and molecular analyses.
Spatial statistical analyses of AFLP data of 954 oca
individuals from 38 localities were done for both
individual AFLP alleles and clonal genotypes, the latter
determined by both AFLP and morphological data. One
finding with important conservation implications is that
many oca clonal genotypes have very restricted
geographic distributions; some were found in only four
or fewer communities. Most of these were restricted to a
particular area in Peru, whereas a few others were found
in scattered, discontinuous areas. Our initial spatial
autocorrelation analyses (Moran's I and join-count)
yielded many very strong but unusual patterns across
both spatial scales and genotypes. This indicates that
there are other factors besides geographic distance which
have shaped the distribution of genotypes, and we
continue to investigate what these factors may be. In
addition to the cultigen, wild Oxalis species were also
collected, including a wild, tuber-bearing taxon found in
highland provinces of Lima Department. The latter taxon
was included in continuing research to determine the
progenitors of cultivated oca, but the results using AFLP
data did not support these populations as likely
progenitors of oca.
Mediterranean flora conservation – the case of
Calabria (S Italy)
Uzunov, D1, Caruso, G1, Gangale, C2
1
Dept of Environmental and Crop Science, Marche
Polytechnic University, Ancona, Italy; 2Natural History
Museum of Calabria, University of Calabria, Italy
Calabria region represents the southernmost part of
Italian Peninsula and is situated in the centre of the
Mediterranean basin. This area has a peculiar geological
history as a part of the Calabrian Arc, quite different
from the rest of the Apennines. Its flora counts more than
2500 species and subspecies, about 150 families and 850
genera. As a typical Mediterranean flora therophytes and
hemicryptophytes are dominant and geophytes (16%) are
relatively abundant. Species with Mediterranean
distribution are about 55% and about 10% are endemic.
In the regional Red List 317 species are included (1 EX,
3 EW, 14 CR, 24 EN, 106 VU, 108 LR and 61 DD).
Present work summarizes the experiences for data
collection and analysis of different type of rare and
endangered species occurring in Calabria with particular
attention to: Woodwardia radicans (L.) Sm. and Primula
palinuri Petagna as relict species inhabiting very narrow
ecological niches; Sarcopoterium spinosum (L.) Spach.
and Lomelosia crenata (Cirillo) Greuter & Burdet subsp.
pseudisetensis (Lacaita) Greuter & Burdet at the limit of
their distribution; Ptilostemon gnaphaloides (Cyr.) Sojak,
Retama raetam (Forssk.) Webb & Berthel. subsp.
gussonei (Webb) Greuter, Aizoanthemum hispanicum L.
and Gentianella crispata (Vis.) Holub as examples of
species with long disjunctions, Pinguicula crystallina
Sibth. & Sm. subsp. hirtiflora (Ten.) Strid. as a very rare
and localized endemic taxon and Limonium sp. div. as a
group with active speciation processes. The experience
for application of the IUCN criteria at global and
regional level for conservation status evaluation is
summarized and critically analyzed. The area is under
active transformation since ancient time and there is a
trend to urbanizing coastal zone and abandon of
mountain regions. The impact of this socio-economical
processes on the flora conservation and the cumulative
effect with other natural and anthropic factors are
difficult to evaluate. Some approaches and models are
discussed together with an analysis of the efficiency of
the system of protected areas and Natura 2000 sites for
plant species protection and as a response to the Global
Strategy for Plant Conservation recommendations. A
model for integration of a dynamic approach into the
classic ex situ and in situ conservation strategies is
proposed.
Botanical education of the next generation to face
national and global grand science challenges:
simulating climate change research in the secondary
classroom
Gerber, DT1, Thomsen, MA1, Thurston, S2
1
University of Wisconsin-La Crosse, La Crosse, WI,
USA; 2American Association for the Advancement of
Science, Washington DC, USA
In a recent report assessing the botanical capacity of the
United States, each of the ‘Recommendations to fill
critical gaps in botanical capacity’ involved an
educational component (1). In essence, an increase in a
botanically educated work force would be required
emphasizing the need for botanically-related student
preparation at the K–12 and collegiate levels. A recent
study (2) in Science suggested that research experience
for K–12 classroom teachers improved high school
student achievement in the classroom. To improve K–12
botanical education, we present a model for providing
botanical research opportunities to pre-service teachers,
i.e. college students in secondary (6th –12th grade)
teacher preparation programs, connected with the
creation of middle and high school level Science
NetLinks’ lesson plans. Based on the pre-service
teachers’ botanical research experience, the free, online,
vetted plans allow middle/high school classroom teachers
to simulate climate change research conducted by field
plant ecologists. References: (1) Kramer et al. 2010; (2)
Silverstein et al. (2009).
Sym012: Flooding stress: mechanisms of
adaptation and escape – 26 July
Adaptation to flooding and submergence – the
hormone story
Jackson, MB1
1
School of Biological Sciences, Bristol, UK
Flooding of the soil or deeper submergence to include
some or all the above-ground shoot threatens the survival
of all vascular plant species. At the heart of the threat is
severe interference with the ready gas exchange required
for life-sustaining rates of aerobic respiration and
photosynthesis. The longer plants are inundated the
greater the risk of their failing. Even species that grow
well and compete strongly in over-wet conditions cannot
survive them unchanged indefinitely, although endurance
varies with species, stage of development and
environmental conditions such as temperature and
turbidity of the flood water. Response-mode changes that
increase the probability of survival are varied but may
conveniently be split into metabolic adaptations that
improve the efficiency with which scarce CO2 and O2 are
used or into structural adaptations. The latter either
improve accessibility to CO2 and O2 or reduce the
severity of the consequences of damage to shoot systems
by root dysfunction. The structural adaptations to
flooding and submergence involve modifications to
developmental pathways that are under the influence of
the major hormones (auxins, cytokinins, gibberellins,
abscisic acid and ethylene). Hormone production,
accumulation and action are, therefore, an integral part of
numerous adaptive responses of plants to flooding or
submergence. Ethylene, in particular, is closely involved
because it is a gas and thus prone to fast and substantial
increases in concentration within plants as a result of
slow escape rates imposed by external water. This offers
a fast and direct signalling route that can give rise to
prompt adaptive changes within hours or minutes. The
paper reviews hormone involvement in developmental
adaptations to flooding. These include adventitious root
formation; lysigenous aerenchyma formation in roots and
leaves; hypertrophic stem swelling; root to shoot
27
signalling of stomatal closure or leaf senescence and
submergence-induced fast underwater elongation by
stems or leaves. Some of these hormone-mediated
phenomena have been studied in great depth and the
findings hold immediate significance for agricultural
productivity through molecular-based methods of
selection. Others are less thoroughly understood but are
increasingly amenable to modern methods of analysis
and exploitation.
Waterproof plants: escape or quiescence
1
1
Utrecht University, The Netherlands
The semi-aquatic dicot Rumex palustris responds to
complete submergence by upward movement of leaves
(hyponastic growth) and elongation of young petioles.
These two escape responses together can bring leaves
above the water surface, thus restoring gas exchange with
the atmosphere and increasing survival in flood-prone
environments. So far our work suggests that these two
responses are regulated via an ethylene-driven signaling
network in which apoplastic acidification, expansin
action and the activity of the hormones abscisic acid
(ABA) and gibberellin (GA) are important. R. acetosa
lacks this escape response when submerged and is
therefore less tolerant to flooding. The entire
transcriptome of these two species during submergence
was characterized using next generation sequencing
technologies. The results will be discussed with special
attention to the complement of genes regulated by
submergence and the differences between the two
species.
Mechanisms of submergence tolerance in lowland rice
Ismail, A1, Septiningsih, E1, Mackill, D1
1
International Rice Research Institute, Philippines
Hydrological conditions in flood-prone rice ecosystems
are harsh and unpredictable, leading to low and unstable
productivity, as most modern varieties are sensitive to
flooding. Major constraints include poor crop
establishment,
high
mortality
after
complete
submergence and low yield in partially or stagnant
flooded areas. Prospects for enhancing yields in these
lands are becoming evident with the recent progress in
genetics and physiology of tolerance. Tolerance of
anaerobic conditions during germination is important
because of increasing interest in direct seeding. Traits
associated with tolerance were studied and major QTLs
were identified and are being fine-mapped for gene
cloning and for use in breeding. Considerable progress
was made in understanding tolerance during vegetative
stage after cloning of the Submergence-1A (SUB1A)
gene. Submergence induces SUB1A expression by
ethylene, which interrupts the elongation escape strategy
by limiting ethylene-induced GA-promoted elongation.
This conditional induction allows SUB1 to substantially
enhance tolerance without changing the original traits of
the popular varieties into which it is introduced. Rice
accessions with reasonable tolerance of stagnant floods
were recently identified and are being studied. An update
28
Internal aeration development and the zonation of
plants in wetlands
Sorrell, B1, Tanner, C2, Sukias, J2
1
1
Voesenek, LACJ , van Veen, H , Vashist, D ,
Sasidharan, R1
1
on current progress will be presented. Traits associated
with tolerance of excess water stress offer considerable
opportunities for developing resilient rice varieties to
cope with current problems and with the progressively
worsening conditions credited to climate changes.
Aarhus University, Denmark; 2National Institute of
Water & Atmospheric Research, New Zealand
Permanent and indefinite survival of plants in flooded
soils depends primarily on adaptations that increase the
supply of oxygen to tissues in anoxic soil and water,
usually associated with features such as (i) increased
tissue porosity, (ii) changes in tissue permeability to
gases, and (iii) changes in the topology of root and
rhizome architecture. Differences in the degree of
development of these features contribute not only to
survival and growth, but are also responsible for species
zonation in relation to hydrological gradients, as will be
shown with examples of a range of species differing in
flooding tolerance. Maintaining species diversity in
managed wetlands therefore involves hydrological
conditions suitable for a variety of plants that differ in
their flooding tolerance. The shallowest areas of
wetlands, in which soils are waterlogged but there is little
standing water, can support many species which have
root aeration adaptations but are otherwise unspecialised
for aquatic life. Permanent standing water is a much
greater challenge for plants, and survival here is
restricted to species with special adaptations to their
oxygen transport physiology such as the development of
pressurized gas flows in their aerenchyma. These close
linkages between flooding tolerance and species
distributions are key considerations for maintaining
species diversity in wetlands.
Submergence tolerance of plants: leaf gas films
enhance oxygen and carbon dioxide exchange under
water
Colmer, T1, Pedersen, O2
1
2
The University of Western Australia,
University of Copenhagen, Denmark
Australia;
Submergence can impact on terrestrial plants in wetlands
and other low-lying areas. Plant survival underwater
depends upon gas exchange for respiration (O2) and
photosynthesis (CO2). Leaves of many wetland species
(e.g. Pragmites australis, Phalaris arundinacea, Oryza
sativa, Hordeum marinum) retain a thin surface layer of
gas when under water. Leaf gas films facilitate O2 and
CO2 exchange with floodwaters. As examples, with gas
films present: (i) O2 uptake rates in darkness were up to
5-fold higher, and (ii) CO2 uptake during light periods
(i.e. net photosynthesis) was enhanced up to 6-fold, as
compared with when these films had been removed.
Improved O2 entry during darkness and higher net
photosynthesis during light periods, in submerged shoots,
both enhanced internal O2 movement via aerenchyma to
roots in an anoxic substrate. When plants were
submerged for 7 days with gas films removed, tissue
sugars declined and shoot and root growth were reduced,
compared to submerged plants with intact gas films. In
summary, leaf gas films enhance O2 and CO2 exchange
during submergence, resulting in higher O2 in tissues and
more CO2 for photosynthesis, and thus contribute to
submergence tolerance of some plants.
Underwater CAM photosynthesis: benefits for carbon
gain in some aquatic plants
Pedersen, O1, Colmer, TD2
1
Freshwater Biological Laboratory, University of
Copenhagen, Denmark; 2School of Plant Biology, The
University of Western Australia, Australia
CAM photosynthesis in terrestrial plant is thought to
have evolved as a trait to conserve water and is thus
particularly frequent among desert plants. CAM is also
present in some aquatic plants inhabiting freshwater
lakes and temporary pools. Here, CAM is unimportant as
a water-conserving feature and instead it is considered of
adaptive importance in carbon limited environments
where CO2 is stored as malate during the night and
subsequently released during the day and fixed in the
normal Calvin cycle. As a consequence of extensive
underwater photosynthesis, CO2 drops to very low
concentration during the afternoon in vegetation-rich
temporary pools. In contrast, CO2 builds up to several
times air-equilibrium during the night when respiration
processes dominates. Under these environmental
conditions, plants with CAM photosynthesis may
maintain positive underwater net photosynthesis also
during times when the external CO2 concentration drops
to sub air-equilibrium values. However, CAM
photosynthesis may also restrict photorespiration which
is often high in aquatic plants as a consequence of the
slow gas diffusion in water compared to in air; CO2 is
only slowly replenished at the site of Rubisco. In
addition, O2 tends to build up in the tissue because of the
lower solubility of O2 compared to CO2. CAM activity in
the present study was indicated by 9.7-fold higher leaf
malate at dawn, compared with at dusk, and CAM
activity was confirmed also as changes in titratable
acidity (µmol H+ equivalents) of leaves. Leaves high in
malate not only showed higher underwater net
photosynthesis at low external CO2 but also less apparent
photorespiration. Suppression by CAM of apparent
photorespiration was evident at a range of O2
concentrations, including values below air equilibrium.
At high O2 of 2.2-fold atmospheric equilibrium, net
photosynthesis was reduced substantially and although it
remained positive in leaves containing high malate,
became negative in those low in malate. In situ
measurements of internal leaf O2 concentrations in
Isoëtes australis, an Australian aquatic CAM plant
inhabiting granite rock pools, showed that late afternoon
O2 increased to 32 kPa in the leaf lacunae while dropping
to below 1 kPa during the night. It is thus suggested that
CAM in aquatic plants enables higher rates of underwater
net photosynthesis over large O2 and CO2 concentration
ranges in floodwaters, via increased CO2 fixation and
suppression of photorespiration.
Sym013: Plant ancient biomolecules:
human history and changing climates –
28 July
Using ancient plant DNA to study prehistoric
agriculture
Brown, T1
1
Manchester Interdisciplinary Biocentre, University of
Manchester, Manchester, UK
The beginning of agriculture around 10,000 years ago
was a major transition in the human past. The cultivation
of plants enabled humans to exert a measure of control
over their food resources, protecting them from climatic
and environmental uncertainty. As a result, populations
grew rapidly, leading to stratified societies and the
elaborate civilisations and world systems of the historic
period. For the plant, domestication was an equally
dramatic event that involved selection for alleles
conferring phenotypes that are beneficial for the farmer,
followed by enforced climate change as the plants were
taken to new geographical regions. Recent work with
modern landraces is emphasising the extent to which the
genomes of crop plants have been shaped by adaptive
evolution that has occurred since domestication. Some
information on the effects of domestication on plant
genomes can be inferred from comparisons of DNA
sequences from landraces and wild plants. However, the
study of modern material can only access genotypes that
have survived to the present day, and hence does not
account for the possibility that some, possibly many, of
the original cultivated varieties did not survive and are
not represented among modern landraces. It is also
difficult to understand the tempo of the evolutionary
changes from comparisons of crops and wild plants that
diverged only 10,000 years ago. To address these
problems, ancient DNA from cultivated plants is being
studied. This work has been held back by the patchy
survival of DNA in charred cereal grains, which are the
commonest type of botanical material found in the
archaeological record. Greater progress has been made
with desiccated plant remains, which are much less
widespread but which survive in reasonable quantities in
South America and in some arid areas of Africa and
Asia. In particular, it has been possible to use ancient
DNA from desiccated maize cobs from Brazil and the
Andes to map the trajectories followed during the
prehistoric introduction of this plant into South America.
Much of the work with plant remains has relied on the
traditional approaches to ancient DNA analysis, in which
small regions of the genome are targeted by PCR and
sequences obtained from the amplified fragments.
Recently, the possibility of obtaining much larger
amounts of sequence data by ‘next generation’ methods
has been explored. These methods are proving
particularly well suited for desiccated plant remains, and
extensive DNA sequences have been obtained from
ancient cotton from South America and Africa as well as
maize from South and Central America. It might
therefore be possible to acquire complete genome
sequences of archaeological plant remains, or at least for
the ‘exome’, the component of the genome that codes for
protein. RNA preserved in maize and cotton specimens
has also been sequenced, enabling gene expression
29
patterns to be studied and regulatory RNA molecules to
be identified.
Archaeogenomic evidence of local adaptation in
barley
Allaby, R1, Palmer, S1, Smith, O1, Rose, P2, Clapham,
A3
1
University of Warwick, UK; 2The Austrian
Archaeological Institute, Austria; Cairo Branch,
Zamalek, Sharia Ismail Muhammed, Cairo, Egypt;
3
Worcester Historic Environment and Archaeology
Service, Woodbury, University of Worcester, UK
Evidence from phylogeographic patterns suggests that
many crop lineages existed in situ at geographic locations
for millennia, giving the opportunity for specific local
adaptation. The genetic variation associated with useful
adaptations may be applicable to modern crop
development. Barley grown by the ancient Nubians is
interesting because of a phenotypic abnormality that
gives the crop a 2-row appearance, despite
archaeogenetic evidence that the crop was originally 6row. Moreover, apparently the same crop lineage was
passed through five successive cultures, even through
violent transitions. This evolutionary sequence is likely
to be explained by drought adaptation, which was
undoubtedly a source of stress in the area in which the
archaeological site, Qasr Ibrim, is situated, upstream of
the first cataract of the River Nile. Using next generation
sequencing with archaeobotanical material we have
established that large-scale genomic level change in
plants of this region has occurred in a punctuated fashion
illustrating the rapidity with which domesticated plants
have evolved within the Holocene. We have also studied
the archaeoepigenome and found fundamental
differences in microRNA levels between the Nubian
archaeological barley, and modern barley, which centre
around the ‘Green Revolution’ gene interactions. These
suggest that the archaeological barley was more primed
than modern for germination, perhaps linked to the very
short growing season available, but also had down
regulation of mitochondria, which may provide the first
clues as to how the abnormal phenotype was generated.
We are also employing a DNA capture approach to study
the portion of the barley genome most likely to be
involved with drought adaptation. The archaeogenomic
evidence so far has turned up a number of surprising and
independent connections to mutations associated with
that part of the genome associated with the ‘Green
Revolution’ that is leading us to speculate about Green
Revolutions across the ancient world.
Molecular reconstruction of Holocene vegetation in
Scandinavia based on pollen and sediment ancient
DNA analysis
Matetovici, I1, Haile, J2, Fontana, SL3, Parducci, L1
1
Dept of Ecology and Genetics, Evolutionary Biology
Centre, Uppsala University, Uppsala, Sweden; 2Murdoch
University Ancient DNA Laboratory, Perth, Australia;
Centre for GeoGenetics, Natural History Museum of
Denmark, Copenhagen, Denmark; 3Dept of Palynology
and Climate Dynamics, University of Göttingen,
Göttingen, Germany
30
Analysis of pollen and sedimentary ancient DNA isolated
from sediment cores is a new emerging tool allowing
past vegetation reconstruction complementary to
traditional pollen and macrofossils analysis. We
compared results from pollen-based vegetation analysis
with results obtained using pollen and sedimentary DNA
and we evaluated the results of DNA analysis using
material from two Holocene sediments sampled in the
Scandes Mountains in central Scandinavia.
Genetic analysis of wheat landraces enables the
location of the first agricultural sites in Italy to be
identified
Brown, KA1
1
Manchester Interdisciplinary Biocentre, Faculty of Life
Sciences, University of Manchester, UK
We typed five microsatellite loci in 52 landraces of
Italian emmer wheat to determine if genetic analysis of
cereals can provide information relevant to the spread of
agriculture. Each of the five loci was polymorphic with
43 allele combinations identified in the 52 landraces. The
allele combinations fell into two groups. Group 1
comprised 27 genotypes found in 42 landraces and Group
2 comprised 15 genotypes found in 10 landraces. The
landraces with Group 1 genotypes showed a strong
correlation between geographical and genetic distances
but those with Group 2 genotypes did not. We inferred
that the Group 1 landraces might therefore retain a
phylogeographical structure that reflects ancient events.
We present a phylogeographical model for the spread of
agriculture that enables the point of origin of crop
cultivation to be predicted by comparison between the
genetic and geographical distances between landraces.
We applied this model to the Group 1 landraces by
positioning 131 hypothetical points of origin around the
coastline and northern border of Italy. The highest
correlation coefficients between genetic and geographical
distances were seen for hypothetical points of origin
located on the coast of northern Puglia. We repeated the
analysis with 1040 hypothetical points of origin located
within the Italian peninsula. Again, the highest
correlation coefficients were located in northern Puglia.
These predicted points of origin correspond with the
location of the earliest agricultural sites in Italy, dated to
c.6000 BC. The results show that plant genetics can be
used to identify the location of early agricultural sites.
Bryophyte DNA extracted from soil for paleo- and
extant community studies
Gussarova, G1, Bellemain, E1, Halvorsen, R1, Hassel,
K2, Stenøien, HK2, Coissac, E3
1
National Centre for Biosystematics, NHM, University of
Oslo, Norway; 2Section of Natural History, NTNUTrondheim, Norway; 3Laboratoire d’Ecologie Alpine,
Université Joseph Fourier, Grenoble, France
Bryophytes, especially mosses, are
important
components in a variety of ecosystems and well known
as indicators of climate change. However, methodologies
utilizing bryophyte ancient DNA in paleoenvironmental
studies are lagging behind those for animals and vascular
plants. We use parallel sequencing technologies and
DNA barcoding that enables species identification from
environmental samples to infer both paleo- and extant
species assemblages. To allow reliable species
identification we built a DNA sequencing database
(chloroplast trnL intron) for the 500 most important
arctic and boreal bryophyte species. Our sampling
comprises several hundreds of permafrost soil cores
collected throughout the Arctic region, dated from 10000
to several hundred thousand years before present. To
recover bryophyte DNA from such samples, we designed
new DNA barcoding markers that are suitable for
amplification of degraded DNA. We also analyze modern
soils sampled along a set of permanent vegetation
transects to correlate soil DNA identifications with the
above-ground species composition. We are now
summarizing DNA sequencing datasets from the
permafrost samples to be used for paleoenvironmental
reconstructions and modeling. Data obtained from the
modern soils will be used for developing a survey
methodology to complement traditional plant community
descriptions for monitoring bryophyte community
structure and dynamics, including possible effects of
climate change.
Paleoecology from the ground up: ancient DNA of
fungi
Cross, H1, 2, Cooper, A2
1
State Herbarium of South Australia, Adelaide,
Australia; 2Australian Centre for Ancient DNA, Adelaide
University, Australia
Genetic information of subfossil fungi can provide
crucial insight into the paleoecology of a region.
However, paleogenetic research on of fungi has lagged
behind other areas of ancient DNA research due to
critical limitations. One such constraint is the high risk of
contamination from environmental sources of any
potentially ancient material: fungi are found everywhere,
so eliminating them is difficult. However, perhaps the
most serious issue preventing progress in this field is the
limited taxonomic information that is available for fungi.
Only an estimated 10% of fungal species have been
described. Therefore, with any ancient DNA sequence of
a fungus it is difficult to determine whether the
differences observed correspond to chronological
changes within taxa or merely the presence of a
previously unknown modern species. Careful work in our
laboratory on sedimentary and other material from a
range of ages have led to progress in resolving some of
the taxonomic impediments in research on ancient fungal
DNA, though serious challenges remain. All work was
done under the strictest standards for ancient DNA with
multiple negative controls, and environmental samples
were taken from both the laboratory and source of the
specimens, thus reducing the possibility of
contamination. Despite the lack of genetic and taxonomic
information on many fungi, by utilizing existing
sequence databases and through careful analyses of
results we have begun to gain an understanding of fungal
species composition and diversity in past environments.
The impact and potential of fungal ancient DNA research
for paleoecological studies will be discussed.
Sym014: Ecological traits of plant species
worldwide – 29 July
Leaf and wood traits and their afterlife effects on
litter decomposition and fuel
Cornwell, W1, Cornelissen, H1
1
Vrije Universiteit, Amsterdam, The Netherlands
Worldwide decomposition rates depend both on climate
and the legacy of plant functional traits as litter quality.
To quantify the degree to which functional differentiation
among species affects their litter decomposition rates, we
brought together leaf trait and litter mass loss data for
both wood and leaf litter. We show that: (i) the
magnitude of species-driven differences is much larger
than previously thought and greater than climate-driven
variation; (ii) the decomposability of a species' litter is
consistently correlated with that species' ecological
strategy within different ecosystems globally,
representing a new connection between whole plant
carbon strategy and biogeochemical cycling. This
connection between plant strategies and decomposability
is crucial for both understanding vegetation–soil
feedbacks, effects on fire, and for improving forecasts of
the global carbon cycle.
Savannas, trees and fires across three continents:
similarities and some interesting differences
Archibald, S1, Lehmann, C2, Hoffmann, B3, Bond, W4
1
Natural Resources and The Environment, CSIR, South
Africa; 2School for Environmental Research, Charles
Darwin University, Darwin, Australia; 3Dept of Plant
Science, North Carolina State University, Raleigh, USA;
4
Dept of Botany, University of Cape Town, South Africa
Understanding the biogeography of the savanna biome
has historically been coloured by the continental
affiliations of the researchers involved, and contradictory
perspectives are often apparent in the literature.
Moreover there is ongoing debate on the extent to which
disturbance-driven feedbacks are essential for the
maintenance of savanna vegetation across its
environmental range. Here we report on a suite of crosscontinental analyses in Africa, Australia, and South
America which were initiated by the ARC–NZ
Vegetation Function Network. We demonstrate that
much of the perceived divergence in the environmental
limits of savanna between continents can be reconciled
with reference to drivers of canopy closure and
disturbance frequency, but that intriguing differences still
remain. In particular, there is divergence between
continents in the extent of arid savanna which points to a
lack of understanding of the factors maintaining closedcanopy formations in arid systems. When environmental
factors can not explain continental differences then
phylogenetic and historical factors might be at play. We
present data exploring how differences in tree allometric
relationships between continents might impact rainfallbiomass relationships – with feedbacks to fire spread.
31
Xylem functional traits: coordination and scaling
among hydraulic traits of plants worldwide
Jansen, S1, Brodribb, T2, Gleason, S3, Mitchell, P4,
Westoby, M3, Choat, B5
1
Ulm University, Germany; 2University of Tasmania,
Hobart, Australia; 3Macquarie University, Sydney,
Australia; 4CSIRO, Australia; 5Australian National
University, Canberra, Australia
In woody plants, xylem structure must balance three
competing requirements, namely transport efficiency,
safety from hydraulic failure and the mechanical support
of the plant. Understanding the traits that govern this
triad is important to identifying the drivers of xylem
evolution as well as our ability to predict species’
response to future climate change scenarios. Because
water loss is an unavoidable consequence of
photosynthesis, the rate of water transport through the
xylem must match the demand for water at the leaf
surface; otherwise the plant may wilt and die. The key
threat to hydraulic function is the suction of air into the
xylem (cavitation) which occurs because plant water
transport takes place under tension. If sufficient in
number, the dysfunctional, air-filled conduits that result
from cavitation can substantially reduce the rate of water
transport and down regulate leaf gas exchange. Transport
efficiency is chiefly a function of conduit size and
density, but how does efficiency and its associated xylem
features balance with cavitation resistance and
mechanical support across a phylogenetically broad,
global sampling of woody plants? With this in mind, we
present a synthesis of literature data examining the
functional diversity of xylem traits using a database of
681 woody species from across the globe. The database
encompasses root and shoot level traits for angiosperms
and gymnosperms from a broad range of biomes and
phylogenetic affinities. Specifically, our analyses address
(a) how xylem traits known to confer drought-stress
resistance or hydraulic efficiency vary across
environmental gradients, (b) the links between transport
efficiency and conduit dimensions, (c) the relationships
between hydraulic and biomechanical traits, and (d) the
co-ordination of xylem traits and branch level sufficiency
of water transport to the leaves. We also apply principal
components analyses to identify how variation in
transport efficiency,
cavitation
resistance and
biomechanical support is coordinated in multivariate trait
space.
Plant population dynamics: how much variation yearto-year, site-to-site, and between species?
Buckley, YM1, Ramula, S2, Ehrlen, J3, Burns, JH3,
Crone, EE5, Wardle, G6
1
The University of Queensland, Brisbane, Australia;
University of Turku, Turku, Finland; 3Stockholm
University, Stockholm, Sweden; 4University of
California, Davis, USA; 5University of Montana,
Montana, USA; 6University of Sydney, Sydney, Australia
2
Explaining variation in population growth rates is
fundamental to predicting population dynamics and
population responses to environmental change. In this
study, we used matrix population models, which link
32
birth, growth and survival to population growth rate, to
examine how and why population growth rates vary
within and among 50 terrestrial plant species. Population
growth rates were more similar within species than
among species; with phylogeny having a minimal
influence on among-species variation. Most population
growth rates decreased over the observation period and
were negatively autocorrelated between years; that is,
higher than average population growth rates tended to be
followed by lower than average population growth rates.
Population growth rates varied more through time than
space; this temporal variation was due mostly to variation
in post-seedling survival and for a subset of species was
partly explained by response to environmental factors,
such as fire and herbivory. Stochastic population growth
rates departed from mean matrix population growth rate
for temporally autocorrelated environments. Our findings
indicate that demographic data and models of closely
related plant species cannot necessarily be used to make
recommendations for conservation or control, and that
post-seedling survival and the sequence of environmental
conditions are critical for determining plant population
growth rate.
What plant traits facilitate long distance dispersal?
Linder, HP1, Arroyo, M2, Jordan, G3
1
University of Zurich, Switzerland; 2University of Chile,
Chile; 3University of Tasmania, Australia
Long distance colonisation has been established as the
most frequent cause of trans-oceanic disjunctions in
plants. Most recent research has been focussed on the
environmental correlates of colonisation, these have been
shown to be habitat or biome similarity, dominant wind
and ocean direction, and the width of the ocean barriers.
Such extrinsic parameters may influence the overall
frequency of dispersal among land areas, but cannot
account for variation among major groups of plants.
Although plant traits that facilitate dispersal attracted
much research attention in the past (e.g. strand floras,
diaspore salt tolerance, ecto- and endozoochory), there
have been no recent, phylogenetically corrected,
investigations. Yet some traits should facilitate dispersal
and establishment, while others can be assumed to be
inimical to either or both these processes. Here we use a
large dataset of over 11,000 austral plant species, from
45 clades, which include more than 200 long distance
dispersal events. These clades were selected from all
major groups of the seed plants. We use these clades, and
the dispersal events they contain, to ask which traits are
positively, which neutral, and which negatively
associated with trans-oceanic colonisation events.
Potential traits include diaspore size, diaspore dispersal
mode, life history traits (annuals vs. perennials) and habit
(herbaceous vs woody). The size of the dataset allows us
to take phylogenetic effects into account by analysing
each clade separately, and also to contrast traits of
species which disperse only within continents, to those
that show trans-oceanic dispersal. Being able to take into
account taxon-specific traits that influence long distance
colonisation may improve the predictiveness of
environmental factors in accounting for colonisation
direction and frequency.
Introducing PrometheusWiki: a Wiki for methods in
ecological and environmental plant physiology
Nicotra, A1, McIntosh, E1, Sack, L2
1
The Australian National
Australia; 2UCLA, USA
University,
Canberra,
Science moves most rapidly when the majority of
researchers use similar methods and can easily repeat and
build upon each others' discoveries. There is a strong
need for standardizing in ecological and environmental
plant physiology. Traditionally information about
protocols has been communicated either through
conventional scientific peer-reviewed publications,
which are slow and formal, or through word-of-mouth
interactions and protocol sharing between specific labgroups, which is inefficient in what is now a global field.
PrometheusWiki seeks to build a new method of
communication about methods within the research
community. Its goal is to combine fast and informal
wiki-based interactions with selected elements of
traditional scientific publishing, to provide editorial
review and a high quality resource. On the
PrometheusWiki site researchers can upload protocols
(and associated images, videos, code, etc) into given
topics and post comments and commentary in a
constructive and civil manner. PrometheusWiki uniquely
combines the open communication of the www with the
traditions of peer review under the oversight of an
Editorial Board of internationally recognized experts in
the field. Together this ensures delivery of an up-to-date,
high quality resource for anyone conducting experiments
in the field of ecological and environmental physiology –
students
and
experienced
researchers
alike.
PrometheusWiki launched in July 2010; here we
introduce its guiding principles and structure and reflect
on what has happened on the site in its first year.
Sym015: Male function and patterns of
paternity in flowering plant populations –
28 July
Size matters: selection favours larger flowers in males
but not females in a dioecious herb
Vaughton, G1, Ramsey, M1
1
Botany, University of New England, Armidale, NSW,
Australia
Background and aims – Sexual selection theory predicts
that male mating success is limited by access to females,
whereas female mating success is limited by access to
resources. In animal-pollinated plants, pollinators
mediate male and female mating success rather than
direct interactions between plants. Accordingly, for plant
species with separate sexes (dioecy), males should be
selected to enhance attractiveness to pollinators by
investing more than females in floral traits that increase
pollinator visitation. Such sexual dimorphism is expected
to vary with sex ratio, and be greater in male-biased
populations. We examine sexual selection in Wurmbea
dioica by addressing the following questions: Is sexual
dimorphism for flower size related to male sex ratio? Is
female mating success limited by pollen availability?
Does flower size exhibit genetic variation? Does
selection on flower size differ between male and
females?
Methods – We assessed male sex ratio and male:female
flower size dimorphism in 18 populations. In 11
populations, we assessed pollen limitation of female
mating success by comparing seed set of hand-pollinated
plants with that of naturally pollinated plants. In a
population with a balanced sex ratio, we assessed broadsense heritability for flower size using clonal replicates.
We also used a selection-gradient approach and
estimated phenotypic selection on flower size in males
and females with pollen removal and seed production as
fitness surrogates.
Key Results – Male sex ratio varied from 0.46–0.89
among populations. Male:female flower size dimorphism
increased with increasing male sex ratio. Female seed set
was not pollen-limited. Broad-sense heritability for male
and female flower size was 0.78 and 0.82, respectively.
We detected strong directional selection for increased
flower size in males, but weak stabilizing selection in
females.
Conclusions – Sex ratio represents a unique context for
selection on floral traits in W. dioica. Consistent with sex
ratio-dependent selection, we found greater flower size
dimorphism in male-biased populations than in lessbiased populations. We suggest that sexual selection for
increased male flower size was stronger when males
competed to attract pollinators, as would have occurred
in male-biased populations. Interestingly, female mating
success was not pollen limited in any of the populations,
and we detected weak stabilizing selection for flower
size. Such asymmetric selection is consistent with the
male-biased attraction hypothesis of sexual dimorphism
in flower size.
Influence of pollinator visitation patterns on multiple
paternity in Mimulus and Narcissus
Karron, JD1, Medrano, M2, Mitchell, RJ3, Herrera, CM2
1
University of Wisconsin–Milwaukee, USA; 2Estacion
Biologica de Donana, CSIC, Spain; 3University of Akron,
USA
Animal-pollinated angiosperms cannot directly control
gamete receipt or export. Instead, these plants depend on
movements of pollinators whose foraging behaviors
often fail to optimize the quantity or quality of pollen
deposited on stigmas. Furthermore, the stochastic nature
of pollinator visits often leads to striking among-flower
differences in mating patterns. One factor likely to
contribute to this among-flower variation is the timing
and composition of sequential pollen loads deposited on
each stigma. Each pollen load may differ markedly in
sire representation, especially if successive pollinators
approach a flower from distinct compass directions and
carry pollen from different donors. Although pollen
deposited during an initial floral visit may have a siring
advantage due to priority, pollen grains deposited during
later visits may also compete successfully for access to
ovules. This multiple mating is likely to increase the
genetic diversity in a sibship, which may influence
competitive interactions among developing seeds within
fruits and among seedlings in the field. We
experimentally tested the hypothesis that sequential
33
pollinator visits contribute to the exceptionally high
levels of mate diversity in fruits of Mimulus ringens
(Phrymaceae), a wetland perennial native to N. America.
We documented all bee visits to individual flowers,
quantified resulting seed set, and determined paternity for
20 seeds per fruit. Most flowers (76%) received multiple
visits, and the interval between visits was usually < 30
min. Flowers visited multiple times produced 44% more
seeds than flowers visited once. All fruits were multiply
sired. Flowers receiving a single visit averaged 3.12
outcross sires per fruit, indicating that single visits
deposit pollen from several donors. The number of sires
was even greater following three or more visits (4.92
outcross sires), demonstrating that sequential visits bring
pollen from donors not represented in the initial visit.
Sequential pollinator visits may also contribute to the
high levels of multiple paternity in Narcissus
longispathus (Amaryllidaceae), a wild daffodil species
endemic to a few mountain ranges in SE Spain. The
effective mate number per flower varies widely among
populations and years, but can be as high as 5.2 effective
sires per fruit. Narcissus longispathus flowers are longlived, lasting 16.5 days in natural populations. We are
currently experimentally testing the hypothesis that
successive pollinator probes over multiple days increase
mate diversity. We are also exploring whether visits by
pollinators likely to have distinct pollen carryover
characteristics lead to differences in mate diversity.
Reproductive functionality, paternity and pollen
dispersal in restored Banksia populations
Krauss, Siegy1
1
Kings Park And Botanic Garden, Perth, Australia
Implicit, but rarely assessed, in the success of ecological
restoration projects is the management of genetic
variation of restored populations and, critically, their
offspring. Management of genetic variation is critical to
achieving functional, self-sustaining restored populations
that are resilient to environmental challenges. The
delivery of robust pollinator services for seed set,
inbreeding avoidance and genetic connectivity is vital,
especially for animal pollinated outcrossing species. In a
keystone Banksia, we assessed genetic variation,
structure and differentiation of restored and natural
populations, and their offspring. We also characterised
mating systems and assigned paternity to offspring to
characterise pollen flow, and genetic connectivity, within
and among restored and adjacent natural populations, and
assessed inbreeding depression through glasshouse
growth trials. Restored populations and their offspring
were genetically undifferentiated from, and displayed
similar levels of genetic variation to, adjacent natural
populations, indicating initial sourcing of genetically
diverse local provenance seed. Mating system parameters
were similar between populations, and extensive realized
pollen dispersal within and between restored and
adjacent natural populations highlight effective delivery
of pollinator services and genetic connectivity and
explain the absence of inbreeding depression in restored
population offspring. Our results indicate successful
genetic management of a restored population, from
which we identify general principles relating to seed
sourcing. These results add to our understanding of the
importance of highly-mobile bird pollinators for the
34
facilitation of wide outcrossing and high multiple
paternity for much of the flora of South West Australia.
Herkogamy influences mate diversity in fruits of the
wild daffodil Narcissus longispathus
Medrano, M1, Requerey, R1, Karron, JD2, Mitchell, RJ,
Herrera1, CM1
1
Estación Biológica De Doñana, CSIC, SPAIN;
University of Wisconsin–Milwaukee, USA; 3University
of Akron, USA
2
The great majority of floral features have traditionally
been interpreted as adaptations that enhance attraction
and effectiveness of pollinators and/or promote
outcrossing. Here we propose that one of the most
ubiquitous floral traits among angiosperm plants, the
spatial separation of anthers and stigmas within flowers
(herkogamy), may have another important function
which is to enhance pollen donor diversity within a
maternal sibship. We hypothesize that flowers with
greater anther-stigma separation may be able to capture
proportionally more diverse outcross pollen on their
stigmas, and consequently increased opportunity for
intense pollen competition and/or higher maternal
?ltering of male gametes could occur. This may lead to
greater heterogeneity among pollen donors in seed siring
success, and increased mate diversity within fruits. We
test this hypothesis in Narcissus longispathus, a wild
daffodil species with extensive variation in anther-stigma
separation, both within and among populations (range =
0.5 to 10.4 mm). The effects of herkogamy on both the
rate of outcrossing and the correlation of outcrossed
paternity within fruits, and whether there is spatial or
temporal variation in the effects of herkogamy on these
mating parameters were studied. Mating system
estimates were calculated separately for plants with high
herkogamy (anther-stigma separation > 6mm) and plants
with low herkogamy (anther-stigma separation < 6mm).
N. longispathus plants with high herkogamy had similar
outcrossing rates (0.650) to plants with low herkogamy
(0.676). However the diversity of pollen donors siring
seeds of high-herkogamy flowers was consistently
greater than the diversity of pollen donors siring seeds of
low-herkogamy flowers. This is the first study to
demonstrate that naturally-occurring variation in a floral
trait influences mate diversity within fruits.
Estimation of pollen dispersal curves and
heterogeneity in male fecundity from genetic data in
plants
Austerlitz, F1
1
Laboratoire d'Eco-Anthropologie et Ethnobiologie,
CNRS/MNHN/Universite Paris 7, Museum National
d'Histoire Naturelle, Paris, France
The availability of highly polymorphic markers has
yielded the possibility of estimating directly
contemporaneous gene flow in plant species, in particular
pollen flow. The methods use as an input genotypic data
of mothers, potential fathers and of seeds collected on the
mothers. They are either direct methods, based mostly on
categorical or fractional paternity analyses, or indirect
methods based on the comparison between the allelic
frequencies in the pollen cloud of the mothers (e.g.
TwoGener or Kindist). Both kind of methods aim at
estimating the dispersal curve and the heterogeneity in
male fecundities. We have now applied these methods on
a substantial set of plant species, including several forest
tree species. We have shown that pollen dispersal is
leptokurtic in many cases, with many events of
reproduction at short distances but also a small but nonnegligible part of long-distance dispersal events. We
have also detected in several cases a heterogeneity of
male fertilities that is generally connected with
differences in some phenotypic traits. These results are
important for instance in the context of conservation
biology for threatened fragmented species, or more
generally for the question of the spreading of
advantageous and deleterious mutations over the
landscape.
Patterns of paternity in populations
endangered Grevillea iaspicula (Proteaceae)
of
the
Hoebee, S1, Young, A2
1
La Trobe University, Bundoora, Australia;
Plant Industry, Canberra, Australia
2
CSIRO
Microsatellite loci were used in a source-sink approach to
establishing patterns of paternity and to directly estimate
pollen immigration into populations of the endangered
shrub Grevillea iaspicula (Proteaceae). Open-pollinated
progeny arrays from 5-8 individuals in each of four
populations were used. In two populations, the spatial
distribution, height of plants and the interaction between
these parameters were assessed in order to identify
whether they influenced the observed mating patterns.
Two philosophical approaches were adopted with regard
to the analyses. The first approach restricted pollen
donors to the source population in the first instance, then
for any seed where paternity was unresolved, or there
were no possible sires, paternity was re-assessed from all
other populations. In the second approach, the complete
dataset was used in the assignment of paternity without
restriction. The majority of all seed (82%) were sired by
plants located within the seed source populations. The
number of pollen donors contributing to seed arrays was
low (range: 1–12; mean = 5.35 ± 1.97) compared to the
number of reproductive individuals, and there was
significant variance in reproductive success among
paternal plants. Pollen immigration rates ranged between
13.6% and 33.1%, reflecting moderate rates of gene flow
(Nm = 1.9 to 2.7). Results regarding the influence of
spatial distribution and plant height were context
dependent. Paternity in the smaller population was
significantly correlated with plant height. Conversely, in
the larger population inter-plant distance was more
influential. However, multiple regression indicated that
there was no simple relationship among the parameters
that was consistent between populations and between
approaches to paternity assignment. For G. iaspicula
populations, factors such as low mate availability, only
moderate gene flow and large variance in male fitness
may result in reduced effective population size,
compounding the effects of already small population
sizes and leaving them more susceptible to
environmental, demographic and genetic stochasticity,
thereby reducing their long term viability.
Sym016: Plant–microbe interactions:
mycorrhizas and environmental change –
30 July
The 'mutualism–parasitism continuum' in arbuscular
mycorrhizal symbiosis: it's time for a re-think
Smith, FA1, Smith, SE1
1
School of Agriculture, Food & Wine, University of
Adelaide, Australia
Growth responses of plants colonized by arbuscular
mycorrhizal (AM) fungi range from highly positive to
negative. Responses depend primarily on individual plant
and fungal taxa and levels of soil nutrients, especially
phosphate (P) and combined nitrogen (N), and have been
equated to a ‘mutualism–parasitism continuum’.
Mutualism results from transfer of P and N to the plant in
exchange for organic carbon (C). Lack of positive growth
responses, or depressions, have been assumed to result
from C transfer to the fungus with little or no P transfer
to the plant, i.e. fungal parasitism. However, recent
research has demonstrated that the amount of P delivered
via the fungus, shown by supplying radioactive P to the
external mycelium, can be very high not only where
plants respond positively but also where they show no or
negative responses. In the last two cases, the AM P
uptake remains ‘hidden’ unless tracer P is used. Because
there is no ‘extra P uptake’ into non-responsive plants,
the direct P uptake via root hairs and epidermis must be
lower than in non-mycorrhizal (NM) comparators; the
underlying mechanism is unknown. At the same time, P
transporter genes in root cortical cells are induced by AM
colonization, again both in positively responsive and
non- or negatively responsive plants. The transporters are
involved in P uptake by the plants from the symbiotic
apoplast, and expression of genes encoding them
provides a marker for the potential operation of the AM
pathway. The demonstration of significant P uptake via
the AM pathway and reduction of direct uptake requires
that researchers re-think the importance of AM symbiosis
in plant nutrition at a range of scales from cells to
ecology and agricultural production. About 80% of
terrestrial plants, including major cereal and vegetable
crops, are naturally AM in the field, except in extreme
soil habitats where AM fungi are lacking. Thus, the NM
condition is most often a (laboratory) artefact. At the
cellular level, delivery of significant amounts of P to
negatively responsive plants (which include some
cereals) means that AM fungi cannot be regarded as
parasitic, and the mechanism underlying the growth
reductions may be P deficiency, rather than ‘excessive C
drain’ as thought previously. Furthermore, research at the
cellular and molecular genetic levels to understand and
enhance P uptake by crops must take both the large
contribution of the AM pathway and decreased direct
uptake into account. Research directed to understanding
and preventing decreased direct uptake may prove
productive in increasing agricultural yield. Further at the
whole plant level, ‘hidden’ AM P uptake may give
advantages to non-responsive AM plants competing with
NM ones, that are not seen when plants are grown singly.
Overall, new information on integration of the two
uptake pathways offers a possible explanation for
evolutionary persistence of AM symbioses in plants that
35
are non-responsive in laboratory experiments. It is clear
that the ‘parasitism’ end of the mutualism–parasitism
continuum is less widespread than originally thought.
Accounting for multifunctionality in mycorrhizal
symbioses when assessing the impacts of
environmental change
Powell, JR1,2, Sikes, BA3, Rillig, MC1
1
Freie Universitaet Berlin, Germany; 2University of
Western Sydney, Australia; 3University of Texas, Austin,
USA
While measuring the symbiotic effects of mycorrhizal
fungi on their plant hosts and the ecosystem-level
consequences of these interactions, researchers typically
quantify either the net effects of one partner on another
(e.g., mycorrhizal dependency) or a functional trait
associated with a symbiont (e.g., tissue P concentration).
However, benefits associated with mycorrhizal
functioning may be derived, simultaneously or
independently, via multiple mechanisms (such as nutrient
uptake, pathogen protection, and modified soil-water
relations, among others). Multifunctionality in
mycorrhizal symbioses can make it more difficult to
predict the effects of environmental change on the
functioning of mycorrhizal communities. Effects may be
perceived to be idiosyncratic but are actually due to the
identity of the symbionts present in the study or changes
in behaviour of the symbionts under different
environmental conditions. In addition, complex
experimental designs are required to sort out the effects
of several factors at once (e.g., fertilization x pathogen
inoculation x drought x mycorrhizal inoculation); having
additional treatment levels for any factor quickly reduces
the feasiblity of the study. An alternative approach is to
target multiple traits, each associated with a functional
pathway, and to simultaneously quantify these traits in
manipulative experiments and observational studies
where the primary gradient is one or more types of
environmental change. Statistical approaches that allow
for the testing of causative hypotheses from correlational
data (e.g., structural equation modelling) can then be
used to establish the relative importance of these multiple
functions along environmental gradients based on the
covariance of traits and estimates of fitness. Previous
work suggests that traits such as fungal root colonization
and soil hyphal length or higher-order taxonomic
affiliation (family, order) can predict arbuscular
mycorrhizal fungal functioning via different pathways for
different host plant species, at least in one system (an
abandoned agricultural field in Canada). Utilizing this
approach will allow researchers to gauge the relative
importance of functions they isolate and, perhaps more
importantly, those they did not consider across different
types of environmental change. An important
consideration will be the choice of traits, or surrogates of
traits, to be measured; these variables need to be useful
predictors of functional outcomes during symbiotic
plant-fungal interactions under the conditions that they
will be estimated, but should also be suitable for highthroughput analysis. The mechanistic understanding of
plant-fungal interactions facilitated by these approaches
should enhance our ability to predict and prepare for the
effects of environmental change in natural and managed
ecosystems.
36
Arbuscular mycorrhizas and plant nutritive value in
a changing environment
Cavagnaro, T1, 2, Gleadow, R1, Miller, R1
1
School of Biological Sciences, Monash University,
Australia; 2Australian Centre for Biodiversity, Monash
University, Australia
The soil biota and the ecosystem services they provide
are increasingly recognized as having an essential role in
sustainable land management. Most terrestrial plant
species, including the majority of crops, form arbuscular
mycorrhizas (AM). These associations between plant
roots, and a specialized group of soil fungi, play an
important role in plant growth, nutrition and ecology.
Under elevated atmospheric CO2 concentrations (eCO2)
plant demand for nutrients is typically increased, due to
the so called CO2 fertilization effect. Given the role of
AM in plant nutrient acquisition, it has been
hypothesised that AM will have an increasingly
important role to play in meeting increased plant demand
for nutrients in a high CO2 world. This however, is only
half of the story. Once plants acquire nutrients,
irrespective of the mechanisms involved, they are
incorporated into a wide array of primary and secondary
metabolites, including nucleic acids, amino acids,
defence compounds and many others. In our research, we
have begun to consider the link between mycorrhizal
acquisition of nutrients, and their fate(s) in plants. In this
paper we first consider the impacts of eCO2 on the
formation and functioning of AM, with an emphasis on
their role in plant nutrient acquisition. Second, we
discuss the impacts of eCO2 on plant allocation of
resources (specifically N) to secondary metabolites
involved in plant defence against herbivores. Finally, we
begin to explore how these two quite different aspects of
plant biology may be linked, and conclude with a number
of readily testable hypotheses with a view to stimulating
further work in this area. In so doing, we seek to better
understand where our own areas of research can inform
one another, and to encourage a more integrated
approach to investigation of all aspects of plant responses
to eCO2.
Effects of elevated atmospheric CO2, increased
temperature and drought on symbiotic fungi of
Australian eucalypts
Anderson, I1, Drigo, B1, Keniry, K1, Curlevski, N1,
Chambers, S1, Ghannoum, O1, Tissue, D1, Cairney, J1
1
Hawkesbury Institute for the Environment, University of
Western Sydney, Australia
Mycorrhizal fungi are central to forest carbon and
nutrient cycles, but little is known about how they will
respond to future climate change, especially in the
context of Australian sclerophyll forests. Our recent
research has used a combination of controlled
environment glasshouse and field experimentation to
investigate the interactive effects of elevated atmospheric
CO2, increased temperature and drought on Australian
eucalypt mycorrhizal fungi. In a glasshouse experiment,
Eucalyptus saligna and E. sideroxylon seedlings were
grown in field soil for a period of 5 months under subambient (280 ppm), ambient (380 ppm) and elevated
(640 ppm) atmospheric CO2 conditions at both 26°C and
30°C. Molecular analyses were conducted on both DNA
extracted from soil and from sand-filled hyphal ingrowth
bags which select for ectomycorrhizal fungal mycelia.
Multivariate analyses showed a significant (P < 0.035)
separation between soil fungal communities associated
with the two different tree species. While there was no
further separation based on CO2 concentration at the
lower temperature (28oC), there was a clear separation
between the soil fungal communities from the 280, 400
and 640 ppm CO2 treatments at 34oC. This response
appeared to be plant-dependent at 280 and 400 ppm CO2;
however, all 640 ppm CO2 samples clustered together
regardless of tree species. In the field experiment, E.
saligna trees were grown in 12 whole tree chambers for
three years under controlled temperature conditions and
exposed to either ambient (ca. 380 ppm) or elevated (ca.
640 ppm) atmospheric CO2 concentrations and different
watering regimes. Multivariate analyses showed that
elevated CO2 intensified the effect of drought stress by
significantly altering fungal community composition.
Collectively, our recent data demonstrate that alterations
to atmospheric CO2 concentrations, temperature and
drought conditions modify mycorrhizal and other soil
fungal communities associated with Australian eucalypts.
We are currently investigating the knock-on effects of
these changes for fungal driven soil processes given the
potential for soil microorganisms to significantly
influence the direction and magnitude of terrestrial
ecosystem/atmosphere feedbacks that regulate global
change.
Sym017: Crassulacean acid metabolism:
evolutionary origins, ecological plasticity
and bioenergy potential – 25 July
land. The following areas of contemporary research on
CAM plants will be covered: (1) Biodiversity and
systematics – in the light of new surveys, approximately
6 % of all angiosperm species are now estimated to
possess CAM, approximately twice the number with C4
photosynthesis, and many of these CAM plants are
important components of threatened biomes, such as
xerophytic succulent scrub and tropical montane cloud
forests. (2) Evolutionary origins – in the absence of any
significant fossil record, molecular-phylogenetic methods
are being applied to certain key groups and have shown
that CAM has arisen multiple times, even within
individual families; date-calibrated phylogenies are being
used to generate specific hypotheses about the
palaeoecological context in which particular CAM
lineages arose. (3) Ecological plasticity – the apparent
physiological flexibility of CAM has been much
discussed in the past and is being reappraised in the
context of new experimental evidence revealing the
extent to which this is developmentally or
environmentally controlled, leading to a reassessment of
the adaptive significance of plasticity in photosynthetic
pathway expression. (4) Bioenergy potential – there is
considerable interest in the potential for CAM plants as a
sustainable bioenergy feedstock, exploiting the
exceptional stress tolerance of high-biomass CAM plants
such as agaves by making use of marginal, degraded land
unable to support other major crops, thereby avoiding
competition with land required for food, and offsetting
the pressure for clearance of primary vegetation for
biofuel crops in tropical regions of the world.
CAM and C4 photosynthesis as separate but related
evolutionary trajectories: examples from the
Portulacineae (Caryophyllales)
Edwards, E
Crassulacean acid metabolism as an ecological
adaptation: current status and future prospects
1
Dept of Ecology and Evolutionary Biology, Brown
University, Providence, Rhode Island, USA
Smith, JAC1, Winter, K1, Holtum, JAM1
CAM and C4 photosynthetic pathways have much in
common: they employ a shared biochemical pathway that
enables the concentration of CO2 inside plant cells, they
are both considered to be adaptations to stressful
environments, and they are both arguably among the
most convergent of complex traits, having each evolved
multiple times in various plant lineages. Historically,
however, they have largely been investigated as separate
and unrelated adaptations, which has led us to mostly
focus on the differences between CAM and C4 plants,
rather than their similarities. A broad look at the
distribution of CAM and C4 evolutionary origins across a
very large phylogeny of angiosperms highlights that
while CAM photosynthesis seems to have evolved more
often and in a greater number of lineages, both CAM and
C4 plants show tight and overlapping clustering in certain
regions of the tree, suggesting that certain plant lineages
are pre-conditioned to evolve both pathways.
Additionally, preliminary dating analyses suggest that the
origins and subsequent diversification of many CAM and
C4 lineages were contemporaneous in time. The late
Miocene/Pliocene is emerging as a critical moment in
angiosperm evolutionary history, having witnessed many
C4 origins in eudicots, the rise of C4-dominated
grasslands, and the diversification of many of the world's
ecologically important succulent CAM lineages. A closer
1
University of Oxford, UK
Crassulacean acid metabolism (CAM) represents,
together with C3 and C4 photosynthesis, one of the three
major pathways of net CO2 assimilation found in land
plants. Because of its close association with waterlimited habitats, CAM photosynthesis is regarded as one
of the clearest examples of the metabolic basis of an
ecological adaptation in the plant kingdom. Whereas the
underlying biochemical and physiological characteristics
of CAM have been established for some time –
comprising in essence nocturnal CO2 fixation coupled
with daytime stomatal closure – considerable research is
now focused on the ecological diversity and evolutionary
origins of this adaptation. Furthermore, as scientists
contemplate a warmer world in which water availability
will represent a major limiting factor for plant growth,
there is intensified interest in understanding how CAM
plants are so well adapted to survive (and show
surprisingly
high
productivities)
in
stressful
environments. Lessons learned from these studies are
expected to be valuable in developing more stresstolerant, water-use-efficient crop plants, and possibly in
the exploitation of CAM plants themselves on marginal
37
look at one of these lineages, the Portulacineae and
relatives (Caryophyllales), reveals multiple origins of
both CAM and C4 pathways in a relatively small group
of ~ 2200 species. I present preliminary data on vein
spacing, quantitative measures of tissue succulence, gene
recruitment, ecological habitat, and life history in C3,
CAM, and C4 lineages in the Portulacineae and
Molluginaceae to begin to reconstruct the various steps in
the evolution of both syndromes, and to identify any
potential 'no turning back' scenarios, where a certain
assemblage of precursor traits strongly favors the
evolution of one syndrome over the other.
Ecological plasticity of crassulacean acid metabolism:
drivers and constraints
Borland, A1
1
Newcastle University, Newcastle Upon Tyne, UK
Approximately 7% of plant species, encompassing 33
families and 328 genera are known to possess a capacity
for crassulacean acid metabolism (CAM). This
taxonomic diversity is mirrored by the range of habitats
favoured by CAM plants which range from semi-arid
deserts, through tropical rainforests to aquatic
ecosystems. It has been suggested that the ecological
plasticity of CAM is driven by the extent to which
nocturnal CO2 uptake can be engaged or disengaged in
response to perturbations in water and/or CO2
availability. On the other hand, the anatomical and
physiological traits that underpin the photosynthetic
performance of CAM plants have the potential to
constrain ecological plasticity in particular environments.
This presentation will highlight the mechanisms that
underpin the photosynthetic plasticity of CAM and will
discuss examples of how photosynthetic divergence
between closely related species can be reconciled with
the ecological constraints imposed by CAM.
CAM plasticity drives evolutionary success in tropical
plants: a case study in Chilean Puya (Puyoideae,
Bromeliaceae)
Schulte, K1,2, Silvestro, D3, Schmidt, M3, Winter, K4,
Smith, JAC5, Crayn, DM1, Novoa, P6, Zizka, G2,3,7
1
Australian Tropical Herbarium, Cairns, Australia;
Biodiversity and Climate Research Centre, Frankfurt/M,
Germany; 3Dept. of Botany and Molecular Evolution,
Research Institute Senckenberg, Frankfurt/M, Germany;
4
Smithsonian Tropical Research Institute, Ancon,
Balboa, Republic of Panama; 5Dept of Plant Sciences,
University of Oxford, Oxford, UK; 6Jardín Botánico
Nacional, Viña del Mar, Chile; 7Goethe University,
Frankfurt/M, Germany
2
The Bromeliaceae are an important Neotropical plant
family that has successfully conquered a great variety of
tropical habitats. Within the family, crassulacean acid
metabolism (CAM) has evolved at least four times
independently: in Tillandsia, Hechtia, the Dyckia clade
and in the clade comprising Puya and the Bromelioideae.
Within the latter, approximately 25 % of species in the
genus Puya and 90 % of Bromelioideae are CAM plants.
Within Puya, a clade consisting of the seven Chilean
species is sister to the rest. This clade is distributed along
38
a steep ecological gradient ranging from the coastal
habitats of the Atacama desert to the Mediterranean and
montane regions of central Chile, and contains both C3
and CAM plants. This renders the Chilean Puya clade an
important group to obtain insights into the evolution of
CAM within the more derived Bromeliaceae and a
promising group to explore the correlation between the
occurrence of C3/CAM plants and environmental
parameters. In this study, phylogenetic relationships
within the Chilean Puya clade were inferred using AFLP
fingerprints obtained from 7 primer pairs yielding 984
characters. Samples were taken from populations of all
seven species (P. alpestris, P. berteroniana, P.
boliviensis, P. chilensis, P. coerulea, P. gilmartiniae, P.
venusta) covering their geographical distribution. The
photosynthetic pathway of the samples included in the
phylogenetic analysis was determined from leaf tissue
carbon-isotope ratio, delta13C. This value reflects the
degree to which plants use the C3 pathway, in which the
primary carboxylating enzyme is ribulose–1,5–
bisphosphate carboxylase–oxygenase, as compared with
the CAM pathway, in which the primary carboxylating
enzyme is PEPC, because of a kinetic isotope effect.
Extensive distribution data were collected from
specimens from 27 herbaria and used to infer the
ecological niche parameters of the species via the
WorldClim database. Phylogenetic analysis using
maximum parsimony and
Bayesian
inference
consistently revealed three well supported main clades
termed the chilensis (P. chilensis, P. boliviensis, P.
gilmartiniae), alpestris (P. alpestris, P. berteroniana),
and coerulea groups (P. coerulea, P. venusta). The
frequency distribution of delta13C values revealed an
unexpectedly high proportion of plants with intermediate
values between -22 and -18 parts per thousand indicating
that these plants do not fully rely on one of the two
photosynthetic modes but are using CAM in a more
flexible way. Only a small proportion of plants exhibited
delta13C values less negative than -18 parts per thousand
indicative of predominantly CAM photosynthesis. The
occurrence of plants with delta13C values indicative of
either C3, CAM, or C3/CAM intermediates was unevenly
distributed among clades. The alpestris clade exhibited
the greatest variability in the photosynthetic mode,
whereas the coerulea clade was the least variable with a
predominance of C3 plants. Among the different climatic
parameters, mean annual precipitation showed the
strongest correlation with photosynthetic mode. The
alpestris clade exhibited the widest ecological niche
breadth, the highest variability in the photosynthetic
mode employed and the widest geographical distribution.
The findings of this study lend support to the hypothesis
that CAM plasticity is an important factor for the success
of tropical CAM plants.
Bioenergy potential of CAM plants
Holtum, J1
1
James Cook University, Douglas, Australia
The sources of most biofuel of plant origin are species
developed for food production that are grown on
productive, well-watered land best suited for growing
food. The use of such prime arable land for the
production of biofuel feedstock is unsustainable in light
of the increasing demands for food production. Similarly,
it is generally economically unrealistic to grow biofuel
feedstock on extremely marginal land because plants
grow slowly when stressed, even those species that are
well adapted to survive stresses. The most suitable land
for growing biofuel crops tends to be land that is suboptimal for conventional crops but productive for biofuel
species. In the tropics and sub-tropics such land is often
seasonally dry, the type of habitat favoured by plants
with crassulacean acid metabolism (CAM), a water-use
efficient mode of photosynthesis. CAM species can
exhibit high rates of biomass accumulation when grown
in seasonally dry habitats under agronomic conditions.
For example, perennial CAM species in genera such as
Agave, Clusia and Opuntia can accumulate dry biomass
at rates of 30+ tonnes ha-1 annum-1 when grown under
rain-fed conditions. Such rates are comparable to, or
better than, rates obtained with C3 and C4 biofuel crops
under irrigated conditions. For most conventional biofuel
crops, irrigation would be required to ensure
commercially meaningful rates of biomass accumulation
on seasonally dry land, thereby increasing the cost of
production and reducing the net energy output of the
crop. The CAM species with potential as biofuel
feedstocks that are attracting commercial interest are
principally within the genus Agave. Agaves accumulate
fructans which have a multiplicity of uses other than for
biofuel production, and contain low-lignin fibres which
are amenable to hydrolysis or can be burnt to produce
energy. Species such as A. tequilana are not new to
agriculture, they have been bred and cultivated for many
generations for alcohol production. Trials are underway
in Australia and in Mexico to assess the suitability of A.
tequilana as a feedstock. Other species also being
considered as biofuel feedstocks include A. americana,
A. fourcroydes, A. sisalana and A. salmiana. Fastgrowing tropical Clusia that can switch between C3 and
CAM photosynthesis in response to changes in the
availability of water also show promise. Physiological
and morphological features of CAM enable high biomass
production in periodically water-limited environments by
allowing succulent CAM tissues to maintain, in a nutrient
efficient manner, daily and seasonal carbon gain in the
face of fluctuations in soil water supply.
Sym018: Composition and dynamics of
urban floras – 29 July
The role of plant species traits contributing to
invasiveness is context dependent and needs to be
assessed in concert with other, potentially
confounding factors
Pyšek, P1,2, Jarošík, V1,2, Chytrý, M3, Pergl, J3
1
Institute of Botany, Academy of Sciences of The Czech
Republic; 2Faculty of Science, Dept of Ecology, Charles
University Prague, Czech Republic; 3Dept of Botany and
Zoology, Masaryk University Brno, Czech Republic
The major dynamic processes occurring within urban
areas. i.e. the introduction of new plant species and their
ability to naturalize and invade, need to be assessed in
the overall context of biological invasions. Determining
which biological and ecological traits predispose a
species to become invasive is a fundamental question of
invasion ecology and many studies have attempted to
profile successful invaders, but traits affect invasiveness
in concert with other factors. In the last decade, it has
been recognized that the traits of a species are only part
of any explanation for invasion success, and that other
factors such as residence time and propagule pressure codetermine whether a species will successfully naturalize
or invade in a new region. This recognition requires
exploration of the role of traits by using models that
analyze, at the same time, several groups of potentially
confounding factors that co-determine the outcome of
invasions. Because of this context dependence, the role
of traits in plant invasions can only be assessed properly
when the main confounding factors are controlled for.
Further, it becomes obvious that different factors are
important at each stage of an invasion, such as
introduction vs. naturalization or naturalization vs.
invasion, with socioeconomic factors being generally
important initially, and biogeographical, ecological, and
evolutionary factors increasing in importance in later
stages. This implies that different traits are crucial at
different stages of the invasion process and that the
relative importance of traits vs. other factors depends on
the stage of invasion. Our recent studies that (i) took the
above-mentioned confounding factors into account, (ii)
addressed the role of traits in different stages of invasion
process, and (iii) used data on the occurrence of the
source species pool in other parts of the world, hence
partly eliminating introduction biases, have shown that
the success of particular species in early stages of
invasion can be predicted by characteristics reflecting
propagule pressure, residence time and adaptation to a
wide range of climate, aquired in their native distribution
ranges, whereas species’ biological traits are important
for determining success at later stages, affecting which
species become serious invaders. The results from our
studies have potential practical implications: Species
which have large native ranges and are common within
these ranges are likely to have been favoured in terms of
residence time, propagule pressure and climatic
tolerance, and should be paid increased attention upon
introductions. Biological traits that proved to have a
direct effect on invasiveness should be taken into account
in screening systems applied to evaluate deliberate
introductions of alien plants to new regions. From a
scientific point of view, future studies searching for
invasive traits need to take into account confounding
factors to avoid misleading conclusions.
Plant traits and extinction in urban areas: a metaanalysis of eleven cities
Williams, N1, Clements, S2, Corlett, R3, Hahs, A4,
McCarthy, M1, McDonnell, M4, Schwartz, MW5,
Thompson, K6, Vesk, PA1, Duncan, RP7
1
The University of Melbourne, Australia; 2Brooklyn
Botanic Garden, Brooklyn, New York, USA; 3National
University of Singapore, Singapore; 4Australian
Research Centre for Urban Ecology, Royal Botanic
Gardens Melbourne, Victoria, Australia; 5The University
of California, USA; 6University of Sheffield, UK;
7
Australia Lincoln University
Urbanisation can cause local and sometimes global
extinction of plant species. Using a plant functional trait
approach may help to distinguish species that persist in
39
urban areas from those that have become extinct. We
analyzed historical and recent survey data from 11 cities
from across the globe (Adelaide, Auckland, Chicago,
Hong Kong, Los Angeles, Melbourne, New York, San
Diego, San Francisco, Singapore, Worcester) using
hierarchical logistic regression models. Data were
obtained for habitat and the following plant traits: growth
form, clonal spread, dispersal mode, nutrient uptake
strategy, spinescence, pollination system, photosynthetic
pathway, plant height and seed mass. We then combined
the results using meta-analysis to look for common and
differing responses to urbanization. The proportion of
native species that became locally extinct varied
substantially among the 11 urban areas, ranging from less
than 1% in San Diego to nearly 28% in Singapore. Five
urban areas had extinction rates of less than 0.05%
species per year, which made identifying clear correlates
of extinction in noisy data difficult. For these cities there
appear to be no consistent determinants of extinction
outcomes and chance and idiosyncratic factors may
overwhelm any trait-extinction patterns. Six cities
(Auckland, Chicago, Melbourne, New York, Singapore
and Worcester) had extinction rates that exceeded 0.1%
species per year which provided more power to detect
patterns. In these cities both seed mass and height were
strongly associated with extinction with small seeded,
short plants consistently more likely to become extinct.
Given that plants in urban environments face a similar
suite of filters that would be expected to select for certain
traits the lack of strong and consistent patterns across
cities suggest other factors such as initial abundance or
preferential habitat loss may be more important drivers of
urban plant extinction than plant traits.
The phylogeny of plant extinctions in Melbourne,
Australia
Hahs, A1, 2, Stajsic, V3, Udovicic, F3, Dobbs, C3,
McDonnell, M3
1
Australian Research Centre for Urban Ecology, Royal
Botanic Gardens Melbourne, Australia; 2School of
Botany, The University of Melbourne, Australia;
3
National Herbarium of Victoria, Royal Botanic Gardens
Melbourne, Australia
Over half the world’s human population now lives in
cities and towns. If we wish to maintain biodiversity
within these urban areas, it is important to begin
developing a stronger understanding of how the impacts
of urbanisation affect the indigenous biota of these
regions. Over the past 165 years, Melbourne, Australia
has grown from a small village to a city of 4 million
people. This development has not occurred without
consequences for the indigenous plants of the area, with
the native plant communities (Ecological Vegetation
Classes; EVCs) now represented by only 4 to 20% of
their original extent. Associated with this loss of habitat
has been the local extinction of fewer native plants that
would be predicted by a species area curve. Recent
research suggests that Melbourne may be carrying an
extinction debt of 55% for its native plant species.
Examining the patterns of loss within the families and
genera of species that are already locally extinct may
provide some insight into which of the remaining plant
species may be most vulnerable to eventual extinction.
This research investigates whether environmental
40
filtering is acting on the flora of Melbourne, and if so,
which lineages appear to be more prone to extinction
than others. In addressing these questions we will be
building upon recent research examining variability in
extinction probabilities of Melbourne’s plant species in
different communities, and with different functional trait
characteristics. We hope by creating a stronger
understanding of the patterns of plant extinctions within
Melbourne we can facilitate the development of more
effective management and conservation strategies,
thereby ensuring a higher level of native biodiversity in
Melbourne than would otherwise be possible.
How lichen floras respond to urbanisation: a case
study
Blanchon, D1, Elliott, C1, Kooperberg, R1
1
Unitec Institute of Technology, Auckland, New Zealand
Lichens sensitive to air pollution have declined or
disappeared in many urban areas, with only pollutionresistant species remaining. Conversely, reduction in air
pollution, particularly sulphur dioxide, has led to lichens
recolonising some cities. In addition to reducing
pollution, many urban authorities are making efforts at
restoring natural habitats. Lichens are usually not
considered in ecological restoration, despite being an
important part of ecological functioning, providing food,
habitat, and in cyanobacterial lichens, nitrogen. Lichens
often appear to have poor diversity in replanted areas,
despite appropriate substrate tree species being present.
Auckland is a city centred on an isthmus on the North
Island of New Zealand. The urban area covers around
500 km2 of a much larger (c. 6 000 km2) region which
includes agricultural and horticultural land, urban areas,
parkland of relatively unmodified native forest, and
basaltic volcanic cones and lava flows. Knowledge of the
original vegetation cover is based on a few remaining
urban fragments, relatively intact regional parks,
herbarium records and historical accounts. This
information is used to inform ecological restoration.
Originally it is thought there would have been areas of
kauri (Agathis australis) and mixed broadleaf–podocarp
forest, coastal broadleaf forest dominated by pohutukawa
(Metrosideros excelsa), broadleaf lava forest and some
wetlands. The original vegetation of the isthmus and
surrounding areas have been modified by c. 700 years of
human habitation, particularly forest clearance and
replacement with non-native tree species. Many of the
volcanic cones and lava flows have been quarried or are
now covered in grasses and exotic trees. Lichens are a
very visible component of the Auckland landscape, but
there is no published information available on the
original lichen flora of the Auckland area, or how lichens
may have been affected by habitat loss or air pollution.
This project aims to identify reference ecosystems for
urban Auckland, with a particular focus on corticolous
lichens of lowland/coastal forest and saxicolous lichens
on basaltic lava flows by examining and recording the
lichens of relatively untouched areas in the nearby
Waitakere Ranges and lava flows such as those of
Rangitoto Island and the Otuataua stonefields. These
reference ecosystems will then be compared with a range
of datasets from Auckland, including four ‘BioBlitz’
studies of urban forest remnants and parks, in
combination with surveys of the lichens of urban exotic
street trees, restoration plantings of native trees and rock
walls to investigate the effects of urbanization on the
lichen flora of Auckland. Initial results suggest that
although high light/edge species are common in urban
Auckland and are able to colonise a range of planted
native and exotic street trees, the lichens adapted to low
light conditions and higher humidity (forest interior) are
rarely found in urban settings. Most of the lichen species
found on lava flows are still present in urban areas on
rock walls.
Assessing exotic and invasive plant species of Pune
urban area (India)
Mahajan, D1, Patil, A2, Waman, M3
1
Dept of Botany, Waghire College, Saswad, Pune, India;
Dept of Botany, Dr D.Y. Patil College, Pimpri, Pune,
India; 3Board of College and University Development,
University of Pune, India
2
Any change in floristic composition is bound to alter the
primary productivity of plant species on spatio-temporal
scale. Therefore, investigation of exotic species has
become an imperative issue as invasion is considered a
serious ecological and socio-economic problem in the
Indian subcontinent and also at a global level. The aim of
this study was to document the composition of exotic and
invasive plants of the Pune urban area (India). All habit
forms including trees, shrubs, palms, herbs and climber
species are taken into consideration. The field surveys
revealed that the number of alien/exotic or introduced
species has increased considerably in Pune urban area.
They were introduced initially for ornamental purpose.
Out of total exotic species the trees represented 31%,
shrubs 32%, herbs 19%, climbers 10% and palms 8%.
These alien species were surveyed and documented with
respect to their place of origin, habit, flowering and
fruiting period, mode of propagation, and family along
with the socio-economic and ecological relevance of the
few species. Out of the total exotic species reported, the
American species (40%) seems to be dominating
followed by Australia (16%). The species from China,
West Indies and Japan represent 7% each; Africa and Sri
Lanka 6% each, Burma 5%, Malaysia 4% and Iran 2%.
The proportion of invasive species was 18% and that of
non-invasive species was 82%. However, occurrence of
too many exotic species and their naturalization cannot
be considered safe for native and endemic flora,
especially for a region like Pune, which is in close
vicinity to the globally considered biodiversity 'hotspot'
belt i.e. Western Ghats. Although exotics are generally
considered harmful, they do sometime play a beneficial
role in ecological restoration, soil conservation and in
generating new economic benefits. Field surveys and
investigations reveals that deliberate introduction of a
few exotics like Eucalyptus sp., Casuarina, Leucaena
leucocephala, Prosopis juliflora has significantly catered
to the demand of fuel, fodder and timber. Exotic species
like Callistemon lanceolatus, Cassia sp., Acacia
auriculiformis, Gliricidia sepium and Bougainvillea sp.
have contributed largely to the aesthetic beauty of the
region. Species like Jacaranda mimosifolia, Delonix
regia, were also reported as dominant ornamental species
in parks and gardens. The gymnospermous exotics like
Araucaria sp., Cycas revoluta, Cycas circinalis, Thuja
compacta and Cupressus sp. grow luxuriantly without
disturbing the native flora. However, some herbaceous
(Parthenium hysteriphorus, Cosmos sp., Cassia
uniflora), shrubby (Eupatorium sp., Lantana camara)
and tree exotics like Leucaena leucocephala, Prosopis
juliflora, etc., have turned harmful for mankind and its
invasion and aggressiveness has caused ecological havoc
to indigenous floristic composition. Xanthium indicum
and Argemone mexicana have also created ecological
problem. Parthenium hysteriphorus and Lantana camara
were found to cause many allergic problems. These
exotics have been naturalized and were distinguishable
from the local flora only by their known history. Since
the Pune urban area is located on the fringes of Western
Ghats, which is a biodiversity hotspot, introduction of
alien plant species may become harmful to local species.
Eukaryotic algae colonizing building surfaces in the
temperate zone – unexpected biodiversity and
ecomorphological approach
Hofbauer, W1, Gärtner, G2, Rennebarth, T1, Breuer, K1
1
Fraunhofer-Institute for Building Physics, Holzkirchen,
Germany; 2Innsbruck University, Dept for Botany,
Austria
From the humid tropics it is known that aerophytic
Cyanoprokaryota form a substantial part in the
colonization of building surfaces in urban areas whereas
in temperate regions eukaryotic algae, especially
Chlorophytes, are prominent on this surfaces. At the
Fraunhofer-Institute for Building Physics, Holzkirchen
(Germany) and at the Botanical Institute of the
University of Innsbruck (Austria), primary microbial
colonization of modern building surfaces was
investigated and its biodiversity and taxonomy studied in
cultures completed by physiological and genetic
methods. Taxonomic investigations of the primary
biological succession on the outer surface of buildings
showed an unexpected rich biodiversity. The results
listed in total more than 75 different species of algae
(Cyanoprokaryota and eukaryotic algae), apart from
fungi, bacteria, lichens and animal organisms (in total
more than 180 species), which are maintained mainly in
cultures. About 20 algal species have been identified for
the first time as components of the primary biological
succession of biological crusts on buildings. Apart from
the identified species, some need further investigation
and some were found to be new species. Among them,
for instance, a very peculiar species of Xanthophyceae
has been isolated which appeared as an unknown species
of the genus Excentrochloris. Within the last few years
some new genera and species of eukaryotic algae have
been described from various habitats. However it is
surprising that even on the surface of modern buildings
hitherto unknown species were found. The biodiversity
of algae appearing on buildings is composed of different
special
adapted
eco-forms.
According
to
ecomorphological characteristics of the principal life
form seven main units (groups, clusters) of aerophytic
pioneer algae at building surfaces in the temperate region
could be outlined. Unit 1 consists of unicellular forms.
This group may be divided into several sub-groups
according to morphological features as form of cell,
structure of cell wall, form and number of chloroplasts
and ecological characteristics like light dependency or
surface preference. Unit 2 is characterized by unicellular
41
forms enclosed within a shell. This group mainly is
connected to rather moist surface conditions. Unit 3
comprises ecomorphologies with cells embedded in a
gelatinous matrix. Unit 4 is represented by forms with a
sarcinoid cell organisation and different drought
resistance. Unit 5 treats unbranched filaments which
sometimes may disintegrate to single cells. This group
can be further organized according to nutrient
requirements. Unit 6 treats with algae that form branched
filaments. Unit 7 comprises macroscopic folious thalli.
Members of Trebouxiophyceae are predominant in
several groups since this taxon shows a preference for
aerophytic habitats. Many of the recorded algae are also
known as phycobionts of different lichens. In a later
stage of succession the presented units may also
represent different vegetation communities, depending on
prerequisites of substrate, microclimate (nanoclimate)
and nutrient-supply.
Sym020: Phenotypic plasticity in a changing
climate – 29 July
Plants and global change: the ubiquity of plasticity
Valladares, F1, Nicotra, A2, Gianoli, E3
1
CSIC, Madrid, Spain; 2The Australian National
University, Canberra, Australia; 3Universidad de la
Serena, Chile
When plants are exposed to changing environments they
exhibit a range of phenotypic changes involving a
plethora
of physiological,
developmental
and
reproductive traits. These changes have consequences not
only for the performance of individual plants but also for
biotic interactions and ecosystem functioning. Efforts of
classifying plants according to their functional traits are
challenged by the importance of adaptive plasticity for
plant fitness because variation in a trait can be
functionally as important as its mean, characteristic value
(or even more). Efforts of predicting future distribution
of plants under different climatic scenarios are
challenged by the capacity of plants to accommodate to a
range of conditions by means of phenotypic plasticity.
Efforts of understanding trait mediated interactions are
challenged by the fact that trait values can vary and thus
the intensity and even the sign of the interaction can vary
accordingly. Phenotypic plasticity is commonplace for
sessile organism such as plants as a way to cope with
changing environments. And phenotypic plasticity is
equally ubiquitous in the research of plant responses to
global change. But we are just beginning to grasp the role
of plasticity not only in changing but also in real,
complex scenarios of interacting factors and species.
Modelling exercises of the outcomes of species
interactions and of species distributions under different
climatic scenarios are hampered by the lack of progresses
in this direction. We argue that progresses can be
achieved by two complementary approaches: i)
compiling available information and explore general
trends that could be used both to model plant responses
and to plan experiments and specific research, and ii)
integrating conceptual approaches from different
disciplines where plasticity is relevant (e.g.
ecophysiology, evolutionary ecology, biogeography,
42
community ecology), which could enhance our
understanding of the overall impact of plasticity for
ecological and evolutionary processes involved in coping
with global change. We discuss potential avenues for
fruitful collaborative research illustrating these two
approaches with representative examples.
Mechanisms of phenotypic plasticity and rapid
evolution in novel and changing environments
Richards, C1, Schrey, A1
1
Dept of Integrative Biology, University of South Florida,
Tampa, FL, USA
Understanding the mechanistic basis of phenotypic
plasticity has long been of interest to evolutionary
ecologists. While our understanding of the translation
from genotype to phenotype is still in its infancy, most
researchers across diverse fields can agree that the ability
of an organism to express plasticity in a given trait must
be mediated at the molecular level. Several well
described environmental signaling pathways and
regulatory processes in particular are amenable to
experimental manipulation, and may lead to important
predictions about phenotypic response to changing
climates. Still, teasing apart the contributions of DNA
sequence level polymorphisms from the ability of the
same genotype to produce multiple phenotypes will
remain a challenge. Invasive species may offer a unique
opportunity for understanding the mechanisms
underlying phenotypic plasticity given the reduced
genetic variation following what is typically a population
bottleneck effect of invasion. While the classic
assumption is that dramatically reduced genetic variation
will severely constrain evolutionary potential, a growing
number of studies have found that many plant invaders
are successful, and can even colonize new habitats with
low DNA sequence based diversity. In fact a recent
survey of 80 species of plants reported that surprisingly
large losses (up to 50%) of heterozygosity compared to
source populations do not necessarily translate into a loss
of phenotypic variation. The Japanese Knotweed
invasion of the northeastern part of the United States
provides a good example. We used AFLPs to document
very low or no DNA sequenced based diversity in
phenotypically diverse populations of Japanese knotweed
growing in roadside, beach and salt marsh habitats.
Using classic greenhouse and reciprocal transplant
studies, we described high levels of plasticity and
persistent differences in plasticity for most traits and
fitness, as well as significant differences in phenotypic
response to the three environments. We also found strong
evidence of differentiation among populations. Given the
low level of AFLP diversity, these studies highlight the
possibility that phenotypic differences can contribute to
establishing in novel environments and that these
differences are heritable, despite low measurable DNA
sequence based diversity. Recent studies show that
heritable phenotypic differences may also arise from
epigenetic effects and several authors have argued for the
potential importance of epigenetic effects for studies in
ecology and evolution. Epigenetic effects have been
shown to play a role in response to hybridization and
exposure to stressful or novel environments, which are
circumstances often experienced by invasive plants.
Using methylation sensitive AFLP, we present evidence
that epigenetic diversity within and among Japanese
knotweed populations is much higher than DNA
sequence based diversity and suggest that these
differences could indicate an epigenetic source of the
phenotypic differentiation found in these as well as other
invasive plants.
Rapid evolution of adaptive plasticity to future
environments in an invasive plant
changes such as the novel environments being created by
global climate change.
Phenotypic plasticity across rainfall gradients: a case
study using a congeneric Erodium species pair
Davidson, A1,2, Sheppard, A2, Nicotra, A1
1
2
Sultan, SE1, Horgan-Kobelski, T1
1
Biology Dept, Wesleyan University, Middletown, CT,
USA
As climate and CO2 conditions quickly change, it is
crucial to understand the potential of plant species to
adapt to these changes. Rapid evolution of adaptive
phenotypic plasticity can allow plants in natural
populations to maintain fitness in the face of novel
environmental conditions. Our recent work has
demonstrated this kind of rapid evolutionary change of
phenotypic expression in populations of the Asian shade
annual Polygonum cespitosum from its introduced range
in northeastern North America. In a series of glasshouse
growth experiments, we tested genotypes sampled from
the same three populations in 1994 and again in 2005 to
track recent adaptive evolution of this invasive annual
species. In only 11 generations of natural selection,
genotypes from these P. cespitosum populations have
evolved changes in physiological and morphological
plasticity that are associated with increased plant fitness
in high light conditions. These changes in plasticity are
consistent with the very recent spread of the species into
more open sites in its introduced range. It is particularly
critical to know whether plants can maintain growth and
fitness in the entirely novel environments that are
predicted to arise through global climate and CO2
change. Future environments within the North American
range of P. cespitosum are expected to include high light,
greater heat, drought stress, and elevated carbon dioxide
concentration. We studied the plastic responses of P.
cespitosum genotypes to these stresses in a manipulative
field experiment at the University of Illinois Free Air
CO2 Enrichment site (SoyFACE). As in the previous
studies, we studied genotypes from the same three
natural populations sampled in 1994 and again in 2005 to
determine the effect of recent adaptive evolution on
plasticity to these novel conditions. We measured
physiological, leaf anatomical and life-history responses
of these genotypes to two predicted future environments.
Both experimental field environments were hot, dry and
in full sun, but one included the elevated CO2 level
predicted to occur by the year 2060.
Our findings reveal several potential limits to plant
success in future environments, even in an evolutionarily
labile species such as this invasive annual. First, our
results show that North American populations of P.
cespitosum have rapidly evolved to increase
photosynthetic rate and delay senescence under full-sun,
dry conditions. However, this adaptive plasticity was not
expressed in the elevated CO2 treatment. Second, the
populations differed markedly in reproductive output in
these novel, stressful, conditions, as well as in genetic
potential for further adaptation. This result suggests that
only certain populations of a species may possess the
evolutionary potential to cope with rapid environmental
Australian National University, Canberra, Australia;
CSIRO, Canberra, Australia
Phenotypic plasticity is frequently referred to as playing
an important role in plant invasions and in coping with
environmental heterogeneity. It is also increasingly
mentioned as one means by which plants, in particular,
may cope with climate change. We assess plasticity in a
model species pair: Erodium cicutarium, an invasive, and
E.crinitum, an Australian native. The species grow along
a natural rainfall gradient and seed was collected from
dry and wet ends of the range. A greenhouse experiment
with five different water availabilities was conducted to
assess plasticity across the full environmental gradient.
Over 30 different physiological, morphological, growth
and phenological response traits were measured. We
assess selection for different trait values across the water
availability gradient and compare these with patterns of
plasticity for each of the species and populations.
Evidence of both local adaption and phenotypic plasticity
were discovered in response to water availability. The
importance of plasticity and its adaptive value often
differed between populations from different native
rainfalls. In particular physiological characteristics such
as water use efficiency (WUE) and stomatal conductance
varied greatly in their plasticity between populations and
was only sometimes adaptive. The implications of these
findings for the species under climate change will be
discussed.
Plastic and adaptive response to climatic gradients in
Waratahs (Telopea; Proteaceae)
Rymer, P1T, Offord, C1, Allen, C1, Weton, P1, Tissue,
D2, Rossetto, M1
1
2
The Royal Botanic Gardens Sydney, Australia;
University of Western Sydney, Hawkesbury, Australia
Climate change is predicted to be the biggest threat to
biodiversity. Current models of the impact of climate
change on plant species do not adequately account for
resilience, dispersal and adaptation, and are therefore
misleading for biologists and managers. Investigations on
common species across environmental gradients can
provide insights into historical patterns and capacity to
respond to future environmental change. The distribution
of NSW Waratah (Telopea speciosissima) across a strong
climatic gradient, and the availability of relevant
background research, makes it an excellent system to
explore the relative importance of phenotypic plasticity
and adaptive evolution to changing climate. Nuclear
microsatellite, morphological variation and climate
modelling indicate coastal and upland populations have
differentiated over evolutionary time scales with
fluctuating levels of connectivity during Quaternary
climatic cycles. We investigated how the seed
germination, seedling establishment, and time of
flowering of coastal and upland populations respond to
43
climatic variables in field, common garden, and
laboratory experiments linked to RNA-sequencing.
Germination shows a plastic response with most events
taking place across a range of temperatures (>80% 10–
30˚C). However, a significant differential population
response to temperature cues is suggestive of weak
adaptive evolution. A pattern supported by a reciprocal
transplant experiment (RTE) of seed. Seedling growth
and survivorship was explored in the field RTE and in
glasshouses manipulating carbon dioxide concentration,
temperature and water availability. Coupled with
characterisation of morphological traits and cell structure
the findings of this experiment provide insights into
adaptive plasticity. Flowering in natural populations is
separated by up to 8 weeks between the coast and
uplands. In a common garden, the pattern flattens but the
sequence of first flowering is retained with flowering of
coastal followed by upland plants. Flowering is strongly
genetically controlled requiring 10 days above 20˚C
(limited plasticity); however, weak differential adaptation
is suggested among populations at either end of the
environmental gradient. Utilising NGS Illumina
platform, a comparative transcriptomic analysis of
populations (coastal, uplands), organs (floral bud,
germinated seed), and conditions (10˚C, 30˚C) was
performed. Variation in gene expression levels and
signatures of selection in coding sequences was revealed.
Functional annotation of transcripts was facilitated by the
strong link with experiments (genotype–response–
transcript). The final analysis will provide detailed
information on the capacity for germination and
flowering to change through phenotypic plasticity and
adaptive evolution. The applied (robust predictions of
population resilience to future climate scenarios) and
theoretical (relative importance of plastic and adaptive
response) will be discussed.
Below-ground stress communication in plants
Novoplansky, A1, Falik, O1
1
Ben-Gurion University of The Negev, Israel
One of the main limitations of phenotypic plasticity is the
lag between the perception of the environment and the
time the products of the plastic responses are fully
operational. Accordingly, selection is expected to
promote responsiveness to cues that bear information
regarding probable future conditions. We tested the
hypothesis that plants are able to perceive cues of
anticipated stress by eavesdropping on their stressed
neighbors. Plants were grown so their roots shared their
rooting volume with the roots of different neighbors.
Unstressed target plants rapidly closed their stomata
following drought induction of their neighbors but no
such communication took place when the roots of the
stressed and the target plants did not share rooting
volumes, demonstrating that the stress cues were
communicated amongst roots rather than shoots.
Furthermore, shortly after the drought induction, more
remote unstressed target plants, which did not share their
rooting volume with the stressed plant also closed their
stomata. The results demonstrate a novel type of
communication whereby unstressed plants not only
eavesdrop on their stressed neighbors but also leak
warning signals which are perceived by additional
unstressed plants. The results may have significant
44
implications for our perception of the functional
organization of plant populations and communities.
Sym022: Polar and alpine plants: coping
with extreme and changing climates –
28 July
Desertification of Antarctic terrestrial communities
provokes rapid community change
Robinson, SA1, Wasley, J2, King, D1, Turnbull, JD1,
Ryan-Colton, E1, Mullany, K1
1
Institute for Conservation Biology and Environmental
Management, University of Wollongong, Wollongong,
Australia; 2Environmental Protection and Change;
Australian Antarctic Division; Dept of Sustainability,
Environment, Water, Population and Communities;
Kingston, Australia
Climate change is predicted to affect high latitudes first
and most severely, and major changes in temperature,
wind speed and stratospheric ozone have already been
observed in Antarctica. Corresponding changes in
vegetation have already been documented in maritime
Antarctica, where temperature changes have been
particularly pronounced. For the remainder of the
continent, vegetation changes have yet to be reported,
and the Intergovernmental Panel on Climate Change
therefore recommended improved monitoring and
analysis of long-term data sets in 2007 (Anisimov et al.
2007). However, changes in temperature have also been
less severe on the continent and, given the slow growth
rates of the vegetation, expectations were that change
might therefore be difficult to detect. Here we report the
first results from a long term monitoring study
established in 2003 to assess changes in vegetation in the
Windmill Islands region of East Antarctica. This area,
close to Casey Station, is a biodiversity hotspot for
Antarctica, supporting some of the best-developed and
most extensive plant communities on the continent. Our
study monitors vegetation along a moisture gradient at
two sites, transitioning from bryophyte to lichen
domination with increasing aridity. Fine scale analysis
shows that relative abundance of several key components
of the ecosystem changed between 2003 and 2008.
Evidence that this is part of a long-term transition
associated with changing water availability will be
presented. Our results suggest that Antarctic terrestrial
communities may be responding to climate change much
faster than previously predicted, raising concerns for
these old growth moss forests.
Vulnerability of Antarctic mosses to freezing injury
with climate warming
Lenne, T1, Egerton, J1, Bryant, G2, Robinson, S3,
Bergstrom, D4, Ball, M1
1
Australian National University, Canberra, Australia;
3
RMIT,
Melbourne,
Australia;
University
of
Wollongong, Wollongong, Australia; 4Australian
Antarctic Division, Kingston, Australia
2
Productivity of mosses in Antarctica is restricted to a
short growing season limited by freezing temperatures
and the availability of liquid water. Analysis of the
responses of mosses from three genera to freezing
temperatures revealed interspecific differences in ice
nucleation temperatures and tolerance of freeze-induced
dehydration consistent with hydraulic anatomy and
distribution along moisture gradients. During summer
conditions, exposure to dehydrating effects of external
ice is generally sufficient to limit vulnerability to
intracellular freezing. Similarly, dehydration protects
over-wintering mosses from intracellular freezing when
ice nucleation temperatures of fully hydrated tissues
remain well above ambient winter temperatures.
However, the mosses can become vulnerable to freezing
injury when rehydration during unseasonal warming
events is followed by rapid return to low winter
temperatures, as occurred during the winter of 2009.
Thus, climate warming may extend the growing season,
but paradoxically, increase potential injury from freezing,
contributing to rapid change in the distribution and
composition of moss vegetation.
Toasting plants: how extreme winter warming events
may reverse the greening of the Arctic
Phoenix, G1
1
University of Sheffield, UK
The Arctic is experiencing greatest warming in winter
and a greater frequency of extreme climatic events, yet
the impacts of winter climatic change and extreme events
have been little studied. Of considerable concern are
extreme winter warming events, during which
temperatures increase rapidly causing snowmelt at
landscape scales and subsequently exposing ecosystems
to unseasonably warm temperatures. Following warming,
ambient cold winter temperatures can return rapidly,
exposing vegetation and soils to extreme cold due to the
absence of the insulating snow layer. Here we report
consistent findings from both a field simulation study
and a natural event that show major damage to plant
communities occurring at landscape scales resulting from
extreme winter warming events. Extreme winter
warming events were simulated in sub-Arctic heathland
using heating lamps and soil warming cables. Warming
resulted in up to 21-fold greater frequency of dead shoots
and 47% less shoot growth of the dominant dwarf shrub
Empetrum hermaphroditum. This damage was strikingly
similar to that observed following a real extreme winter
warming event that occurred in December 2007. In the
growing season following this event, dead dwarf shrub
vegetation could be observed over large areas. Ground
measurements revealed 16 times greater frequency of
dead shoots and 87% less summer growth of E.
hermaphroditum in visibly damages areas compared to
neighbouring undamaged areas. Satellite-derived
Normalized Differential Vegetation Index values (a
proxy for leaf area or photosynthetic capacity) confirmed
the landscape extent of this damage and showed a
considerable 26% reduction in NDVI over an area of
1424 km2. With increasing winter temperatures predicted
along with a greater frequency of extreme climatic
events, these findings suggest major consequences for the
productivity and diversity of arctic ecosystems.
Critically, the damage from these winter events is
opposite to the shrub expansion and greening of parts of
the arctic currently attributed to summer warming. Given
that the arctic is warming more in winter than summer,
these impacts place a significant challenge in predicting
the future of arctic vegetation in a warmer world.
Responses of boreal dwarf shrubs to changing snow
conditions – a snow manipulation experiment
Saarinen, T1, Rasmus, S1, Lundell, R1, Åström, H1,
Hänninen, H1
1
University of Helsinki, Finland
Snow is known to have a major impact on vegetation in
arctic and alpine ecosystems, but little is known about
how snow affects plants in boreal forests, where the
snowpack is uneven because of the tree canopy. The
responses of two ericaceous dwarf shrubs, the evergreen
Vaccinium vitis-idaea (lingonberry) and the deciduous V.
myrtillus (bilberry), to changing snow conditions were
studied in a boreal coniferous in southern Finland. The
following manipulations were carried out on 1 m2 sample
plots: (1) partial removal of snow to 15–20 cm; (2)
addition of snow (the amount added was equal to the
amount removed in the first treatment); (3) compression
of snow to 20 cm; (4) formation of an artificial ice layer
by adding distilled water on the plots. The manipulations
were maintained through the winter and the
ecophysiological and phenological responses were
recorded. Additionally, the diurnal variation of CO2
exchange in lingonberry leaves was estimated in late
March at the time of maximum snow depth. The thermal
environment of the overwintering shoots differed
substantially among the treatments. Both partial removal
and compression of snow increased the occurrence of
low-temperature extremes. No significant differences in
winter damage, as assessed by the electrolyte leakage of
the leaves (lingonberry) or shoot tips (bilberry), were
recorded among the manipulations. However, partial
removal of snow resulted in decreased Fv/Fm ratios of
chlorophyll fluorescence in the leaves of lingonberry,
which indicates increased winter stress under a thin layer
of snow. Like in our previous studies, lingonberry
retained its photosynthetic capacity through the winter.
The diurnal course of CO2 exchange, estimated at the
time of maximum snow depth, showed that net gain of
CO2 was achieved at noon on all the manipulation plots
excluding those of snow addition, where the intensity of
PAR remained low through the day. When integrated
over the whole day, the subnivean photosynthesis
compensated for a substantial proportion of the
respiratory CO2 losses. On both density increase and
control plots, the compensation percentage was 50. The
lowest percentage of compensation was calculated for the
addition plots (15 %) and the highest percentages for the
density increase and partial removal plots (72% and 80%,
respectively). Snow melted on the partial removal plots
on 14 April and on the addition plots on 25 April. The
subsequent phenological development of lingonberry
showed no significant differences among the treatments.
Bud burst occurred on 7 May and the new leaves
completed their unfolding by 1 June. The timing of
phenological events in bilberry showed small but
significant differences among the treatments. Bud burst
occurred two days earlier on the addition plots than on
partial removal plots. Comparable differences were
45
observed in the timing of leaf unfolding and the
beginning of flowering. In conclusion, the present study
shows species-specific responses of boreal plants to
changing snow conditions. Both the thickness and
physical properties of snow, both of which are expected
to change due to global warming, affect the
overwintering success and photosynthetic performance of
plants and, to lesser extent, the phenological
development.
Australian alpine seed germination strategies
Hoyle, G1, Steadman, K2, Good, R3, McIntosh, E1,
Nicotra, A1
1
The Australian National University, Canberra,
Australia; 2University of Queensland, St Lucia,
Australia; 3Australia National Botanic Gardens,
Canberra, Australia
Successful plant reproduction via seed is closely
associated with the seasonal timing of germination,
influenced most significantly by temperature, soil
moisture and light. Timing of germination dictates a
seedling’s seasonal experience and thus has strong fitness
consequences. Physiological dormancy mechanisms are
one way seeds control the timing of germination, often
postponing germination until a time when the emerging
seedling has optimum chances of survival, despite
dispersal into pseudo-favourable conditions. We
investigated the germination strategies of 24 Australian
tall alpine herb field species, spanning 11 families.
Further we examined the composition of the soil seed
bank and the prevalence of dormancy in those species.
Here we present the evident range of germination
phenologies throughout Australian alpine flora, in
relation to plant and seed traits, and the potential
consequences of a warmer, drier future climate on the
optimisation of seedling establishment in the Alps.
Determining when seeds will germinate in the field
contributes to our understanding of fundamental
processes of population establishment, range expansion
and geographic spread in order to estimate the resilience
of plant and plant communities to future climate
scenarios.
Sym023: Environmental effects of
ultraviolet radiation on terrestrial
ecosystems – 26 July
Current status and future predictions of UV radiation
and climate change interactions
Bornman, JF
1
1
University of Waikato, New Zealand
A depleted stratospheric ozone layer (10–50 km above
the Earth’s surface) has caused concern in the last few
decades because of ozone’s important UV-filtering role.
In particular, the UV-B portion (280–315 nm) of the
sun’s spectrum is most affected by small changes in
stratospheric ozone and thus any decrease in this UVabsorbing layer has implications for the environment and
living organisms. With the successful adoption of the
46
Montreal Protocol for phasing out production of ozonedepleting substances a catastrophic situation has been
prevented where the UV Index, or sunburning UV
radiation, could have tripled by 2065 at mid-northern
latitudes (Newman et al. 2009). However, because of the
long life-times of the ozone depleting substances, there
are projected lag times for stratospheric ozone recovery,
further complicated by a warming climate. Current
prediction for the return to 1980 levels of annually
averaged total column ozone at a global scale is between
2025 and 2040, while that for southern and northern midlatitudes is 2030–2040, and 2015–2030, respectively.
Over the poles, the prediction for the return to 1980
levels is between 2045–2060, and 2020–2035, for the
Antarctic (October) and Arctic (March), respectively
(Scientific Assessment of Ozone Depletion 2010). In
parallel with the projected recovery of stratospheric
ozone, UV irradiance will not necessarily follow this
recovery, but will likely be modified by other climateinduced processes such as changes in cloud cover,
aerosols, land-use (following, e.g., deforestation), and
decreasing vegetative cover from rising desertification in
certain regions. Changes in ozone also influence natural
and human-induced climate processes, and this is
resulting in complex feedback reactions not only on a
climate scale, but also on the affected ecosystems. The
challenge ahead in the endeavour to achieve a more
stable climate will involve addressing potential future
outcomes of the linkages between climate change and
ozone. These include not only the biophysical, but also
the political links between the Kyoto and Montreal
Protocols. There is increasing focus on modifications to
plant systems by UV radiation and the interactions of
different climate variables. This approach has widened
our perspective on the responses to multiple stresses.
Cross-tolerance to different stresses in plants reflects
some of the relationships among stresses that may lead to
resilience or increased sensitivity. Thus terrestrial
ecosystem response and functioning are being altered by
the complexity of the impacts and feedback processes of
climate change, and this is likely to intensify.
Consequently, the likely continuous evolving of plant
acclimation and adaptation strategies, or in some cases,
impaired functioning, underlines the importance of UV-B
radiation effects within the framework of a changing
climate. Regulatory and acclimative adjustments to
changes in UV-B irradiance include accumulation of
UV-screening compounds, induction of antioxidants,
stimulation of repair processes, as well as anatomical
modifications.
Environmental effects of UV radiation on terrestrial
ecosystems: cross-tolerance and ecological strategies
Hofmann, R1, Reichman, S2, Wong, C1, Stilwell, S1,
Campbell, B3
1
Faculty of Agriculture and Life Sciences, Lincoln
University, Canterbury, New Zealand; 2School of Civil,
Environmental and Chemical Engineering, RMIT
University, Melbourne, Australia; 3Plant & Food
Research, Mt Albert Research Centre, Auckland, New
Zealand
In their natural environment, plants are exposed to a wide
spectrum of environmental variables. This may include
peak levels of ultraviolet (UV) radiation in summer,
limited availability of water and nutrients, temperature
extremes, salinity, pressure from herbivory and diseases,
as well as other abiotic and biotic factors. While the
effects of these variables can impose considerable stress
on plants, frequently they can also contribute to crosstolerance. In this, one or more stress factor/s can render
plants more resistant to another stress factor. A particular
interest in our lab is the role of UV radiation in
aboveground – belowground stress interactions. In many
of these cases, flavonoids have been implicated as
biochemical mediators of cross tolerance. This can be
attributed to a wide array of functions for these
secondary plant metabolites, including UV-screening,
energy dissipation, antioxidant and herbivore-deterring
capacities, involvement in signalling and modification of
plant growth regulator functions. Here we use several
examples to illustrate the role of flavonoids in the
interplay of UV radiation with other environmental
factors in natural and agricultural ecosystems. Our
studies highlight the importance of UV radiation in
preconditioning plants to better withstand drought stress.
In turn, we also show the importance of drought stress
for mitigation of UV sensitivity, e.g. under elevated UV
radiation levels in a long-term pasture ecosystem study in
New Zealand. Plant strategy theory implies that species
investing constitutively into biochemical means of stress
protection (‘stress tolerators’) are likely to invest less
carbon into constitutive productivity. ‘Competitors’ are
plant species with the opposite strategy, usually showing
high levels of biomass productivity, but also higher stress
sensitivity. Our findings indicate that flavonoid
accumulation comes at a cost for productivity attributes
in white clover populations grown under New Zealand
outdoor conditions. We also present findings that show
an inhibitory role of UV-B radiation on important
belowground functions in wheat plants exposed to Fe
deficiency. Similarly, Fe-deficiency resulted in higher
UV-B-induced increases of UV-absorbing compounds.
Our findings are currently being implemented in
breeding programs for future cultivar development. In
conclusion, understanding the relationships of UV
radiation with other environmental variables will be
crucial in the context of global climate change, where
many of these interactions are likely to increase.
Increased exposure to UV-B radiation during early
development leads to enhanced photoprotection and
improved long-term performance of a model crop
species – the role of ultraviolet radiation in
sustainable crop production
Wargent, J1, Elfadly, E2, Moore, J2, Paul, N2
1
Massey University,
University, UK
New
Zealand;
2
Lancaster
Ultraviolet (UV) radiation is a significant environmental
factor, and the range of responses regulated by UV,
specifically UV-B radiation (290–320nm), is vast.
Historically, responses to UV radiation have been studied
largely due to concerns regarding stratospheric ozone
depletion, and there is marked current uncertainty
regarding the possible influence of global climate change
on local UV environments throughout this century.
Despite the fact that UV-B responses have typically been
considered to be damaging in nature, there are now good
indications that UV-B may act as a valuable tool to
enable exploitation of typical UV-B responses, leading to
beneficial changes in crop quality and yield. We have
evaluated such consequential changes in several crop
production systems, with subsequent increases in yield
observed in leafy vegetable crops following early-stage
exposure to UV-B, and a variety of casual mechanisms
are considered. The knock-on effects of manipulating the
UV environment for plant pathogens, herbivorous pests,
and other biotic and abiotic components which comprise
the majority of agroecosystems must also be considered
when appraising the effects of UV-B exposure within the
context of crop production. Increasing our understanding
of those inherent trade-offs between negative and
positive outcomes of exposure to sunlight for
agroecosystems as a whole can only strengthen our
ability to understand and predict UV-B response in plants
and related interactions in order to further consider the
now growing role of UV radiation as a regulator of crop
productivity.
Cell wall sunscreens: moss sends important message
about protecting against elevated UV radiation
Waterman, MJ1, 2, Smith, LB1, Keller, PA2, Robinsons,
SA1
1
1Institute for Conservation Biology and Environmental
Management, University of Wollongong, Australia;
2
Centre for Medicinal Chemistry, University of
Wollongong, Australia
Ceratodon purpureus is a cosmopolitan moss species that
can grow in harsh environments ranging from the icy
deserts of Antarctica to hot, dry and high ultraviolet (UV)
radiation Australian climates. High concentrations of
ultraviolet-B (280–320 nm; UVB) absorbing compounds
within the cell walls of Antarctic C. purpureus have been
identified as an important photoprotective mechanism
against damaging UVB radiation levels due to reduced
stratospheric ozone. These compounds allow this species
to be highly UV tolerant even whilst desiccated. We
aimed to determine 1) the specific chemical structure of
the cell wall UVB absorbing compounds in C. purpureus
and 2) whether their production was induced specifically
by UVB radiation. Using Australian C. purpureus as a
model system we show that mosses grown in low UV
environments (glasshouse conditions) have reduced cell
wall UVB screening compounds. Such moss samples
were then exposed to screening treatments that either 1)
blocked UVB only, 2) blocked UVA and UVB or 3)
transmitted 90% of solar radiation (including both UVA
and UVB radiation) for 12 weeks. Moss gametophyte
tissues harvested during this period were freeze-dried for
methanol and alkali hydrolysis extractions. These plant
extracts
were
analysed
using
UV-visible
spectrophotometry and analytical high pressure liquid
chromatography to monitor any change in total and
specific UVB absorbing compound concentrations. These
experiments show that the synthesis of cell wall-bound
UVB screens in Australian C. purpureus is induced by
UV radiation and that the time taken for UV induction
suggests this enhanced synthesis occurs as new cells
grow. This implies that these cell wall UVB screens have
a long-term protective role in this species. This role and
the structural elucidation of the cell wall-bound UVB
absorbing compounds that are specifically induced will
be discussed.
47
A meta-analysis of plant responses to UV-B radiation
exposure in polar regions
Newsham, K1, Robinson, S2
1
British Antarctic Survey, Cambridge, UK; 2Institute for
Conservation Biology, University of Wollongong,
Australia
Vegetation in polar regions is exposed to elevated
springtime UV-B radiation arising from stratospheric
ozone depletion, with possible consequences for plant
growth and ecosystem functioning. However, conflicting
data exist in the literature as to whether plants in polar
regions respond to UV-B exposure or not. In order to
arrive at a consensus for how plants in these regions
respond to UV-B exposure, meta-analytical methods
were used to analyse data from 34 field studies into the
effects of UV-B radiation on Arctic and Antarctic
bryophytes and angiosperms. The studies measured plant
responses to decreases in UV-B radiation under screens,
natural fluctuations in UV-B irradiance, or increases in
UV-B radiation applied from fluorescent UV lamps.
Exposure to UV-B radiation was found to increase the
concentrations of UV-B absorbing compounds in foliage
by 7% and 25% (expressed on a mass or area basis,
respectively). Exposure to UV-B radiation also reduced
aboveground biomass and plant height by 15% and 10%,
respectively, and increased DNA damage by 90%. No
effects of UV-B exposure were found on total carotenoid
or chlorophyll concentrations, photosynthetic parameters,
belowground biomass, total biomass, individual leaf
mass, total leaf area or specific leaf area (SLA). The
methodology adopted was found to influence the
concentration of UV-B absorbing compounds expressed
per unit of mass, with screens and natural fluctuations in
UV-B irradiance promoting significant changes in the
concentrations of these pigments, but fluorescent UV
lamps failing to elicit a response, raising concerns about
the use of fluorescent lamps in cold environments.
Greater reductions in leaf area and SLA, and greater
increases in the concentrations of carotenoids, were
found in experiments based in Antarctica than in those in
the Arctic. For all but one of the response parameters
(UV-B absorbing compounds expressed on an area
basis), bryophytes responded in the same way to UV-B
exposure as angiosperms. Regression analyses indicated
that the percentage difference in UV-B dose between
treatment and control plots was positively associated
with the concentrations of UV-B absorbing compounds
and carotenoids, and negatively so with aboveground
biomass, height and leaf area. By comparison with two
other meta-analyses of plant responses to UV-B
radiation, we show that the vegetation of polar regions
responds to UV-B exposure in a similar way to higher
plant-dominated vegetation at lower latitudes. In broad
terms, plants appear able to protect themselves from
elevated UV-B radiation by synthesizing UV-B
absorbing compounds, whilst aboveground biomass and
height are reduced by UV-B exposure, and DNA damage
is increased.
48
Sym024: Interactions between abiotic and
biotic stress – susceptibility of droughtaffected plants to pest and disease – 25 July
Drought effects on growth and physiological status of
trees
Veneklaas, E1
1
Plant Biology, The University of Western Australia,
Australia
Suboptimal water availability affects vegetative and
reproductive growth and causes significant changes in
chemical and physical properties of plant biomass. These
changes may make plants more or less attractive for other
organisms as a source of food, habitat, or other use. In
addition, drought affects plant defence mechanisms that
can control pest and disease. This paper will summarize
general responses of plants to drought that are likely to
affect associated organisms such as fungi and insects.
Water deficits result in reduced water status in plants,
which is usually expressed (relative to well-watered
plants) as reduced water content, lower turgor, more
negative water potentials, and higher osmotic values. The
significance of different aspects of water deficit depends
on the type of relationship between host plant and
pathogen or pest organism. For example, fungal
endophytes are embedded in the host and their water
status is closely coupled with that of the host. Leaf- and
stem-sucking insects are probably more affected by
hydrostatic pressures. Insects that eat whole leaves or
parts of leaves may not be as much affected by water
status. Insects that eat through wood have been reported
to prefer lower water contents. Low water availability
inevitably requires plants to reduce their water use.
Plants may reduce rates of transpiration by reducing leaf
area and/or controlling stomata. These responses differ in
their implications for the amount of leaf biomass present
and the rate of growth, but both will reduce whole-plant
productivity. Changes in leaf turnover and associated leaf
age structure can alter the nutritional value of the foliage.
Longer-term adjustments of plants to low water
availablity include anatomical changes. Trees produce
denser wood under drought and leaves become more
scleromorphous, and possibly less palatable. Shorterterm and more reversible effects of drought include
changes in chemical composition of tissues. Besides
dehydration-induced concentration effects, chemical
changes are due to changes in metabolism and transport
processes. Carbohydrates can accumulate or be depleted,
depending on severity and duration of stress, and sourcesink relationships. Certain organic and inorganic
compounds accumulate in leaves and roots in the process
of osmotic adjustment, aimed at maintaining turgor
despite dehydration. Nutrient concentrations may be
affected to a greater or lesser extent by drought,
depending on the relative magnitude of impacts on
growth and root nutrient uptake. Belowground effects of
drought are much less studied and probably more
variable than aboveground effects, even in terms of root
growth and physiology. Moderate drought can stimulate
root growth, whereas severe drought reduces it. Roots in
dry soil are architecturally, structurally and chemically
different from roots in moist soil. Soil fauna and
microbes that consume roots or have parasitic or
symbiotic relationships with roots are therefore affected
by changes in soil moisture. Methodological limitations
as well as the huge diversity and complexity of
belowground microbial and fauna communities will
continue to pose challenges to our understanding of host–
pathogen/pest relationships.
Environmental influences on
pathway in Forage Sorghum
the
cyanogenesis
O'Donnell, N1, Blomstedt, C1, Stuart, P2, Neale, A1,
Hamill, J1, Gleadow, R1
1
School of Biological Sciences, Monash University, Vic,
Australia; 2Pacific Seeds, QLD Australia
Sorghum is a C4 plant with high water use efficiency,
making it drought and heat tolerant. Forage Sorghum is
used widely in the dry tropics as fodder for cattle.
However it also produces the cyanogenic glycoside,
dhurrin, and when the plant tissue is disrupted hydrogen
cyanide (HCN) is released. It is thought that dhurrin may
be produced as a defence to herbivory. The HCN
potential (HCNp) of sorghum differs greatly between
varieties, and within a variety sorghum is subject to
spatial and temporal regulation. The HCNp of sorghum is
known to be affected by environmental factors including
drought, frost and soil fertility and varieties can differ
from one season to the next. Experienced farmers know
that young sorghum plants, or older plants that have been
subjected to drought, are often toxic and can kill cattle.
There are three key genes that catalyse the cyanogenesis
biosynthetic pathway in sorghum, two cytochrome P450s
(CYP79A1
and
CYP71E1)
and
a
(UDP)glycosyltransferase (UGT85B1). However, it is not
known how these genes are regulated. We have
conducted numerous experiments that have looked at the
accumulation of dhurrin in various parts of sorghum
plants subjected to certain stresses such as water stress,
high/low nitrogen and different hormone treatments. The
results have shown that the dhurrin concentration is
increased under water stress, high nitrogen and when
treated with some hormones. We have also look at
whether there is an increase in the transcript levels of the
three genes in the cyanogenesis biosynthetic pathway.
When interpreting the results we have tried to determine
if the increase in dhurrin concentration is due to a
reduction in plant growth or increase in activity of the
three biosynthetic genes, or both. These findings are
relevant to the efficient production and use of forage
sorghum for farmers globally.
Cadmium exposure modifies biotic and abiotic stress
signaling
pathways
in
the
cadmium
hyperaccumulator Thlaspi praecox
Llugany, M1, Martín, S1, Barcelo, J1, Poschenrieder, C1
1
Universidad Autónoma De Barcelona, Spain
Metal-based defense is among the most attractive
hypothesis concerning the evolutionary advantages of
metal hyperaccumulation in plants. Among the different
modes of action of metal defenses, the metal-therapy
hypothesis is based on the frequent observation that
hyperaccumulators, when grown with low metal supply,
usually are highly sensitive to biotic stress.
Overproduction of signaling molecules like salicylate, as
observed in a Ni-hyperaccumulating Thlaspi species, has
been proposed to render these plants insensitive to
infection signaling. In fact, biotic and abiotic stress
responses in plants share common signaling molecules
that can activate unspecific and/or specific defense
mechanisms. Such biotic and abiotic elicitors include,
among others, microbial cell wall molecules, compounds
present in herbivore oral secretions, molecules derived
from the mechanically or enzymatically damaged plant
cell walls, and certain heavy metals. Jasmonic (JA) and
salicylic acids (SA) are well-established components of
signal transduction pathways. These molecules can act
synergistically or antagonistically in the response to a
variety of stress factors, leading to fine-tuning of the
complex defense reactions. To further test the metaltherapy hypothesis in the heavy metal hyperaccumulation
phenomenon here we analyzed endogenous levels of
jasmonic and salicylic acid in T. praecox, a Cd
hyperaccumulator, exposed to different biotic and abiotic
stressors. Hydroponically grown plants treated or not
(control) with 50 µM Cd were exposed to different
stressors: snail herbivorism, mechanical wounding, and
infection by biotrophic fungus Erysiphe cruciferarum.
Endogenous levels of SA and JA were analyzed in leaf
extracts of stressed and unstressed plants by liquid
chromatography–electrospray ionization tandem mass
spectrometry system in multiple reaction monitoring
mode. Leaf SA levels in T. praecox were relatively high;
in the same range as those reported by others in Ni
hyperaccumulator T. goesingense. Both fungal and
herbivore attack enhanced SA production in control
plants. Cd supply alone tended to increase leaf SA levels,
while plants exposed to both Cd and fungal or snail
attack showed lower SA levels. Only when exposed to a
combination of mechanical wounding and Erysiphe
infection the high Cd-containing leaves showed enhanced
SA levels. Leaf JA concentrations were not enhanced by
Cd supply. This is in contrasts to the results in non
hyperaccumulating species reported by others. Fungal
infection and mechanical wounding tended to increase
JA levels both in controls and Cd-treated T. praecox
plants, while herbivore attack induced JA production
only in control plants with low Cd leaf concentrations. In
conclusion, high
Cd
leaf concentrations in
hyperaccumulator T. praecox hamper biotic-stress
induced SA production, while JA signaling is less
affected by Cd hyperaccumulation. To our best
knowledge this is the first report on the endogenous
levels of the stress signaling compounds JA and SA in a
Cd hyperaccumulator exposed to different biotic and
abiotic stressors. Our results support the view of a strong
influence of metal hyperaccumulation on SA signaling.
Acknowledgment: Supported by the Spanish Ministry of
Science and Innovation projects BFU2007-60332/BFI &
BFU2010-14873/BFI
Characteristics of drought-induced tree mortality and
the activity of woodboring insects in the northern
jarrah forest of Western Australia
Matusick, G1, Ruthrof, K1, Hardy, G1
1
Centre of Excellence for Climate Change Woodland &
Forest Health, Murdoch University, Australia
49
A persistent and long-term downturn in annual
precipitation accentuated by an historic drought is
thought to be the cause of a recent mass collapse of forest
canopy species on multiple, key sites in the Northern
Jarrah-dominated forest (approx. 10,500 km2). The
patterns of mortality were characterized using data
obtained from aerial sketch-mapping, aerial photography
and geospatial databases. High levels of mortality were
associated with shallow soils, which were determined by
distance from outcropping granite. Eucalyptus marginata
(jarrah), Corymbia calophylla (marri), Banksia grandis,
and Allocasuarina fraseriana (she-oak) have been
severely affected along with a host of understorey
associates. The prominence of woodboring beetle larvae
(Cerambycidae) feeding in the active sapwood and
cambium of affected jarrah and marri suggests the
potential for epicormic re-growth and survival is low.
These observations are exceptional considering both
jarrah and marri commonly prevent mass woodborer
attacks even while sustaining extensive crown dieback.
Given the exponential increase in woodborer populations
and the possibility of continued tree mortality, the
potential collateral effects on the jarrah forest will be
discussed based on examples from native woodborer
populations from Australia and around the world.
Sym025: Evolutionary ecology of
adaptation during plant invasion – 29 July
Fiendish flexibility: novelty and constraint in the
adaptive phenotypic plasticity of invasive plants
Rice, K1
1
University of California – Davis, California, USA
Very early discussions on the potential importance of
evolutionary processes in biological invasions included
the concepts of phenotypic plasticity and suggested that a
‘general purpose genotype’ strategy may represent an
important adaptive route for invasive species. Phenotypic
plasticity was considered to represent a key mode of
adaptation for species invading new ranges often
characterized by novel and highly variable selective
pressures. I will discuss some new modes of adaptive
plasticity in invasive plants, in particular, the potential
importance of trans-generational plasticity (also known
as maternal environmental effects) as a factor promoting
plant invasion into stressful or heterogeneous
environments. Trans-generational plasticity represents a
form of adaptive cueing and can affect traits ranging
from physiology to dispersal. As a counterpoint to this
discussion of the effectiveness of adaptive plastic
responses in invasive plants, I will also provide examples
of factors that constrain the expression of adaptive
plasticity. For example, within the invasive grass,
Bromus tectorum, genetic differentiation in phenology
reduces the capacity of certain ecotypes to respond in an
adaptively plastic manner to shifts in precipitation
regimes. I will also present results indicating a reduction
in physiological plasticity within populations of the
desert weed, Bromus madritensis ssp. rubens, that have
rapidly evolved lower rates of conductance in response to
elevated atmospheric CO2. I will also discuss how
phenotypic canalization, associated with stressful
50
maternal environments, may reduce the capacity of the
serpentine soil invader, Aegilops triuncialis, to respond
to selection. Finally I will discuss how the expression of
adaptive plasticity in the invasive legume Medicago
polymorpha may be amplified or constrained by variation
in its rhizobial symbiont.
Temperate
Asian
bamboos
lack
common
characteristics of plant invaders but not the potential
to invade
Mack, RN1, Smith, MC1
1
Washington State University, Pullman, USA
Bamboos play prominent roles in Asian coniferous
forests: persistent colonizers of sites after disturbance,
strong competitors for light and nutrients, a source of
seed and vegetative growth for predators and grazers, and
fuel for recurring fires. Montane coniferous forests in the
Western United States bear striking floristic and
physiognomic similarity to these Asian forests, although
these forests (and much of North America north of
Mexico) are devoid of native bamboos. The increasing
potential for frost-tolerant Asian bamboos to escape
cultivation and become naturalized and even invasive in
U.S. coniferous forests rises as their popularity grows in
ornamental horticulture. This potential occurs in spite of
characteristics of these grasses that do not fit the
common paradigm of invasive plants: each bamboo
species displays synchronous flowering, in which each
flush of flowering may be separated by many decades.
Persistence and local spread is then almost totally
dependent on vigorous vegetative growth. As a result,
genetic diversity in the introduced range is
extraordinarily low, with representatives of single clones
widely dispersed. In contrast, many bamboos possess
substantial phenotypic plasticity to shade, drought and
low temperature, thereby allowing them to occupy a
broad environmental gradient with little or no genetic
variation among individuals. Unresolved is whether their
infrequent opportunities for out-crossing, natural
selection and adaptive evolution will prove a severe
constraint as they encounter new predators, grazers and
especially parasites, while becoming much more widely
distributed in North America.
How does genetic variation change during biological
invasion? A study of Pinus strobus
Mandak, B1, Hadincova, V1, Mahelka, V1, Wildova, R1
1
Institute of Botany, Pruhonice, Czech Republic
Many alien species show a substantial time lag between
initial establishment and the appearance of strong
ecological impacts. Time lags can exist for both
ecological and evolutionary reasons. Basically two
scenarios could be taken into account. Firstly, a time lag
can result simply from the fact that a new alien species
requires time to disperse into favourable habitat patches
throughout the region and to build up populations
capable of producing abundant offspring. Secondly, an
initial population may lack evolutionary adaptations that
permit explosive population growth. After some period,
through genetic reorganization within a population, an
evolutionary breakthrough may occur, enabling the alien
to become an invasive species. We have tested
abovementioned hypothesis using North American tree
Pinus strobus invasive in the Czech Republic. We have
tested the differences in population genetic composition
between native and introduced populations and compared
genetic diversity among invasive and non-invasive
populations within the Czech Republic. The European
populations of Pinus strobus are more likely to be
derived from several regions in the native range. Further
analysis of population structure indicate that intraspecific
hybridization among genotypes from geographically
distinct regions of the native distribution range occurred
following colonization in the Czech Republic.
Ecological genomics of species invasions: identifying
adaptation, hybridization, and genetic tradeoffs in
invading lineages
Dlugosch, K1
1
University of Arizona, Tucson, USA
Two of the most commonly identified threats to plant
diversity are loss of habitat and invasion by non-native
species. While there are many clear and direct impacts of
habitat loss on species abundance, it is often less clear
why introduced plants become problematic for native
species. Invaders can seem to be competitivey superior
without displaying obvious trait differences from native
weedy species. One major explanatory hypothesis for
invasions is that invaders have evolved along fitness
tradeoffs that are common to all plants, gaining
competitive advantages at the expensive of other
functions not selected in their new environment (such as
defenses). An alternative (though not mutually exclusive)
hypothesis is that hybridization associated with species
introductions generates novel genetic benefits for
invaders. Together with my collaborators, my work is
aimed at evaluating the contributions of both adaptation
and hybridization to species invasions, using genomic
approaches to augment our understanding of the sources
of trait variation in plants.
In particular, we are currently using comparative
genomic techniques to identify traits and tradeoffs that
facilitate the establishment and superior growth of yellow
starthistle (Centaurea solstitialis), a noxious invader of
grasslands in Mediterranean climates. We are quantifying
fitness levels in response to various biotic and abiotic
environments, comparing expression level and genomewide sequence variation among native and invading
genotypes, and mapping the genetic basis of observed
evolutionary increases in growth rate. Integrating these
approaches, we show evidence for tradeoffs in fitness
between benign and stressful environments, identify loci
putatively under selection along these tradeoffs, and
discuss potential roles for admixture and cryptic
hybridization in this evolutionary change.
I also report on several methodological issues for which
we have released freely-available public software,
including the editing and assembly of next-generation
transcriptome (EST) sequence data, and the comparison
of genetic variation among outbred (wild) individuals
with incomplete genomic information.
The evolutionary dynamics involved during and
following colonization in an invasive plant (Silene
latifolia)
Wolfe, L1
1
Georgia Southern University, Statesboro, USA
The perennial plant Silene latifolia has emerged as a
model system for investigating the evolutionary
dynamics involved in biological invasions. This species'
post-glacial expansion involved both neutral and adaptive
evolution of life history traits along gradients of
environmental variation in its native Europe and
introduced North American range. Experimental
common garden experiments conducted on both
continents reveal that there has been an evolutionary shift
in life history traits with N. American plants expressing a
more aggressive phenotype with shorter lifespans
compared to populations in the native range. One
explanation for invasiveness is that selection resulting
from enemy escape favors a shift in investment from
defense to growth and reproduction. A large-scale survey
of populations across the species' European and N.
American ranges revealed that Silene has escaped a suite
of specialist enemies during colonization. Interestingly,
when N. American plants are grown in the native range,
they perform worse than their European conspecifics
indicating that adaptation to the introduced range has
occurred at the expense of performance in the native
range. Yet, in addition to the importance of natural
selection, aspects of Silene's colonization history suggest
that it is important to consider the role that genetic drift
may play in the evolution of novel phenotypes.
Molecular studies reveal the presence of genetic structure
in the native range and that both a bottleneck and founder
event occurred during colonization. These results hint at
the prospect that the non-random introduction of a preadapted phenotype was involved during this species'
initial colonization of N. America.
Rapid evolution in chemical defense despite genetic
constraints in the invasive plant Melaleuca
quinquenervia
Franks, S1
1
Fordham University, New York, USA
Introduced species are likely to show rapid evolution, but
rarely have quantitative genetic analyses been used to
evaluate past and predict future evolutionary changes in
invasive populations. I collected seeds of known
maternity of the invasive plant Melaleuca quinquenervia
throughout its native range in Australia and introduced
range in Florida and planted them in common garden
plots in Florida with and without the presence of two
biological control insects. I quantified 20 terpenes and
terpenoids from plant leaves using GC/MS. Eleven of
these compounds showed higher concentrations in the
native compared to introduced populations, and only one
compound had a higher concentration in introduced
populations. This finding indicates a potential loss of
defense in the new range, in keeping with predictions of
the evolution of increased competitive ability (EICA)
hypothesis. I focused on three compounds (1-8 cineole,
E-nerolidol, and viridiflorol) for quantitative genetic
51
analyses. All three compounds showed positive selection
differentials. Genetic variances and covariances were
significant and generally larger in the native than in the
introduced range populations. This suggests that the
species introduction resulted in the loss of quantitative
genetic variation. I found that this loss of genetic
variation would potentially constrain (though not
prevent) evolution based on analyses of selection
gradients and G-matrix geometry. Overall the results
suggest that evolutionary changes in secondary
compounds have occurred following introduction of this
invasive species and that the direction of evolutionary
change is generally consistent with predictions from
EICA and from estimates of quantitative genetic
parameters.
Sym026: Algae and environmental change –
impacts and opportunities – 30 July
Algal productivity in the 21st century : the impacts of
environmental change
Beardall, J1, Young, E2, Raven, J3
1
School of Biological Sciences, Monash University,
Clayton, Australia; 2Dept of
Biological Sciences,
University of Wisconsin–Milwaukee, USA; 3Division of
Plant Sciences, University of Dundee at SCRI, Scottish
Crop Research Institute, UK
Climate and environmental change scenarios suggest
various direct and indirect impacts on algae and aquatic
plants. Key environmental change factors likely to affect
productivity and species diversity of marine and
freshwater algae include (1) effects of elevated
atmospheric CO2; (2) effects of elevated temperatures on
algal growth and physical and chemical processes in
waterbodies; and (3) changing nutrient availability
related to climate change influences on ocean currents
and terrestrial runoff. Ocean acidification is already
occurring from increasing anthropogenic CO2 released to
the atmosphere which dissolves in the ocean increasing
the dissolved CO2 concentration. This results in a much
smaller relative increase in HCO3- and total inorganic
carbon, but a decrease in CO32- and release of H+,
reducing pH. Experiments designed to predict effects of
ocean acidification on phytoplankton have varied in
methodology and experimental organisms and have
suggested a variety of responses. While most
phytoplankton are likely to show little direct effect of
elevated CO2 and total inorganic C, some species,
including some strains of the ecologically important
coccolithophorids in marine systems, are likely to show
significant stimulation of photosynthesis and growth. In
addition to effects of the changed inorganic carbon
system on algal photosynthesis, decreases in CO32- affect
extracellular calcification in benthic coralline red algae,
and increase the energy cost of intracellular calcification,
as occurs in coccolithophores, although effects may vary
with species and strain. Functional calcified structures
are on the surface of organisms, so are vulnerable to
dissolution if the surface ocean becomes undersaturated
with aragonite (affecting many calcified macroalgae) or
calcite (affecting coccolithophores). The projected rises
in temperature associated with elevated greenhouse gases
52
will stimulate growth of some species but in some areas
may increase ocean temperatures beyond the optima for
some algal species, potentially influencing species
competition. More importantly, increasing global
temperature will stimulate water column stratification in
lakes and in tropical and mid-latitude areas of the oceans,
which will exacerbate nutrient limitation in surface
waters as the photic zone is isolated from nutrient-rich
deeper water. Shallower mixed layers in these areas
could also increase mean exposure to photosynthetically
active and UV radiation, inducing greater photoinhibitory
damage to phytoplankton. Physiological experiments
suggest that effects of elevated CO2 on algae need to be
considered in context with photosynthetically active
radiation and the supply of other limiting nutrients.
Freshwater and coastal algae will be affected by
changing nutrient availability from terrestrial runoff
resulting from altered precipitation patterns and increased
intensity of storm events, as well as atmospheric nutrient
deposition related to anthropogenic emissions. Many of
these changes will induce additive stress factors upon
algae, e.g. nutrient limitation can increase sensitivity to
UVB radiation. Environmental change factors are also
not expected to have uniform effects on all taxa within a
habitat and so will contribute to alterations in
phytoplankton and benthic algal assemblage composition
and diversity. Finally, there are very few studies on
genetic adaptation of algae to components of
environmental change: more data are needed.
Ocean acidification: calcifiers are only the tip of the
iceberg
Hurd, C1, Roleda, M1, Hutchins, D2, Fu, F2, Hunter, K1,
Boyd, P3
1
University of Otago, New Zealand; 2University of
Southern California, USA; 3National Institute of Water
and Atmospheric Research, New Zealand
The world’s oceans have absorbed up to 50% of the
carbon dioxide released by human activity since the
Industrial Revolution. The result is that our oceans are
becoming more acidic, a process termed ocean
acidification. Research has focused on how ocean
acidification will affect the ability of marine shellfish and
corals to build and maintain their calcium carbonate
shells and skeletons. Marine algae (seaweeds and
microscopic phytoplankton) are responsible for half of
global primary productivity, and require carbon dioxide
for photosynthesis. Because ocean acidification alters the
availability of carbon dioxide, and other dissolved carbon
sources to algae, it has the potential to affect the
productivity of ALL marine algae. This fact has been
largely overlooked but changes to algal productivity have
wide ranging implications for marine food webs and
fisheries. Using targeted physiological studies we
examine which algal groups, calcifying and noncalcifying, macroscopic and microscopic, will be most
susceptible to ocean acidification. Results allow
predictions of the future vulnerability of algal-based
coastal and open ocean ecosystems to ocean
acidification.
Taxonomic and ecological studies on cyanobacteria in
the catchment of Te Waihora – Lake Ellesmere
Merican, F1, Broady, PA 1
1
University of Canterbury, New Zealand
The distribution patterns of algal periphyton in streams
are controlled by environmental factors that include land
use, catchment geology, nutrient supply, shading by
riparian vegetation and currents associated with stream
bed morphology. These patterns could be used to monitor
stream health and to inform management so as to avoid
potentially detrimental proliferations. A taxonomic
survey is being conducted on periphytic cyanobacteria in
Kaituna River, a tributary stream of the highly eutrophic
Lake Ellesmere / Te Waihora. Selection of sites included
locations above and below human settlements and
agricultural areas. Descriptions have been made of all
visible macroscopic growths in the form of mats, crusts,
tufts and gelatinous colonies from different in-stream
microhabitats. Twenty-one morphospecies have been
recorded. Gelatinous colonies comprised four
morphospecies of Nostoc and one of Placoma. Matforming morphotypes are dominated by three
morphospecies of Phormidium, one of Oscillatoria and
one of Anabaena. The remaining thirteen morphospecies
from the genera Heteroleiblenia, Tapinothrix, Calothrix,
Chlorogloea, Cyanodermatium, Pleurocapsa and
Xenococcus are major components of epilithic crusts and
tufts. Distinct patterns have been revealed in the
distribution of different macroscopic growths along the
stream. Although growths are more extensive in the
lower reaches, fewer morphospecies are present.
Increased cover of potentially toxic oscillatorialean mats
are encountered downstream of intense dairy farming
activity while epilithic crusts are more common upstream
where the catchment consists of native vegetation in a
reserve and patches of regenerating native vegetation in
low intensity sheep pasture. Cultures have been
established of several dominant morphospecies for more
detailed morphological analysis and investigation of
morphological plasticity under different conditions. It is
planned to extend the study to Selwyn River in order to
compare algal periphyton in this contrasting catchment of
different geology and intensity of human activity.
Algae provide solutions for global energy, water, and
nutrient-sustainability challenges
Young, E1, Graham, L2, Graham, J2, Pfleger, B2, Smith,
B2, Zulkifly, R2
zones, and (3) increasing costs of fertilizer inputs to
improve agricultural production. Algal cultivation can
offer low-cost solutions to all three sustainability
problems: algae can produce renewable algal biofuel
feedstocks and other high-value materials, algal growth
in wastewaters can remediate effluents to reduce mineral
nutrient content before discharge to aquatic ecosystems,
and harvesting of the algae also offers recovery of
nutrient resources from effluent waters. The growth of
algae as a source of biofuels has been contemplated since
before the 1970s, but traditional approaches to algal
cultivation for biofuels production have focused on
unialgal cultures in ‘bioreactors’ which present
considerable challenges for culture maintenance and cell
harvesting and have often used artificial lighting or
ambient conditions only available at lower latitudes.
However, recent engineering life cycle comparisons
indicate that algal cultivation in wastewater has the
potential to offset many of the environmental burdens of
algal biomass production for biofuel feedstocks over a
wider range of climatic regimes. We also propose that
use of natural algal assemblages, often including a range
of taxa well adapted to eutrophic conditions, is a more
feasible, cheaper and is thus a more sustainable approach
to algal cultivation, and can be combined with growth in
wastewater effluents. Our recent experimental advances
include cultivation of hypereutrophic-adapted diatoms
producing up to 60 µg total lipids/mL and high cell
population densities (>2.5 million cells/mL). Using a
sewerage effluent water medium, we have also
demonstrated cultivation of a natural community of
carbohydrate-rich filamentous green algae, which are
easy to harvest and can sequester substantial N and P
from the effluent water, drawing soluble reactive P down
to below 0.005 mg/L. This filamentous green algal
community also contains a particularly desirable
chemical form of cellulose that we have readily purified
and hydrolyzed to glucose feedstock for bacteria
genetically-modified to produce specific and uniform
biofuel substrates. The addition to wastewater treatment
facilities of algae-based cultivation for nutrient removal
and recovery offers industry opportunities to meet
increasingly stringent regulatory standards for effluent
waters. This combined with a mechanism for recovering
costs by the sale of organic feedstocks for industrial
production of biofuels and fine chemicals offers financial
incentives for municipalities and benefits to the public
and environment. The co-construction of revenueproducing algal feedstock production facilities could
allow developing nations to build wastewater treatment
plants, thereby reducing nutrient pollution in water
resources world-wide.
1
University of Wisconsin–Milwaukee, USA; 2University
of Wisconsin–Madison, USA
Promising culture medium for Chlorella to reduce
atmospheric CO2
While productivity and diversity of marine and
freshwater algae in natural habitats will be affected by a
range of environmental change factors, algae can also
offer opportunities for mitigating some of the challenges
related to global energy and water quality. The major
environmental problems faced by societies worldwide
include (1) dwindling supplies of fossil fuels and
greenhouse gas pollution associated with their continued
use, (2) the economic and ecological impacts of excess
eutrophication of freshwater resources and marine coastal
habitats resulting in harmful algal blooms and dead
Aizawa, K1, Miyachi, S1
1
Institute for Clean Earth, Japan
Green house gases such as CO2 and N2O are important
factors which cause climate change. Biological
mitigation of atmospheric CO2 relies on photosynthesis.
The rate of CO2 fixation for the forest is estimated at ca.
8 g CO2/m2.day. In contrast, most aquatic microalgae can
more efficiently utilize CO2 (max. 60 g CO2/m2.day, [1,
2]) at high (0.5 ~ 60 %) and air level of CO2
53
concentration [3, 4]. CO2 fixation, wastewater treatment,
and/or the production of valuable chemicals can be
carried out by the production of microalgal culture. Such
production does not compete with the conventional crop
production and the forestry. Therefore, photosynthetic
microalgal culture has a high potential for mitigating
CO2. However, it has been shown that the present
microalgal culture eventually emit CO2 and N2O.
Especially, the amount of CO2 emitted (i.e., CO2 debt)
during the production of chemicals used for the culture
media of microalgae is relatively high. Therefore, the
current well-known culture media cannot be used for
CO2 mitigation. We have tried to develop new culture
media for several microalgae which are applicable to
CO2 mitigation. At present, an improved autotrophic
culture medium for freshwater Chlorella sp. which used
urea at N-limiting growth conditions was found to have
very low CO2 debt. The cells such as Chlorella regularis
grew well in the new medium under high CO2 condition
as in the case of conventional ones.
Dimethyl
sulphide
production
by
marine
phytoplankton: implications of climate change for an
important biogeochemical process
Beardall, J1, Larsen, S1
1
School of Biological Sciences, Monash University,
Clayton, Australia
Phytoplankton
are
major
producers
of
dimethylsulphoniopropionate (DMSP) and its product
dimethyl sulphide (DMS) which is thought to play a role
in sulphur cycling and modulation of climate through
cloud formation and its effect on Earth's albedo. With
global climate change leading to increasing sea surface
temperatures and, in some cases, freshening of marine
waters, it is important to understand the impacts of these
parameters on DMSP production and calcification. In this
paper we present an overview on DMSP production by
algae, its modulation by environmental factors such as
temperature and salinity and evidence for its potential
role in regulating global change. We will also present
some new data on DMSP production by the
coccolithophorid Gephryocapsa oceanica. DMSP
production rates and cellular DMSP concentration both
decreased with increasing temperature, but increased
with increasing salinity. Net DMSP production became
less sensitive to temperature as salinity decreased. The
implications of this data for the proposed role of DMSP
as a regulator of global warming will be discussed.
Sym027: Fungal symbioses in cryptogamic
land plants – 25 July
Ecological associations of plants–fungi from Late
Paleozoic coal-ball deposits
1
1
2
3
Wu, W , Labandeira, CC , Wang, S-J , Hilton, J
1
Dept of Paleobiology, Smithsonian Institution, National
Museum of Natural History, USA; 2State Key Laboratory
of Systematic and Evolutionary Botany, Institute of
Botany, Chinese Academy of Sciences, Beijing, China;
54
3
School of Geography, Earth and Environmental
Sciences, University of Birmingham, Edgbaston, UK
Ecological associations among plants, fungi and
arthropods long have been recognized as a critical trophic
step in the evolution of wetland ecosystems, despite a
sparse and uninformative fossil history. Our study
examines fossil fungal and their associated plants and
arthropods from anatomically preserved, permineralized
coal balls from three Late Paleozoic deposits. The
earliest deposit is the Late Carboniferous Calhoun Coal
of the Mattoon Formation, of Kasimovian–Gzhelian age
from Berryville, Illinois, USA. Of Early Permian
Asselian–Sakmarian age is a coal-ball deposit of the
Taiyuan Formation, from Xiedao Village, Xishan
Coalfield, Shanxi Province, northern China. The
youngest deposit is a Late Permian coal-ball deposit from
the Wangjiazhai Formation, of Changhsingian age, from
the Shuicheng Mining District of Guizhou Province,
southern China. The relationship of the Chinese Taiyuan
floras have been determined as a major, timetransgressive expression of similar plant assemblages
established earlier in wetland communities of
Euramerica. The Cathaysian floras floristically diverged
during the Mississippian and continued into the Early
Permian. The latest Permian floras of southern China
record the persistence of key elements of lowland swamp
plant communities from the Early Permian of China and
the Late Carboniferous to earliest Permian of Europe and
North America. Collectively, these units represent
considerable evolution during an interval of 55 million
years and a position within 15º of the paleoequator. For
earlier Calhoun vegetation, plant–fungus interactions
occurred principally in the extinct marattialean tree-fern
Psaronius, the dominant plant constituent, and less so for
the subdominant seed fern Medullosa and the
sphenophyte Sphenophyllum. For Psaronius, symbiotic
and parasitic fungal structures have been found
endophytically, respectively, in root and rachis tissues.
Spores and vesicular and arbuscular mycorrhizae with
intra- and intercellular hyphal structures frequently occur
in root tissues. Fungi in rachis cells feature complete
reproductive and vegetative life stages. In one endophytic
association between an insect galler and its Psaronius
plant host, we note fungal colonization in the vacuities
among insect coprolites (fossilized fecal pellets) and
galled tissue, probably indicating a diffuse, tritrophic
association. By comparison, the plant–fungus–arthropod
interactions in the Xiedao plant assemblage exhibit more
pervasive relationships with subdominant cordaites rather
than the dominant lycopsids. The Latest Permian
Shuicheng deposit display the more active relationships
between the arthropods and the host plants, including the
aerial and subterranean parts. The symbiotic fungi occur
principally within tissues of Psaronius group, though
these tree ferns were not the dominant plants at the close
of the Permian.
Aneuraceae (Metzgeriales) and Tulasnelloid fungi
(Basidiomycota): model organisms for early steps in
symbiotic fungus–host plant interactions
Nebel, M1, Garnica, S2, Krause, C2, Quandt, D3
1
Staatliches Museum für Naturkunde, Stuttgart,
Germany; 2Eberhard Karls Universität Tübingen, FB1
Biologie, Tübingen, Germany; 3Rheinische Friedrich-
Wilhelms-Universität, Nees-Institut für Biodiversität der
Pflanzen, Bonn, Germany
Liverworts of the family Aneuraceae are suitable
organisms for comparative ultrastructural analyses
because they are widespread, common, and have a
relatively simple morphology. The Aneuraceae show a
wide range of fungus–host plant interactions including
full heteromycotrophy, which is unique among
liverworts. Mycorrhizal fungi from the order
Tulasnellales (Basidiomycota), which are common in
orchids, are found among liverworts only in the
Aneuraceae. Molecular phylogenetic reconstructions of
the Aneuraceae resolve Riccardia as sister to the
remaining monophyletic genera, with Verdoornia being
the sister to Aneura (incl. Cryptothallus) and
Lobatiriccardia. Morphological characters from the
gametangia and the sporophyte formation and the
mycothallus development corroborate these molecular
results. The following states of fungus–host plant
interactions can be observed in the Aneuraceae: 1) The
fungus-free stage (e.g. Riccardia amazonica, R. andina)
2) The epiphytic stage (e.g. R. multifida) 3) The
intercellular stage (R. intercellula) 4) The endophytic
stage: 4A) – in epidermal cells (genus Riccardia) 4B) –
in epidermal and adjacent parenchymal cells (genus
Riccardia) 4C) – in parenchyma cells (and occasionally
in epidermal cells): 4Ci) – The Riccardia type (genus
Riccardia) 4Cii) – The Aneura type (genera Aneura,
Verdoornia and Lobatiriccardia) 4Ciii)
– The
exploitative mycothallus (Aneura [Cryptothallus]
mirabilis) Some observations support the hypothesis that
the ecological influence is decisive for the occurrence of
a particular type of fungus in a host species at the
population level. For example, plants of Riccardia
palmata and R. latifrons that grow on logs host closely
related fungi that are usually not found in Aneura pinguis
and R. multifida, which grow in wet soil and also often
share closely related tulasnelloids. Different colonisation
patterns of the same fungus may indicate a control of the
fungal penetration by the host plant. This is the case in A.
pinguis and R. multifida, where the fungi showed
identical or nearly identical LSU and ITS sequences, but
the colonisation type is totally different and specific.
A review of the mycorrhizae in ferns and lycophytes:
their potential significance in phylogenetic and
ecological studies
Lehnert, M1, Kessler, M2
1
2
State Museum for Natural History, Stuttgart, Germany;
Systematic Botany, University of Zurich, Switzerland
We gathered information from literature and personal
surveys about the presence, type, and abundance of
mycorrhizal fungi in the sporophytes of ferns and
lycophytes. Records for 1009 species and 36 of the 40
recognized fern and lycophyte families show an average
presence of mycorrhiza of 68%. Only mycorrhizae
involving glomeromycetes (a.k.a. arbuscular mycorrhizal
fungi, AMF; 75% of infected samples) and dark-septate
endophytes including ascomycetes (25% of infected
samples) are known from these taxa. Glomeromycetes
are dominant in terrestrial ferns and change in prevalence
according to the phylogenetic position of their hosts.
Phylogenetically old lineages tend to have high
colonization rates of up to 100 % while some young
lineages
have
below-average
presence
of
glomeromycetes. The general pattern is disturbed by
young clades with strong presence of glomeromycetes
(Onocleaceae) and by old lineages with low rates of
colonisation (Equisetaceae, Selaginellaceae). Epiphytic
lineages are either non-mycorrhizal or have switched to
another type of mycorrhizal fungus (e.g., ascomycetes),
irrespective if they belong to older (Hymenophyllaceae)
or younger lineages (Polypodiaceae). A reassessment of
ancestral state reconstructions adding the information of
mycorrhiza supports the hypothesis of a synchronous
evolution of the epiphytic habit in ferns, coinciding with
the angiosperms’ gain of dominance of the worldwide
vegetation. The information about the mycorrhizal
colonisation of some groups (e.g., lycophytes,
Oleandraceae, Dennstaedtiaceae, Tectariacaeae) is still
insufficient and calls for more intensive studies. Reports
for gametophytes indicate a much clearer trend of
successive independence of ferns and lycophytes from
mycorrhizae with advancing evolution.
Insights into the multiple origins of symbioses
between Acrospermum and polypod ferns: evidence
from plant and fungal sequence data
Sundue, MA1, Doyle, V2, Ranker, TA3
1
Pringle Herbarium, Plant Biology Dept, University of
Vermont, Burlington, USA; 2The New York Botanical
Garden, Bronx, NY, USA; 3Dept of Botany, University of
Hawaii, Honolulu, Hawai'i, USA
Among ferns, Polypodiaceaeare unique in having welldeveloped relationships with the bitunicate ascomycete
genus
Acrospermum
(Dothidiomycetes
+
Arthoniomycetes), a genus of about 60 spp. known from
temperate and tropical America, and Europe. Most
species of Acrospermum are saproprobic; however, some
are epibiotic and are known to inhabit mosses and
ferns.This is best developed within two clades of tropical
American grammitid ferns which correspond to the
genera Ascogrammitis Sundue(17 spp.) and Mycopteris
Sundue ined. (ca. 30 spp.)These genera of ferns have a
near constant relationship with Acrospermum; the
ascomes of which can be found on nearly every leaf of
every plant throughout the range of both genera. One
species, A. maxonii Farlow ex Riddle, has been described
from the leaves of grammitid ferns, and is accepted as the
species that is present upon all grammitid ferns.
However, morphometric studies suggest that above 3000
m on the eastern slope of the Andes, a second
undescribed species with more orbicular ascomes is
present instead of A.maxonii. The non-grammitid
polypod ferns Pleopeltis ballivianii (Rosenst.) A.R.Sm.,
P. furfuraceum (Schltdl. & Cham.) A.R.Sm., and
Campyloneurum lorentzii (Hieron.) Chingare also host to
Acrospermum, but with less consistent relationships
associations, and with the range of the host-plant
exceeding that of the fungus. Phylogenetic analysis of a
broad sampling of Ascomycetes using [SSU, LSU]
support the monophyly of Acrospermum, and the sister
relationship between A. maxonii and the aforementioned
undescribed high-elevation species. Phylogenetic
analyses of polypod ferns using chloroplast markers
[atpB, rbcL, trnL-F] support four independent
colonization events of Acrospermum onto these ferns.
55
Results also suggest that within the grammitid clades that
are associated with Acrospermum, the fungi are more
closely associated with habitat than they are with
particular host species.
Mycorrhizal colonizations of ferns and lycophytes on
the island of La Réunion in relation to nutrient
availability
Kessler, M1, Jonas, R2, Strasberg, D3, Lehnert, M4
1
University of Zurich, Switzerland; 2University of
Göttingen, Germany; 3University of La Réunion, La
Réunion; 4Staatliches Museum für Naturkunde, Stuttgart,
Germany
Very little is known about the degree and ecological
correlates of mycorrhization of lycophytes and ferns,
although mycorrhizae are believed to be crucial for the
majority of land plants. We screened the degree of
mycorrhizal colonization for all 75 fern species recorded
in nine survey plots across a wide range of soil
conditions on the island of La Réunion, including five
plots on lava flows of different age. Overall, 66% of all
samples had mycorrhizae, but ground-dwelling species
had significantly higher colonization levels (78%) than
epiphytes (58%). Among ground-dwelling species, 98%
of the individuals belonged to species with mycorrhizae,
which was significantly higher than at the species level.
Most samples had glomeromycetes as fungal partners,
but septate endophytes were found in 41% of the
colonized samples. While we found no significant
relationship between the percentage of fern species with
mycorrhizae per plot and seven ecological parameters,
the percentage of fern individuals with mycorrhizal
colonizations per plot significantly increased on shallow
soils with high pH values and high base-saturation. This
supports the idea that mycorrhizal colonizations confer
an ecological advantage to colonized individuals, and
that this advantage is more pronounced on nutrientdeficient sites. Our study thus provides evidence for an
ecological advantage of mycorrhizae for ferns, but raises
the question why, despite this advantage, species-level
mycorrhization among ferns (68%) is so much lower than
the average for land plants (85%).
Sym126: Self-incompatibility: population
genetics, evolution, and ecology – 26 July
Self-incompatibility and interspecific hybridization in
Senecio
Hiscock, SJ1, Brennan, AC2
1
School of Biological Sciences, University of Bristol,
Bristol, UK; 2Royal Botanic Garden Edinburgh,
Edinburgh, UK
The Senecio (ragwort) study system is a well known
example of recent homoploid hybrid speciation. Two
species of Senecio, S. chrysanthemifolius and S.
aethnensis, are capable of producing fertile hybrids and
form a natural stable hybrid zone along an altitudinal
gradient on Mount Etna, Sicily. A third species, S.
squalidus, is recognized as a recent homoploid hybrid
56
species derived from this hybrid zone that originated
following the introduction of hybrid plants to the UK
about 300 years ago. Invasive S. squalidus now occupies
novel urban wasteground, railway, and motorway
habitats throughout the UK. All three Senecio species
have an outcrossing mating system based sporophytic
self-incompatibility
(SI).
Self-incompatibility
in
Asteraceae is controlled by a single S locus expressing
pollen and pistil allele-specific recognition factors and is
subject to negative-frequency-dependent selection, a
form of balancing selection that favours new or rare
alleles due to their greater population mate availability
relative to more common S alleles. Balancing selection
typically results in extensive S allele polymorphism over
evolutionary time. We investigated the population
genetics of self incompatibility in these species to
determine how their different population histories have
impacted upon their mating system and to examine the
interaction between SI and hybridization. Strength of SI
was measured and S alleles were identified in population
samples of these species and wild hybrids through
controlled cross-pollination studies and analysis of
subsequent diallel cross results. Data on S allele diversity
was combined with molecular genetic marker genotype
data to identify the effects of balancing selection on
patterns of diversity. These investigations confirmed a
reduction in S allele diversity and mate availability in
invasive S. squalidus due to the population bottleneck
incurred during introduction. However, strength of SI
was similar across all study species indicating that
sporophytic SI can be robust to extreme population
events such as introductions. We found extensive sharing
of functional S alleles between species and reduced
population structure at the S locus relative to molecular
markers indicating that balancing selection at the S locus
is an important force for introgressive gene flow between
related species.
Evolution of breeding systems in Brassicaceae
Shimizu, KK1, Yasumoto, AA1, Tsuchimatsu, T1,
Kaiser, P1, Shimizu-Inatsugi, R1
1
University of Zurich, Institute of Plant Biology,
Switzerland
In flowering plants, the transition from outcrossing to
predominant selfing through loss of self-compatibility
(SI) is one of the most prevalent evolutionary trends. In
many species of Brassicaceae including Arabidopsis,
selfing is prevented by the sporophytic SI system, which
is controlled by SRK and SCR/SP11, encoding the
female and male SI specificity determinants,
respectively, at the S-locus. Dozens of highly divergent
sequence groups at the S-locus, called S-haplogroups (or
S-haplotypes or S-alleles), confer specificity in selfrecognition. Haplogroups are characterized by low
nucleotide diversity within each haplogroup and by high
divergence and suppressed recombination between
haplogroups. We have studied two genera Arabidopsis
and Cardamine, in which the transition to SC occurred
many times independently. Cardamine is one of the
largest genera in Brassicaceae with >200 species. The
prevalence of allopolyploid species suggests the
importance of hybridization. To study the reproductive
barriers and breeding systems, we conducted reciprocal
crossing among 13 species. When outcrossing species are
used as maternal parents, fruit elongation was rarely
observed. In contrast, when selfing species serves as
maternal parents, seed development tends to start
although many of then abort later. The results suggest
that the breeding system of maternal parents is critical for
the hybrid development, and may be consistent with SI X
SC rule.
Evolution and maintenance of mixed si/sc mating
system
in
Hypochaeris
salzmanniana
DC.
(Asteraceae), an endemic species to the west
Mediterranean
Casimiro-Soriguer, R1, Ortiz, MA 1, Garcia-Castaño,
JL1, Tremetsberger, K2, Talavera, M1, Balao, F1, Stuessy,
TF3, Talavera, S1
1
University of Seville, Dpto Biología Vegetal y Ecologia
(Area Botanica), Spain; 2University of Natural Resources
and Life Sciences, Vienna, Austria; 3Institute of Botany,
University of Vienna, Austria
Hypochaeris salzmanniana DC. (Lactuceae, Asteraceae)
is an annual herb endemic to the Atlantic coasts of S
Spain and NW Morocco. Previous research has shown
that this species exhibits a flexible sporophytic selfincompatibility system, including populations with only
self-incompatible individuals, populations with only selfcompatible individuals, and mixed populations with selfincompatible and self-compatible plants. Little is known
about the inheritance of self-compatibility and how
become to be fixed within the populations. Following
different approaches as molecular techniques (AFLPs),
demography and reproductive traits (incompatibility tests
in the glasshouse and in the wild, pollinator activity) we
study the population dynamics, the stability and diversity
of the mating systems in natural populations of
Hypochaeris salzmanniana. We found a geographical
pattern, from south to north, related with the genetic
diversity and the proportion of self-incompatible and
self-compatible individuals in the populations. The south
side of the distributional area (Morocco) correspond with
self-incompatible plants with the highest levels of genetic
diversity, probably the ancestral area of the species. The
northern populations exhibit different levels of
incompatibility in its populations as well as the genetic
diversity being lowest in the complete self-compatible
populations and vice versa. The establishment of the
Spanish populations probably was originated by
migration events from Morocco, when the sea level was
lower than today, and the founder effect followed by
bottleneck events favoured the appearance and
establishment of the self-compatible individuals in the
populations. In addition, the pollinators, mainly solitary
bees, were efficient enough to get high levels of
reproductive success in the wild. Therefore pollinators, at
least nowadays, seem to cause no selective pressure on
the self-compatible plants.
Are self-incompatible plant species particularly
threatened by pollen limitation effects in fragmented
populations: what the theory tells us and why
empirical approaches are inconclusive?
Vekemans, X1
1
Université Lille, France
Plant conservation biologists have raised the issue of a
potentially greater fragility of self-incompatible species
to population fragmentation. This would be caused by a
reduction in compatible mate availability due to a lower
number of alleles maintained at the self-incompatibility
locus (S-locus) in small isolated plant populations.
Indeed, when the number of incompatibility alleles is
reduced in a population, a larger fraction of pollen
landing on a given pistil will share the same specificity as
the pistil, and will thus be rejected. If the pollination
service is inefficient for ecological reasons associated to
fragmentation, this will lead to an overall reduction in
seed production that is expected to be stronger in selfincompatible, as compared to self-compatible species.
This phenomenon is expected to generate a 'mate-finding
Allee effect' specific to self-incompatible species
(sometimes called the' S-Allee effect'), a process
generating a positive relationship between reproductive
success and population size because of an increase in
access to mates in larger populations. Theory predicts
that the strength of the S-Allee effect will strongly
depends on the genetics of the self-incompatibility
system, on the number of extant alleles present in the
populations, which itself depends on current and past
population sizes and on the rate of gene flow among
populations, on the spatial genetic structure at the Slocus, and on ecological attributes of the populations,
such as the efficiency of the pollination system.
Empirical studies in the field, however, have failed to
demonstrate formally the S-Allee effect. This is because
molecular or genetic typing of alleles at the S-locus has
rarely been performed in these studies, and also because
alternative processes influencing seed production have
not been assessed simultaneously. In this presentation,
we review ecological genetics theory about selfincompatibility systems in small populations. We present
results from experimental approaches aiming at testing
the S-Allee effect. Then, we review empirical approaches
in the field, and try to highlight the difficulty to
disentangle different causes of seed production
constriction in small populations. Finally we suggest
areas for further investigation, and provide
methodological guidelines.
Polyploidy and evolution of breeding systems in
Tibetan poppies (Meconopsis Vig., Papaveraceae)
Xie, H1, Nicotra, A1, Ash, J1, Cunningham, S2
1
Research School of Biology, The Australian National
University, Canberra, Australia; 2Australian National
Insect Collection, CSIRO Entomology, Canberra,
Australia
The genus Meconopsis Viguier (1814) was erected to
contain a single European poppy (M. cambrica) that had
an elongate style: in contrast to other Papaver species in
which the stigma is broad and sessile on the carpels.
Subsequent exploration revealed poppies with a style
(placed in Meconopsis) in California and especially in the
Himalayan–Tibetan region: including species with large
blue, yellow or red corollas that became prized in
horticulture. Recent DNA-based phylogenies suggest that
the style and flower colour are both variable traits within
poppy clades, and Meconopsis now refers only to a clade
of about 45 cold-tolerant polyploid Himalayan–Tibetan
species. It is arguable that Meconopsis is a subgenus
57
within Papaver. Self-incompatability (SI) is well
understood in diploid Papaver (2n=14); however, some
polyploid Papaver are self-compatible (SC). The
breakdown of incompatability seems necessary for novel
polyploids (with no possible mates) to persist, though it
may re-evolve. Breeding systems in eight Meconopsis
species were tested: species with 2n=56 were SI but
those with 2n=76 or 84 were partially SC. Based on
phylogenetic reconstructions, some SC species have
undergone additional changes: petals enclosing anthers
and stigma; a short style; and a shift from blue-violet to
yellow or red petals. The SI species that were examined,
e.g. M. racemosa, were buzz-pollinated by Bombus or by
large Diptera: well suited to outcross pollination. In
contrast, enclosed SC species had abundant small Diptera
(e.g. Agromyzids in M. punicea) that feed and remain
within flowers, facilitating self-pollination. We speculate
that (1) creation of 2n=76–84 species (from putative
2n=56 + 28 ancestors) was associated with a breakdown
in SI, enabling (2) a shift from dependence on large
outcross vectors to smaller Dipterans that could live and
self-pollinate within flowers, and (3) this led to selection
for changes in colour and morphology of flowers that
favoured the small Dipterans.
Characterising self-incompatibility in Australian
populations of Wild Radish (Raphanus raphanistrum)
Mable, B1, Newbigin, E2
1
University of Glasgow, UK; 2University of Melbourne,
School of Botany, Australia
Self-incompatibility (SI) in the Brassicaceae is controlled
by a single Mendelian locus (the S-locus) but with
separate genes coding for male (SCR) and female (SRK)
recognition proteins. These genes must be maintained in
tight linkage to one another to maintain the ability to
recognize self-related proteins in order to prevent selffertilization. Due to this lack of recombination at the Slocus and the 'obligate outcrossing' resulting from having
a genetically controlled SI system, high inbreeding
depression is expected if the system breaks down to
allow self-fertilization. Nevertheless, transitions from
outcrossing to inbreeding are frequent between, but also
within, species. Although mixed mating used to be
considered to be evolutionarily unstable, it is now clear
that even in species with genetically controlled SI
systems, variation in outcrossing rates occurs across
populations in many species. In addition, in some species
there is variation in the strength of SI among individuals
within populations. In Arabidopsis lyrata, we have found
that some populations that maintain high outcrossing
rates contain a mixture of self-incompatible (SI) and selfcompatible (SC) individuals, while others contain mostly
SC individuals and are highly inbreeding. This
emphasizes that a shift to inbreeding in species with a
genetically controlled SI system is a two-step process,
with different types of selection pressures potentially
operating during the two phases. Deciphering the
mechanisms for loss of SI can thus be obscured by
subsequent changes associated with selection for
inbreeding. In addition, the ‘selfing syndrome’ that is
often observed in inbreeding species may evolve later to
improve the efficiency of inbreeding. We have been
using A. lyrata as a model to understand the genetic and
58
ecological causes and consequences of this multi-phase
transition from SI to inbreeding.
Sym127: Genetics, demography and
conservation of rare and endangered plants
– 25 July
Incorporating genetics in the population viability
analysis of threatened plants
Gerard Oostermeijer1, Voznesenskaya, EV2, Koteyeva,
NK2, Edwards, GE3
1
Institute for Biodiversity and Ecosystem Dynamics,
University of Amsterda,
Amsterdam, Netherlands;
2
Laboratory of Anatomy and Morphology, VL Komarov
Botanical Institute of RAS, Russia; 3School of Biological
Sciences, Washington State University, Pullman, USA
Already in the 1980s, pioneer conservation biologists
discussed the possibly important role of genetics in the
viability of small and isolated populations. Since then, an
enormous amount of research has shown that such
populations are experiencing loss of genetic variation
through drift and inbreeding, and that gene flow is often
insufficient to compensate for that. However, when it
comes to the question how detrimental this is to their
viability, we are still not able to present very many
empirical studies that clearly demonstrate this. This is
largely due to our failure to effectively integrate genetics
with other important components of plant population
viability, such as demography and reproductive biology.
Nevertheless, the studies performed on each of these
components separately suggest that there are major
changes in each of them. The still painfully scarce studies
that have attempted to integrate them into single PVAs
show that demography, reproduction and genetics act
synergistically, and cause the often mentioned but rarely
demonstrated extinction vortex. As a result of habitat
destruction and fragmentation, many plant populations
are genetically depauperate, and show reduced viability
that cannot be alleviated by habitat management and
restoration alone and requires additional genetic rescue
measures. Our knowledge of the implications of
outbreeding depression after genetic rescue is still
insufficient to provide conservation managers with
scientifically sound advice. The rapid developments in
ecogenomics will provide exciting new avenues of
implementing genetics into plant conservation.
Nevertheless, we still need to combine these new
approaches with appropriate field experiments in order to
obtain the best answers to still urgent questions. To better
implement genetics into practical conservation,
researchers need to (i) pay more attention to translating
their scientific results, and (ii) focus on the specific
questions of conservation managers.
Molecules, monitoring and modelling: integrating
genetic and demographic data into conservation
planning for the grassland endemic Rutidosis
leptorrhynchoides
Young, A1, Murray, B2, Thrall, P1, Pickup, M3, Hoebee,
S4, Dudash, M5
1
CSIRO, Canberra, Australia; 2University of Auckland,
New Zealand; 3University of Toronto, Canada; 4La
Trobe University, Bundoora, Australia; 5University of
Maryland, USA
Effective management of endangered plants must
account for both genetic and demographic limitations to
population viability and local species persistence that
may compromise long term conservation outcomes. The
endangered daisy Rutidosis leptorrhynchoides is endemic
to the temperate grasslands of south-eastern Australia
where it has been subject to severe habitat loss. This
species has been the subject of a long term research study
combining analysis of reproductive ecology, population
demography, population genetics of S allele diversity,
cytogenetic variability and outbreeding depression in an
effort to understand population trajectories and develop
active conservation strategies. These results are
integrated in a simulation modelling framework to
provide predictions of population viability, identify key
threatening processes, and provide management options
that maximise the likelihood of long-term maintenance of
current populations. Implications for the establishment of
new populations are also discussed.
Conservation implications of recognizing polyploid
plants: are more species better?
Severns, P1
1
Washington State University–Vancouver, USA
Small population size, inbreeding depression, and the
intentional inflation of within population genetic
diversity to cope with impending global climate change
induced habitat modifications, are common rationales for
within species, inter-population lineage transfer. Assisted
migration and intentional between population lineage
transfer (from seeds and transplants) carries the
possibility of introducing incompatible, as well as,
beneficial, compatible genotypes. Conventionally, the
primary concern with inter-population lineage mixing has
been the unintentional introduction of incompatible
genotypes that, upon crossing, produce progeny with
lower relative fitness and vigor than crosses within either
parental population. Outbreeding depression can yield
comparable reductions in plant fitness and vigor to
inbreeding
depression,
but
crosses
between
‘intraspecific’ individuals that differ in ploidy (and other
types of cytological variants) commonly produce sterile
progeny, defining them as separate biological species.
With the well-developed genetic barriers that isolate
ploidal variants from each other, conservation genetics
research into the landscape patterns of chromosome
number variation should be common, yet it is not. In this
talk, I will present evidence that polyploid species are
likely to be more common in protected, rare plants than
realized, that the delimitation of polyploid species is
important research if rare plant persistence depends on
reintroduction and supplemental plantings, and that the
formal recognition of polyploid species could enhance
rare plant conservation despite policy tradeoffs and an
increase in taxonomic complexity.
Are island endemics characterized by low levels of
genetic diversity? A case study from the Canary
Islands
Meloni, M1, Reid, A2, Caujapé-Castells, J3, FernándezPalacios, JM4, Soto Medina, M3, Conti, E1
1
University of Zurich, Institute for Systematic Botany,
Zurich (Switzerland); 2Institute of Integrative Biology,
ETH Zentrum, Zurich, Switzerland; 3Jardin Botanico
Canario 'Viera y Clavijo', Unidad Asociada CSIC, Las
Palmas de Gran Canaria, Spain; 4Island Ecology and
Biogeography Research Group, Universidad de La
Laguna, Tenerife, Islas Canarias, Spain
Islands constitute unique ecosystems, often comprising
species found nowhere else on Earth. These endemics,
characterized by a unique evolutionary history, represent
irreplaceable natural treasures. Island endemics are often
rare and/or endangered. One of the reasons for the
susceptibility of island endemics to extinction is the low
level of genetic diversity that is thought to characterize
these species. Genetic variation allows populations to
evolve in response to environmental changes; low levels
of this ‘evolutionary potential’ limit the ability of insular
species to genetically adapt, making them more prone to
endangerment and extinction. While there is a trend for
insular/rare species to exhibit reduced genetic diversity,
recent studies show that island endemics exhibit
equivalent levels of genetic diversity compared to closely
related, widespread species. Therefore, an extensive
knowledge of the amount and distribution of genetic
diversity of endemic species and the mechanisms that
underlay this diversity are fundamental for their
conservation. A population genetic analysis is being
performed on three species of the genus Ruta endemic to
the Canary Islands. Newly developed SSR
(microsatellites) markers are used to investigate the
genetic structure and diversity at both the intra- and interspecific level. By studying the patterns of genetic
variation within and between islands, we provide
important information on the genetic effects of isolation
and small population size on the evolution of insular
species. In addition, our results will afford insight on the
possible consequences of human-driven processes (i.e.
habitat fragmentation, species invasion in response to
global warming, etc.) that share some similarities with
the evolutionary processes of island colonization.
Finally, knowledge on the genetic variability of endemic
species is fundamental for maintaining species’ survival
in a changing environment and to direct conservation
programs. Águedo Marrero, Ricardo Mesa-Coello and
Félix Manuel Medina contributed samples that were
necessary for the molecular genetic analyses performed
for this project.
Conservation and genetics of Acacia in arid NSW –
the tyranny of distance, climate and clonality
Denham, AJ1, Ayre, DJ2, O'Brien, EK3, Forrest, CN2,
Roberts, DG2, Gilpin, A-M2
1
Office of Environment and Heritage (NSW), Australia;
University of Wollongong, Australia; 3University of
Bristol, UK
2
59
Active conservation of arid zone plant species is often
necessary to prevent their declines due to chronic
recruitment failure. This is largely attributed to direct
effects of grazing pressure from domestic, feral and
native herbivores and other anthropogenic impacts like
soil erosion and climate change. In western NSW some
acacias are keystone species – a major structural
component of vegetation and thus are likely to be integral
to ecosystem function and biodiversity. Management of
grazing impacts alone has rarely led to recovery from
population declines in these species. Compounding this
recruitment failure is the fact that seed production has
rarely been observed in many of these acacias, while
clonal reproduction of root suckers is common.
Reproductive failure probably reflects either disruption
of normal pollination systems or genetic effects of
reduced population size and increased isolation.
Nevertheless, it is possible that in stable environments,
clonality has been favoured by selection because it
replicates successful (i.e., locally adapted) genotypes and
episodes of sexual reproduction are naturally rare.
However, sexual reproduction with genetic re-assortment
and seed production facilitating dispersal and
colonisation should be valuable attributes in the face of
significant climate change. Our research programme will
attempt to unravel potential genetic and pollination
bottlenecks in a number of arid zone Acacia species with
a view to facilitating or increasing seed production. We
first aim to utilize controlled breeding experiments
determine if reproductive success is currently limited
either by severe inbreeding depression (in selfcompatible species) or by lack of variation at
histocompatibility loci (in outcrossing species), and to
compare the diversity of pollinators and patterns of
pollinator behaviour for populations and species that vary
in their level of seed production. We will also use genetic
surveys to determine if populations with little or no seed
production are generally lacking in variation at nuclear
gene loci and ultimately aim to determine when and how
genetic rescue techniques may be applied to promote
self-sustaining populations. To date we have begun
genetic surveys of several Acacia species including
Acacia carneorum (federally listed as Vulnerable), A.
homalophylla/melvillei (an Endangered Ecological
Community in NSW), A. ligulata (not considered at risk),
A. loderi (an EEC in NSW), and A. pendula (a federally
listed EEC in part of its range). AFLP surveys of genetic
variation in A. carneorum found that all populations
surveyed were genetically distinct, implying that outcross
pollinations would enhance genetic variation in recipient
populations. There was no consistent trend of within
population genetic diversity and natural seed set, but the
two fruiting populations did have intermediate and high
levels of polymorphic loci. We have commenced
pollination studies of these species and found that for the
relatively successful A. ligulata, natural flower visitation
and pollen harvesting is dominated by the exotic
honeybee Apis mellifera, resulting in high levels of self
pollen transfer. However, hand pollination trials
involving outcross pollen transfers both within and
among populations have yielded good levels of seed
production.
60
Sym149: Community and ecosystem
genetics: the extended genetic effects of
plant species – 29 July
Extended genetic effects of a forest dominant: the case
of Eucalyptus globulus
Potts, B1, O’Reilly-Wapstra, J1, Barbour, R1, Gosney,
B1, Freeman, J1, Hamilton, M1, Bailey, J1, Schweitzer, J1,
Whitham, T2, Vaillancourt, R1
1
University of Tasmania, Australia; 2Dept of Biological
Sciences, and The Merriam-Powell Center for
Environmental Research, Northern Arizona University,
USA
There is increasing evidence that genetic variation in a
foundation species may have significant flow-on effects
to the associated biota and even to ecosystem processes.
Such extended genetic effects are no better seen in forest
trees which dominate many terrestrial ecosystems and
provide habitat for numerous dependent organisms. We
have been studying these extended genetic effects in
Eucalyptus globulus, a dominant tree of lowland forests
of south-eastern Australia. While native to Australia, the
species is widely grown in plantations in temperate
regions of the world and its molecular and quantitative
genetic diversity is amongst the most extensively studied
of any forest tree species. An extensive network of
progeny trials from large, range-wide open-pollinated
seed collections from native races and sub-races of E.
globulus have been established for breeding and research
purposes. The natural colonization of these pedigreed
field trials by local fungi, insect and marsupial species
have provided a robust experimental system in which to
study individual species, as well as community and
ecosystem level responses to genetic variation in E.
globulus. This talk will over view the insights we have
gained on the extended genetic effects on canopy and
bark communities on E. globulus as well as more distal
effects on litter and log decay communities. Community
responses have been explored at multiple genetic levels
from genetically divergent geographic races, additive
genetic effects within races, to within family QTL
effects. We address the genetic drivers of insect,
marsupial and fungal responses to this genetic variation
at the species and community level, the relative
importance of direct and indirect genetic effects, and the
potential for co-evolution through genetic co-variance
amongst dependent organisms and feedbacks on tree
fitness.
Historical evolutionary dynamics results in
convergent ecological consequences for biodiversity
and ecosystem function
Bailey, J1
1
University of Tasmania, Australia
Understanding how historical evolutionary dynamics
impact contemporary ecological interactions represents a
major frontier linking ecology and evolution. Whether
genetic variation in one species can affect associated
species interactions and the ecosystem processes
mediated by those interactions is fundamental to
understanding the links between ecological and
evolutionary dynamics. Over the last decade, an
emerging body of work provides support for the
hypothesis that genetic variation in one species can have
extended consequences for associated species. These
genetically-based species interactions can also result in
significant variation in biodiversity as well as patterns of
energy flow and nutrient cycling. Building upon the links
between genes and ecosystems, emerging studies suggest
that evolutionary divergence in one species can also alter
community structure and nutrient cycling. While these
studies show that historic evolutionary patterns of race
formation can impact biodiversity and soil nutrient
availability, it is difficult to determine whether the
ecological effects that have been observed are an
idiosyncratic consequence of historic evolutionary
dynamics or do similar evolutionary processes lead to
convergent ecological outcomes? Here we show that
parallel evolutionary dynamics can result in convergent
ecological outcomes.
Parasitic plants – puppets or puppet masters of
community genetic effects?
Rowntree, J1
1
University of York, UK
Rhinanthus is a genus of hemi-parasitic plants (yellow
rattles) common in the grasslands of Europe and North
America. Species of Rhinanthus are generalist parasites
with a wide range of documented host plants, particularly
associated with grasses and legumes. They have been
described as keystone ecosystem engineers, capable of
driving change not only in the diversity and structure of
associated plant communities, but also the structure of
arthropod and soil microbial communities and the
cycling of nutrients through the system. Until recently,
the role of genetic diversity in these complex grassland
systems has been ignored. In greenhouse experiments,
we have demonstrated that genetic diversity within a
grass host species, and among populations of Rhinanthus,
alters the suitability of an individual host plant and the
impact of infection by the parasite. We have also shown
that parasitic infection of a host grass changes intraspecific competition among aphid herbivores feeding
exclusively on the host, while genetic diversity among
aphids determines survival of the parasitic plant. Both the
effects of the parasitic plant on the aphids and the aphids
on the parasitic plant are mediated via genetic diversity
in the host plants themselves. Therefore, within species
genetic variation in all interacting species (host plants,
parasitic plants and herbivores) determines the outcome
at various levels of the tripartite interaction. So, are the
parasitic plants really driving community level changes
or is their success controlled by indirect interactions with
herbivores? Current work focuses on teasing out and
determining the importance of community genetic effects
in natural populations of Rhinanthus.
Genotype by genotype interactions: above- and
belowground consequences in Solidago
Genung, M1
1
Community genetics research has emphasized the idea
that species are embedded in a matrix with many other
species in variable environments, and this perspective
suggests that the effects of genetic variation should not
only be assessed in a focal species but also in the
neighboring species with which the focal species
interacts. Plant–neighbor interactions represent a
common type of genotype by environment interaction in
which the ‘environment’ (e.g., neighbor plant) contains
genes. Additionally, in plant–neighbor interactions
participants are fixed in space and forced to interact for
resources. Therefore, genetic variation in an individual’s
neighbors can have important consequences for overall
plant fitness and performance. However, plant–neighbor
studies which have examined genotype by genotype
interactions have typically focused on the aboveground
productivity and fitness of the plants involved, and less is
known about how these interactions affect belowground
traits and associated communities. We used common
garden experiments which manipulated genotype identity
and neighbor genotype identity to examine the effects of
genotype by genotype interactions on a range of plant
traits, including rhizome biomass, coarse root biomass,
vegetative biomass, and floral biomass. The effects of
plant genotype identity were stronger for aboveground
traits than for belowground traits, while the opposite
pattern was observed for the effects of neighbor genotype
identity. These results show that genotypic variation in a
plant’s neighbors can have significant ecological
consequences, and that studies which only examine
aboveground biomass may underestimate the importance
of plant–neighbor interactions.
Genetic feedbacks impact ecosystem processes:
linkages between above and belowground processes
Schweitzer, J1, Bailey, J1, Madritch, M2
1
University of Tasmania, Australia; 2Appalachiain State
University, USA
A growing interest in the consequences of biodiversity
on ecosystem processes has led to researchers examining
the effects of intraspecific variation on energy flow and
nutrient cycles. Fine-scale intra-specific variation in plant
traits among genotypes, evolutionarily diverged plants or
genetic variation at the population level leads to
phenotypic variation, such as differences in productivity
and phytochemistry. Across multiple plant groups this
variation often leads to heritable organic matter dynamics
in the soil system by having large effects on rates of litter
decay, influences the composition and activity of
heterotrophic soil microorganisms and influence rates of
carbon and nitrogen cycling. When seedlings from across
a genetic gradient as well as individual genotypes are
planted in soils previously conditioned with other species
or genotypes, a home-field advantage occurs whereby
seedlings have 2-fold higher survival, perform up to 35%
better and maintain higher rates of genetic variance in
their home soil than in soil conditioned by other plants.
These data suggest that there may be evolutionary
consequences for tight plant-soil linkages and that
positive feedback may have a role in maintaining plant
populations and community dynamics in forest
ecosystems.
University of Tennessee, USA
61
Conservation issues associated with the community
genetics of foundation forest trees as drivers of
community diversity, structure, stability, and
evolution
Whitham, T1
1
Northern Arizona University, USA
The community phenotypes and genetic structure of
foundation species, often forest trees, are especially
important to quantify as these species are by definition,
‘community and ecosystem drivers’. Using examples
from Populus and Pinus, our findings show that different
tree genotypes support different communities of
organisms (soil microbes, mycorrhizae, arthropods,
vertebrates, understory plants, lichens, pathogens) and
that these differences can be quantified as heritable plant
traits. Thus, genetic diversity in foundation tree species
affects biodiversity and is very important to conserve
even when these trees are extremely common on the
landscape. Using diverse examples, the community
phenotypes of forest trees can be traced from the
individuals possessing the trait, to the community, and to
ecosystem processes such as leaf litter decomposition
and N mineralization. Any agent of selection such as
climate change that affects the distribution and genetic
structure of foundation trees is likely to have cascading
impacts, both ecological and evolutionary, on the rest of
the ecosystem. Such a community genetics approach
allows us to place community and ecosystem ecology
within an evolutionary framework, and make better
management decisions concerning conservation,
biodiversity, climate change, and genetic engineering.
Sym150: Diversity, ecology and evolution of
extrafloral nectaries – 25 July
Distribution of plants with extrafloral nectaries
Keeler, KH1, Weber, MG2
1
School of Biological Sciences, University of Nebraska–
Lincoln, USA; 2Dept of Ecology and Evolutionary
Biology, Cornell University, Ithaca, NY, USA
Extrafloral nectaries (EFNs) are plant glands that secrete
sugar water and are located outside the flower. Most
studies of their function show them attracting
invertebrate predators whose presence reduces herbivory.
EFNs have been reported on a few ferns and in diverse
Angiosperms but no Gymnosperms. The actual number
of plant species with EFNs is unknown but more than
4000 species, from over 750 genera in 117 plant families
have been reported, about 1.9% of vascular plants.
Plotting the known plant families with EFNs in the
angiosperm phylogeny (P. F. Stevens, Angiosperm
Phylogeny Website, Version 9, May 2010) shows EFNs
widely but irregularly scattered throughout the Orders.
They are uncommon in the basal Magnoliid families,
although present in the Aristolochiaceae. EFNs are
infrequent in monocotyledons, yet found on a few
grasses, among the Liliaceae (sensu latu), and frequent
on the pedicels and peduncles of orchids. Basal Eudicot
families such as the Proteales and Gunnerales have no
62
reported EFNs, although they are present within the
Ranunculaceae. Core Eudicots include many families,
genera and species with EFNs, including species within
the Asterales, Lamiales and Gentianales although EFNs
have not been reported in the Apiales. Within some
Orders and a number of families, clustering allows use of
EFNs as taxonomic characters, as within the Fabaceae. In
some families, e.g. the Ebenaceae, they are present on all
species. Having all or nearly all species with EFNs is
most common within genera, e.g., Passiflora
(Passifloraceae), not at higher levels of classification.
The data is consistent with separate origins of EFNs in
different lineages (e.g., Viburnum, Adoxaceae) and
likewise with loss of the trait in lineages within some
taxa where EFNs are otherwise common (e.g. Ipomoea,
Convolvulaceae). EFNs are morphologically diverse and
can occur on virtually every aboveground plant tissue.
They have not been reported underground. All life forms
have EFNs, but they seem particularly common in vines
and particularly uncommon in annual herbs. EFNs are
largely if not entirely absent from aquatic plants. EFNs
appear to be more common in tropical taxa than
temperate ones, even allowing for the greater species
richness in the tropics. Considering that EFNs release
water, they are surprisingly common on desert plants.
The duration of activity and the complexity of EFN
structure varies greatly between taxa. The diversity of the
morphology and distribution of EFNs suggests a strong
role of selection on them, but the joint impact of
phylogeny and ecology has made recognition of patterns
difficult. New technologies and better phylogenies offer
much hope for new insights in the coming decades.
Nectaries in ferns: their distribution and ecological
role in pteridophytes
Koptur, S1
1
Florida International University, USA
The oldest group of plants in which nectar secretions
have been observed are the pteridophytes; nectaries have
been reported in a dozen extant genera. The function of
these nectaries has been investigated in several fern
species, and in some circumstances has been
demonstrated to have an antiherbivore role, attracting and
maintaining biotic defense (ants and/or other predatory
arthropods). The widespread bracken fern, Pteridium
aquilinum, has been studied in many places around the
world; the benefit from the nectaries varies with
geographic location, nectary visitors involved, and array
of herbivores present in each location. More
experimental work is needed in genera with nectaries
about which we have little ecological information,
especially about their plant/animal interactions. Nectaries
in ferns are most often morphologically simple, and may
be overlooked if the exudates are removed by various
visitors in nature. When plants are grown in a
greenhouse, or in protected areas such as gardens or
nurseries where potential nectar drinkers are absent for
various reasons, one may observe either droplets of
nectar, or sooty mold that grows on, and consumes,
accumulated nectar. The presence of sooty mold may be
the first indication that nectar is being produced (once
honeydew from phloem-feeding insects is ruled out), and
then a simple sugar detection method can reveal if nectar
is the reason for the sooty mold accumulation. Sooty
mold occurs at the base of fronds of Pleopeltis
crassinervata, a widespread epiphyte growing on a
variety of trees found in cloud forest areas of Veracruz,
Mexico. This species, segregated from the former genus
Polypodium, is not in the section of Polypodium known
to possess leaf nectaries, and so is a new record for this
species, and this group of ferns. Previous experimental
work on other epiphytic species of Polypodium
demonstrated the protective role of ants for developing
fronds, so we conducted similar experiments (using
nylon polish to cover nectaries, rather than excluding
ants as in earlier work) as the fronds of Pleopeltis
crassinervata are small, and often lie flat against the trees
upon which they grow. Fronds with nectaries covered
suffered greater damage from herbivores over the course
of their development, compared with fronds that had
nectaries functioning normally. A parallel experiment
conducted on a sympatric fern species without nectaries
showed no difference between manipulated and control
fronds. Seven species of ants were observed visiting
nectaries and on fronds of P. crassinervata, but differed
in their response to herbivore larvae placed on the ferns.
The presence of nectaries, and the relationship with ants,
may explain why this epiphytic fern is the most
widespread and persistent species, resilient to
disturbance, and found on shade trees in coffee
plantations throughout its range.
Diversity and evolution of extrafloral nectaries in
Leguminosae
Marazzi, B1, Bronstein, JL1, Simon, M2, Delgado
Salinas, A3, Luckow, MA4, Sanderson, MS1
1
Dept of Ecology And Evolutionary Biology, University
of Arizona, USA; 2Embrapa Genetic Resources and
Biotechnology, Brasília, Brazil; 3Instituto de Biología,
Universidad Nacional Autónoma de México, Mexico;
4
Dept of Plant Biology, Cornell University, Ithaca, New
York, USA
Extrafloral nectaries (EFNs) are nectar-secreting organs
on plant parts external to flowers, which commonly
attract ants that feed on the nectar and, in return, protect
the plant from herbivores. EFNs occur in up to 117
angiosperm families, and are common in Leguminosae.
Not only is Leguminosae the third largest and
economically the second most important angiosperm
family, but it also dominates many kinds of vegetation
worldwide and is highly diverse in its interactions with
ants and other organisms. Indeed, ant-legume interactions
may play an important role in shaping the ecology and
evolution of entire ecosystems. Leguminosae display an
impressive diversity in EFN morphology, location on the
plant, nectar features, and ecological role. The
phylogenetic distribution and evolution of EFNs have not
yet been characterized for this family. Here we explore:
How many legume genera have at least some species
with EFNs? How many times and when did EFNs evolve
in legumes? Of the 105–116 legume genera with EFNs
(in at least some species), we compiled, primarily from
published reports, 46–47 belonging to the subfamily
Mimosoideae, 32–37 to the Papilionioideae, and 27–32
to the Caesalpinioideae grade. Within subfamilies, EFN
genera represent only 7–8% of all papilionoid genera,
whereas caesalpinioid and mimosoid EFN genera
represent up to 16–19% and 56–57% of their genera,
respectively. The phylogenetic distribution of EFNs in
Leguminosae thus appears to be diffuse, dense, and
patchy simultaneously, with most EFN genera – and
probably also most EFN species – concentrated in the
sister clade of the Papilionoideae, which includes many
caesalpinioid lineages and the Mimosoideae. Foliar and
stipular EFNs appear to be most common (ca. 65% and
15% of the genera). Parsimony reconstruction of EFN
presence reports mapped on a Bayesian mega-phylogeny
of 829 legumes (ca. 400 genera) inferred at least 35
independent EFN origins (not considering reversals or
gains after losses). While EFNs seem to have originated
multiple times in the Caesalpinioideae grade and
Papilionoideae (at least 24 and 10 times, respectively),
they appear to have originated only once in
Mimosoideae. Based on Bayesian divergence time
analyses of the legume mega-phylogeny, we present
results of the tempo and mode of EFN evolution in
legumes. We also explore implications of our results for
the current definition(s) of EFNs in Leguminosae and the
associated levels of homology/homoplasy. Our findings
provide new insights that increase our understanding of
the evolution of EFNs in Leguminosae, as well as of the
natural history of ant-plant associations and ant-mediated
anti-herbivore defense strategies.
Passiflora as a model system for studying nectary
diversification: insights and implications
Krosnick, S1, Gasser, C2, Potter, D3
1
Dept of Biology, Southern Arkansas University,
Magnolia, USA; 2Dept of Molecular and Cellular
Biology, University of California, Davis, USA; 3Dept of
Plant Sciences, University of California, Davis, USA
Passiflora is a diverse genus consisting of more than 520
species of vines, lianas and small trees. The group
displays remarkable variation in floral and vegetative
features, even among closely related species. A key
characteristic of the genus is the presence of complex
nectaries throughout the plant. These nectaries encourage
pollination, deter herbivores, and attract bodyguards.
Floral and extrafloral nectaries are present on all species
of Passiflora within flowers, on floral bracts, stipules,
petioles, on leaf margins, and abaxial leaf surfaces. In
Passiflora, the position, shape, size, and arrangement of
nectaries is so variable that homology assessment among
the different nectary classes is difficult. As nectaries
likely represent a key morphological innovation for the
genus, the need for clear statements of homology among
the different nectary classes is great. Examination of
nectary form and function in Passiflora has yielded
several important insights regarding the evolution of
nectaries in the genus. First, initial hypotheses of
homology between floral and extrafloral nectaries have
been rejected based on molecular and morphological
data. This is in contrast to the situation in other Eudicots,
where the two types of nectary have been shown to share
molecular similarities. Second, the use of nectar sugar
profile data to assess variation among extrafloral nectary
classes has not yet yielded informative differences in
sucrose, glucose, or fructose. Amino acid content may be
of greater importance for extrafloral nectaries compared
to floral nectaries. Nectar secretion occurs much earlier
in development than originally expected and appears to
be passive in the mode of release. This calls into question
63
earlier accounts citing cuticle rupture as the primary
mode of nectar release. Third, scanning electron
microscopy has revealed a unique thinning pattern in the
cuticle of petiolar nectaries. These thinning areas
eventually develop into pore-like structures in the cuticle,
a relatively uncommon mode of nectar release in
angiosperms. Fourth, anatomical and developmental data
collected thus far suggest similarities between glandular
leaf teeth found on the margins of stipules and the lamina
with those found on the petiole and abaxial surface.
These data suggest that a similar developmental program
is acting during leaf development to create diverse kinds
of extrafloral nectaries. Thus, the final location and form
of the nectaries may depend most on the maturity of the
leaf tissue that this shared developmental program is
active within. These data are considered with regard to
the overall phylogenetic framework of Passiflora. The
patterns of diversification in extrafloral nectaries are
closely tied to the lineages in which they are found,
supporting a preliminary hypothesis that nectaries do in
fact represent a key innovation for the genus.
Implications for homology assessment are considered not
only for Passiflora, but for other relevant angiosperm
lineages as well.
Glands and geography: geographic variation in
extrafloral nectaries in the genus Adriana
(Euphorbiaceae)
1
Mackay, D , Whalen, M
1
1
Flinders University, Adelaide, Australia
Plants in at least 93 families possess extra-floral nectaries
(EFNs) that secrete nectar that is attractive to ants
(Koptur 1992). Plants in a wide range of habitats that
attract ants to their foliage by providing nectar from
EFNs often experience reduced herbivore loads or levels
of herbivory. Temporal and spatial variation in the
quality of the defence provided by ants against
herbivores has also been noted by various authors and
has been ascribed to variation in weather conditions,
altitude, the density and diversity of ants and herbivores
and the quality of nectar rewards (Koptur 1992, Bluthgen
et al. 2004, Rico-Gray and Oliveira 2007). To further
investigate factors influencing variability in the outcomes
of this association, we examined geographic variation in
the associations between ants and plants of Adriana, a
genus of dioecious shrubs which is widely distributed in
Australia. Both male and female plants possess stipular
EFNs at the bases of the petioles and nectaries on the
floral bracts. Here we review and discuss a series of
studies examining the associations between ants and
Adriana plants across a continental scale. Consequences
of ant visitation to male and female plants were studied at
sites near Broome, Western Australia; Toowoomba in
south-east Queensland; east Gippsland in Victoria and
near Adelaide in South Australia. Ant and herbivore
communities on adrianas varied among geographic
locations, as did the effects of experimental ant
exclusions. Ants in five to ten genera were observed
visiting EFNs at different locations and significant
effects of ants in lowering herbivore densities were
observed at several locations. Significant effects on
levels of foliar herbivory were only detected near
Adelaide and only on male plants which were visited by
four times as many ants as were female plants. The
64
studies above were conducted under variable climatic
and local conditions, some in periods of drought, and we
explore the association between geographic variation in
climate and the potential role of EFNs as a plant defence.
The provision of water-based nectar from EFNs may
incur greater costs in attracting ant bodyguards under dry
conditions, and in general, conditionality in the outcomes
of defensive mutualisms may reflect variation in the
relative costs of different defences. We examined the
effects of variation in climatic variables, including
rainfall, on geographic variation in nectary sizes across
the ranges of three taxa within Adriana in Australia. For
each taxon, there was a significant association between
gland size and climatic variables related to moisture
availability. A glasshouse experiment testing the effects
of water stress on nectary longevity also revealed that
secretory activity declined more rapidly on droughtstressed plants. Conditionality in the outcomes of
associations between ants and plants with EFNs are
discussed in the context of predicted patterns of future
rainfall and also in relation to the expected investment by
male and female plants in anti-herbivore defences.
Extrafloral nectaries
mutualistic networks
the
basis
for
ant–plant
Rico-Gray, V1, Diaz-Castelazo, C1
1
Instituto de Ecologia, AC, Xalapa, Mexico
Interspecific interactions evolve as a geographic mosaic,
generating not only differences across space and time in
traits and ecological outcomes but also in the number of
species involved. The network structure of these
interactions influences the nature of these ecological and
evolutionary outcomes. Mutualistic networks exhibit
complex but predictable patterns of interaction,
frequently involving many species that form complex
networks of interdependence. Recent analyses have
shown that mutualistic networks among free-living
species are nested. The overall pattern is one of weak and
asymmetric links among species. These network patterns
may be explained by ecological variables and
evolutionary history but few data exist on their spatial
and temporal stability. Several questions have been
addressed using ant–plant interactions: Are ant–plant
mutualistic interactions nested? Which ecological
conditions may result in differences in nestedness among
communities? Does interaction intimacy affect network
structure and species richness? Do networks change in
time? Most of the results are based on the analysis of the
structure of a multispecific network of interacting ants
and extrafloral nectary-bearing plants sampled between
May 1989 and April 1991, and again between October
1998 and September 2000 in La Mancha, Veracruz,
Mexico. Data analysis and statistics were performed
using: Microsoft Excel, Pajek, Aninhado, UCINET, and
XL-Stat. The structure of ant–plant networks exhibits
nested patterns. Interaction intimacy markedly affects the
structure of these networks. When interaction intimacy is
high, the interactions are compartmentalized, when
interaction intimacy is low, they exhibit nested patterns.
These results support a promising approach for the
development of multispecies coevolutionary theory,
leading to the idea that specialization may coevolve in
different but simple ways in antagonistic and mutualistic
assemblages, and that simple features of mutualistic
interactions are likely to have important consequences
for the coevolutionary process and the patterns it
generates in the organization of biodiversity. When
compared in time, the nested topology of the network
remains similar, group dissimilarity increases,
standardized number of interactions for ant species
increases and shifts towards higher values for plant
species, more ant species and less plant species
constituted the core of the more recent network, and
presence of invasive/ruderal species increased while their
contribution to nestedness remained the same. Generalist
species characterized these patterns and appeared to
maintain the stability of the network, since the new
invasive/ruderal species incorporated in the communities
were linked to this core of generalists: the overall
network structure remains unmodified.
the effects of increased carbon dioxide and ultraviolet
light as well as changes in precipitation are being studied,
using bryophytes, in many different countries on several
continents. Research in a variety of ecosystems from
desert to peatlands to rain forest will be discussed. Some
of this research has recently been published in Bryophyte
Ecology and Climate Change. In addition our current
research on the effect of temperature increase on rare
alpine plants including bryophytes in Northeastern U.S.
mountains will be reported. The habitat for alpine
bryophytes is diminishing and plants from lower
elevations are invading the tundra habitat, as is also true
in the European Alps.
Nothofagus as a keystone host for bryophyte diversity
in cool temperate rainforest
Dalton, PJ1
Sym158: Ecology, environment and
conservation of bryophytes – 25 July
Where is the greatest diversity of liverworts and
where are the threats greatest?
Söderström, L1, Hagborg, A2, Von Konrat, M2, Séneca,
A3
1
Dept of Biology, Norwegian University of Science and
Technology, Norway; 2Dept of Botany, The Field
Museum, Chicago, USA; 3Dept of Biology, Faculty of
Science, University of Porto, Portugal
Bryophytes are important components of the vegetation
in many regions of the world, constituting a major part of
the biodiversity in moist forest, wetland, mountain and
tundra ecosystems. Because of their sensitivity to the
immediate microhabitat, these groups of plants are
important environmental indicators and have been used
as predictors of past climate change, to validate climate
models and as potential indicators of global warming.
Yet, alarmingly, our understanding of the degree of threat
of these organisms is scant. In order to understand the
threat level of bryophytes one needs to know i) where
they occur (geographically and habitat) and ii) what the
threats are for that region or that habitat. This talk will
give a global overview of the liverwort diversity using
the Early Land Plants Today (ELPT) database. The
diversity will be compared with the threat to habitats
using the 'Global 200' Ecoregions as larger scale units of
threatened regions. In addition, human population
density is added as an additional layer of threat. This will
be compared with figures for threats for areas where
IUCN Red Lists occurs to evaluate the overall trends. We
also test correlations between high levels of liverwort
diversity and existing international priority areas for
conservation.
Recent research on bryophyte ecology in relation to
climate change
Slack, N1
1
Biology Dept, The Sage Colleges, Troy, USA
Bryophytes are currently being used in many types of
climate change research. Not only global warming but
1
School of Plant Science, University of Tasmania,
Hobart, Australia
Cool temperate rainforest (CTR) in Tasmania is a climax
vegetation characterised by the dicot tree species from
the genera Nothofagus, Atherosperma and Eucryphia and
the conifer tree genera Athrotaxis, Phyllocladus and
Lagarostrobos. In comparison to tropical rainforests,
CTR have fewer woody tree species and the major
floristic component is the bryophytes, whose occurrence
dominates the epiphytic flora. A total of 61 bryophytes
were recorded from the trunk of N. cunninghamii across
its distribution in western Tasmania with hepatics
outweighing mosses up to 5:1. Most species were
facultative epiphytes and the study analysed overall
cover, species richness and liverwort to moss ratios.
Results clearly indicate that there was considerable
variation and it would appear that microclimatic factors
rather than bark characteristics are having the greater
influence for a change in composition of the epiphytic
flora from one forest system to another. Within a single
type of cool temperate rainforest, there is a marked
zonation of the epiphytic flora on the major host tree and
it is further proposed that moisture/humidity is primarily
responsible for the partitioning of bryophyte species. The
results of these studies support the hypothesis that
Nothofagus cunninghamii is a keystone species for
diversity of bryophytes in cool temperate rainforest.
Conservation of the New Zealand bryoflora
Fife, AJ1, Glenny, D1
1
Allan Herbarium, Lincoln, New Zealand
New Zealand is considered a global hotspot for
bryophyte diversity. The latest figures for the number of
documented and described species are 534 mosses, 616
hepatics and 13 hornworts. There is a high level of
endemism: c. 21% of mosses, c. 53% of hepatics, and c.
60% of hornworts are considered endemic. A panel of
New Zealand specialists has met 3 times since 1992 (and
once prior) to evaluate rare and poorly documented
bryophyte taxa using a nationally developed 'New
Zealand Threat Classification System'. In the most recent
ranking threatened or uncommon status has been applied
to 269 described taxa (c. 24% of the total) and to another
25 entities, mostly taxa awaiting description. Forty-four
65
species of bryophytes are considered Threatened, with 28
(12 mosses; 16 hepatics) Nationally Critical, 9 Nationally
Endangered (2 mosses; 7 hepatics); and 7 Nationally
Vulnerable (4 mosses; 3 hepatics). A further 138 taxa and
undescribed entities are considered to be At Risk and 135
Data Deficient. Two mosses (Lindbergia maritima
Lewinsky and Epipterygium opararense Shaw & Fife)
and two hepatics (Petalophyllum australe Colenso and
Schistochila nitidissima R.M.Schust.) are highlighted to
illustrate difficulties and successes associated with their
listing and with preliminary efforts at active
conservation. Each species present unique challenges.
We need to distinguish naturally rare species from those
which have become rare through human activities, but
sometimes cannot do this confidently. Lindbergia
maritima and Schistochila nitidissima illustrate the
former condition, while the rarity of Epipterygium
opararense and Petalophyllum australe probably results
from an interplay of both factors. For species truly in
decline, we need to assess the threat/s and plan
appropriate management efforts. Such efforts are in their
infancy in New Zealand. There is a lack of resources for
those who know the plants sufficiently well to conduct
the needed surveys, although a limited amount of funding
for investigating 'Data Deficient' taxa is now available
through the NZ Dept of Conservation. This should assist
assessing the main threat types and permit efforts to
reverse them for a limited number of taxa. Our most
urgent needs are additional surveys and learning how to
raise bryophytes in vitro and to transplant them back into
the wild.
Conservation of bryophytes in tropical oceanic
islands: study case of La Réunion
Ah-Peng, C1,2, Bardat, J3, Hedderson, T1, Strasberg, D2
1
University of Cape Town, Botany Dept, South Africa;
Université de La Réunion, La Réunion; 3Muséum
National d'Histoire Naturelle, Département de
Systématique et Evolution, Paris, France
2
Islands are unique systems due to their isolation,
restricted area and natural oceanic barriers. Their
environments are particularly vulnerable to the impacts
of climate change, natural hazards (tropical storms,
volcanic eruptions) and the pressures of human activities.
Despite the fundamental importance of their biodiversity
for economic development, less interest has been
focussed on small organisms. Réunion Island
(Mascarenes archipelago), along with Madagascar and
the neighbouring islands forms a hotspot of diversity in
the Western Indian Ocean. The island possesses the
highest summit in the geographical area, the Piton des
Neiges (3070 m), providing a myriad of habitats along
this extensive climatic gradient. Compared to the sister
islands, the bryoflora of Réunion has always been more
well known especially now with the increase of
ecological studies on the island. Presently more than 800
species of bryophytes are reported from Réunion, its
diversity is by far dominated by mosses followed by
liverworts and hornworts. Interestingly the rate of
endemism for bryophytes is low (<10 %) in comparison
with the 30 % for the vascular plant flora. Bryophyte
richness on the island peaks in the cloud forests (~ 1150
m), which provide favourable habitats for their
development. Due to a growing population, especially in
66
the littoral area, some habitats and consequently some
bryophytes species are endangered. As a consequence it
is necessary and urgent to address which measures
should be taken to protect this rich flora. Multiple actions
have been initiated with the aim of increasing knowledge
and awareness of the diversity and distribution of
bryophytes on Réunion. A taxonomic and nomenclatural
index was created, a GIS for bryophytes was
implemented allowing the distribution of species to be
mapped and areas of interest identified both in terms of
diversity and where distribution data of bryophytes was
lacking. Conservation tools in the form of floras and Red
Lists are a priority for the island. Training in bryophyte
identification remains key for enhancing knowledge and
interest of the local bryoflora. Indeed, it is important to
determine research directions and measures to be taken
for these lesser-known plants that, nevertheless, form an
important part of the diversity on the island. How do we
best conserve this important and diverse bryoflora on
such a small island which is threatened by high
anthropogenic pressures? In the coming future we wish
to use Réunion as a model for conservation actions for
bryophytes in similar systems (tropical oceanic islands),
setting up a methodology for taking into account
bryophytes by nature managers, and promoting target
actions to encourage authorities to include bryophytes in
their conservation plans. Réunion is part of the European
outermost regions and territories, these places have an
exceptional biodiversity and the pressures they face make
them sentinels of global change, there is a target
goal/task to unite actions to slow down biodiversity
depletion before even describing it between these
different regions (Indian, Atlantic and Pacific Oceans).
What are we trying to conserve? The role of
phylogenetics in taxon recognition and prioritization
for conservation
Mishler, B1
1
University of California, Berkeley, USA
Much greater attention needs to be paid to conservation
of bryophytes, and to do this effectively a number of
aspects of their biology must be advanced. I will focus on
systematic aspects of the problem – what is to be
conserved? Many bryophyte taxa, especially in the
tropics, are poorly characterized, and the names given
them under the current code of nomenclature cannot
clearly indicate their meaning and status. Because of
many problems with instability and lack of comparability
of ranks in the current Linnaean system, we need a new
rank-free phylogenetic basis for taxonomy (e.g., the
Phylocode). In such a system, all taxa to be named
should be hypothesized monophyletic groups. Not all
such groups need be named, but those that are named
formally should be given unranked (but hierarchically
nested) uninomials. The applicability of a name should
be fixed using multiple specifiers rather than a single
type specimen as in the current system. What about the
species rank? This is controversial even within the
Phylocode community, but I argue that the least inclusive
taxon (formally known as 'species') should be treated in
the same rank-free manner as taxa at other levels. Current
entities ranked as species are not comparable in age,
internal genetic diversity, ecology, the amount of
morphospace they occupy, the size of the phenetic 'moat'
around them, or the amount of interbreeding within them
(or lack thereof between them), nor can they be made to
be comparable through any massive realignment of
current usage. Finally, I will explore the practical
implications of eliminating the rank of species for such
areas as education, ecology, evolution, and conservation,
and conclude that these purposes are better served by this
move. The basic element of biodiversity is not species,
but rather the semaphoront, a specimen along with all
associated metadata. These semaphoronts can be built up
into hypotheses of clades using molecular and
morphological data, to study all aspects of biodiversity
science. How can we inventory biodiversity without
species? New quantitative measures for phylogenetic
biodiversity, which take into account the number of
branch points (and possibly branch lengths) that separate
two lineages, should be applied. What does ‘rarity’ mean
without ranks? The phylogenetic worldview described
above can clarify greatly what 'rarity' means. Rarity
fundamentally means having few living close relatives,
where ‘few’ and ‘close’ are measured quantitatively on
cladograms. Conservation priorities can be better guided
by phylogenies rather than a list of species names. The
need for biodiversity inventories has never been greater;
fortunately recent advances have been made in the
discovery, characterization, and presentation of
biodiversity information. High-throughput molecular
techniques, faster phylogenetic methods, highly
improved geographic information systems and databases,
and better web visualization approaches are all welcome
aids in this crucial task. Biodiversity assessment no
longer needs to rely on pre-evolutionary, species-centric,
list-making approaches, but instead can focus on
biodiversity discovery and understanding at many
phylogenetic scales. Examples will be presented from the
Moorea Biocode Project in French Polynesia, and the
Jepson Flora Project in California.
Sym163: Medicinal plants – 26 July
Diversity of medicinal plants in Maruthamalai,
Coimbatore District, Tamil Nadu, India
1
Narayanasamy, V
1
Sir Thiagarajar College, Chennai, India
Biodiversity is the totality of genes, species and
ecosystems of a region. It is not evenly distributed due to
variation in environmental conditions. Diversity
consistently measures higher in the tropics and lower in
other climatic zones generally. The aesthetic value of
biodiversity is well realized and it could not be valued
ideally with the current economic valuation models. Of
late, biodiversity is more reckoned for its unbelieved
potential for supplying novel genes for a variety of
applications in biotechnology and pharmacology.
Western Ghats are themselves renowned as one of the
world’s great biodiversity hot spots. Maruthamalai, a part
of Western Ghats in Tamil Nadu have arid climatic
condition with tropical dry deciduous forest vegetation.
In the present study 62 medicinal plants of 32 families
were identified. Medicinal plants like Capparis
zeylanica, Flueggea leucocephala, Erythroxylon
monogynum, Spergula arvensis, Croton bonplandianum,
Cleome viscosa, Mollugo ceruviana, Oldenlandia
umbellate, Grewia hirsuta, Pavetta indica, Gardenia
resinifera, Eucalyptus longiflorus, Zizyphus trinervia,
etc., are used for various ailments such as cough, cold,
headache, fever, jaundice, diabetes. Still to bring out the
information on therapeutic uses, further studies are
suggested in this region.
Ethno-pharmacological studies of medicinal flora in
Palamalai, the Western Ghats, Tamil Nadu, India
Srinivasan, N1
1
Gurunanac College, Chennai, India
The conventional knowledge of folk-medicine is now
deteriorating drastically along with loss of species in
many biodiversity nations. The floral diversity of
Palamalai is recognized for conventional therapeutic
values. However, no floristic list was prepared with
respect to medicinal uses in this region. Therefore, it is
necessary to collect and document medicinal plants in
Palamalai. In this regard, a survey on the medicinal
plants of Palamalai was made. The study revealed that
the plant species such as Commiphora wightii, Grewia
obutifolia, Sapindus emarginatus, Cassia auriculata,
Phyllanthus reticulate; Waltheria indica, Plumbago
zeylanica, Trichodesma indica, etc., were tested for
different pharmacological activities viz., antipyretic,
antiulcer, anti-inflammatory, antidiabetic, anticancerous,
etc. The study confirmed the traditional on these species
for medicinal uses.
Genetic diversity and its conservation implications of
two endangered medicinal plants of the Western
Ghats of South India using ISSR markers
John De Britto, A1
1
PG & Research Dept of Plant Biology and
Biotechnology, St Xavier’s College (Autonomous),
Palayamkottai, Tamilnadu, India
The demands of the majority of the populace for
medicinal plants have been met by indiscriminate
harvesting of spontaneous flora, including those in
forests. This has resulted in severe loss of habitat and
genetic diversity. As long as the destruction of forest
continues, medicinal and aromatic plants and their
natural habitats will remain under the threat of
overexploitation than ever before. The ultimate goal of
conservation is to preserve the natural habitats of
vulnerable medicinal plant species and to achieve their
sustainable exploitation in less vulnerable areas.
Conservation genetics plays a major role in guiding
relocation and reintroduction efforts and in prioritizing
species for conservation. Genetic approaches allow us to
assess the variability in these populations, as well as to
assess whether there is any history or future danger of
loss of genetic variability. Genetics can help to do
viability analyses by testing hypotheses concerning how
long genetic variation might persist into the future. Two
endangered medicinal plants Piper barberi Gamble and
Adhatoda beddomei C.B.Clarke were collected from ten
locations in the Western Ghats of south India and the
genetic variability and genetic differentiation within each
species were examined. Inter-simple sequence repeat
67
(ISSR) marker data were obtained and analyzed with
respect to genetic diversity, structure and gene flow.
Natural factors such as unprecedented climatic changes
and anthropogenic pressures such as habitat degradation
and over harvesting are largely responsible for genetic
depletion and rarity of these medicinal plant species.
New means and mechanisms are to be worked out for
long-term conservation and sustainable utilization of
these rare and economically important medicinal plants.
The populations of both the species urgently need
protection to maximize the genetic diversity and diminish
further substantial loss within the populations.
Conservation strategies for these two endangered species
are proposed. The strong genetic differentiation among
populations of these two species indicates that the
management for the conservation of genetic variability
should aim to preserve every population of these species.
It is suggested that in situ conservation be an important
and practical measure for maintaining the genetic
diversity of these species. Ex situ conservation should
sample from different populations across the distribution
range of these species to conserve high genetic diversity.
High altitudinal aromatic plants and their uses as
religious purposes by local peoples and bhotias in
Ganga Valley of Uttarkashi District (Uttrakhand),
India
Kumar, S1, Dhingra, GK1, Arya, R1, Rawat, AS1,
Rather, MA2
1
RCU Govt PG College Uttarkashi, Uttarakhan, India;
Dept of Chemistry, RCU Govt PG College Uttarkashi,
Uttarakhand, India
2
It has been known for a long time that aromatic
substances (essential oils, extracts) contained in plants
often exert psychological effects ranging from sedative to
excitatory actions. Medicinal effects have also been
confirmed through numerous experiences. Aromatic
compounds from plants for the purpose of affecting a
person's mood or health. In ancient times, aromatic trees
and herbs were offered to deities, mostly as incenses that
were believed to carry people's wishes, such as requests
to cure sick people, and to gain Para psychological
experience, to Heaven. It therefore may not be surprising
that aromatics were often used in medicine, which once
had close ties with shamanism, animism and other
religious activities. The ingredient or raw materials used
in hawan are basically herbs and roots of various
aromatic plants. The study area is concentrated around
the Ganga (Bhagirathi) Valley (Harsil, Bhagirathi Peak,
Gangotri-1, Gangotri-2, Tapoban, Nandan Ban,
Banderpunch, Satopant and Gowmukh, etc.) of
Uttarkashi district in Uttarakhand state. The purpose of
this research work is to describe the importance of
aromatic plants, habits, identification and their uses by
local peoples/ Bhotias in the form of Dhoop sticks,
Agarbatii sticks and Havan as religious purposes. Plants
belonging
to
the
families
Boraginaceae,
Caryophyllaceae,
Chenopodiaceae,
Compositae,
Cruciferae,
Gramineae,
Labiatae,
Leguminosae,
Geraniaceae, Liliaceae, and Rosaceae were reported
highly aromatic in nature at research sites. In study areas
Geranium himalayense, Ocimum bacillicum, Lavandula
angustifolia, Cymbopogon Citratus Eucalyptus globulus,
Rosmarinus officinalis, Actinopteris dichotoma, Skimmia
68
laureola, Skimmia anquetelia and Artemisia sp., etc,
were recorded. Local peoples and Bhotia tribes used
these plants to made agarbattis, Dhoop and Havan
materials, etc. Powdered gummy wood as an adhesive
medium for binding the paste to the stick. The use of
hands and fingers has resulted in the hand rolling process
as no machines were used since ancient times.
Sym164: Environmental adaptation –
26 July
Traversing the continent: local adaptation in poplar
(Populus trichocarpa) along western North America
geographic clines
McKown, AD1, Guy, RD1
1
University of British Columbia, Vancouver, Canada
Cottonwood poplar (Populus trichocarpa) is a
widespread, deciduous tree in western North America
that shows local adaptation and selection for traits in
relation to local growing season and climate. The
genomically sequenced tree is a model for understanding
tree biology, and there is strong interest for its use in the
agro-biofuels industry. Over 2000 trees (representing
replicate plantings of 499 collected genotypes in 150
provenance localities from Alaska to Oregon) were
grown in a common garden in Vancouver, Canada. Our
studies investigated inherent trait variation within P.
trichocarpa focusing on numerous traits relating to
seasonal (phenological) events, biomass accumulation
and growth rates, C and N isotopes, and photosynthetic
traits. Traits were analyzed in relation to photoperiodic
(latitudinal) and climatic (temperature, precipitation)
clines, and in trait-trait combinations to understand
relationships between plant structure and plant
performance. Collaborative work using single nucleotide
polymorphism data showed that there is no population
structure in P. trichocarpa across western North
America; however, there is evidence for selection in
some genes suggesting local adaptation. Our findings
showed that trees grown in a common garden still
demonstrate substantial differences in phenological
events, growth rate, biomass accumulation, C and N
isotopes, and photosynthesis for the different genotypes.
Many traits had strong correlations with latitude, and
some showed weak association with climate parameters.
In general, the northern genotypes tended to show faster
incipient growth rates, higher photosynthesis and greater
stomatal conductance. Total biomass in these trees was
far lower than southern genotypes because northern trees
set bud entering ‘fall phase’ earlier and lost their leaves
sooner than southern genotypes. Thus, despite faster rates
of growth and higher photosynthesis in northern
genotypes, the innate response to photoperiod shortened
the active growing season resulting in smaller trees with
less accumulation in biomass. Southern trees showed the
opposite trends, and generally showed higher water use
efficiency, lower leaf mass per area, and lower nitrogen
use efficiency. Numerous traits measured in this study
point to response to photoperiod (i.e. latitude) as a strong
driver of local adaptation in P. trichocarpa, and multiple
lines of evidence from our common garden experiment
suggest that northern genotypes show selection for
specific traits relating to maximizing a shortened active
growing season, compared to southern genotypes. Thus,
northern trees of P. trichocarpa are intrinsically adapted
for a short growing season by adopting fast growth rates
and investing in short-lived, high-output leaves, whereas
southern genotypes of the same species are adapted for a
longer growing season overall.
Diversity patterns of plant dispersal syndromes found
in Colombian tropical forests, and their potential
biotic and environmental determinants
Correa-Gómez, DF1, Stevenson, P1, Álvarez-Dávila, E2
1
Centro de Investigaciones Ecológicas de la Macarena
(CIEM), Bogota, Colombia; 2Instituto de Investigaciones
Alexander von Humboldt (IAvH), Colombia
Dispersal syndromes are key functional traits found in
every species of vascular plants. Because of their
importance for plant recruitment, they help us to uncover
the complex relationships found in tropical forests, and in
a similar way to structural diversity and floristic
composition, they show patterns along environmental
and anthropogenic gradients. Through this study, we
evaluated the possible relationships found between
dispersal syndromes and biotic and environmental
factors, using the largest database of vascular plants
found in permanent vegetation plots in Colombia (101
permanent plots, equivalent to 101 hectares). The plots
are found throughout the different biogeographic regions
of Colombia (Pacífico, Amazonas, Orinoco, Magdalena
Medio, Andes, Magdalena Alto, and Caribe), and include
vascular plants with diameter at breast height (DBH)
equal or higher than 10 cm. Based on morphological
features, dispersal syndromes were assigned to each
species, calculating their abundance and percentage per
plot. Preliminary results show that forest fragmentation,
flooding influence, wind speed and annual mean rainfall
are related with the observed dispersal syndromes trends.
Sinzoochory was negatively related with forest
fragmentation, hydrochory increased in flooded areas,
anemochory increased in windy areas and endozoochory
diminished from wet to dry regions. It is proposed that
further spatial correlation analysis, as well as plants
phylogenetical relationships are needed in order to
correctly assess the influence of environmental and biotic
factors in the observed dispersal syndromes trends. Also,
additional field studies on animal dispersers would give
more insight on dispersal syndromes patterns found
along tropical forests.
Adaptability of rare edge populations to climate
change
Schwarzer, C1, Heinken, T1, Luthardt, V2, Joshi, J1
1
University
of
Potsdam,
Biodiversity
Research/Systematic Botany, Germany; 2University of
Applied Sciences, Eberswalde, Vegetational Science and
Applied Plant Ecology, Germany
The mires of Northern Germany are inhabited by several
rare plant populations, which grow there at the southern
margin of their species´ ranges. During the Pleistocenic
glaciations, these cryophilous species were possibly
widespread in Central Europe followed by range
contractions to higher latitudes and altitudes during
periods of global warming. Today, the few remaining
populations in Northern Germany persist in isolated
habitat fragments. According to the ‘Rear-edgehypothesis’,
these
populations
experienced
a
comparatively long selection for tolerances of heat and
drought stress, which could have resulted in specific
local adaptations lacking in the Northern ‘core’
populations. Therefore, the role of these habitats for the
past and future evolution of bog plant communities could
be crucial as a possible shelter for well adapted
populations to future climate changes. To test for
differences in adaptive traits between core and edge
populations, we planted populations of several bog plant
species collected along a gradient from Northern Sweden
to Northern Germany in a common garden into
microcosms that (1) differed in species diversity and (2)
were subject to different environmental conditions
mimicking future climate projections (experimental
drought in spring, artificially enhanced temperature in
winter, enhanced nutrient supply). The expected data will
allow predictions on prospective responses of wetland
plant communities to climate change. These data may be
important for the conservation of the few mires left in
Central Europe and for other populations that occur at the
margin of their species´ ranges especially if the southern
populations perform better in a drier and warmer climate
compared to their northern conspecifics. In the first
season, the dominant matrix species, Sphagnum
magellanicum, grew better in mixtures than
monocultures. This effect was especially pronounced in
the most Northern populations that therefore benefitted
most from species diversity.
Do large flowers have to be short-lived in stressful
environments? Insights from the Cistaceae in a
Mediterranean ecosystem
Teixido, AL1, Méndez, M1, Valladares, F2
1
Biodiversity And Conservation Area, Rey Juan Carlos
University, Mostoles, Spain; 2Instituto De Recursos
Naturales, Consejo Superior De Investigaciones
Científicas, Spain
Larger flowers receive more pollinator visits increasing
the reproductive success, but may also involve high
maintenance costs associated with water use, especially
in hot and dry ecosystems. In this context, short-lived
flowers could play an important role to buffering such
costs. We evaluated the factors influencing floral
longevity in the Cistaceae, a large-flowered
Mediterranean family. Specifically, a study of floral
longevity in response to differences in temperature,
flower size and pollen deposition was conducted in the
largest-flowered species, Cistus ladanifer. Floral
longevity was recorded in 12 species covering diverse
ecological ranges and differing in flower size. For C.
ladanifer we conducted an observational study along an
altitudinal gradient and an experimental manipulation of
floral longevity. We pollinated and capped flowers along
with flowers exposed to natural pollination. Different
GLMMs were used to evaluate both phenological and
treatment effects on floral longevity. We included air
temperature (ºC) and flower size as additional predictors
to statistically control their potential effect on floral
longevity. Flowers of Cistaceae tended to last one day,
69
independently of differences in flower size amongspecies. However, our specific study of C. ladanifer
reported some intraspecific variability in floral longevity,
which was negatively related to flower size, pollen
deposition and, especially, temperature. Flower size was
significantly variable both among and withinpopulations, and also within-individuals; overall, larger
flowers tended to be shorter-lived along the populations.
Relative to treatment effects, capped flowers lasted
longer (1.56±0.55 days) that control (1.25±0.36 days)
and hand-pollinated (1.04±0.11 days) flowers. Lastly,
high temperature (approx. 20ºC) had a differential effect
since limited floral longevity to one day independently of
pollen deposition. Our results show a relationship
between large and short-lived flowers in stressful
environments such as the Mediterranean, and highlight
the importance of floral longevity in this context. They
also show that intraspecific variability in flower size as
well as variation in temperature and disproportion in
pollination can adjust floral longevity. We suggest that
the adjustment of floral longevity in response to flower
size and temperature is adaptative in large-flowered
plants inhabiting Mediterranean ecosystems, where an
adequate water use determines the floral maintenance
costs under these conditions. The observed intraspecific
variation in flower size could buffer the stress,
minimizing these costs, and thereby, smaller flowers are
persistent in populations.
Stomatal density of Quercus pannosa change over
altitudinal gradient in Himalayas
Zhou, Z-K1, Xing, Y2, Su, T2, Huang, Y2, Hu, J2
1
Kunming Institute of Botany, Chinese Academy of
Science, China; 2Xishuangbanna Tropical Botanical
Garden, CAS, China
The observation that changes in atmospheric CO2 partial
pressure have led to changes in stomatal density provided
a proxy to reconstruct paleo-elevation in geological time
by counting stomatal density from fossil leaves. Quercus
pannosa is a middle size tree which is widely distributed
from 2500 to 4500 m in the Himalaya region. A lot of
fossil leaves were found from the Neogene in the same
region. Quercus pannosa has been identified as the
nearest living relative of those fossils. Variations of
stomata of this species among altitudinal gradient were
reached in order to find the relationships between
stomatal and venation density with CO2 density and
reconstruct paleo-CO2 density. Stomatal density increase
with altitude in Quercus pannosa from 565 to 752 /mm2
when altitude increasing from 2500 to 4160 m. However,
stomatal density is sharply decreased from 752 to
539/mm2, when altitude is over 4200 m. Fossil stomatal
density of Quercus pannosa were counted. The CO2
density in the Neogene and present-day can be compared.
Anthropogenic influence on atmospheric composition
can be discussed. The project is support by National
Natural Science Foundation of China (41030212,
30970206)
The relationship between leaf margin characters and
climate: a case study in China
Su, T1,23, Zhou, Z1, Jacques, FMB4, Xing, Y5, Huang, Y5
70
1
Key Laboratory of Biodiversity and Biogeography,
Kunming Institute of Botany, Chinese Academy of
Sciences, Kunming, China; 2Graduate University of the
Chinese Academy of Sciences, Beijing, China; 3Current
address: Key Laboratory of Tropical Forest Ecology,
Xishuangbanna Tropical Botanical Garden, CAS,
Mengla, China; 4Dept of Palaeobotany and Palynology,
Nanjing Institute of Geology and Paleontology, CAS,
Nanjing, China; 5Xishuangbanna Tropical Botanical
Garden, CAS, Mengla, China
The morphology of a leaf is largely affected by the
surrounding environment. In this study, fifty samples
from mesic to humid forests in China were chosen to
understand the relationship between leaf margin
characters and climate. the proportion of woody
dicotyledonous species with untoothed leaves (P) shows
a strong linear regression with mean annual temperature
(MAT), among the several currently proposed LMA
equations, the one resulting from North and Central
American and Japanese data, yields the closest values to
the actual MATs of the Chinese samples (mean absolute
error = 1.9˚C). A new equation derived from the Chinese
forests is therefore developed, where MAT (°C) = 1.038
+ 27.6 x P. Besides, the relationship between P and
precipitation is found. P shows a high correlation to
growing season precipitation (GSP, which is the total
precipitation with mean month temperature more than
10°C). Whereas former works demonstrate that leaf size
correlates most to precipitation parameters among leaf
characters. A new equation is proposed, where GSP
(mm) = 200.9 + 1755.9 x P. This study improves the
unique relationship between leaf margin characters and
climate under the influence of monsoon over China.
Sym165: Plant invasions – 29 July
A primary study on invasive plants in China
Ma, J1, Yan, X1
1
Shanghai Chenshan Plant Science Research Center,
Chinese Academy of Sciences, China
Plant invasions have been attracting increasing attention
worldwide because of their significant ecological impacts
and economic costs. China is the world's third largest
country with high plant diversity, spanning 50 degrees of
latitude and five climatic zones, so it is vulnerable to the
establishment of invasive species, especial alien species.
Therefore, it is essential for us to investigate the invasive
species and their distribution area in China. In order to
better understand their invasive characteristics, we intend
to collect the primary data of these invasive or potential
invasive plants in China by literature review and
investigation, including the composition of plant taxa,
their habits, invasive origin, introduced time, ways of
introduction, most invasive habitats, invasive grades, and
distribution in each province of China. A geographic and
taxonomic overview of the invasive plants in China is
given based on various reports in references. A total of
563 species have been recognized as invasive plants or
potential invasive plant from China. The invasive plants
are represented by 308 genera within 71 families, of
which the Compositae, Gramineae and Leguminosae are
most important. Most invasive species in China originate
from the Americas and Asia. Southeast coastal areas and
south provinces of China, such as Guangdong, Hainan,
Fujian, have higher number of invasive plants than that
in north areas. In order to evaluate the harmfulness, we
divided these invasive species into 5 grades: (I) Most
aggressive with large economic loss, like Eichhornia
crassipes (Pontederiaceae), Eupatorium odoratum
(Compositae), etc; (II) Aggressive with ecologic and
economic loss, but less than largely or broadly, like
Mikania micrantha (Compositae), Spartina alterniflora
(Gramineae), etc.; (III) Common weeds or unwelcome
trees or shrubs, with damage less or not too evident, like
Solidago canadensis (Compositae), etc.; (IV) Locally
aggressive, especially in Jilin, Beijing and Hong Kong,
etc.; (V) Invasive occasionally, rarely, sparsely,
scattered, or once invasive or widespread but more or
less invasive, or not invasive yet but with potential
ability in the future. The aim of our study is to provide
basic information on the number and harmfulness of
invasive plant species in China, and to seek more
attention of the public for the increasing problems with
invasive plants, besides further research work in the
future.
How to conquer the desert? The neophytic flora of the
Southern Atacama Desert
Stoll, A1,2, Nickerl, J3, Squeo, F4
1
Center of Advanced Studies in Arid Zones, Chile;
University of La Serena, Chile; 3Dept for Botany,
Technical University Dresden, Germany; 4Institute of
Ecology and Biodiversity
2
Neophytic invasions are one of the most challenging
issues within conservation biology. Chile, like most of
the other parts of the world, is faced with that problem
with the particularity of being a biogeographical island.
Human activities, especially land use change, and
globalization have become more intensive with a lasting
effect on the Chilean flora. In our study we focus on the
neophytic flora of 29 priority areas for biodiversity
conservation defined in Atacama Region (Chile). Within
these priority areas we registered 59 neophytes, mostly
with a Holarctic origin (76%), but currently are
cosmopolites. We reveal that neophyte plant species are
spread over nearly 40% of the surface of the priority
areas. More than half of this extent is occupied by
neophytic annuals (61%), which are also the most
represented life form (56%). In contrast native annuals
only constitute 24% of the flora in Atacama Region.
Parallels between the patterns of native and neophytic
flora are detected in terms of the most diverse families
(Asteraceae and Poaceae) and altitudinal distribution of
species diversity (high in the Coastal sector). A
comparison with similar regions in the world reveals
highest similarities with the neophytic flora of Argentina
and Australia. The main invaders of different native
ecosystems
are
Erodium
cicutarium
and
Mesembryanthemum crystallinum, special attention is
laid on worldwide invaders as Arundo donax and
Tamarix ramosissima. Meanwhile most species still not
present invasion characteristics, they represent a potential
risk for the conservation efforts of the threatened native
flora and natural ecosystems of the Southern Atacama
Desert.
Catchment scale dispersal of the invasive willow,
Salix cinerea, in south-eastern Australia
Hopley, T1,2, Young, AG2, Zwart, A2
1
Research School of Biology, Australian National
University, Canberra, Australia; 2CSIRO Plant Industry,
Canberra, Australia
Willows are aggressive exotic components of many river
systems in south-eastern Australia and they have the
potential to expand their range. Current control efforts
for the most highly invasive willow species, Salix
cinerea, are extensive, costly and not always successful
due to rapid post-removal reinfestation. An improved
knowledge of the reproductive ecology and dispersal
dynamics of this species will help to minimise future
expansion and make current control efforts more
effective. The species was found to be predominately
insect pollinated but can exhibit wind pollination which
has the potential for long distance dispersal. Seed
production is highly variable across the catchment with
average seed production over 300,000 seed per tree,
equating to over 150 million seed produced in just 12 km
of infested river. The sites with the highest density of
larger trees are producing the most seed. A
disproportionally high reduction in propagule pressure
may be attained by first clearing those sites with the
highest contributions. Clearing just 20% of the sites
sampled would reduce seed production in the catchment
by over 50%. This high reproductive output combined
with high initial germination rates, above 95%, gives the
species the potential to reinfest cleared areas and expand
its range. A survey of populations in the Ovens River
catchment of south-eastern Australia was undertaken to
determine seed and pollen movement within and between
populations of S. cinerea. Paternity analysis using
molecular markers show that nearly 40% of seed on trees
are sired from outside the home location. Genetic
profiling of populations in surrounding rivers has
allowed us to identify the most likely pollen and seed
sources to give an estimate of the scale of gene flow.
Results suggest that at least 40% of pollen is moving
more than 15 km between rivers. Seed dispersal shows
similar patterns with 50% of seed dispersal at more than
15 km and a small amount travelling over 30 km. These
results suggest that land managers need to co-ordinate
control efforts across rivers for more effective long term
eradication.
Impacts of the invasive vine Merremia peltata on the
rainforest tree Dillenia biflora and its bat pollinators
in Fiji
Scanlon, A1, Petit, T1
1
University of South Australia, Adelaide, Australia
The invasive vine Merremia peltata (Convolvulaceae)
blankets tree canopies in the rainforest and cultivated
areas of Fiji, but its effects on forest processes is
unknown. We monitored flower and fruit production in
two groups of the common rainforest tree Dillenia
biflora (Dilleniaceae), a bat-pollinated species. Five trees
were cleared of the vine and five remained covered with
it. We counted buds, flowers, and fruits each month for
19 months (2009–2011). Evidence of animal visits to
71
flowers (bite marks and infrared camera footage) was
recorded. Trees with no M. peltata produced significantly
more buds, flowers, and fruits than did covered trees, but
flower abortion rates did not differ between the two
treatments. The proportion of D. biflora flowers that
were pollinated under M. peltata was much smaller than
that of flowers without the M. peltata blanket, indicating
that the vine is decreasing access to the bat pollinators.
The study shows that M. peltata decreases forest
productivity, including resources for bats. M. peltata
should be controlled in protected rainforest reserves.
The adaptive capacity of native and exotic grasses
under climate change
Godfree, RC1
1
CSIRO Plant Industry, Canberra, Australia
Over the coming century, an increase in the frequency
and severity of extreme climatic events is expected to
result in global shifts in vegetation structure, composition
and distribution, as plant populations increasingly face
abiotic stresses that lie beyond their physiological
tolerances. However, in most cases we know little about
the specific traits that are likely to be placed under
selection pressure, the magnitude and distribution of
population- and species-level variation in these traits, and
the relative roles of demography, evolution and plasticity
for coping with increased abiotic stress. Here I present
preliminary results from a study aimed at determining the
adaptive capacity of populations of two perennial, mainly
inbreeding
stipoid
grass
species,
Austrostipa
bigeniculata, which is native to Australia, and the
invasive exotic Nassella neesiana, to future climate
change. Four populations from both species sourced from
a dominant climatic gradient were assessed for variation
in climate-linked physiological and morphological traits,
and then, using a new experimental system for simulating
climate change in the field, subjected to a range of
abiotic stress levels. The results suggest that interpopulation
variation
for
most
climate-linked
physiological and morphological traits is higher for N.
neesiana than for A. bigeniculata, but that withinpopulation genetic variation and heritability is low in
both species. This suggests that populations of many
dominant native and exotic Australian grasses may have
limited capacity to respond to climate change via
selection for climate-related traits.
Sym166: Plant conservation – general –
29 July
Biotechnology and ex situ conservation: the ‘last
resort’ for critically endangered plants in biodiverse
regions
Bunn, E1,2, Turner, S2, Dixon, K2
1
Botanic Gardens And Parks Authority, Perth, Australia;
2Faculty of Natural and Agricultural Sciences, School
of Plant Biology, University of Western Australia,
Nedlands, Australia
2
72
Implicit in ‘Priority for change 1: Building ecosystem
resilience’ in Australia’s Biodiversity Conservation
Strategy 2010–2020 document is the need to ‘Maintain
and enhance ex situ conservation measures as a last
resort for biodiversity conservation’. Biotechnology has a
key role to play in the form of molecular, in vitro and
cryogenic research that provides ‘emergency treatment’
for saving endangered species threatened with imminent
extinction. Selected provenances that can ensure
sufficient genetic representation for restoration can be
identified by genetic fingerprinting technology. In vitro
research can be utilized to micropropagate scarce plant
material (and where seed may not be available), then in
vitro culture lines of key provenances can be maintained
ex situ permanently in culture collections and/or
cryopreserved in liquid nitrogen until required for
propagation and restoration of declining populations or
reintroduction of species that may have become extinct in
the wild. Cryopreserved material can be efficiently stored
than revived and utilized to ensure remedial stocking of
restoration sites to boost genetic representation as
required. Monitoring and further genetic sampling can
provide early warning of inbreeding depression among
offspring in repatriated populations. Examples of
biotechnology research for conserving critically
endangered plants in biodiverse regions (such as the
SWAFR) are presented.
Predicting success in the reintroduction of the
endangered Hawaiian fern Marsilea villosa: an
experimental case study
Chau, M1, Ranker, T1
1
University of Hawaii at Manoa, USA
Conservation of rare and endangered plants can be
accomplished by the practice of outplanting, but
ecological management is often required for new
populations to become established. In species with
narrow habitat requirements, it can be difficult to predict
which management methods will be successful at new
locations. Marsilea villosa (‘ihi‘ihi) is an endangered
Hawaiian fern with only seven populations, all in
ephemerally flooding drylands. Among its unique traits
are long-lived sporocarps (i.e., highly modified leaves
containing sporangia and spores), a requirement of flood
and drought to complete its sexual life cycle, and
vegetative growth in absence of flood. Much of Hawai‘i
experienced an extended drought from summer 2009 to
winter 2010, prompting concern for many endangered
plants. Despite ‘ihi‘ihi’s high drought-tolerance, its cover
at three O‘ahu populations decreased from January 2009
to January 2010 (peaks of rainy seasons). A common
garden experiment was performed to address the
question: Which restoration management techniques will
facilitate growth of outplanted M. villosa? The following
effects were tested in a split-plot factorial design: two
flooding levels (once/none), two light levels (50%
shade/full sun), two weeding levels (bi-monthly/none),
and the interactions of these factors. Clumps of ‘ihi‘ihi
rhizomes were collected from a natural population at
Lualualei, O‘ahu and grown in pots, and 48 similar plants
were randomly transplanted into experimental plots, in
soil also collected from Lualualei (containing a weed
seed bank). Percent cover was measured for M. villosa
and analyzed using multiple-factor ANOVA to determine
how much it expanded in response to treatment
combinations. Sporocarps were counted at the end of the
12-week experiment. Results showed that, as expected,
flooding had the most significant single-factor effect on
increased M. villosa cover (P=0.001) and sporocarp
production (P=0.002). However, shade also increased
cover over the full sun treatment (P=0.004) when the
plants began to experience drought at the end of the
experiment. There was an interaction effect of
light*flooding (P=0.004) because M. villosa grew best in
flooding, shaded plots. Weeding had no significant effect
throughout the experiment. Beyond protected status,
current in situ management of ‘ihi‘ihi populations
consists entirely of weed management, by mowing or
herbicide. While managers hope that extant populations
can recover with subsequent flooding, there is concern
that the dry environments where M. villosa currently
exists may only become drier with climate change.
‘Ihi‘ihi was historically found in a few moderately wetter
valleys on O‘ahu, but those populations were lost to land
development. The results of this study show that laborintensive weed management may be unnecessary if
reintroduced M. villosa is planted under conditions of
flooding and moderate shade, and if planted at the start of
a rainy season, will require minimal management to
become a self-sustaining new population.
Sussex communities: plants and people
Sutcliffe, J1
1
Manhood Wildlife And Heritage Group, West Sussex,
UK
The importance of volunteers and the need for local
communities to be involved in protecting their local
wildlife is enshrined in the Convention on Biological
Diversity (1992) and, in turn, by national governments
such as that of the United Kingdom. In 1997, an
innovative project was established by local people in
Selsey, West Sussex, UK. Their work is presented as a
case study. This pilot initiative has been extended to
involve all 11 parishes on the Manhood (derived from
Main Wood) Peninsula which lies south of Chichester. In
2004, the creation of a Biodiversity Duty for public
bodies and an increasing workload which exceeded the
time available to the volunteers led to the group
appointing a part-time member of staff and a new
working relationship with Chichester District Council.
2010 was the United Nations International Year of
Biodiversity. In June, the group was awarded the
Queen’s Commendation for Voluntary work – a fitting
tribute for some 200 volunteers who have contributed
over 11,000 hours to conservation.
Landscape structure and pollinator behaviour do not
predict reproductive connectivity among populations
of the bird-pollinated shrub Eremophila glabra
Elliott, CP1,3, Zwart, A2, Lindenmayer, D3, Cunningham,
S4, Young, A1
1
CSIRO Plant Industry, Canberra, Australia; 2CSIRO
Mathematics, Informatics and Statistics, Canberra,
Australia; 3Fenner School of Environment and Society,
ANU, Canberra, Australia;4CSIRO Entomology,
Canberra, Australia
The maintenance of viable populations in heavily
fragmented landscapes is thought to be mediated by
connectivity among populations. Connectivity can be
measured structurally (spatial configuration of the
landscape) and functionally (behavioural responses of
organism's to fragments and landscape structure). Given
this, understanding how structural connectivity translates
to functional connectivity is important, especially from a
management perspective, because such landscapes are
often managed structurally but it is the functional
connectivity that is the desired conservation management
outcome. To investigate this relationship we assessed
connectivity in fragmented landscapes in south-eastern
Australia, by examining plant-pollinator interactions of a
common,
bird-pollinated,
autohexaploid
shrub
(Eremophila glabra ssp. glabra). We contrasted
populations occupying three replicated landscape
contexts that ranged from large intact vegetation patches
to small isolated linear strips. We compared the response
of pollinator communities and plant reproduction to these
conditions, and measured functional connectivity by
linking the movement of pollinators and pollen together.
Reduced structural connectivity resulted in significantly
different pollinator communities and lower seed set in the
small linear strips compared to large intact patches.
However, two lines of evidence suggested this did not
translate into reduced functional connectivity. First,
pollinator behaviour of the different communities was
similar among the different populations, and second, all
had similarly high levels of pollen immigration as
assessed by paternity analysis. We attribute this
maintenance of high functional connectivity to notably
mobile pollinators and a self-incompatibility system that
enhanced the genetic connectivity among populations by
favouring foreign pollen. Therefore, we conclude that
reduced structural connectivity did not result in
equivalent loss of functional connectivity, and pollinators
were key to maintaining the current immigrant gene flow
crucial for these highly fragmented plant populations.
Floral biodiversity in New Guinea: how many species
are there?
James, S1, Allison, A1, Snow, N1
1
Bishop Museum, Honolulu, USA
New Guinea, the world’s largest (~890,000 km2) and
highest (4,980 m) tropical island, is considered one of the
most species rich areas on Earth, hosting approximately
6% of the world’s flora and a high level of species
endemism. However, there remains considerable
speculation as to the size of the vascular flora, with
published estimates ranging from 11,000 to 25,000
species. An ongoing systematic and collaborative effort
to develop a species checklist from published literature,
online resources, taxonomic experts, and cross-correlated
with specimen vouchers, suggests that the number of
currently accepted native vascular plant species is about
13,500, with almost a quarter of the species comprising
the extremely diverse orchid family. Because New
Guinea is one of the most poorly collected regions of
Melanesia, localities predicted to be species rich and
currently under-collected are actively being surveyed.
The databasing of herbarium label data, georeferencing
of locality information, imaging of specimens, and
making this data available online, is aiding the
73
clarification and study of the biodiversity and distribution
of the vascular flora of New Guinea. Such uncertainty in
the knowledge of the taxonomy and extent of botanical
diversity of the region hampers both the prediction of the
effects of anthropogenic actions, such as forestry,
mining, and climate change, and the effective
development of conservation plans. With forest across
New Guinea being removed or degraded at the rate of at
least 1.4% per year, the number of species threatened
with extinction is, no doubt, greater than the 1%
currently listed by the IUCN.
Understanding New Guinea botany: collecting density
and floristic patterns
De Kok, R1, Utteridge, T1, Briggs, M1
1
Royal Botanic Gardens, Kew, UK
The large tropical island of New Guinea is considered
one of the world's last remaining wilderness areas with
extensive areas of intact lowland forest surrounding a
mountainous central range. Botanical exploration on the
island has a long history closely linked to European
settlement in SE Asia and Australia and the associated
scientific development in the region. We will briefly
discuss these historical collecting programmes and the
resulting legacy of botanical research available for
contemporary researchers. Using data from historic
herbarium collections as well as data from modern
general collecting floristic programmes, we will examine
collecting patterns on the island. Through this we hope to
highlight particular habitat types and areas of the island
that can be considered over- and under-collected. We
will discuss these patterns in light of conservation needs,
and hope that this paper will provide the botanical, as
well as the wider science and conservation communities,
with a direction for future work on the island.
Sym167: Plant conservation – population
biology – 29 July
Seed ecology of threatened species: implications for
long-term management
Turner, S1, Bunn, E2, Dixon, B2, Merritt, D2, Dixon, K2
many years of absence. Since the beginning of 2009 the
seed biology and seed ecology of two critically
endangered species, Commersonia sp. Mt Groper
(Malvaceae) and Symonanthus bancroftii (Solanaceae),
has been investigated. Commersonia sp. Mt Groper has
fewer than 80 plants remaining in the wild and is only
known from three small populations from the Albany
region near the south coast of WA. In comparison,
Symonanthus bancroftii is a small dioecious shrub known
from only one location near Bruce Rock in the WA
wheat belt, where just two plants were discovered in
remnant bushland in 1996 and 1998. Seed from both
species when fresh were found to be highly dormant –
the seeds of C. Mt Groper were found to possess physical
dormancy while seeds of S. bancroftii were found to have
physiological dormancy. Subsequent research has since
found that C. Mt Groper seeds readily germinate when
they are either nicked or exposed to hot water prior to
incubation, while fresh seeds of S. bancroftii only
germinate when precision nicked and treated with 100
ppm GA (81%) – other treatments assessed (i.e. Kar1 and
dry heat (100°C for 10 mins)) proved to be completely
ineffective. The use of nicking and GA for S. bancroftii
while a good way to stimulate germination under
laboratory conditions nevertheless does not shed any
light on the drivers of dormancy loss under natural
conditions. Subsequent experimentation has since found
that S. bancroftii seeds become Kar1 (smoke) responsive
during after-ripening though the rate of after-ripening is
relatively slow with only 41 % germination after 12
months dry storage. A seed burial trial (still underway)
has also confirmed that seeds maintain high viability
(90%) during soil storage over the first season and also
become Kar1 responsive. Base on these preliminary
results it appears that S. bancroftii may be a fireresponsive species only recruiting following a bushfire
after a period of after-ripening in the soil seed bank,
while Commersonia Mt Groper seeds in comparison have
physical dormancy and as with other species with this
form of dormancy are likely to recruit following some
type of soil disturbance as well.
Management
rather
than
climate
explains
demographic variation in Caladenia orientalis, a
threatened orchid from south-eastern Australia
Coates, F1, Duncan, MJ1
1
1
Dept of Sustainability and Environment, Heidelberg,
Victoria, Australia
For the long-term conservation of threatened flora there
are many factors that need to be investigated to ensure
the maximum likelihood that a species will continue to
exist in situ. A number of these factors are well
recognised including conservation genetics, ecology and
the factors that are likely to influence in situ reintroduction. The seed ecology of threatened species is
one of those often overlooked research areas that may
take longer to yield results (potentially many years) but
nevertheless is of significant importance as it will allow
current and future managers to predict the likely
longevity of the soil seed bank or even provide
information as to the likelihood that a species that is
locally extinct may still persist in the soil seed bank and
what factors are likely to stimulate its germination after
Caladenia orientalis (G.W.Carr) Hopper & A.P.Br. is a
critically endangered orchid. The largest known
populations are confined to fire-managed coastal
heathland in southern Victoria. Trends in population
dynamics at two closely occurring sites were evaluated
against time since fire and rainfall to provide ecological
and biological information relevant to population
management. At both sites, decreased plant size was
inversely correlated with time since fire and the number
of non-reproductive plants was positively correlated with
time since fire. Rates of flowering were inversely
correlated with time since fire at only one site. The
vegetation at this site rapidly accumulated after fire,
whereas recovery was relatively slow at the other site.
Rainfall was not correlated with rates of flowering or leaf
width at either of the study sites, although there was a
University of Western Australia, Perth, Australia;
2
Kings Park and Botanic Garden, Perth, Australia
74
weak inverse relationship between rainfall and the
number of non-reproductive plants at one site. Rates of
pollen transport and fruit set were within reported ranges
for deceptive species. Fruiting plants were significantly
smaller in the following year, whereas non-reproductive
plants remained the same size. The results suggest that
there may be substantial costs associated with
reproductive effort, and that hand-pollinating plants to
boost seed production may lead to decreased plant size in
the following year. Annual variation in rates of flowering
may be influenced by previous reproductive effort.
However, long-term population trends are better
explained by competition from dominant shrubs, which
become increasingly abundant with a lack of fire. Both
populations are fire-managed according to prescriptions
generally considered necessary to maintain the structure
and floristics of heathland although sites differ markedly
in their topographic position. This difference may
underpin the differences in behaviour between the two
populations and may provide insights for site
management. Although increased drought is predicted in
south-eastern Australia as a consequence of global
warming, implementation of appropriate fire regimes is
likely to be a more immediate issue than rainfall at our
study site. The use of fire to manage C. orientalis habitat,
prevent over-abundance or further encroachment of the
dominant shrub Leptospermum laevigatum and preserve
broader biodiversity values is likely to be a prime
challenge for preventing the decline of this critically
endangered orchid. However, these relatively large C.
orientalis populations occur close to land now highly
sought after for development and there is increasing
concern that prescribed fires might escape control lines
and damage adjacent properties. Our results imply that
alternative methods to boost fecundity of selected plants,
such as hand-pollination, may actually compromise
population fecundity. Developing site-specific fire
regimes to promote better habitat is the way forward.
other management regimes were recorded, such as
vegetation height and openness of the vegetation, as well
as groundwater levels near the plots. Climatological data
were obtained from official meteorological stations in the
vicinity. Soil samples were taken in order to investigate
the nutrient requirement of the species. Additionally, the
soil seed bank of two populations was analysed by means
of a long lasting germination experiment. Our field
observations and demographic results have given a good
insight in the life history characteristics of this
unsufficiently known species, as well as in the threats
that weight upon it. A life cycle graph was developed,
making a distinction between main ramets, grown up
from seedlings, and clonally formed side ramets of
different orders, thus quantifying both the clonal and the
sexual reproduction. The plants have a perennial life
cycle, individual ramets being able to survive for several
years in favourable conditions. They form a soil seed
bank with a germination that is delayed over several
years. Analyses of population matrices display different
growth rates in different localities and periods. There
have been dramatic decreases in three of the four
populations during our investigation period. Population
growth rates are related to the applied management
regimes, showing this to be a key factor for survival of
this species. Nonetheless, large differences in number of
ramets were also found, that were only attributable to
climatological parameters, mainly drought. We found a
significant relationship between the number of ramets,
the groundwater level and some management parameters,
such as vegetation height. The flowering and seed setting
were influenced by climatological parameters. Overall, it
appears that the main threat for this endangered species is
the loss of suited habitat, and that there has been a shift
in type of habitat.
Demographic studies result into adapted management
strategies for the rare Helosciadium repens (Apiaceae)
Moreno Saiz, JC1, Fernández-Mazuecos, M2, Génova
Fuster, MM3, Pérez García, N4, Domínguez Lozano, F5
Ronse, A1
1
1
National Botanic Garden of Belgium, Meise, Belgium
Helosciadium repens (Jacq.) W.D.J.Koch, an umbellifer
formerly known as Apium repens (Jacq.) Lag., is a clonal
plant species that is rare and endangered throughout its
natural distribution area (mainly Atlantic northwest
Europe). It is mentioned in annex II and annex IV of the
Habitat Directive of the European Union (Directive
92/43/EEG), listing the species of community interest in
need of strict protection. In Belgium, that lies in the
central part of its distribution area, it is a very rare
species and only five populations exsist. Aiming at
developing a conservation strategy for this species, a
research programme on its conservation biology was
carried out. In a preparatory phase European populations
of Helosciadum repens were screened on their habitat
ecology
and
vegetation
characteristics,
and
phytosociological releves were made. From 2003 to 2007
demographic monitoring measurements were carried out
six times a year in twenty permanent plots in four
Belgian populations. Germination, flowering, seed
setting and clonal growth were recorded in the plots. At
the same time several parameters relating to grazing or
Conservation
gypsophytes
challenges
on
Mediterranean
Dept Biología (Botánica), Universidad Autónoma de
Madrid, Spain; 2Real Jardín Botánico de Madrid, CSIC,
Spain; 3Dept Producción Vegetal, Universidad
Politécnica de Madrid, Spain; 4Dept Biología Vegetal,
Universidad de Barcelona, Spain; 5Dept Biología
Vegetal I, Universidad Complutense de Madrid, Spain
Semiarid environments over gypsum soils occupy a large
area in the Mediterranean basin and, accordingly, in the
Iberian Peninsula as well (c. 150,000 ha). The flora of
peninsular Spain includes no less than 140 gypsophytes
(J Mota et al. 2009) usually occurring in open grasslands
and scrublands within a matrix of heavily humanmodified landscapes. Among the most characteristic taxa
of those communities is the sub-shrub Vella
pseudocytisus L. (Brassicaceae), including two endemic
subspecies in Spain. Their distribution areas are heavily
fragmented and placed c. 200 km apart. Both subspecies
have been included as Endangered in the national Red
List (J.C. Moreno. 2008) and protected by regional laws
in Madrid and Aragón. Since 2001, our research group
performs a demographic monitoring of Vella
pseudocytisus using matrix models to analyze population
dynamics and future trends in vital rates. Seedlings
experience mortality rates of 90%, but mortality drops
75
dramatically as individuals reach the adult stages. Adult
survivorship is key for population viability, with changes
in vital rates at that stage having a strong impact in
overall
population
dynamics.
Fortunately,
a
dendrochronological study in course shows that the
species is a relatively long-lived shrub with their eldest
individuals achieving nearly 50 years. Although some
between-population variability in demographic rates has
been assessed in our studies, 30 to 100 years projections
performed for all populations result in a negative growth
rate. Such observed population trends are discussed in
relation to other studies performed on threatened Spanish
or Mediterranean gypsophytes and xerophytes. Global
and land-use changes will play a crucial role in the
conservation of these species and their communities.
Creating rare from common species – seed sourcing
and restoration of iconic yellow box (Eucalyptus
melliodora)
Broadhurst, L1
1
CSIRO Plant Industry, Canberra, Australia
Yellow box (Eucalyptus melliodora) is a valuable and
iconic tree once broadly distributed from western
Victoria, New South Wales and southeastern
Queensland. The soils coinciding with this distribution
are favourable to cropping, horticulture and grazing
which has resulted in severe loss and fragmentation of
this species and the ecological community in which it
resides. This ecological community is now protected
under both Commonwealth (EPBC) and State (NSW)
legislation. Yellow box is valued for its shade, shelter
and timber qualities as well as being important for
wildlife habitat and honey production. As such it is
important restoration species throughout its distribution.
However, given the high levels of fragmentation that this
species has undergone it is likely that low genetic
diversity and elevated inbreeding may limit the utility of
some populations to act as restoration quality seed
sources. Seed collected under current seed sourcing
protocols from across the southern tablelands of NSW
were assessed for levels of genetic diversity to help
improve yellow box restoration within this region.
Excess seedlings from this analysis were later planted
into two provenance trails and similarly assessed to
determine how much diversity was captured during this
process. Finally, mating patterns and pollen dispersal
were assessed in five reproductively mature restored sites
to determine whether these would be suitable seed
sources for future restoration projects.
Plant breeding systems in alpine ecosystems in the
southern South American Andes – searching for signs
of vulnerability under climate change
Arroyo, MTK1, Humaña, AM1
1
Instituto de Ecología y Biodiversidad, Facultad de
Ciencias, Universidad de Chile, Santiago, Chile
Alpine plants may cope with climate change by upward
migration along steep altitudinal gradients. The ability of
plants to keep up with the pace of climate change will be
influenced by dispersal capacity and breeding system.
Among species with different breeding system, those
76
with strong autonomous selfing capacity should be best
adapted for migration along altitudinal gradients on
account of their capacity to produce seed without the
intervention of biotic pollinators. At the other extreme,
successful migration of self-incompatible and sexually
dimorphic species with specialized pollination might be
impeded if pollinators and plants migrate upward at
different rates, as would be expected from their
respective life history attributes. The autonomous selfing
hypothesis posits that generally cold temperatures and
variable weather conditions at high elevations will select
for autonomous selfing in high elevation ecosystems,
which might suggest that alpine plants are well adapted
to cope with climate change. Here using data from a
published community study for the Patagonian alpine
(50°S) in southern Chile and a parallel ongoing study in
the central Chilean Andes (33°S) (together >200 species)
we investigate the incidence of breeding systems along
the self-incompatibility (SI)-self-compatibility (SC)
gradient. Considering the dominant perennial herb lifeform, where good breeding systems records are most
abundant, both alpine sites show a wide range of
breeding systems, there being large contingents of selfincompatible and partially self-compatible species
habitually serviced by biotic pollinators, in addition to
strongly autogamous species. Contrary to expectation,
the frequencies of SC and SI species in the warm and
sunny central Chilean alpine and the cold and windy
Patagonian alpine are similar, despite wide communitylevel differences in flower visitation rates. Large
breeding system data sets are scarce worldwide. The
available information suggests that in spite of the cold
and variable weather conditions at higher elevations, SI
in perennial herbs is as well represented in the high South
American Andes as in some lowland communities, and
that many alpine species in this region of the world could
indeed be vulnerable under climate change. Research
financed by Fondecyt Grant 1085013 and IEB grants,
Chile.
Plant architectural and genetic diversities in Coffea
native from Madagascar: towards an architecturalfunctional plant growth model applied to Coffea
biodiversity perservation
Sabatier, S1, Andrianasolo, D1, Rakotomalala, J-J2,
Hamon, P3, de Reffye, P1, Letort, V4
1
CIRAD, UMR AMAP, Montpellier, France; 2FOFIFA,
Antananarivo, Madagascar; 3IRD, Montpellier, France;
4
ECP, Paris, France
The Coffea genus includes 103 species with 53 endemic
to Madagascar (namely Mascarocoffea).The three main
centres of species diversity for coffee trees are
Madagascar (naturally low-caffeine species), Cameroon
and Tanzania. However, Madagascar has the higher
Coffea diversity in terms of total number of species due
to the great variety of forest types including littoral,
evergreen, gallery, mixed deciduous, dry, xerophytic and
high-altitude. During these last 20 years, deforestation in
Madagascar has become dramatic and has drastically
reduced the distribution area of Coffea species. The
collection maintained at the Kianjavato Research Station
is unique since no living material is authorized to be
conserved out of Madagascar. Conservation strategies
based on scientific data are needed and become urgent in
terms of biodiversity preservation and sustainable
development. Recent studies in Coffea trees showed that
their phenotypic plasticity could be explain the restricted
distribution of Coffea species. Our recent preliminary
results showed a high architectural diversity (i.e.
architectural model, growth process, branching degree,
branch location) between Coffea species and an
interspecific variability of functional traits (Leaf Area
Mass, wood density). The functional-structural model
GreenLab is a dynamic model taking into account
architectural plasticity of the plants and biomass
allocation to organ level. Potentials of GreenLab model
to represent environment x genotype interactions, in
particular through its stable endogenous parameter as
such the organ sink functions have been demonstrated in
some species and they will be tested for Coffea species.
The present study focuses on 5 species endemic to
Madagascar with different phenotypic traits and forest
habitats. For each species, architecture and genetic
comparative analyses between individuals growing in
situ (natural forest) and ex situ (common garden test) will
be performed. In addition, we have set up two
experimental stands to analyse the site effect. These
whole results will be used to introduce genetic factors
into the GreenLab model. The global aim of our
approach is to analyse the adaptive capacity and
phenotypic plasticity at the individual level within Coffea
populations.
THEME 02: ECONOMIC
BOTANY INCLUDING
BIOTECHNOLOGY,
AGRICULTURE AND PLANT
BREEDING
Sym028: Novel approaches to engineering
C4 photosynthesis into C3 crops – 26 July
C4 Rice Project
Quick, WP1
1
International Rice Research Institute, Philippines
Future global population increases of some 2 billion
people by 2050 will require an extra 250 million tonnes
of rice per year in Asia alone. To feed this increased
population, agriculture will need to improve food
production by some 50% equivalent to a second green
revolution that first occurred in the 60's and 70's. The C4
Rice Project was launched 18 months ago to address this
problem and will need substantial financial investment
now and in the future if it is to succeed. Excellent initial
progress has been made in the project which is predicted
take 15–20 years. This talk will provide a description of
the consortium, outline the research strategies being
employed, give an update on current research progress
and outline some of the challenges to be tackled in the
coming years.
Engineering the C4 pathway into rice
Hibberd, J1, Covshoff, S1, Woodfield, H1, Karki, S2,
Slamet-Loedin, I2, Quick, P2
1
University of Cambridge, UK; 2IRRI, Philippines
It has been proposed that integrating C4 photosynthesis
into C3 crops could be used to increase their maximum
yields. This is a challenging undertaking because the C4
pathway is complex and involves alterations to the
biochemistry, cell biology and development of leaves.
However, C4 photosynthesis has evolved independently
at least 62 times, and this biological precedent implies
that changes to a relatively small number of factors may
generate the complexity of a C4 leaf. Recent advances in
proteomics, transcript profiling and the release of
genome sequences for sorghum and maize, two important
C4 crops, have filled some of the gaps in our
understanding
of
mechanisms
underlying
C4
photosynthesis. Further advances are being made by
comparative analysis of closely related C3 and C4 plants
because this reduces signal noise associated with
phylogenetic distance. We will consider both our
understanding of global alterations to gene expression in
C4 compared with C3 leaves, and also provide specific
examples of how the regulation of genes has altered as
they are recruited into the C4 pathway. We will discuss
evidence that distinct lineages of C4 plants share
regulatory circuitry that generates accumulation of
photosynthesis proteins in specific cells. A summary and
progress report of current efforts at placing the
biochemistry of C4 photosynthesis into rice will be
provided.
Evidence for the essential components of the C4
mechanism
Furbank, R1, Pengelly, J2, Martin, A3, Evans, J2,
Voznesenskaya, E4, Grof, C3, Byrt, C3, Edwards, G5,
Von Caemmerer, S2
1
High Resolution Plant Phenomics Centre, CSIRO Plant
Industry, Canberra, Australia; 2Research School of
Biology, The Australian National University, Canberra,
Australia; 3University of Newcastle, Newcastle,
Australia; 4VL Komarov Botanical Institute, St
Petersburg, Russia; 5School of Biological Sciences,
Washington State University, Pullman, USA
Recently there has been a renewed interest in the C4
photosynthetic mechanism due to the desire to improve
yield potential and radiation use efficiency in C3 crops by
introducing elements of the C4 pathway (C4 Rice
Consortium; http://beta.irri.org/projects15/c4rice). To
facilitate this process, strategies need to be developed to
identify the subset of key genes necessary to transfer a
functional C4-like mechanism to C3 crops. This
presentation describes development of phenotypic
screens for ‘C4-ness’ which can be used in analysis of
transgenic C3 plants in which partial C4 pathway
components are being installed, analysis of
photosynthesis in sorghum with impaired lignification
and secondary thickening of leaf tissues, and
photosynthetic characterisation of maize husk, and leaf
sheath, tissue thought to operate a biochemical and
structural blend of C4 and C3 photosynthesis. These data
77
are synthesised to delineate the challenges of measuring
‘C4-ness’, the role of bundle sheath cell wall properties in
the efficiency of the C4 CO2 concentrating mechanism
and the key steps in attaining a C4-like C3 crop plant.
Do rice mutant populations offer variation in traits
useful for C4 engineering ?
Murchie, E1, Quick, P2, Leung, H2, Ahamadeen Nagoor,
MM1, Feldman, A1
1
University of Nottingham, School of Biosciences, Div.
Plant and Crop Sciences, UK; 2International Rice
Research Institute, Los Banos, Philippines
A large proportion of global rice production takes place
in conditions where high temperatures induce substantial
levels of photorespiration resulting in deterioration of
radiation use efficiency. The introduction of the C4
pathway would be of substantial benefit under these
conditions and provides a solution for the attainment of
2050 yield targets. The rice genome may contain
sufficient ‘plasticity’ to enable the introduction, or preconditioning of some traits that would be essential for the
engineering of the C4 pathway in rice. The C4 rice
consortium at the International Rice Research Institute
(IRRI) in the Philippines has begun a high throughput
screening program for available rice mutant collections
including both irradiation/chemical mutagenesis lines
and tagged lines. To date around 12,000 M4 lines from
the existing IR64 deletion mutant collection have been
screened at IRRI for vein density and 5,000 have been
screened for tolerance to low CO2. Ten progeny of each
line were visually scored for vein density and then
screened in a chamber for 6 days at 30 µL L-1 CO2. High
vein density candidates were further screened for leaf
structure including inter-veinal mesophyll cell number
and size. Initial results indicate a detection frequency of
1–2 candidates per 1,000 lines with both increased vein
density and reduced mesophyll cell number. Vein density
was stable during different growth stages in the field.
After 6 days at low [CO2] mutant lines were identified
that had a similar loss of chlorophyll to the C3–C4
intermediate Panicum milioides control which suffered
only marginal loss. We are testing the hypothesis that
chlorophyll loss is a sufficiently robust and convenient
proxy to use in high-throughput screens. A continuous
program of phenotype confirmation, backcrossing and
genetic analysis is underway in order to seamlessly
incorporate promising traits into a breeding program.
‘State of play’ results will be described and discussed.
The roles of C4 acid decarboxylases in plants
Leegood, R1
1
University of Sheffield, UK
Any attempt to engineer C4 photosynthesis into crop
plants will require the recruitment of a decarboxylase in
the form of NAD- or NADP-malic enzyme, or PEP
carboxykinase (PEPCK). NAD-malic enzyme is probably
ubiquitous in plant cells (although it may be enriched in
some of them), but both NADP-malic and PEPCK show
discrete locations. For example, NADP-ME is present in
the trichomes, hydathodes, vasculature (cytosolic) and
guard cells. PEPCK is present in many plant tissues and
78
appears to be located exclusively in the cytosol, although
it may be plastidic in diatoms. Within leaves, although
not abundant overall, PEPCK may be present in phloem
companion cells, hydathodes, trichomes and stomata and
its abundance is often dependent on developmental stage.
PEPCK is regulated in some, but not all, plant tissues by
reversible protein phosphorylation, whereas the
regulation of NADP-malic enzyme lacks such
mechanisms and the regulation of NAD-malic enzyme
remains unclear. In recent years it has become apparent
that PEPCK functions in far more metabolic processes in
plants than was previously realised, but, as in many
animal tissues, its function has been less easy to discern.
It has been identified in a range of tissues, such as
developing seeds, flowers, roots, vascular tissue and
fruit. In developing seeds laying down storage proteins it
is implicated in the metabolism of incoming nitrogenous
compounds, as it also is in the phloem. In stomata, new
data from Arabidopsis knock-outs suggest that it plays an
important role in stomatal closure, a role that may also be
played by NADP-malic enzyme.
Is corn husk photosynthesis C4-like?
Pengelly, J1, Evans, J1, Voznesenskaya, E3, Edwards, G4,
Furbank, R2, Von Caemmerer, S1
1
Research School of Biology, The Australian National
University, Canberra, Australia; 2High Resolution Plant
Phenomics Centre, CSIRO Plant Industry, Canberra,
Australia; 3VL Komarov Botanical Institute, St
Petersburg, Russia; 4School of Biological Sciences,
Washington State University, Pullman, USA
The husk tissue surrounding the ear of Zea mays
(maize/corn) has been described as operating a partial C3
photosynthetic pathway in contrast to its foliar leaves
which function using the NADP-ME C4 pathway for CO2
assimilation. Here we characterized photosynthesis in
maize husk and leaf, measuring the defining C3/C4
characteristics including vein density, combined gas
exchange and carbon isotope discrimination, the O2
dependence of the CO2-compensation point, and
photosynthetic enzyme localisation. Vein density in husk
tissue was 88% less and an altered stomatal number and
distribution were observed in relation to leaf tissue. The
CO2 response of CO2 assimilation rate in husk was less
than in leaves and did not saturate at high CO2 indicating
CO2 diffusion limitations. However, at high CO2 and
irradiance, photosynthetic rates were similar between leaf
and husk tissue when expressed on a chlorophyll basis.
The CO2 compensation points of husk tissue were high
compared to leaf tissue, but did not increase with
increasing O2 concentration as is commonly observed in
C3
photosynthetic
systems
suggesting
compartmentalisation of the primary carboxylating
enzyme Rubisco as it operates in C4 plants. Both Rubisco
activity and the ratio of PEP carboxylase to Rubisco
activity were reduced in husk and immunolocalisation
measurements indicated Rubisco was present not only in
bundle sheath cell chloroplasts but also in mesophyll
cells distant from the vascular bundles. However realtime
carbon
isotope
discrimination
measured
concurrently with gas exchange indicated that the
Rubisco present in distant mesophyll cells of maize husk
was unlikely to be contributing significantly to fixation
of CO2 as a low discrimination against 13C was observed
(~ 4 ‰). From this study we conclude that CO2
assimilation in maize husk tissue is most likely operating
via a C4 pathway with the expression of Rubisco in
distant mesophyll yet to be explained.
C4 rice – an ideal arena for systems biology research
Zhu, X1
1
Partner Institute for Computational Biology, Xuhui,
China
Engineering C4 photosynthetic pathway into C3 crops has
the potential to dramatically increase the yields of major
C3 crops. The genetic control of features involved in C4
photosynthesis are still far from being understood; which
partially explains why we gained little success in C4
engineering so far. Next generation sequencing
techniques and other high throughput technologies are
offering an unprecedented opportunity to elucidate the
developmental and evolutionary process of C4
photosynthesis. Two contrasting hypotheses about
evolution of C4 photosynthesis exist, i.e. master switch
hypothesis and incremental gain hypothesis. These two
hypotheses demand two different research strategies to
proceed in parallel to maximize the success of C4
engineering. In either case, systems biology research will
play pivotal roles in identifying key regulatory
controlling development of C4 features, identifying
essential biochemical and anatomical features required to
achieve high photosynthetic efficiency, elucidating
genetic mechanisms underlining C4 differentiation and
ultimately identifying viable routes to engineer C4 rice.
As a highly interdisciplinary project, the C4 rice project
will have far-reaching impacts on both the basic and
applied research related to agriculture in the 21st century.
Sym030: Resource use efficient plants and
crop systems – 25 July
Halophytes: what makes them special? Revealing
ionic mechanisms of salinity tolerance
Shabala, S1, Moreno, AR2, Hariadi, Y3, Mackay, A1,
Tian, Y4, Bose, J1, Jacobsen, S-E5
1
addition, some halophytes have already been tested as
vegetable, forage and oilseed crops in agronomic field
trials, whilst others show good potential to be developed
as crops. Surprisingly, our knowledge of fundamental
ionic and molecular mechanisms conferring salinity
tolerance in halophytes is rather limited, and at best is
restricted to several model species. This talk summarises
the current knowledge of physiological mechanisms
regulating ion uptake and sequestration in halophytes and
provides insights into the identity of membrane-transport
systems mediating ion transport in halophyte root and
leaf tissues. The focus of this study was on two species:
quinoa (Chenopodium quinoa Willd.) and Atriplex
(Atriplex lentiformis L.). A range of physiological
techniques (leaf gas exchange and photosynthetic
characteristics; sap osmolality; tissue elemental
composition) were used to reveal mechanisms of osmotic
adjustment and tissue-specific ion compartmentation in
both species at the whole-plant level. It was found that
95% of osmotic adjustment in old leaves and between 80
and 85% of osmotic adjustment in young leaves was
achieved by means of accumulation of inorganic ions
(Na+, K+ and Cl-) when plants were grown at elevated (up
to 500 mM NaCl) salinity levels, whilst the role of
organic osmolytes was very limited. Both species also
possessed an efficient mechanism to control Na+ and K+
loading into the xylem, as well as for efficient Na+
sequestration in leaves. Whole-plant experiments were
complemented by a range of microelectrode studies (noninvasive ion flux measurements; membrane potential;
patch clamp) aimed to reveal the identity of specific ion
transporters mediating the above process. We compare
the kinetics of net K+ and Na+ fluxes between different
root zones (e.g. elongation vs mature zone) and report a
differential sensitivity of quinoa and Atriplex root tissues
to NaCl and oxidative (hydroxyl-generating Cu/ascorbate
mixture) stress. We show that regulation of both
depolarization-activated outward-rectifying K+-selective
(GORK) channels and non-selective cation (NSCC)
channels are instrumental to halophytes adaptation to
saline conditions, and reveal an important role for a H+ ATPase pump in this regulation. We also demonstrate a
feasibility of using the MIFE technique to map ion flux
profiles from intact plant leaves and report, for the first
time, in situ data on patterns of net K+, Na+ and H+ flux
kinetics from halophyte bladders in response to a range
of salinity treatments.
School of Agricultural Science, University of Tasmania,
Australia; 2Unitat de Fisiologia Vegetal, Universitat
Autònoma de Barcelona, Spain; 3Dept of Physics,
University of Jember, Indonesia; 4Institute of Grassland
Science, Northeast Normal University, China; 5Dept of
Agriculture and Ecology, University of Copenhagen,
Denmark
1
Molecular Ecology Laboratory, Dept of Botany,
Hamdard University, New Delhi, India
The increasing problem of global land salinisation and
associated multibillion dollars losses in crop production
require a better understanding of key physiological
mechanisms conferring salinity tolerance in crops. The
effective way of gaining such knowledge comes from
studying halophytes. Halophytes have always attracted
the attention of plant physiologists, due to their
remarkable ability to tolerate and even benefit from salt
concentrations that kill most other plant species. At the
very least, halophytes may provide genes that allow
transgenic conference of salinity tolerance to crops. In
Nitrogen (N) deficiency in agricultural fields is a major
limitation that poses a serious threat to the food supply in
the world. Differential nitrogen efficiency of 135 wheat
genotypes was investigated on the basis of their
performance under N-insufficient and N-sufficient
conditions in terms of growth and N uptake and
assimilation capacities. Changes in the proteome of Nstress sensitive and N-stress tolerant wheat varieties were
studied using two-dimensional gel electrophoresis (2DE) via liquid chromatography–tandem mass
spectrometry (LC-MS/MS) in order to find out the
Nitrogen stress-induced alterations in the leaf
proteome of wheat varieties
Ahmad, A1, Chandna, A1, Iqbal, M1
79
mechanism involved in the differential response of these
genotypes to N levels. Forty protein spots were
significantly altered by exposure to the nitrogen
treatments. Among them, 10 protein spots were downregulated and 30 protein spots were up-regulated. The
proteins involved in the energy production/regulation and
metabolism in plant leaf tissue were found to be
differentially expressed under N treatments. The proteins
involved in energy production included those having a
role in glycolysis, respiration, electron transport and
photosynthesis whereas the proteins involved in
metabolism included those concerning the metabolism of
sugars, polysaccharides, sterols and cofactors. Our data
suggest that Rubisco and glutamine synthetase enzymes
might act as suitable targets for genetic manipulation of
plants, which can grow and yield well at low nitrogen
levels.
Implications of inefficient use of nitrate by sugarcane
Robinson, N1, Brackin, R1, Vinall, K1, Rennenberg, H2,
Lakshmanan, P3, Schmidt, S1
1
University of Queensland, St Lucia, Australia;
University of Freiburg, Freiburg, Germany; 3BSES Ltd,
Indooroopilly, Australia
2
Recommended N fertilizer rates for sugarcane crops
varies greatly between countries, ranging from 120–220
kg N ha-1 in Australia to 750 kg N ha-1 in China. Only
20–40 % of N-fertilizer is recovered in sugarcane
systems supplied with 100–200 kg N ha-1 and up to 10%
of fertilizer-N is emitted as greenhouse gas N2O. To
discover reasons for the comparatively low N-fertiliser
use efficiency of sugarcane, we examined the use of
nitrate and ammonium by sugarcane, its ancestral species
and grain crops sorghum and maize. N forms were
supplied simultaneously and mimicked the N availability
in sugarcane soils. Results indicate that (1) commercial
sugarcane varieties and ancestral Saccharum spontaneum
under non-limiting N supply incorporated substantially
less nitrate (40–45% of ammonium uptake) than related
species Erianthus sp., sorghum and maize, and (2) intact
roots in a commercial crop incorporated less nitrate than
ammonium. We conclude that commercial sugarcane
varieties and ancestral species have a much lower ability
to use nitrate than related species in the supertribe
Andropogonodea. Our study challenges the paradigm
that nitrate is the preferred N source for crops, and
provides an explanation for the inefficient N use in
sugarcane systems. Potential avenues for improvement of
N-fertilizer use include selection of sugarcane genotypes
with better nitrate use and improved fertilizer and soil
management aimed to reduce production of nitrate.
Sym031: Organic molecules in plant
nutrient acquisition: forest to crop system –
26 July
Complex organic nutrients as nutrient sources for
plants and triggers of root growth
Paungfoo-Lonhienne, C1, Lonhienne, TGA1, Rentsch,
D2, Schmidt, S1
80
1
School of Biological Sciences, The University of
Queensland, St Lucia, Australia; 2Institute of Plant
Sciences, University of Bern, Bern, Switzerland
Pollution of land, water and air derived from inefficient
use of nitrogen (N) fertilisers is of great global concern.
Phosphorus (P) deposits are rapidly being depleted and
accompanying price increases will threaten food security
in coming decades. Organic nutrients are increasingly
considered as alternatives to currently used inorganic and
urea-based fertilisers, but the long-held view remains that
plants rely on inorganic forms of nutrients and entirely
depend on microbial conversion of soil organic nitrogen
and phosphorus prior to uptake into roots. Using green
fluorescence protein (GFP) and fluorescent-labelled
phosphorothioate oligonucleotides (S-DNA) as sources
of organic N and P, we show that protein and DNA are
taken up by plant roots. We further show that addition of
protein or DNA to nutrient-replete growth medium
enhances the growth of lateral roots and root hairs. While
uncertainty remains about the mechanisms of uptake,
these findings change our view of the spectrum of N and
P sources accessible to plants and also demonstrate that
protein and DNA trigger morphological responses. The
proliferation of roots in response to the tested organic
compounds may enhance access to organic matter-rich
patches in the soil. Our research challenges the current
paradigm that plants rely on microbes and soil fauna for
break-down of organic matter and provide further
evidence for heterotrophy in plants.
Role of organic nitrogen in sugarcane cropping
Lakshmanan, P1, Holst, J2, Robinson, N2, Vinall, K2,
Brackin, R2, Schmidt, S2
1
1Bureau of Sugar Experimental Stations, BSES Ltd,
Indooroopilly, Australia; 22School of Biological
Sciences, The University of Queensland, St Lucia,
Australia
Sugarcane is a crop of industrial scales and has a great
potential of sugarcane to supply food, biomaterials and
fuels in future economies. However, sugarcane farming
in Australia and elsewhere is accompanied by a large
nitrogen footprint with up to 750 kg N applied per
hectare per crop cycle. In Australia, up to 70% of the
applied N fertiliser in sugarcane cropping is lost to the
environment and pollutes waters of the Great Barrier
Reef and causes emissions rates of potent greenhouse gas
nitrous oxide which exceed IPCC estimates several fold.
Our research shows that high N losses occur within the
first 2-3 months of fertiliser application indicating that
plant-N demand and soil-N supply are ill matched.
Analyzing the contribution of inorganic and organic
(amino acids) N forms in the soil over a year's crop
cycle, we show that organic N is a likely N source for
sugarcane, representing up to 70% of soluble, lowmolecular weight N in soils. We discovered that
sugarcane prefers ammonium and amino acids as N
sources for growth and discriminates against nitrate when
provided with a choice of N sources. In addition to being
a potential N source which has a longer resident time in
soil than inorganic N, organic N also enhances root
branching in sugarcane which could benefit the
acquisition of resources from soil. We will present an
overview of Australian farming practices including the
techniques of 'trash blanketing' which results in a thick
blanket of plant residue on the soil surface after harvest.
How organic N can contribute to sustainable sugarcane
farming is discussed.
Improvement in the growth and quality of green
onion (Allium cepa L.) plants by some bioregulators in
the new reclaimed area at Nobaria region, Egypt
1
Abd El Wahed, M , El-Awadi, M
1
Novel functions of pea MCM6 single subunit as DNA
helicase and in promoting salinity stress tolerance
without yield penalty
Tuteja, N1
1
National Research Center, Dokki, Egypt
Two field experiments were conducted in the
Experimental Station of the National Research Center at
Nobaria region, Behira Governorate, Egypt during two
successive seasons 2007–2008 and 2008–2009. The trial
was carried out to study the effect of some bioregulators
(glutathione, cysteine and methionine) on growth, quality
and some chemical constituents of green onion (Allium
cepa L. cv Giza 6) plants. Cultivation of onion bulb (1
cm diameter) was performed on 29th Oct. in both
seasons. The treatments included one foliar application of
glutathione, cysteine or methionine at four concentrations
i.e. 0, 25, 50, and 75 ppm after 33 days from sowing.
Results indicated that foliar application of the three
bioregulators promoted growth and quality of green
onion criteria: shoot length, length of white part, bulb
diameter, No. of leaves and fresh and dry weight of plant.
Chemical constituents were significantly influenced by
bioregulators treatments especially in plants treated with
the lower concentrations (25 ppm) of glutathione,
cysteine and methionine. Our results cleared that
significantly increment of photosynthetic pigments, fixed
oil percentage, total protein, total phenol, and total free
amino acids. On the other hand, flavonoid content and
total soluble salts were significantly reduced.
Review of developmental and anatomical changes
under the influence of cesium uptake in Chenopodium
album
Tajadod, G1, Mogoei, R1, Mazhar, F1
1
Sym032: Engineering crops for the future –
25 July
Islamic Azad University,North Tehran Branch, Iran
Chenopodim album belongs to the Chenopodiaceae
family and is an annual plant which can be found in most
parts of Iran. This plant has the ability to absorb and
refine heavy metals, specially cesium, from the
environment. Cesium (Cs) is one of the alkali metals in
soil which plants desire to absorb because of its
similarity to calcium. While absorption of Cs from the
environment, its impacts upon plant developmental and
anatomical structure were studied. For this study seeds of
C. album were grown using hydroponic culture with
Hogland solution. After 2 months, seedlings (6 cm height
) were transferred to a medium with different amount of
Cs. Three groups, including one control and two treated
groups (watered with 2 and 5 ppm Cs ), were studied.
Considering the ability of absorption of Cs by C. album,
and its accumulation in the plant, cells suffer serious
injuries in terms of anatomical and developmental
structure. By increasing Cs concentration, changes,
including destruction and irriguarity of cells, especially
in stem meristem layers is headed with shortening of
plant height and yellow color of its leaves.
1
International Centre for Genetic Engineering &
Biotechnology, New Delhi, India
The initiation of DNA replication starts from origins and
is controlled by a multiprotein complex, which involves
many protein factors. One of the important factors is
hetrohexameric minichromosome maintenance (MCM27) protein complex which is evolutionarily conserved and
functions as essential replicative helicase for DNA
replication. However, to date, helicase activity in the
single eukaryotic MCM subunit and the role of MCMs in
abiotic stress tolerance in plants have not been reported.
Salinity stress tolerance is an important trait that is
required to overcome salinity-induced reduction in plant
productivity. Here, we report the following: (a)Pea
MCM6 single subunit (cDNA: 2.98 kb, protein: 93 kDa)
alone contains 3’-5’ DNA helicase, ATP-binding and
ATPase activities. (b) The DNA helicase activity was
stimulated by replication fork-like substrate. (c) In vitro
it forms a homohexamer and is localized in nucleus and
cytosol. (d) The MCM6 transcript is upregulated in pea
plant in response to high salinity and cold stress and not
with ABA, drought, heat stresses. (e) MCM6
overexpression in tobacco plants confers salinity
tolerance. The T1 transgenics plants were able to grow to
maturity without yield penalty. (f)It was observed that in
salt-grown T1 transgenic plants Na+ ions is mostly
accumulated in mature leaves and not in seeds. These
findings provide first direct evidence that single subunit
MCM6 contains DNA helicase activity which is unique
to plant MCM6 protein, as the activity was only reported
for heteromultimers of MCM proteins in animal system.
These findings also provide first direct evidence that
single subunit MCM6 is involved in salinity stress
tolerance without yield loss. Overall, this discovery
should make an important contribution to a better
understanding of DNA replication in plants and the
findings also suggest that DNA replication machinery
can be exploited for promoting stress tolerance in crop
plants.
New resources for hybrid rice breeding
Toriyama, K1
1
Graduate School of Agricultural Science, Tohoku
University, Japan
Hybrid rice has an average 15% to 20% yield advantage
over inbred lines. In China, it is planted on
approximately 16 million hectares – more than half of
China’s total rice area of 28 million hectares (Barclay
2007). Other than China, Vietnam, India and Philippines
have commercialized hybrid rice. Bangladesh, Indonesia,
Pakistan have also achieved recent success with hybrid
rice. Hybrid rice is expected to be a magic wand for
world hunger. For hybrid rice breeding, cytoplasmic
81
male sterility (CMS) has been widely utilized. Most of
the commercial rice hybrids are based on a single CMS
source, the WA (wild abortive) cytoplasm.
Approximately one-tenth of the world rice fields rely on
a single CMS-cytoplasm. If WA-CMS-specific disease
would emerge, Hybrid rice would be completely
destroyed, leading food panic. To avoid the potential
threat of genetic vulnerability of rice hybrids, the
development of several CMS/Rf systems is desirable. We
have been studying three types of CMS in rice: BT-CMS
originated from Chinsurah Boro II, LD-CMS from Lead
Rice and CW-CMS from Chinese Wild rice. We have
achieved positional cloning of the fertility restorer genes,
RF1 for BT-CMS, RF2 for LD-CMS and RF17 for CWCMS. RF1 has been shown to encode pentatricopeptide
repeat protein, which binds mitochondrial atp6-orf79
RNA and promote RNA processing, suppressing the
translation of cytotoxic orf79 (Kazama et al. 2008). We
have shown that RF17 encodes an unknown protein
containing a part of acyl-carrier protein synthase-like
domain and involved in perception of retrograde
signaling from CW-mitochondria and, named RF17 as
RETROGRADE-REGULATED MALE STERILITY
(RMS) (Fujii and Toriyama 2009). We have recently
found that RF2 encodes a glycine-rich protein (Itabashi et
al. submitted). We have also determined the whole
genomic sequences of LD- and CW-mitochondria and
found unique ORFs in each genome (Fujii et al 2010).
Elucidation of the RF genes and unique mitochondrial
ORFs will enable us to incorporate LD-CMS/RF2 and
CW-CMS/RF17 systems, as well as BT-CMS/RF1
system, to practical hybrid rice breeding program.
Molecular findings of these mechanisms also provide us
useful information for engineering hybrid varieties in
various crops for the future.
The reproductive biology of wheat and barley: from
developmental genetics to crop improvement
Trevaskis, B1
1
CSIRO Division of Plant Industry, Canberra, Australia
Advances in molecular biology and functional genomics
that have been pioneered in model plant systems are now
being applied to the study of reproductive development
in cereals. This is providing profound insights into the
biological processes that control flowering and grain
production in economically important crops such as
wheat and barley. Genes controlling the seasonal timing
of flowering of temperate cereals have now been
isolated, including genes that regulate the vernalization
response (the promotion of flowering by prolonged cold
during winter) and the long-day flowering-response. This
presentation will describe the genes controlling
vernalization and daylength flowering-responses in
cereals and examine how interactions between these
genes regulate the process of floral development in wheat
and barley. The historical importance of these genes to
the Australian grains industry will be used to highlight
how cereal breeders have utilised variation in genes
controlling these seasonal flowering-responses to adapt
modern varieties to a wide range of growing regions,
sowing times and climates. The potential for these genes
to contribute to future crop improvement strategies will
also be discussed.
82
Study of storage protein composition of barley with a
focus on improving the baking quality
Vincze, E1, Hansen, M1, Aaslo, P1, Falkiewicz, A1,
Langkilde-Lauesen, A1
1
Aarhus University, Denmark
Barley is grown in many regions throughout the world, in
part due to its ability to adapt to less favourable growing
conditions. Approximately two-thirds of the worldwide
annual barley production is used for feed, one-third for
malting and a small (2%) but increasing percentage used
as food and in food processing. As barley has the
potential to offer considerable human nutritional benefits,
there is renewed interest in developing barley for a wider
application in the food sector. Considerable focus is on
supplementing wheat-based breads with barley to
introduce the inherent nutritional advantages of barley
flour. Until recently, the most important selection criteria
of breeding under modern high input agriculture
conditions have been yield. Consequently, the present
day cultivars are characterised by unfavourable protein
content with inferior leavening and baking properties.
Using knowledge from wheat baking quality parameters,
one of the most important storage protein called glutenins
has its highly homologue counterpart in barley, called Dhordein. The first step in our study was to gain more
knowledge of the storage protein accumulation and AA
metabolism in the barley grain. The chosen method was
gene expression analysis using cDNA microarrays.
Grain-specific cDNA microarray was used to investigate
amino acid biosynthesis and storage protein
accumulation in the developing grains of field-grown
barley. A distance matrix was constructed which enabled
the identification of three clusters corresponding to the
early, middle and late phase of grain development. The
gene expression pattern associated with the clusters was
investigated using a pathway-specific analysis with
specific reference to the temporal expression levels of a
range of genes involved mainly in the photosynthesis
process, amino acid and storage protein metabolism.
Furthermore we have been able to show that different
members of the storage protein families, including Dhordeins are synthesized during different stages of grain
filling. Studying the importance of D-hordein, the
predicted allelic variation and exploiting the substantial
genetic variation in storage protein composition in the
barley gene pool might enable us improving the baking
qualities of barley flour. From our high protein barley
collection 49 were selected and grown in field
conditions. We analysed storage protein concentration,
protein patterns and AA composition and performed
small scale baking trails. Our results indicate that there is
genetic variation in the relative proportions of the storage
proteins affecting the amino acid compositions and
baking quality. Some of the cultivars have better baking
quality and the better baking quality correlates with the
higher MW protein band(s). We isolated these higher
MW protein band(s) from the SDS-PAGE gels and
showed by mass spectrometry that the proteins belonged
to the D-hordein family. The analysed protein from
different cultivars had no major differences on the 5’ or
3’ ends. The highly repetitive middle part of the protein
was not accessible by the mass spectrometry studies. The
first cloned corresponding genes showed differences in
the number of repetitive motifs. These variations could
be further exploited in conventional breeding programs
as well as by genetic modification (under progress) to
increase this crop baking and nutritional qualities.
Transcriptomics and proteomics to identify
component isoenzymes in the metabolic pathway for
triricinoleate biosynthesis in Castor bean
Slabas, A1, Kroon, J1, Brown, A1, Simon, W1
1
University of Durham, Durham, UK
Castor bean [Ricinus] oil is a rich source of ricinoleic
acid [12-hydroxyoleic acid: 18:1 12-OH] a raw material
for the production on N-11, a polymer extensively used
by the automotive industry to carry hydraulic fluids at
high temperatures. The key gene involved in conversion
of oleic acid to ricinoleic acid was identified using an
EST approach in 1995. Expression of the 18:1 12-OH
lase in transgenic plants has resulted in up to 20% 18:1
12-OH in seed oil which is well below the 90% level
found in Ricinus. To try and identify components
involved in the assembly of Triricinoleate in Ricinus we
have employed a dual transcriptomic and proteomic
approach. Key to the proteomic approach has been the
use highly enriched endoplasmic reticulum and the use of
MUDPIT. The availability of the complete genome
sequence of Ricinus supplied the necessary framework
for identification purposes. Here we will describe our
approach to the identification of key isoenzymes which
are candidates for the assembly of ricinoleic acid onto the
glycerol backbone.
Sym034: Crops for a changing climate in a
high carbon dioxide world – 29 July
Rice genotypes responses to elevated CO2 obtained
from two free air CO2 enrichment field trials
Hasegawa, T1, Sakai, H1, Tokida, T1, Nakamura, H1,
Zhu, C1, Usui, Y1
1
National Institute for Agro-Environmental Sciences,
Japan; 2Taiyokeiki Co. Ltd, Japan
Atmospheric CO2 concentration [CO2] is an important
environmental variable for plant growth, because it is the
substrate for photosynthesis. It is less variable than air
temperature, solar radiation and precipitation, so the
effect of day-to-day or season-to-season variation is not
large. However, the increase in [CO2] since the industrial
revolution has already exceeded 100 ppm (280 ppm in
1800 vs 388 in 2009), and is projected to increase to
470–570 ppm in by the middle of the century (IPCC,
2001). This is the range in which plants are highly
responsive. The current level of [CO2] is limiting to the
CO2 fixation process of C3 plants, so that rising [CO2]
promotes leaf-level photosynthesis and thereby biomass
production and grain yield. This CO2 fertilization effect
is one of few positive impacts on crops by the climate
change, which may even change the sign of the overall
climate change impacts on crop production. Free-air CO2
enrichment is so far the best approach in determining the
CO2 fertilization effect under field conditions. However,
CO2 responses could be dependent on environmental
conditions. Considering a wide range of environmental
conditions where rice production is practiced, we need to
determine the FACE environment interactions for the
results to be widely applicable. Recent rice FACE studies
have shown that there is a significant difference in grain
yield among genotypes. Identifying the genotypes FACE
environment will provide us with invaluable information
as to the rice adaption strategy to climate change. We
started our rice FACE study at Shizukuishi (39º38' N)
Japan since 1998 but finished in 2008. However, we have
just opened a new FACE site at Tsukuba (35º 58' N) in
2010. The two sites differ significantly in the growth
temperature conditions; seasonal mean air temperature
was 19.9ºC at Shizukuishi and 23.5ºC at Tsukuba. This
allows us to test the CO2 responses of the varieties
common to both Shizukuishi and Tsukuba FACE sites. In
this study, therefore, we attempted to determine the traits
that can confer better CO2 responsiveness of the rice
genotypes based on the two FACE experiments in Japan.
Exacerbation rather than amelioration of drought
stress in soybean grown at elevated CO2 in the field
Leakey, A1, Gray, S1
1
University of Illinois At Urbana–Champaign, USA
By 2050, summer precipitation in the Midwest U.S. is
projected to decrease by 5–40%. Concurrently,
atmospheric [CO2] is projected to increase to at least 550
ppm. Many models of future ecosystem function and
food supply assume that elevated atmospheric CO2, by
reducing stomatal conductance, will decrease plant water
uptake and soil moisture depletion, ameliorating the
impacts of drought on photosynthesis and productivity.
We tested whether this mechanism operates in fieldgrown soybean exposed to ambient (385 ppm) or
elevated (585 ppm) CO2 combined with either naturally
occurring precipitation (high-H2O) or reduced
precipitation (low-H2O) at the soybean free air CO2
enrichment (soyFACE) facility in Champaign, IL.
Rainfall was intercepted with retractable awnings to
reduce Jun–Sep water inputs into low-H2O plots by 57%
in 2009 and 32% in 2010. Contrary to the current
paradigm, soybean grown at elevated CO2 responded to
soil moisture deficit with greater decreases in stomatal
conductance and photosynthesis compared to ambient
CO2-grown plants. This was associated with greater root
length in shallow, drying soil layers at elevated CO2. We
are currently testing if greater chemical root-to-shoot
signaling was responsible for the enhanced sensitivity of
soybean to drought under elevated CO2. Greater drought
sensitivity can eliminate the yield benefits of elevated
CO2, and raises the possibility that current projections of
ecosystem function and food supply are overly
optimistic.
Will elevated CO2 change comparative performance
of dryland wheat cultivars?
Tausz, M1, Posch, S2, Thilakarthne, LC2, Lakmini, R3,
Bourgault, M5, Dreccer, F5, Wockner, K5, Palta, J5,
Chapman, S5, Fitzgerald, G4, Seneweera, S2,
1
Dept of Forest and Ecosystem Science, Melbourne
School of Land and Environment, The University of
Melbourne, Australia; 2Dept of Agriculture and Food
83
Systems, Melbourne School of Land and Environment,
The University of Melbourne, Australia; 3International
Plant Nutrition Institute, Australia; 4Victorian State Dept
of Primary Industries, Australia; 5CSIRO Plant
Industries, Climate Adaptation Flagship, Australia;
Wheat (Triticum aestivum) cultivars have long been bred
to perform under dry and hot conditions, for example, by
selecting for traits such as superior transpiration
efficiency or low tillering types. With climate change
expected to affect rainfall patterns and raise temperatures
in dryland agriculture regions, the importance of drought
and heat tolerance will most likely increase. On the other
hand, elevated atmospheric CO2, the ultimate cause for
predicted climate change, can have a positive direct
effect on crop growth and performance. Cultivars with
superior performance under elevated CO2 will therefore
be important for sustainable future crop production, yet
there is some evidence that past breeding activities have
not resulted in high CO2 responsiveness. Despite the
certainty of rising CO2 concentrations, intra-specific
variation of crop response to elevated CO2 has received
little attention. We have little information on what
particular traits enable maximum gains under elevated
CO2, and even less knowledge about how to ensure that
optimum responsiveness to elevated CO2 is compatible
with other desirable properties such as superior
transpiration efficiency, reliable yield under dry
conditions, or stress tolerance. Climate chambers are the
ideal set-up to test CO2 responsiveness of wheat
cultivars with specific traits under fully controlled
conditions with high throughput capacity. Tunnel
exposure systems allow field exposure under semicontrolled conditions including controlled variations in
temperature. The Australian Grains Free Air
Carbondioxide Enrichment facility (AGFACE) in the
dryland wheat cropping region in Horsham, Victoria,
allows exposure of a range of wheat varieties to elevated
CO2 under realistic field conditions. A combination of
results from such different systems will give a robust
picture of how different traits govern CO2 responsiveness
of wheat. Contrasting pairs of commercially available
wheat cultivars were tested in these systems including:
near-isogenic lines Drysdale and Hartog, with Drysdale
previously selected for superior transpiration efficiency
using carbon isotope (13C) composition. H45 and Yitpi,
with H45 selected for reliable performance in dry areas
showing lower tillering, and Yitpi a freely tillering type.
In addition to growth and yield parameters, we measured
in situ leaf gas exchange and chlorophyll fluorescence to
investigate whether elevated CO2 changes the
comparative performance of the contrasting pairs of
cultivars in terms of stomatal behaviour, leaf level carbon
assimilation,
light
use
and
photoprotection
characteristics. Such information is important to guide
future cultivar selection and breeding programmes.
Acknowledgements: The presented research received
funding from The Australian Commonwealth Dept of
Agriculture, Fisheries and Forestry (DAFF) and the
Grains Research and Development Corporation (GRDC).
Effects of free-air CO2 enrichment on grain quality
traits of spring wheat (Triticum aestivum)
Hoegy, P1, Wieser, H2, Selmair, P2, Koehler, P2,
Schwadorf, K1, Breuer, J1, Franzaring, Jürgen1,
Zhunusbayeva, Dina1, Fangmeier, Andreas1
84
1
Universitaet Hohenhei, Germany; 2German Research
Centre for Food Chemistry and Hans-Dieter-BelitzInstitute for Cereal Research, Gemany
Understanding how elevated CO2 will affect food quality
is currently an often overlooked aspect in terms of
climate change and food security in the 21st century.
Spring wheat (Triticum aestivum L. cv. Triso) was thus
exposed to elevated and ambient atmospheric carbon
dioxide (CO2) concentrations (571.0 versus 418.0 µl l-1,
24-h average) using free-air CO2 enrichment (FACE)
technology at Stuttgart-Hohenheim (Germany) in the
year 2008 to examine its impacts on crop yield and grain
quality. In the high-CO2 treatment aboveground biomass
production and grain yield were promoted by 8.5% and
10.8%, respectively, although these effects were not
statistically significant. The thousand grain weight was
significantly increased by 5.4% as size distribution was
shifted towards larger grains, which may directly relate
to a higher market value. In contrast to these positive
effects in terms of food quantity, most grain quality traits
were adversely affected. Total protein concentration
decreased significantly by 7.9% in the high-CO2
treatment, which is associated with a deterioration of
important grain quality parameters for end-use purposes.
Correspondingly, elevated CO2 resulted in an overall
decrease in the concentrations of protein bound amino
acids by 4.2 to 7.9%. Amino acid composition remained
unaffected as calculated on a per protein basis except for
a negative trend for serine. Moreover, CO2-induced
impacts on the composition of protein fractions are
important for bread-making processes due to their
association with mixing and rheological properties of
dough. Minerals such as calcium and iron decreased
significantly and there was a negative trend for
magnesium, suggesting that adjustments of the diet may
be required to tackle malnutrition if C3 crops such as
wheat provide the primary source of both protein and
micronutrients under CO2 enrichment. The resulting
decline in the nutritive value of wheat grains was
probably not simply caused by conversion of the extra
CO2 into carbohydrates such as fructose, raffinose and
fructan, the concentrations of which were increased.
Although soluble non-starch polysaccharides constitute
less than 3% of the total grain mass, they are important as
they substantially contribute to the water binding
capacity of flour thus enabling the production of highquality bread. In contrast, starch, as the main compound
in grains, was significantly decreased by 5.2% due to
elevated CO2, which is in accordance with our findings
on lower concentrations of total non-structural
carbohydrates and carbon. At the same time,
concentrations of total lipids, which are essential for the
milling properties of flour and also for bread-making
quality, remained unaffected by the CO2 treatment.
Overall, the carbon to nitrogen ratio was significantly
increased by 8.5% under CO2 enrichment. On the basis
of the results described before, it is concluded that
implications may occur for consumer nutrition and health
as well as for industrial processing of wheat grains in a
future high-CO2 world.
Will elevated CO2 change the form and function of
wheat root systems?
Palta, JA1, Benlloch-Gonzalez, M1, Bramley, H2,
Milroy, SP2
CSIRO, Plant Industry, Wembley, Australia; 2The
University of Western Australia Institute of Agriculture,
Crawley, Australia
Sym035: Nutritional quality of plants in a
new climate – 29 July
1
Several studies investigating the effects of elevated
atmospheric CO2 on wheat have concluded that the main
effects are increases in photosynthesis, biomass, grain
yield and the efficiency of water use. These are effects
measured directly in the above-ground parts of the plant.
Measurements of the below-ground parts, particularly the
root system, have received little direct attention, despite
the root system being a key part of the crop. One of the
reasons is because root systems cannot be readily
observed in the soil environment. However, the recent
use of new experimental techniques to observe root
system growth, proliferation, rooting patterns and their
functioning will provide opportunities to elucidate the
effects of elevated atmospheric CO2 on wheat root
systems. The aim of this paper is to explore the effects
that elevated atmospheric CO2 may have on the form and
function of wheat roots systems. In particular we will
focus on whether elevated atmospheric CO2 can affect
root system traits for water and nutrient uptake. In
answering this question we used published and
unpublished data collected from wheat genotypes grown
in pots and glass-walled root growth boxes under
elevated atmospheric CO2 in glasshouse conditions. We
focus on root systems traits such as increased root
distribution at depth, deeper rooting, fast root elongation
rates, reduced diameter of the xylem vessel in the
seminal roots, root proliferation through branching and
improved
root:shoot
ratio
of
dry
matter.
Acknowledgements: The presented research received
funding from CSIRO, Australian Commonwealth
Department of Agriculture, Fisheries and Forestry
(DAFF) and Grains Research and Development
Corporation (GRDC).
Systems model of canopy photosynthesis
Zhu, X1
1
Partner Institute for Computational Biology, Xuhui,
China
Optimizing canopy photosynthesis, instead of leaf
photosynthesis, is critical to gain crop yields. Though
leaf photosynthesis and canopy photosynthesis have both
been studied extensively in the past, we lack good
method to scale from leaf to canopy photosynthesis. This
is partly due to the complex canopy architecture and
variability of photosynthetic properties inside canopy.
We developed systems models of canopy photosynthesis
which include kinetic models of photosynthesis and a
three dimensional model of canopy architecture. This
model enabled us to study the responses of canopy
photosynthesis upon changes in the expression levels of
different proteins involved in photosynthesis and related
metabolism. This model provides a new framework to
enable study the adaptation, optimization and evolution
of features associated with canopy photosynthesis under
the past, present and future changing climates.
The evolutionary ecology of plant chemical defenses
in agroecosystems: past, present and future
McKey, D1, Gleadow, R2, Cavagnaro, TR2
1
Centre d'Ecologie Fonctionnelle et Evolutive,
Montpellier, France; 2School of Biological Sciences,
Monash University, Clayton, Australia
Plant chemical defenses mediate interactions between
plants, their herbivores and pathogens, and the natural
enemies of these plant parasites. In domesticated plants,
farmers are added to this web of interactions. Plant
defenses have been subjected to complex selection
pressures under domestication, leading both to decreases
and to increases in their concentration, and to shifts in
their intra-plant distribution. This complexity is
explained partly by variation in the kinds of plants
farmers chose to domesticate, and partly by the kinds of
environments that nature and farmers combined to create
in agroecosystems. Today, the interactions mediated by
plant defenses are affected by changing climate, rising
temperature and increased atmospheric concentrations of
carbon dioxide. These changes can threaten food security
by lowering not only the production of food but also its
nutritional quality. The strategies proposed to counter
these threats envisage a wide range of ways, not mutually
exclusive, to
manage biotic interactions in
agroecosystems. These include modifying crop plants’
natural constitutive and induced defenses and other
sources of resistance; engineering crop plants to express
novel defenses; and increasing the effectiveness of
‘integrated pest management’ (through natural enemies,
other components of agrobiodiversity and pesticides) by
modifying the structure and functioning of
agroecosystems. In this presentation, we examine these
proposed solutions through the evolutionary ecologist’s
lens: What are their respective costs and benefits, and
how do these affect the ecological situations in which
each could help farmers produce sufficient amounts of
high-quality food? How can the coevolutionary dynamics
of interactions between crop plants and their biotic
environment be managed to avert catastrophic fluctuation
of yield?
Growing populations under changing climates call for
more nutritious crops
Johnson, AAT1,2, Kyriacou, B1, Stangoulis, J3, Tester,
M2
1
School of Botany, The University of Melbourne,
Australia; 2Australian Centre for Plant Functional
Genomics, Glen Osmond, Australia; 3Flinders University
of South Australia, Australia
The ‘Green Revolution’ that occurred between the 1940s
and 1970s saw an enormous increase in agricultural
productivity worldwide. The adoption of semi-dwarf and
hybrid cereal varieties, as well as improved irrigation,
fertilizer and pesticide practices, greatly increased food
production in developing countries of the world.
However, not all changes brought about by the Green
85
Revolution were desirable. Cereal crops such as rice and
wheat, while high in calories, do not contain significant
quantities of nutritionally important micronutrients such
as iron (Fe), zinc (Zn) and Vitamin A. As increasing
numbers of people have come to rely on cereal crops to
meet their energy needs we have seen a reduction in the
number of people suffering from caloric hunger but a
massive increase, in fact billions of people, suffering
from micronutrient hunger – a nutritional disorder often
referred to as ‘hidden hunger’ because the effects, while
devastating, are not always apparent at first glance. The
effects of climate change are likely to further compound
this problem. In particular, rising atmospheric carbon
dioxide concentrations are predicted to decrease the
protein concentration of most crops. Additionally, the
concentrations of many essential elements in food crops,
such as Fe and Zn, are predicted to decrease as a result of
increased atmospheric carbon dioxide. These findings
suggest that climate change may further compound
severe micronutrient malnutrition problems already
affecting billions of people throughout the world and
highlight a need for the development of more nutritious
crops. Because rice (Oryza sativa L.) serves as the
primary source of calories for more than half of the
world’s population, we are working to improve the
micronutrient content of the white rice grain.
Nicotianamine (NA) is a natural metal cation chelator
that plays important roles in metal acquisition and
transport in all plants. To generate rice lines with
increased levels of Nicotianamine, the three rice
Nicotianamine synthase (NAS) genes – OsNAS1,
OsNAS2, and OsNAS3 – were constitutively
overexpressed using the 35S cauliflower mosaic
promoter. Elemental analysis showed that the resulting
rice lines contain three-fold more Fe and two-fold more
Zn in white rice. Seed Nicotianamine content is tightly
correlated with Fe and Zn content, providing strong
evidence that increased Nicotianamine levels are
responsible for the observed increased loading of Fe and
Zn into white rice grain. The levels of Fe in these
biofortified rice varieties could meet the recommended
daily allowance of Fe in a daily serving of rice. We
anticipate that biofortification of all major food staples
will take on an increasingly vital role as the human
population continues to grow under changing climatic
conditions.
Abiotic factors alter defense of cyanogenic lima bean
(Phaseolus lunatus L.) against a natural insect
herbivore
Ballhorn, DJ1, Hegeman, AD1, Schmitt, I2, Kautz, S1
1
University of Minnesota, Dept of Plant Biology, St Paul,
USA; 2University of Minnesota, Dept of Horticultural
Science St Paul, USA; 3Biodiversity and Climate
Research Centre BiK-F, Frankfurt, Germany; 4Goethe
University Frankfurt am Main, Frankfurt, Germany;
5
Field Museum of Natural History, Dept of Zoology,
Chicago, USA
Plants cannot escape when being attacked or exposed to
unfavorable conditions, but they are far away from being
helpless organisms. In the last decades, research has
demonstrated how plants can actively up-regulate a wide
array of defensive traits when subjected to stress factors.
However, effects of changing environmental conditions
86
on variability of plant defensive traits and consequences
of this variability for higher trophic levels are still little
understood. We used wild lima bean (Fabaceae:
Phaseolus lunatus L.) to analyze effects of various
abiotic factors (drought and salt stress, nitrogen
availability, and CO2) on the expression of two
exemplary chosen plant defensive traits: cyanogenesis
(nitrogen-based) and phenolics (carbon-based). In growth
chamber experiments, exposing cyanogenic lima bean
plants to drought stress, soil salinity as well as enhanced
nitrogen-availability resulted in a quantitative upregulation of cyanogenic precursor concentration in
leaves by approximately 12, 7, and 9%. In contrast to
plant cyanogenesis, concentration of phenolics remained
unaffected by the treatments. Feeding trials with Mexican
bean beetles (Coccinellidae: Epilachna varivestis Muls.),
a specialist herbivore, showed that the up-regulation of
plant cyanogenesis resulted in a significantly improved
defense against larvae and adult beetles. While the
effects of drought, salt stress and nitrogen availability on
cyanogenesis were observed among leaves of different
age, treating plants with enhanced CO2 (ambient
conditions to serve as control as well as 500, 700 and
1000 ppm CO2) atmospheres resulted in a distinct
chemical responses depending on leaf developmental
stage. While under elevated CO2 the amount of
cyanogenic precursors decreased in young, intermediate,
and mature leaves, the concentration of total phenolics
was significantly increased in intermediate and mature
leaves. As a result of this dramatic change in chemical
composition among different leaf developmental stages,
in feeding trials with Mexican bean beetles we observed
a complete shift from highest herbivore damage in
mature leaves in controls to highest damage of young
leaves under elevated CO2. Using cyanogenic lima bean
as model plant we could demonstrate that (i) different
abiotic parameters quantitatively affect the plant
chemical phenotype, that (ii) changes of plant defensive
traits can have strong impacts on natural insect
herbivores, and (iii) that changes in plant chemical
phenotype and effects on herbivores can depend on
ontogenetic development of specific plant organs. Since
in the long run preferred consumption of young leaves as
we observed under elevated CO2 concentrations can
strongly affect plant fitness, effects of abiotic factors on
different leaf stages should receive highlighted attention
in future research.
Nutrient supply, below ground processes and elevated
CO2 change the partitioning of resources between
growth and defence in cyanogenic plants
Gleadow, R1, Cavagnaro, T1, Isherwood, S1, Seneweera,
S2, Miller, R1
1
Monash University, Australia;
Melbourne, Australia
2
The University of
The challenge for agriculture in the 21st century is to
increase productivity in the face of rising global
concentrations of atmospheric CO2, higher temperatures,
reduced water availability, and possibly in conjunction
with more expensive fertilisers. Our focus is on the
changing balance between plant growth and resource
allocation with climate change and its impact on food
security. Plants grown at elevated CO2 experimentally
have lower leaf nitrogen and typically allocate less of
that N to protein and photosynthesis. There is very often
a concomitant increase in concentration in secondary
metabolites. This is expected to decrease the nutritional
quality of pastures. We are developing Trifolium repens
L. (clover) as a model species suitable for high
throughput experiments in temperate Australia as a
companion to our work on the tropical crops, sorghum
and cassava. Clover is one of over 2000 species
(including many crops) that produces cyanogenic
glycosides, which release hydrogen cyanide (HCN) in
response to plant tissue damage (cyanogenesis),
primarily as a defence against hervicores. Clover is
polymorphic for cyanogenic glycosides and represents an
ideal system to strengthen knowledge of defence
chemistry, allocation and resource trade-offs under
different environmental conditions. It forms symbiotic
associations with mycorrhizae as well as Rhizopus, both
of which enhance nutrient uptake. Previous contained
environment experiments showed that clover allocates
more N to endogenous cyanogenic glycosides when
grown at elevated CO2 but only when phosphate is
added. We grew clover (cv Haifa) plants for 5 months at
ambient and elevated CO2 under field conditions in the
AGFACE facility at Horsham. Half the plants received
supplemental water. In a parallel experiment we grew
cyanogenic and non-cyanogenic clover in agricultural
soil in a glasshouse and supplied them with fertiliser
containing different proportions of N and P. Plant growth
and colonisation rates were determined and leaves
analysed for cyanogenic glycosides, nitrogen,
phosphorus and micronutrients. Ratios of stable isotopes
of N were used to indicate the proportion of N in the
plant taken up through N fixation, and C isotopes were
used to measure the degree of water stress. We found that
the change in relative proportions of Carbon, Nitrogen
and Phosphorus affect the allocation of resources to
defence. We were, however, unable to detect any cost to
the plants (in terms of growth sacrifice) in the production
of cyanogenic glycosides. Understanding what drives
changes to resource allocation in plants, and particularly
the role of below ground processors, will be crucial in
determining successful management of agriculture and
animal health into the future.
FTIR spectroscopy for characterisation of sorghum
cell wall variants
Martin, A1, Byrt, CS1, Furbank, RT2, Sirault, XRR2,
Grof, CPL1
1
University of Newcastle, Australia; 2CSIRO Plant
Industry and High Resolution Plant Phenomics Centre,
Australia
Sorghum bicolor cell wall composition was investigated
using Fourier Transform Infrared (FTIR) spectroscopy
and Focal Plane Array (FPA)-FTIR. Cell walls from stem
tissue of a number of Sorghum cell wall variants,
including reduced lignin (Brown midrib, Bmr) lines,
were isolated and FTIR spectra were collected. The
digestibility of the isolated cell wall samples were
determined by a cellulase digestion method and the
composition of isolated cell walls, such as Acetyl
bromide lignin, cellulose and hemicellulose content were
measured. FTIR absorbance peaks were assigned in
accordance with the literature. Peaks associated with
lignin and cellulose differed for the Bmr lines as
compared with the wild type lines, consistent with wet
chemistry data. Pre-treated spectral data was analysed by
principle component analysis (PCA). Examination of the
loadings plot for the principal components revealed
which peaks most influenced the PC scores. FTIR data
clearly distinguished differences in cellulose, lignin, and
lignin monomers in the Sorghum variants. The
correlation between peak assignment data, collected by
FTIR spectroscopy and data for cell wall components
such as cellulose, total lignin, lignin monomers and
suberin, measured using traditional methods, was
investigated. Spectral differences were mapped in stem
sections, using FPA-FTIR, and the images were
compared with data from histological staining, including
berberine, calcofluor white and mäule staining. A partial
least squares (PLS) predictive model was developed
which incorporated spectral and cell wall digestibility
data. For an independent validation set of samples the
model accurately predicted the digestibility of the
Sorghum stem tissue from spectral data. This model may
be useful for high-through-put screening of Sorghum
germplasm to identify variation in cell wall recalcitrance
to digestibility.
A free air CO2 enrichment (FACE) study of the
important staple food cassava (Manihot esculenta)
Miller, RE1,2, Rosenthal, DM3, Slattery, B4 , Gleadow,
RM1, Cavagnaro, TR1,2,Fauquet, CM6, Ort, DR3,4,5
1
School of Biological Sciences, Monash University,
Australia; 2Australian Centre for Biodiversity, Monash
University, Australia; 3 Global Change and
Photosynthesis Research Unit, Agricultural Research
Service, United States Dept of Agriculture, Urbana,
USA; 4Depts of Plant Biology and 5Crop Sciences,
University of Illinois, Urbana, USA; 6 International
Laboratory for Tropical Agricultural Biotechnology,
Donald Danforth Plant Science Center, St Louis, USA
Cassava (Manihot esculenta Crantz., tapioca, manioc) is
an important staple food for over 800 million people in
Africa, South America, Asia and the Pacific. Tubers are
the main agricultural product, although leaves are also
eaten. Globally, up to 70% of cassava is used for food,
but cassava is particularly important in sub-Saharan
Africa. Sometimes referred to as the drought, war and
famine crop of the developing world, cassava yields well
under low nutrients and dry conditions, and is easy to
propagate. Consequently, its production worldwide has
doubled in the past 30 years, reaching 250 million tonnes
in 2009, due largely to increases on small-scale
subsistence farms in Africa, but also to greater
cultivation for industrial applications. While cassava is
an incredibly important source of carbohydrates, it is low
in nutrients and protein, and also contains cyanogenic
glycosides that release the respiratory toxin hydrogen
cyanide. Many cultivars require processing to reduce
cyanogen content before consumption, but intake of
insufficiently processed cassava can result in chronic
medical conditions such as permanent paralysis of the
legs (Konzo). Given the importance of cassava to food
security, it is essential that we understand how this crop
will respond to global climate change, both in terms of
yield and chemical composition. The few studies of the
87
response of cassava to increasing atmospheric CO2
(eCO2) to date – conducted in glasshouses or small
chambers – have produced contrasting findings. While
one study reported an increase in tuber yield, a recent
study reported a decrease in tuber yield under 550 and
710 ppm CO2. Furthermore, in the latter study, increases
in the toxicity of tissues were also reported under eCO2
suggesting the prospect of both reduced yield and
nutritive value under future CO2 concentrations. It is now
well established that the extent of stimulation of C3 crop
yields by eCO2 varies not only with species and
environmental conditions, but also with experimental
methodology. Clearly, there is a need for
experimentation to assess how cassava might respond to
elevated CO2 under fully open air CO2 enrichment
(FACE). We conducted a field-based eCO2 study of
cassava at the soyFACE facility, Illinois, USA, as there
are currently no FACE sites in areas where cassava is
cultivated. Physiological, growth and biochemical
responses of cassava to eCO2 (585 ppm) were measured.
In the fertile soils at soyFACE, cassava responded as
typical C3 plant, showing increased biomass in response
to eCO2. In addition, there were significant changes in
the nutritional quality of both foliage and tubers. The
consequences of the growth and biochemical responses
of cassava to eCO2 will be discussed in relation to future
food security.
Sym036: Exploiting root:soil interactions to
minimize impacts of below-ground stress on
food production – 30 July
Plant signalling networks underpinning crop yield
under environmental stress
Davies, W1
1
Lancaster University, UK
Soil drying commonly limits plant productivity even
when there is still a substantial amount of water in the
soil. This limitation occurs, initially at least, through an
impact on both gas exchange and canopy development
and if we are to minimise these restrictions of growth and
yielding, it is important to understand their mechanistic
basis. We highlight the importance of the influence of
both hydraulic and chemical limitations of functioning,
growth and development of plants in drying soil and
suggest that by processing and responding to these
signals, plants are able to optimize growth and
development relative to the amount of water and nutrient
available in the soil. We propose that via enhancement or
suppression of different ‘root signal’ cascades we can
intervene to sustain plant yielding under different
environmental stresses (Morison et al. 2007). We review
the identity of signals limiting leaf conductance, leaf
growth and harvest index (e.g Foulkes et al. 2010) and
consider prospects for manipulation of signalling, with
special reference to the impact of changes in sap pH,
modified fluxes of abscisic acid (ABA) and of the
ethylene precursor ACC (e.g. Jia and Davies 2007;
Wilkinson and Davies 2009). We can use both synthesis
and sensitivity mutants and transgenics to investigate the
genetic manipulation of signalling in agriculture but there
are many other ways to modify stress signalling cascades
88
for the benefit of crop yield. For example, management
techniques such as deficit irrigation, fertilizer
applications and buffer treatments can all impact long
distance chemical signalling. Such techniques can be
operated in conjunction with plant improvement to
sustain yielding and increase water use efficiency in
dryland agriculture.
Root thermotolerance mechanisms from whole-root
to molecular biology
Huang, B1
1
Rutgers University, New Brunswick, USA
Heat stress is becoming an increasingly significant
limitation to the growth of temperate plants due to global
warming. Roots are more sensitive to heat stress than
shoot growth due to their lower temperature requirements
for optimal growth. Understanding mechanisms of root
thermotolerance is of great significance for developing
heat-tolerant plants that can adapt to areas with elevated
temperatures. This presentation will review current
research in mechanisms of root-mediated heat tolerance
from whole-plant to molecular biology. From the wholeplant level, root dieback precedes growth decline and leaf
senescence under heat stress, suggesting that root
systems play critical roles in sensing high soil
temperatures and regulating whole-plant responses to
heat stress. Root responses to heat stress are reflected in
changes of water uptake, nutrient uptake, and hormone
synthesis. Along the three major root functions, hormone
metabolism is most sensitive to heat stress. Roots are
primary sites for the synthesis of some plant hormones,
such as cytokinins. Cytokinins metabolism in roots may
affect leaf responses to heat stress by regulating leaf
senescence and other physiological processes, including
leaf photosynthesis. Roots depends on shoots for carbon
supply, therefore, efficient carbon utilization could play
important role for maintaining root survival under
elevated temperatures. Heat tolerance in root systems is
also associated with changes at proteomic, metabolic,
and molecular levels. The specific proteins, metabolites,
and genes associated with the whole-plant physiological
changes and superior heat tolerance will be discussed.
Altering root architecture of wheat to increase the
water productivity in India and Australia
Wasson, AP1, Richards, RA1, Chatrath, R2, Misra, S3,
Prasad, S4, Singh, SK2, Rebetzke, GJ1, Kirkegaard, JA1,
Christopher, J5, Watt, M1
1
CSIRO Plant Industry, Canberra, Australia;
Directorate of Wheat Research, Karnal, India;
3
Agharkar Research Institute, Pune, India; 4Indian
Agricultural Research Institute, Regional Wheat
Research Station, Indore, India; 5Dept of Employment
Economic Development and Innovation, Leslie Research
Centre, Toowoomba, Australia
2
India and Australia produce approximately 100 million
tonnes of wheat per year. Almost all of the 75 Mt grown
in India is consumed within country; over half of the
approx 25 Mt grown in Australia is exported such that
wheat is Australia’s most important soft commodity.
Both countries are focused on increasing crop yields per
unit available water to meet future food demands. The
aim of our joint research is to identify and validate new
wheat lines that have faster growing, deeper root systems
that capture more water around flowering and grain
development in both Australia and India. Modelling and
field evidence has shown that relatively small increases
in root system descent rate and root length density at
depth can lead to up take of an extra 10 mm of water that
is converted into 0.5 tonnes of grain – a very high water
productivity. The approach is largely field-based because
mature wheat roots cannot be selected in the laboratory,
and the mechanisms and genes regulating deep root
growth are not known. Diverse wheats being evaluated
include unique CSIRO lines with double the shoot and
root vigour of released varieties in controlled conditions,
lines with modified shoot and root architecture through
tiller inhibition, prolonged green-leaf duration, synthetic
wheats, and varieties from India and Australia with
historically high yields in water-limited regions. A novel
planting configuration is used with one line per square
meter for high density and replication and uniform water
availability per line. Non-destructive imaging methods
are used to measure leaf transpiration and green leaf area,
and root water uptake is measured using electrical
resistivity tomography. At the end of the season roots are
measured directly by coring to 2 metres in Australia and
India then relate to shoot measurements. An objective is
to develop and validate a rapid non-invasive method for
breeders. The best lines for further study are narrowed
down annually using a ranking algorithm. These lines
will be used to identify the mechanisms underlying root
architecture variation and to quantify the water
productivity gain in India and Australia. In future they
may be used for the development of mapping populations
to identify molecular markers. Two seasons at six sites in
India and Australia indicate more than two fold variation
in the root and shoot parameters.
Hormonal changes in rice plants under alternate
wetting and drying irrigation
Yang, J1, Zhang, H1, Huang, Z1, Zhang, J2
1
Key Laboratory of Crop Genetics and Physiology of
Jiangsu Province, Yangzhou University, Yangzhou,
Jiangsu, China; 2Dept of Biology, Hong Kong Baptist
University, Hong Kong, China
Plant hormones may reflect soil water status and mediate
rice (Oryza sativa L.) growth and development. This
study investigated the changes in hormonal levels in rice
plants and their relations with tillering, panicle initiation,
and grain filling under alternate wetting and drying
irrigation. Two rice cultivars were field grown. Three
irrigation regimes, alternate wetting and moderate soil
drying (WMD), alternate wetting and severe soil drying
(WSD), and conventional irrigation (CI, continuously
flooded), were imposed during the whole growing
season. The WMD significantly increased, whereas the
WSD significantly decreased, productive tiller number,
spikelet number per panicle, grain filling rate, and grain
yield when compared with the CI. Abscisic acid (ABA)
levels in root bleedings, leaves, and spikelets were
significantly increased during the soil drying period
under both WMD and WSD regimes. During the soil
drying period, levels of ethylene and 1aminocylopropane -1-carboxylic acid (ACC) were
decreased under the WMD, but they were increased
under the WSD. The WMD increased, while the WSD
reduced, the ratio of ABA to ACC (ABA/ACC). Levels
of zeatin (Z) + zeatin riboside (ZR) in both root
bleedings and shoots (spikelets and leaves) at the soil
drying time under the WMD were comparable with those
under the CI, but they were significantly increased when
plants were re-watered. The WSD significantly reduced
Z + ZR contents in root bleedings and shoots either
during the soil drying or during the re-watering period.
Level of indole-3-acetic acid (IAA) and gibberellins
(GA1 + GA4) in rice plants were significantly reduced
under the WSD, and they showed no significant
difference between WMD and the CI regimes. Productive
tiller number, spikelet number per panicle, grain filling
rate, and grain weight were very significantly correlated
with the ratio of ABA to ACC and Z + ZR levels in
plants. The results suggest that an increase in ABA/ACC
in plants during the soil drying period and an
enhancement in cytokinin levels during the re-watering
time contribute to increases in rice growth and grain
yield under a moderate wetting and drying regime.
Exploiting rhizobacterial impacts on hormonal rootto-shoot signalling to ameliorate water stress
Dodd, I1, Arkhipova, T2, Belimov, A3
1
Lancaster University, UK; 2Ufa Science Centre, Russia;
All Russia Research Institute of Agricultural
Microbiology, Russia
3
Soil drying alters the synthesis, metabolism and xylem
loading of various plant hormones (1). Plant growth
promoting rhizobacteria (PGPR) are commonly found in
the rhizosphere (adjacent to the root surface) and may
promote plant growth via several diverse mechanisms,
including the production or degradation of the major
groups of plant hormones that regulate plant growth and
development. Although rhizobacterial production of plant
hormones seems relatively widespread (as judged from
hormone measurements of bacterial culture media), there
is increasing evidence (particularly from seedlings grown
under gnotobiotic conditions) that rhizobacteria can
modify plant hormone status (2). This not only has local
effects on root elongation and architecture, thus
mediating water and nutrient capture, but can affect
hormonal root-to-shoot signalling that alters shoot
hormone status and regulates leaf growth and gas
exchange. Water stress can stimulate production of the
plant hormone ethylene, which is often inhibitory to root
and shoot growth. Soil inoculation of pea (Pisum
sativum) seedlings with the PGPR Variovorax paradoxus
5C-2 containing the enzyme ACC deaminase (which
breaks down the ethylene precursor ACC into carbon and
nitrogen sources for bacterial growth) attenuated an
increase in xylem ACC concentration caused by soil
drying, thereby promoting vegetative growth, and
increasing plant yield (3). The plant hormones known as
cytokinins stimulate cell division and elongation and
retard leaf senescence, yet water stress decreases plant
cytokinin concentrations. Soil inoculation of lettuce
(Lactuca sativa) seedlings with the cytokinin-producing
PGPR Bacillus subtilis IB-22 doubled shoot cytokinin
concentrations presumably by enhancing root-to-shoot
cytokinin transport, and promoted shoot vegetative
growth (and thus plant yield) of plants grown in drying
89
soil (4). Further work is required to substantiate whether
individual PGPR affect root-to-shoot signalling of more
than one hormone class, and whether these systemic
effects described under controlled environment
conditions occur when field crops are inoculated.
Nevertheless, rhizobacterial amendments offer the
potential to ameliorate deleterious effects of water stress
on shoot hormone status and thence crop yield (5).
Acknowledgements: We thank BBSRC, DEFRA, RFBR
and the Royal Society for supporting work in our
laboratories. (1) IC Dodd (2005). (2) IC Dodd et al.
(2010). (3) AA Belimov et al. (2009). (4) TN Arkhipova
et al. (2007). (5) IC Dodd (2009).
Effects of soil organisms on aboveground
multitrophic interactions are consistent among plant
genotypes mediating the interaction
Kabouw, P1, Kos, M2, Vockenhuber, E3, Biere, A1, van
der Putten, W1, van Dam, N1
1
Netherlands Institute of Ecology (NIOO-KNAW), Dept
of Terrestrial Ecology, The Netherlands; 2Wageningen
University, Laboratory of Entomology, The Netherlands;
3
Georg-August-University, Agrarökologie, Germany
In an experimental study we demonstrate that
manipulation of interactions between plants and soil
organisms can profoundly affect the herbivore load
aboveground. To assess whether the outcome of these
below–aboveground interactions can be affected by plant
genotype we selected two white cabbage (Brassica
oleracea var. capitata) cultivars. These cultivars were
known to differ in their resistance against below- and
aboveground pests due to their different profiles of
secondary metabolites, including glucosinolates.
Belowground we inoculated soils of the cultivars either
with nematodes or micro-organisms and included a
sterilized soil as a control treatment. Aboveground we
monitored population development of aphids and fitness
parameters of parasitoids as a bio-control mechanism.
Soil treatments affected aphid population sizes; microorganisms increased and nematodes tended to decrease
aphid population growth. Soil treatments did not affect
parasitoid performance, thus not decreasing their
efficiency
for
bio-control.
The
glucosinolate
gluconasturtiin was lacking from one of the cultivars,
making this cultivar more susceptible to plant feeding
nematodes. Nevertheless, the relative effect of soil
treatment on aphid population growth or parasitoid
performance was similar for both cultivars. This indicates
that, although the soil community did affect the
aboveground community, this effect was independent of
the cultivar that was mediating the interaction.
Additionally the effect of cultivar on the aboveground
community was overall larger than soil treatment effects.
The two cultivars sustained different aphid population
growth rates and the parasitoids had a higher mass and a
faster developmental time on the cultivar that had the
highest aphid population growth. In conclusion, in our
study altering belowground interactions consistently
altered herbivore loads aboveground.
90
Sym152: Reproductive development and
yield potential in cereals – 28 July
Inflorescence development in maize
McSteen, P1
1
Division of Biological Sciences, University of MissouriColumbia, Columbia, USA
Maize (Zea mays or corn) produces two types of
inflorescence – the male inflorescence or tassel, which
produces the pollen and the female inflorescence or ear,
which produces the kernels and is harvested. An
understanding of yield potential requires an
understanding of the development of the inflorescence
and in particular the activity of meristems within the
inflorescence. We are using a genetic approach to
determine the mechanisms regulating inflorescence
development in maize. The spikelet (a small branch
bearing the florets) is the fundamental unit of yield in all
cereals. Maize and all species in the tribe Andropogoneae
produce paired spikelets while grasses outside this clade
produce single spikelets. To identify genes controlling
spikelet number in grasses, we have been identifying
maize mutants which produce single spikelets. One class
of these mutants have defects in the biosynthesis,
transport or response to the plant growth hormone, auxin,
implicating auxin in the process of axillary meristem
initiation and spikelet production. This class of mutant
often produces no ear shoot, implicating auxin also in the
initiation of the ear in maize. Another class of mutants
have smaller meristem size implicating the signaling
pathways regulating meristem size in the control of
spikelet number in the ear. A third class of mutants have
defects in nutrient metabolism implicating essential
nutrients in the maintenance of the apical meristem and
hence ear size. An understanding of the process of
inflorescence development is essential for efforts to
sustain and improve yield in all cereals. Our current
understanding of the mechanism of inflorescence
development in maize will be presented.
Specification of spikelet meristem identity directly
influences the inflorescence form of rice
Kyozuka, J1
1
Graduate School of Agriculture and Life Sciences,
University of Tokyo, Japan
Number of grains, one of major determinants of yield in
grass species, depends on the inflorescence form.
Flowers of grass species are formed in spikelets and the
inflorescence form is described as the pattern of spikelet
formation. During rice inflorescence development,
panicle branch formation precedes spikelet formation. A
delay of spikelet identity specification leads to prolonged
branch formation, which results in the formation of
bigger inflorescences. On the other hand, precocious
specification of the spikelet identity causes production of
small inflorescences containing less spikelets. We
identified TAWAWA 1(TAW1) and PANICLE
PHYTOMER 2 (PAP2) genes as novel key players in
control of the spikelet meristem identity in rice. Semidominant taw1-D1 and taw1-D2 mutants exhibit a highly
branched inflorescence phenotype, indicative of the
delayed specification of the spikelet meristem identity.
TAW1, encoding a nuclear protein of unknown function,
is expressed in the SAM during vegetative phase and its
expression level gradually decreases after transition to
the reproductive phase. Higher levels of TAW1 mRNA
accumulate in taw1-D1 and -D2 mutants and the severity
of the phenotype well correlates with the level of TAW1
expression. Based on these observations, we propose
TAW1 as a negative regulator of the spikelet meristem
fate in rice. PAP2 is a positive regulator of spikelet
meristem identity. Loss of PAP2 function causes an
increase of the inflorescence branch formation indicative
of the delayed specification of spikelet identity. PAP2
encodes OsMADS34, a member of SEP subfamily
MADS box proteins. Phylogenetic analysis indicated that
SEP subfamily is expanded in grass species and PAP2 is
in a grass specific sub-clade of the SEP genes. Our
analysis suggested that PAP2 is central in the control of
early stages of rice inflorescence development. The
genetic interaction between TAW1, PAP2 and other
genes which are involved in the control of spikelet
identity will be discussed. Possible application of TAW1
and PAP2 genes for rice breeding to increase yield will
be also discussed.
Molecular pathways controlling the response to high
temperature in cereals
Hemming, MN1, Dennis, ES1, Trevaskis, B1
1
CSIRO Plant Industry, Canberra, Australia
Rising global temperatures have the potential to decrease
yields in staple crops such as cereals. High temperature
accelerates flowering in cereals, but nothing is known
about the molecular pathways controlling this response.
Using barley as a model, we are examining the effect of
increasing ambient temperature on vegetative and
reproductive development in cereals at the physiological
and molecular level. Plants are grown under highly
controlled and replicable growth conditions in the High
Resolution Plant Phenomics Centre in Canberra to screen
germplasm for variability in response to temperature and
to conduct gene expression analysis. We aim to identify
genes controlling the developmental response to high
temperature. I will present a model for the way in which
changes in gene expression control reproductive
development in response to increasing ambient
temperature and describe the contribution of key
flowering-time genes to development under high
temperature. Finally, I will discuss how identification of
key genes controlling the response to increasing
temperature in cereals will enable selection of allelic
variants that provide positive adaptation to specific
climatic conditions.
Genetic regulation of spike development and yield
potential in wheat
Swain, S1, Cavanagh, C1
1
CSIRO, Canberra, Australia
Cereal yield potential is determined by a combination of
the number of grains formed in a given area and the
average grain weight. The number of grains produced by
each plant is determined by the number of fertile florets
that develop, each of which has the potential to form a
single grain. Consequently, a major limit on yield is the
number of fertile florets/grains that develop. Fertile
florets per plant is a major target for genetic
improvement of cereals, including wheat. In wheat,
florets are produced by groups of approximately 20
specialized branches (spikelets) which together form a
structure known as a spike. The number of florets
produced by each spikelet, and the number of spikelets
per spike, are under strong genetic (and possibly
epigenetic) control. Altering spike architecture, by
modifying both the number and position of spikelets, and
the number of fertile florets produced by each spikelet,
can potentially increase the number of florets/grains per
spike, and hence yield potential. We are using a unique
wheat mapping population that segregates for variation in
several aspects of spike development, including both
spikelet number and florets per spikelet, to investigate
the relationship between spike architecture and yield
potential. One trait we are investigating is the formation
of supernumerary spikelets which can form adjacent to
normal spikelets leading to a pair of spikelets at a single
rachis node of the spike. Detailed analysis reveals that
the formation of these paired spikelets varies along the
length of the spike, and their number is also affected by
different growing conditions, suggesting a link between
this trait and assimilate partitioning to the developing
spike. Quantitative Trait Locus (QTL) analysis reveals
several major loci that control paired spikelet formation
and ongoing work is aimed at identifying the genes
involved based on the function of rice and maize genes
that regulate related processes in these crops.
High temperature stress and plant reproduction
Sage, T1
1
Dept of Ecology & Evolutionary Biology, University of
Toronto, Canada
One consequence of global climate change is the
detrimental effect of increased frequency of high
temperature stress (HTS) on crop yields. The primary
focus of this research is to assess the impact of HTS
(32ºC and 36ºC) on morphological yield components
contributing to Harvest Index in the eudicot, Arabidopsis
(accessions Ler and Cvi) and the monocotyledonous
species, Brachypodium distachyon and Oryza sativa.
HTS has a negative impact on Harvest Index all species
by significantly reducing initiation of vegetative
branching and flowers. In Arabidopsis, 32ºC reduces
seed set/silique in Cvi to almost zero whereas Ler still
produces a high number of seed/silique. Pollen
deposition is directly correlated with reductions in seed
yield/silique such that 32ºC almost eliminates pollen
deposition in Cvi but not in Ler. Pollen deposition, and
hence seed production, is also severely reduced at 32ºC
in Oryza and Brachypodium. HTS of 36 C eliminates
seed set for all species examined. In comparison to
processes leading to reductions in seed set at 32ºC, an
absence of seed set at 36ºC results from termination of
microspore mother cell development prior to meiosis or
abortion of uninucleate microspores. Developmental
studies indicate that miscarriage during maturation of
microspore mother cells and uninucleate microspores
involves autophagic cell death. Analysis of reproduction
91
at 32ºC in LerXCvi Recombinant Inbred Lines has
identified QTL involved in filament and anther
development that play an important role in anther
dehiscence and pollen deposition. Within these QTL are
genes involved in cell division and elongation, ethylene
response and signaling, and heat shock. With the use of
cryofixation to examine ultrastructural features of anther
development at 32ºC in Oryza and Brachypodium, it has
been determined that HTS prevents anther indehiscence
by interfering with endothecial contraction and not the
development of the stomium and pollen swelling. These
results shed light on the stages of reproduction that are
most sensitive to HTS in both a eudicot and monocots;
HTS has an unfavorable impact on Harvest Index by
interfering with male reproductive development and
suppressing vegetative and reproductive meristem
development. QTL that influence these developmental
processes in Arabidopsis will be of interest for future
studies aimed at improving crop yield of both eudicots
and monocots under increased global temperatures.
Sym159: Plants in human health and
well–being – 26 July
Bioprospecting flavonoid and terpenoid pathways in
target plants tea, Picrorhiza and Arnebia
Singh, K1, Rani, A1, Kawoosa, T1, Singh, RS1, Mahajan,
M1, Dutt, S1, Kumar, S1, Gulati, A1, Bhushan, S1,
Sharma, M1, Ahuja, PS1, Kumar, S1
1
Biotechnology Division, Institute of Himalayan
Bioresource Technology, Palampur (HP), India
Plants are the source of a range of bioactive metabolites,
which are used for good health, to treat various ailments
and as important constituents of colours, dyes, flavours
and fragrances. Most of these metabolites are synthesised
through flavonoid (FL), and terpenoid [2-C-methyl-Derythritol 4-phosphate (MEP) and mevalonate (MVA)]
pathways. One of the critical issues is to unravel the
molecular control of synthesis of these compounds in the
relevant plant systems. Catehcins, shikonins and
picrosides are medicinally important metabolites
synthesized in tea (Camellia sinensis), arnebia (Arnebia
euchroma), and picrorhiza (Picrorhiza kurrooa),
respectively. Using a range of genomic and biochemical
tools, molecular regulation of FL pathway in tea, MVA
pathway in arnebia, and MVA and MEP pathways in
picrorhiza were deciphered and analyzed. Use of
germplasm with varying levels of metabolites and
environmental cue mediated modulation of metabolite
content, followed by transcriptome analysis and
functional validation of genes led to important outcomes
as follows: (1) deciphered various genes involved in the
biosynthetic pathways, (2) regulatory genes of the
pathway were identified, (2) within a plant system,
crosstalk existed between the connecting pathways, (3)
early genes were important in determining the final
product content, (4) environmental cues determined
metabolite level through gene regulation; identified plant
system specific critical cues, (5) product mediated
feedback inhibition was evident. Using clues from the
data generated, heterologous expression of important
genes of FL pathway produced flavonoides in alternative
92
system and also fermentor-based shikonins production
system was developed. Plants of medicinal value have
been analyzed in detail to define pathways responsible
for the synthesis of compounds of interest to human
health. The symposium brings together a diverse range of
interests dealing with gene networks involved in the
production of compounds of medicinal interest as well as
those involved in detoxifying environmentally harmful
pollutants.
Improving the micronutrient content of the white rice
grain
Johnson, A1
1
The University of Melbourne, Australia
The 'Green Revolution' that occurred between the 1940s
and 1970s saw an enormous increase in agricultural
productivity worldwide. The adoption of semi-dwarf and
hybrid cereal varieties, as well as improved irrigation,
fertilizer and pesticide practices, greatly increased food
production in developing countries of the world.
However, not all changes brought about by the Green
Revolution were desirable. Cereal crops such as rice and
wheat, while high in calories, do not contain significant
quantities of nutritionally important micronutrients such
as iron (Fe), zinc (Zn) and Vitamin A. As|increasing
numbers of people have come to rely on cereal crops to
meet their energy needs we have seen a reduction in the
number of people suffering from caloric hunger but a
massive increase, in fact billions of people, suffering
from micronutrient hunger – a nutritional disorder often
referred to as 'hidden hunger' because the effects, while
devastating, are not always apparent at first glance. The
effects of climate change are likely to further compound
this problem. In particular, rising atmospheric carbon
dioxide concentrations are predicted to decrease the
protein concentration of most crops. Additionally, the
concentrations of many essential elements in food crops,
such as Fe and Zn, are predicted to decrease as a result of
increased atmospheric carbon dioxide. These findings
suggest that climate change may further compound
severe micronutrient malnutrition problems already
affecting billions of people throughout the world and
highlight a need for the development of more nutritious
crops. Because rice (Oryza sativa L.) serves as the
primary source of calories for more than half of the
world's population, we are working to improve the
micronutrient content of the white rice grain.
Nicotianamine (NA) is a natural metal cation chelator
that plays important roles in metal acquisition and
transport in all plants. To generate rice lines with
increased levels of Nicotianamine, the three rice
Nicotianamine synthase (NAS) genes – OsNAS1,
OsNAS2, and OsNAS3 – were constitutively overexpressed using the 35S cauliflower mosaic promoter.
Elemental analysis showed that the resulting rice lines
contain three-fold more Fe and two-fold more Zn in
white rice. Seed Nicotianamine content is tightly
correlated with Fe and Zn content, providing strong
evidence that increased Nicotianamine levels are
responsible for the observed increased loading of Fe and
Zn into white rice grain. The levels of Fe in these
biofortified rice varieties could meet the recommended
daily allowance of Fe in a daily serving of rice. We
anticipate that biofortification of all major food staples
will take on an increasingly vital role as the human
population continues to grow under changing climatic
conditions.
Sym160: New variation in crops for climate
change – 28 July
Lupin–wheat bread protein: modification of the
bread matrix for improved health attributes
Interactions between regulatory pathways for abiotic
stress tolerance in cereals
Shahidul, I1, Ma, W1, Yan, G1, Gao, L1, Yan, Y1, Appels,
R1
Dolferus, R1, Ji, X1
1
Murdoch University, Australia
Nutritional qualities of lupin suggest bread rich in lupin
has the potential to provide a number of health benefits.
Mixing of lupin flour to wheat has major effects on bread
properties including the extractability of proteins that is
crucial to define the ultimate attributes of food. Present
study investigated the lupin and wheat proteome
dynamics as affected by the baking of lupin–wheat bread
by using 2-D electrophoresis and direct mass
spectrometry. Many of the proteins from both lupin and
wheat remained unchanged in baked lupin–wheat bread,
while the others were incorporated into the bread matrix
and could not be extracted. Most of the α-conglutins
could be readily extracted from the lupin–wheat bread
even at milder extraction. In contrast, most of the βconglutins lost extractability. The structural attribute that
correlates with this difference in behaviour is the greater
in thermal stability of α-conglutins relative to βconglutins. Most of the beta and gamma conglutins
showed relatively higher peptide sequence coverage of
corresponding matched proteins compare to alpha
conglutin due to lack of information regarding this group
of protein in the database.
Diversity of seed storage protein among narrowleafed lupin cultivars (Lupinus angustifolius L.) with
reference to contributing to health
Shahidul, I1, Ma, W1, Appels, R1, Buirchell, BJ1, Yan,
G1
1
Murdoch University, Australia
Narrow-leafed lupin (NLL) is one of the major legume
crops in Australian farming system which is largely used
as animal feed. A number of modern cultivars have been
developed through breeding making NLL possible to be
consumed as human food. Significant health benefits
have been recognised when NLL seeds are consumed.
This study characterised protein polymorphism among
the 25 Australian cultivars through mass spectrometric
(MALDI-TOF) with the aim of developing molecular
breeding strategies to improve protein quality and
content. Altogether, 364 seed storage proteins were
identified by the MALDI-TOF profiling and fifty
proteins were cultivar specific. Nine common proteins
(present in all cultivars) and 61 rare proteins (present in
2–3 cultivars only) were recorded. Phylogenic analysis
based on the protein profile clustered the cultivars into 2
major groups and 5 subgroups which are generally
supported by the pedigree information. Small number
(2.4%) of common proteins among the cultivars
suggested a high level of genetic diversity in seed storage
protein of NLL.
1
CSIRO Plant Industry, Canberra, Australia
The reproductive stage is very sensitive to a variety of
abiotic stresses (drought, cold, heat and salinity).
Adverse environmental conditions during flowering lead
to loss in grain number and high levels of sterility in the
world's most important staple crops. Experiments under
controlled environment conditions using precisely
controlled applications of stress periods have indicated
that the young microspore stage of pollen development is
the weakest link in the reproductive cycle. Both cold and
drought stress cause abortion of pollen development in
rice and wheat. This is associated with stress-induced
repression of sugar transport in the anthers. Germplasm
tolerant to cold and drought stress has been identified in
rice and wheat respectively and it was shown that
tolerance to cold and drought stress is associated with
maintenance of sink strength. Cold and drought tolerant
germplasm in rice and wheat is able to maintain lower
ABA levels in the spike during stress conditions. ABA
represses cell wall invertase expression in anthers and
transgenic rice plants over-expressing ABA 8'hydroxylase under the control of a strong tapetumspecific promoter results in significantly improved coldtolerance. The control of ABA homeostasis is therefore
critical for maintaining pollen fertility and grain number
during abiotic stress conditions. The high degree of
similarity between cold-induced pollen sterility in rice
and drought-induced sterility in wheat suggests that a
common regulatory mechanism is involved in tolerance
to both stresses and possibly other abiotic stresses.
Drought-tolerant wheat germplasm is also very tolerant
to shading stress, suggesting that different stress
tolerance pathways (including response to light intensity
and quality) converge at a common regulatory node that
controls reproductive development. Preliminary data
suggest that auxins may play an important role in
controlling ABA homeostasis and pollen development.
Molecular and genomics approaches, combined with
QTL mapping, will be used to identify genes responsible
for reproductive-stage abiotic stress tolerance in cereals.
Water deficit and the anther tapetum
Parish, R1
1
Botany Dept, La Trobe University, Melbourne Campus,
Victoria, Australia
Pollen fertility is one of the limiting factors in crops such
as rice and wheat. Interference with normal tapetal
development leads to pollen abortion and tapetal cells in
many crops are sensitive to environmental stress.
Knowledge of the mechanisms underlying this sensitivity
may facilitate the development of molecular approaches
aimed at increasing the stress tolerance of the tapetum.
There is now considerable information available about
the genes regulating tapetal development in Arabidopsis
93
and rice, many of which are homologs. The timing of
programmed cell death is critical for pollen development
and any interference results in loss of pollen fecundity.
One of the transcription factors we are studying regulates
the timing of tapetal PCD by controlling the transcription
of an aspartic protease gene.
Stem carbohydrate remobilization as a key variable
for wheat undergoing terminal drought
Zhang, J1, Dell, B1, Appels, R1
1
Murdoch University, Australia
Terminal drought is an increasing risk for wheat
production in many parts of the world, especially those
with mediterranean type climate. The improvement of
drought tolerance has been identified as a research
priority. Under terminal drought, the impact of stem
carbohydrate
remobilization
makes
significant
contributions to grain filling. Our study showed that the
stem water soluble carbohydrate (WSC, main
components fructan) level is not, on its own, a reliable
criterion for the drought tolerance, the performance of
the key enzymes involved in the WSC remobilization,
which varied among different varieties, were critical in
the terminal drought response. The genes involved in the
mobilization of stem WSC, 1-FEHs and 6-FEHs (fructan
exohydrolases), have been studied in detail to define their
role in contributing to water deficit tolerance. The study
includes the isolation of mutations where genes of
interest have been deleted.
Molecular dissection of genotypic variation in
accumulation of water soluble carbohydrates in
wheat
McIntyre, CL1, Casu, RE1, Rattey, A1, Kam, J1, Seung,
D1, Dreccer, MF1, Van Herwaarden, AF1, Shorter, R1,
Xue, GP1
1
CSIRO Plant Industry, QBP, St Lucia, QLD, Australia
Water soluble carbohydrates (WSC) stored in the wheat
stem are an important contributor to wheat grain yield
and grain size in all environments but especially when
water is limiting. We are using both genetic and genomic
approaches to determine the genetic basis of this
important drought-adaptive trait. We have identified
quantitative trait loci (QTL) for WSC in several wheat
populations with individual QTL explaining small
amounts of phenotypic variation. We have evaluated
variation in gene expression in high and low WSC wheat
progeny lines from a wheat population and found
significant differences in expression of gene from
different gene categories. For example, high WSC
progeny lines have higher levels of expression of genes
involved in carbohydrate metabolism and lower levels of
expression of genes involved in cell wall and amino acid
metabolism than low WSC lines. Genetic mapping
reveals that several candidate genes co-locate with QTL
for WSC. In addition, we have identified expression QTL
(eQTL) for candidate genes that co-locate with WSC
QTL; co-location of the genes and eQTL with WSC QTL
make these genes stronger candidate genes for the WSC
trait.
The cell wall invertase (IVR1) gene from wheat
Webster, H1, Fosu-Nyarko, J1, Keeble, G1, Moolhuijzen,
P1, Bellgard, M1, Appels, R1
1
Centre for Comparative Genomics, Murdoch University,
Perth, Australia
Genetic analyses of controlled crosses in wheat have
identified a region on chromosome 3B (short arm) that
controls variation in water stress tolerance. The region,
near the Sr2 resistance locus, is covered by a series of
well studied BAC clones that are being sequenced as part
of a large 3B sequencing program in France (led by
Catherine Feuillet, INRA, and the International Wheat
Genome Sequencing Consortium). A 1Mb region from
this part of the wheat genome (ctg506) was assembled
based on sequence data from overlapping BAC clones.
The sequencing of the BAC clones combined standard
Sanger sequencing (5-8 x coverage) and Solexa/Illumina
short read sequencing. Annotation of the sequence
identified the IVR1 gene considered to be important in
conferring drought and frost tolerance to wheat when the
stress occurs early in head development. Alignment to
the rice and Brachypodium genome sequences indicated
very little synteny and detailed analyses provided a
sequence based model accounting for the evolutionary
instability in this region of the genome.
94
Sym161: The genomes of economically
significant plants – 25 July
Generating plant reference genomes
Xun, X1, Jun BGI, W1
1
BGI-Shenzhen, China
For those important crops, only one reference is
insufficient to capture (for example) the more than 300
functional novel genes that differentiate between maize
inbred lines. The variations between two different strains
were as significant as the difference between human and
chimpanzee. To understand the genomes, use it as a
reference or find markers, the old strategy by only 'resequencing' is not enough for such variety species,
especially for plant species. In potato genome annotation,
the transcriptomes from more than 50 tissues or stages
were mainly used and demonstrated the power of this
approach for annotation especially where genes have
long introns. Due to the complexity of some plant
genomes such as highly heterogeneity (such as potato),
polyploidy (wheat, cotton) and highly repetitive sequence
(maize, wheat), finishing a reference genome is a major
challenge. To solve these problems, the BGI assembly
now utilizes the BAC by BAC approach purely by Hiseq
2000 data, making it high quality and cost efficiency.
This illustrated by showing finished variation maps for
some important crops, including maize, soybean and rice.
A multifaceted approach to enhance switchgrass as a
bioenergy crop
Devos, K1
1
University of Georgia, Athens, USA
Switchgrass is a grass native to the prairies of the United
States. In the 1990s, it was earmarked as a crop with a
potential for cellulosic bioenergy production because of
its ability to produce high yields under marginal inputs.
However, it is only in the past few years that genetic
research on switchgrass has started in earnest.
Switchgrass belongs to the subfamily Panicoideae, tribe
Paniceae. Lowland switchgrass is usually tetraploid
(2n=4x=36), with a 1C content of 1350 Mb. It is also an
obligate outcrosser, which greatly complicates genetic
analyses. We therefore are using a multifaceted approach
to create the genetic, genomic and breeding resources
that are required for building a successful switchgrass
biofuel production program. A comprehensive genetic
map using SSR and DArT markers has been constructed
in a cross between Alamo AP13, a lowland clone, and
Summer VS16, an upland clone. The map is used for
both trait mapping and to enhance our understanding of
the organization of the switchgrass genome relative to
that of its sequenced relative, foxtail millet (Setaria
italica). A fosmid library with ~6X coverage has been
generated and >30 fosmids containing genes involved in
switchgrass cell wall synthesis/composition have been
selected, sequenced and annotated. More than seven
million ESTs have been sequenced from AP13 and VS16
and placed in a searchable database. The EST data will
be used for the identification of SNPs to further enhance
the genetic map. We are also assessing the diversity that
is present in switchgrass germplasm. A panel of 384
switchgrass genotypes has been genotyped with SSR
markers to assess the population structure and is
currently being phenotyped for the presence of natural
variation in components that affect recalcitrance to
ethanol production, biomass yield and disease resistance.
This information is fed into the breeding program to
enhance the development of switchgrass cultivars with
desirable cell wall composition and increased yield for
commercialization. In summary, our project provides the
essential resources to conduct structural and functional
analyses in switchgrass.
Foxtail millet as a model for biofuel feedstocks
Bennetzen, J1
1
University of Georgia, USA
Grasses of the genus Setaria, including the domesticated
Foxtail millet (S. italica) and one of the world’s most
problematic weeds, Green foxtail (S. viridis), have many
of the properties that are essential for the development of
a model system for basic and applied research. In
addition, Setaria is closely related to several candidate
biofuel feedstocks, including Switchgrass (Panicum
virgatum), Napier grass (Pennisetum purpureum) and
Pearl millet (Pennisetum glaucum). S. viridis is the
apparent progenitor of Foxtail millet and is one of the
most widely distributed grasses on the planet, including
its common occurrence as a weed wherever wheat is
grown. Both S. italica and S. viridis are true diploids,
with some Green foxtail accessions that mature at less
than 20 cm and produce mature seed in as little as 8
weeks after planting. The genome of a Foxtail millet
cultivar, Yugu1, has now been fully sequenced (8.4X) by
the Sanger approach, along with 454 sequencing of
numerous EST libraries. Annotation is underway, as is
the analysis of one deeply sequenced (by an Illumina
approach) S. viridis accession, A10, and eight other S.
viridis accessions sequenced at a lower redundancy.
Projects are underway to assess diversity, population
structure, plant morphology, biomass productivity,
herbicide tolerance, cell wall composition, and several
other properties in a range of germplasm and in mapping
populations. Results of these studies, especially the
comparison to other grasses and to the Setaria genetic
map, will be discussed.
The amaizing genomes of maize
Chia, J-M1
1
Cold Spring Harbor Laboratory, USA
The first high quality reference sequence of Zea mays
(B73) provided insight into its origin from ancient
tetraploidy and is propelling research to describe the
tremendous diversity of this species. The reference
coupled with the enabling sequencing technologies allow
us to capture genomic, epigenetic and expression
variation. I will discuss the results of several
collaborative projects aimed at mapping variation and
understanding its sources and consequences. The Maize
Diversity Project has developed a high-resolution
variation map that integrates millions of segregating
SNPs, indels, and copy number variations (CNV)
obtained from more than 100 different maize
backgrounds. This panel included domesticated
improvement lines, early-domestication landraces, and
pre-domestication teosinte, which were subjected to resequencing at extremely deep coverage (500X). This
sequence depth and sample breadth enabled us to identify
regions of genetic fluidity versus rigidity in the face of
selection pressures. A separate study focused specifically
CNV and presence–absence variation (PAV) within a
large panel of diverse inbreds and teosinte lines. These
polymorphisms were found to be more prevalent among
particular gene-classes, including members of tandem
arrays, large families, recently duplicated, and recently
evolved genes. These results suggest that many gene
losses are buffered by redundant functions encoded
elsewhere in the genome.
Updated genome information of Lotus japonicus and
status of legume comparative genomics
Sato, S1
1
Kazusa DNA Research Institute, Japan
In order to investigate the whole genetic system of
legume species, we have been analyzing the genome of a
model legume, Lotus japonicus. In 2008, we have
released the 315 Mb sequences determined by
combination of two independent approaches; clone-byclone sequencing of large insert clones and random
sequencing of selected genomic regions. We continued
our efforts on sequencing of genome clones, and the
95
sequence information on 460 clones has been
accumulated. Thus, we have updated the sequence
information by adding these clone sequences. As a result,
the total length of the pseudomolecule, which means
genome regions covered by genome clone sequences,
was increased from 167 Mbp to 201 Mbp, and the total
size of finished (phase 3) sequences was increased from
97 Mbp to 139 Mbp. The detailed information on the
updated sequences and annotation is available through
our
web
database,
'miyakogusa.jp'
(http://kazusa.or.jp/lotus/). Using the updated genome
sequence and predicted gene information, we have
carried out comparative genome analysis against
Medicago truncatula and soybean. As a result, high level
of syntenic relationship was identified among these
legume species. We extended our efforts on comparative
genome analysis in legume species to red clover
(Trifolium pratense) and white clover (T. repens) using
their genetic linkage maps created by EST-derived
markers, and identified significant level of syntenic
relations against L. japonicus, M. truncatula and
soybean. Toward the completion of L. japonicus genome
sequencing, we started an additional approach by using
the sequence data from the second generation sequencers.
By integrating paired end sequences generated from 454
and Solexa sequencers, scaffolding and gap filling of
current contigs are on going. Status of this integration
approach will also be presented.
Structure–function studies in the wheat genome
Keeble, G1, Black, M1, Moolhuijzen, P1, Barerro, R1,
Bellgard, M1, Appels, R1
1
Centre for Comparative Genomics, Murdoch University,
Perth, Australia
Two separate 1Mb regions of the wheat genome
comprising extensive stretches of repetitive sequences
were assembled based on sequence data from
overlapping BAC clones located in a section of the
chromosome 3B of particular interest with regards to
disease resistance. The sequencing of the 24 BAC clones
combined standard Sanger sequencing (5-8 x coverage)
and Solexa/Illumina short read sequencing (>300 x
coverage). In addition, available BAC end and 454-based
sequences were utilized to provide a good quality
reference sequence that was annotated with a particular
focus on the repetitive elements. Alignment to the rice
and Brachypodium genome sequences identified a
repetitive locus that is conserved between these genomes
and the wheat genome. The conserved repetitive protein
kinase like genes at this conserved locus showed a good
alignment to the bacterial effector protein AvrPto
(Weiman et al. 2007).
96
Sym162: Molecular and genetic analysis of
features important for economically
significant plants – 29 July
A systems approach to defining C4 networks in the
grasses
Brutnell, TP1
1
Boyce Thompson Institute, USA
C4 photosynthesis has evolved at least 60 times in the
angiosperms and at least 17 times in the grasses, leading
to some of the most productive food, feed, and bioenergy
crops on the planet. Yet, we know very little of the
regulatory networks that drive this process in any major
crop plant. I will describe our efforts to use maize and
Setaria viridis as models for a systems biology approach
to understanding regulatory networks driving C4
differentiation. We have recently analyzed the maize leaf
transcriptome using Illumina sequencing (RNAseq) to
define gene structure and to quantify transcript
abundance along a calibrated leaf developmental gradient
and in mature bundle sheath and mesophyll cells.
Complementing this analysis, detailed histological,
proteomic and metabolite datasets have been collected
along the same gradient and analyzed by several
collaborators. We are now developing methods to
integrate these diverse datasets and I will discuss our
current strategies and findings. To provide community
access to this data, we implemented Gbrowse and an
electronic fluorescent pictograph browser to display and
query the datasets. Finally, I will describe our recent
efforts to develop Setaria viridis as a model system for
dissecting C4 gene expression.
Plant epigenetics : stories from beyond the double
helix
Rival, A1, Jaligot, E1, Beule, T1, Richaud, F1, Aberlenc,
F1, Adler, S1, Debladis, E1, Ilbert, P1, Finnegan, J2
1
2
UMR DIADE. IRD, Cirad BioS, Montpellier, France;
CSIRO Plant Industry, Canberra, Australia
Epigenetics is the study of heritable changes in gene
function that occur without a change in the DNA
sequence. In recent years, this field has attracted much
attention as more epigenetic controls of gene activities
are being discovered. Such controls involve a complex
interplay of DNA methylation, histone modifications,
and RNA-mediated pathways from non-coding RNAs,
notably silencing RNA (siRNA) and microRNA
(miRNA). In plants, although epigenetic mechanisms
help to protect cells from parasitic elements, this defence
can complicate the genetic engineering process through
transcriptional gene silencing. Furthermore, these
phenomena have economic relevance, for example, in
somaclonal variation: a genetic and phenotypic variation
among clonally propagated plants from a single donor
genotype. The loss of phenotypic fidelity is now a major
impediment to the development of large scale
propagation of plants through in vitro processes such as
somatic embryogenesis. Examples of aberrant
phenotypes in regenerated plants include abnormal leaf
structures and variant floral morphology, both organs
being of paramount importance for applications in
horticulture and/or agriculture. Changes in DNA
methylation have been hypothesised playing a key role in
the mechanism underlying tissue-culture induced
changes. Indeed, studies of both global methylation
levels and the methylation of specific sites show that
variation in DNA methylation occurs frequently during
growth in tissue culture. In vitro plant regeneration, like
somatic
embryogenesis,
bypasses
the
normal
developmental process of fertilisation and plant
development, thus potentially resulting in the instability
of epigenetic patterns. The large-scale clonal propagation
of oil palm (Elaeis guineensis Jacq.) is being hampered
by the occurrence of the mantled somaclonal variation.
Indeed, this abnormality which presents a homeotic-like
conversion of male floral organs into carpelloid
structures, hampers oil production since the
supernumerary female organs are either sterile or
produce fruits with poor oil yields. Beyond its primary
interest in the search for discriminating markers against
an economically crippling phenotype, the study of the
mantled abnormality also provides a unique opportunity
to investigate the regulation of reproductive development
in a perennial tropical plant. The present interest on food
and energy security as well as the concerns raised by the
possibility of climate change further stress the need for a
global comprehension of how crop plants react to their
fluctuating environment and how their productivity can
be affected.
Comparative genomics in clovers (Trifolium spp.)
using Medicago truncatula Gaertn. as a reference for
candidate genes controlling agronomic traits
Ghamkhar, K1, Isobe, S2, Nichols, P3, Faithful, T1,
Ryan, MH4, Snowball, R3, Sato, S2, Appels, R5
1
University of Western Australia, Australia; 2Kazusa
DNA Research Institute, Japan; 3Dept of Agriculture &
Food Western Australia, Australia; 4School of Plant
Biology, Faculty of Natural and Agricultural Sciences,
The University of Western Australia, Australia; 5Centre
for Comparative Genomics, Murdoch University,
Australia
Background: Molecular markers and genetic linkage
maps are pre-requisites for molecular breeding, but no
genetic map is currently available for subterranean clover
(Trifolium subterraneum L.), a diploid and inbreeding
pasture legume. A total of 2,646 microsatellite or simple
sequence repeat (SSR) markers either available in the
public domain or unpublished obtained from Kazusa
DNA Research Institute, were screened on four
genotypes (Denmark, DGI007, Woogenellup and Daliak)
that are parents of two F2 mapping populations. Results:
A total of 343 SSR loci could be mapped into 8 linkage
groups with 6–31 loci per linkage group and 27 SSRs
shared between the two populations. Phenotyping data
obtained for flowering time, isoflavonoid content
(formononetin, genistein, biochanin A), hardseedness,
leaf marks, calyx pigmentation and hairiness of stem
were analyzed together with genotyping data. For each
trait, 1–3 QTLs were identified; the phenotypic variation
explained by these QTLs was in the range of 5.5–59.8%.
In addition, alignment of linkage groups was possible
with the genetic maps of red clover (Trifolium pratense
L.), white clover (Trifolium repens L.)and Medicago
truncatula Gaertn. using shared loci. Segmental
duplications were identified within subterranean clover
genome and between the legume species. Candidate
genes for isoflavone content were identified.
Conclusions: The present study reports on comparative
genomics among three clover species as well as
Medicago truncatula following the construction of the
first genetic map for subterranean clover. It demonstrates
the utility of a comparative genomics approach for
molecular mapping of QTL controlling seed hardness,
flowering time and specifically isoflavone content traits,
as well as establishing relationships between
subterranean clover and genomes of red clover, white
clover and model legume M. truncatula. The
comparative mapping carried out demonstrated the value
of the map to identify candidate genes controlling
important traits such as isoflavone content.
Sucrose accumulation in stems of sweet Sorghum
bicolor
Byrt, CS1, Milne, R1
1
University of Newcastle, Australia
Stem juice sugar content and juice volume were
measured in 135 diverse Sorghum bicolor ecotypes.
Pressed juice contained up to 25% sucrose and juice
volumes of up to 500 mL per plant were measured. The
higher yielding ecotypes produced the equivalent of 10
000 Kg of sugar per ha. Sucrose transporter (SUT)
proteins play an important role in the accumulation of
sucrose in stems of sweet Sorghum bicolor varieties and
six putative SUTs have been identified in Sorghum. The
diversity in stem sugar yields and the availability of the
full genome sequence makes Sorghum an ideal C4
monocotyledonous species in which to study the role of
SUTs. Differing patterns of expression were observed
when transcript levels of all six SUTs were compared in
a low and high sugar line of Sorghum at two
developmental stages, immediately prior to anthesis and
at the stage of peak stem sugar content. Complementary
DNA (cDNA) of all six SUTs was isolated from a low
and a high sugar line and the predicted protein sequences
of a number of the SUTs were found to differ between
the two lines. A number of SUTs of interest were
expressed in Saccharomyces cerevisiae and functional
transport characteristics compared. The cellular location
of the SUTs was also investigated, using two antibodies.
The PEP2 antisera, raised against a highly conserved
region of sucrose transporters between loops 2 and 3
corresponding to amino acids 87 to 106 of the potato
StSUT1, was considered likely to bind to five of the six
SbSUTs, based on peptide sequence homology. The
second antibody raised against ShSUT4, was expected to
bind specifically to the remaining Sorghum SUT,
SbSUT4. SUT transcript levels, protein localisation and
SUT transport rates will be discussed.
Cross-species characterization of APOSTART for
unveiling its role in apomixis
Marconi, G1, Galla, G2, Conner, J3, Raggi, L1, OziasAkins, P3, Barcaccia, G2, Falcinelli, M1, Albertini, E1
1
Applied Biology Dept, University of Perugia, Perugia,
Italy; 2Environmental Agronomy and Crop Science Dept,
97
University of Padova, Legnaro, Italy; 3Dept of
Horticulture, University of Georgia Tifton Campus,
Tifton, USA; 4Leibniz Institut für Pflanzengenetik
Kulturpflanzenforschung, Gatersleben, Germany
Although most desirable crop traits are polygenic, no
plant breeding tools exist which allow the efficient
fixation of multigenic traits over successive generations.
Among several reproductive system-related strategies for
fixation of desirable agronomic traits, one of the best
choices is apomixis (i.e. clonal seed production), which
would enable the instantaneous fixation of the complete
genome of the best plants. Moreover, when coupled with
male-sterility systems, apomictic reproduction (e.g.
autonomous systems, with no need for male contribution)
could help in addressing issues related to transgene
escape from GM crops to organic or conventional crops,
and thereby allow for better coexistence systems in
Europe. The development of apomixis technology is
expected to have a revolutionary impact on food and
agriculture production by reducing cost and breeding
time, avoiding complications typical of sexual
reproduction (i.e. incompatibility barriers) and of
vegetative propagation (e.g. viral transfer). The financial
and economic impacts of the development of apomixis
technology and its application to major crops are
considerable. It is estimated that apomixis technology in
the production of hybrid rice alone could provide benefits
exceeding 1,800 million Euros per annum. The
development of apomixis technology in agriculture will
require a deeper knowledge of the mechanisms
regulating reproductive development in plants. We have
isolated one gene, which was termed APOSTART
because of its START domain and its putative
involvement in apomixis. START was named after the
discovery of the StAR gene involved in human
congenital lipoid adrenal hyperplasia whose clinical
phenotype includes the onset of profound adrenocortical
insufficiency
shortly
after
birth
and
male
pseudohermaphroditism. Our results demonstrate that
some APOSTART members are expressed exclusively in
inflorescences of Poa pratensis. In situ hybridization
analyss revealed that APOSTART is expressed during
both male and female meiosis in all micro- and
megaspores. Strong signals were recorded up to the
mature embryo sac stage. Overall data suggest that
APOSTART may be related to the programmed cell
death that is involved in the non-functional megaspore
and nucellar cell degeneration events that permit
enlargement of maturing embryo sacs. To confirm its
involvement in apomixis, we have isolated APOSTART
members from two other aposporic species: Pennisetum
squamulatum and Hypericum perforatum.
Uncovering genome features of crops with high
throughput sequencing
Michael, T1
1
Monsanto, St Louis, USA
High throughput sequencing has fundamentally changed
the way that we do genome discovery. The time that it
takes from sample to genome can be days for hundreds of
dollars, compared to just five years ago when it would
have taken months and cost hundreds of thousands.
Moreover, high throughput sequencing has enabled yet
98
another interesting turn of events: sequencing has
morphed into functional genomics. The ability to
generate trillions of sequences at a time turned
sequencing into a genomic discovery tool for such
applications as RNA expression analysis, metagenomics,
DNA binding studies, histone and nucleosome mapping,
and
DNA
methylation
detection.
Sequencing
technologies have matured into platforms for molecular
genome phenotyping, which changes the paradigm and
scale of understanding the link between genotype and
phenotype. This fundamental shift has fueled the
innovation of now emerging genome tools such as real
time single molecule detection (Pacific Biosciences RS),
and post-optic sequencing (ION Torrent/PGM).
However, these genome machines cannot deliver biotech
products by themselves. New bioinformatic and analysis
tools are emerging to derive knowledge from the growing
mountains of data. I will talk about how high throughput
sequencing is enabling genome discovery in crops.
THEME 03: GENETICS,
GENOMICS AND
BIOINFORMATICS
Sym037: The Eucalyptus genome – 26 July
Comparative mapping in Eucalyptus genomes
Vaillancourt, RE1, Hudson, CJ1, Kumar, AR2, Myburg,
AA2, Faria, DA3, Grattapaglia, D4, Kilian, A5
1
University of Tasmania & CRC for Forestry, Hobart,
Australia; 2University of Pretoria, Pretoria, South
Africa; 3EMBRAPA, Brasilia, Brazil; 4Universidade
Catolica de Brasília, Brasilia, Brazil; 5Diversity Arrays
Technology Pty Ltd, Canberra, Australia
The completion of the Eucalyptus grandis reference
genome sequence reinforces the need for a better
understanding of genome homology in the genus.
Genome homology can occur at multiple levels from the
location of loci on homologous linkage groups (synteny),
the congruent ordering of loci on chromosomes
(colinearity), to conservation of DNA sequence. It also
involves understanding the extent to which gene
polymorphisms (SNP) and their effects on the phenotype
(QTL) are shared across species. Differences in genome
structure may explain variation in the fitness of hybrids
at various taxonomic scales. In addition, sharing of QTL
for genes of adaptive significance may explain cases of
phenotypic convergence in the genus. From a practical
point of view, this knowledge would help guide the
transfer of molecular information across species and
accelerate molecular breeding. Most commercially
important eucalypts belong to the largest of the eucalypt
subgenera:
Symphyomyrtus. Despite nearly 50%
variation in DNA content across these species, all appear
to be diploid with 2n = 22. There is no evidence of
chromosome rearrangements, although the chromosomes
are so small that these would be difficult to detect
microscopically. We conducted comparative genomic
studies between Symphyomyrtus species using highdensity linkage maps based predominantly on DArT
markers in five large E. globulus (section Maidenaria)
families and a double pseudo-backcross mapping family
involving the species E. urophylla and E. grandis (both
in section Latoangulatae). Comparison within sections
(E. globulus versus E. globulus or E. grandis versus E.
urophylla) found very high synteny and colinearity.
While the degree of co-linearity between homologous
chromosomes in the inter-sectional comparison (E.
globulus consensus versus the E. grandis – E. urophylla
consensus) was similar to that found in the within section
comparisons, the percentage of non-syntenic markers
increased more than four-fold. While some of these nonsyntenic markers may be mapping errors, there is
evidence for three very small rearrangements, which are
probably translocations. This is because the map position
of these non-syntenic markers were consistent between
different maps of E. globulus and consistent between the
E. grandis map and the genome sequence. There is also
evidence that some QTL for developmental, defensive
chemistry, physical and chemical wood property traits
are shared between species. Our results argue for high
genome homology overall and high transferability of the
E. grandis genome sequence information and
marker/trait
associations
across
the
subgenus
Symphyomyrtus. This high transferability will facilitate
the identification of genes underlying phenotypic
variation in this ecologically and economically important
lineage of tree species.
Molecular adaptation
Eucalyptus
to
water
availability
in
Bragg, JG1, McEvoy, R1, Dillon, SK1, Thumma, BR1,
Southerton, SG1
1
CSIRO Plant Industry, Canberra, Australia
The genus Eucalyptus radiated during a time of great
environmental change on the Australian land mass, and
extant eucalypts populate diverse ecosystems across
Australia. The genus therefore provides excellent
opportunities for exploring the genomic basis of
adaptation to a wide range of environmental conditions.
We are studying adaptation to water availability in
Eucalyptus camaldulensis and several other species. This
research is being carried out at a range of different
taxonomic and spatial scales (among species and among
populations), using both candidate-gene and genomewide approaches. Our aim is to identify loci that exhibit
signatures of natural selection in populations from
environments that vary in water availability.
Using the Eucalyptus genome to understand the
evolution of plant secondary metabolites in the
Myrtaceae
Kulheim, C1, Webb, H1, Wallis, I1, Moran, G1, Foley,
W1
1
Australian National University, Canberra, Australia
Eucalyptus trees (family Myrtaceae) are well known for
their high foliar content of several classes of secondary
metabolites and these have a strong effect on the feeding
patterns of several species of marsupials and at least
some insects. Best known are the essential oils, which are
mostly a mixture of terpenoids but there are also
significant concentrations of flavonoids and formylated
phloroglucinol compounds. Quantitative and qualitative
variation within and between species in all these groups
is large with evidence that much of this variation is under
strong genetic control (heritabilities of between 0.3 and
0.9 for all three groups of compounds). As well as being
important ecologically, the terpenes in particular are
valued as industrial and medicinal products and Australia
supports a strong essential oil industry focused on
Eucalyptus and Melaleuca foliar oils. 1. The Eucalypt
genome provides the opportunity to discover the genetic
makeup of the biosynthetic pathways for secondary
metabolites. We present data from pathways leading into
the biosynthesis of terpenes and flavonoids. The
homology of genes and gene families were investigated
and compared to a variety of model species including
poplar (Populus trichocarpa), grape (Vitis vinifera) and
apple (Malus x domesticus). For example the gene family
that commits the final step in the terpene biosynthesis
(terpene synthase family) has 120 members in the
genome of Eucalyptus grandis, compared to 44 and 99 in
poplar and grape, respectively. 2. Levels of genetic
variation within and between species of the Myrtaceae
were compared on the basis of multiple loci from the
secondary metabolite biosynthetic pathways. Eleven loci
were amplified from 110 individuals of Eucalyptus
globulus and seven from 400 individuals of Melaleuca
alternifolia. These loci were barcoded for each individual
and sequenced on a next-generation sequencing platform.
This allowed to discover and genotype 100s of
polymorphisms instantaneously. Population genetics
parameters were estimated and compared to other
Eucalyptus species. The gene discovery was made
possible through the Eucalypt genome. 3. Understanding
the genetic basis of trait variation in quantitative traits
may help breeders in the essential oil industry and also
provide insights into ecological processes. We have
characterized trait associations with polymorphisms from
Eucalyptus globulus, investigating 200 SNPs and roughly
70 traits including, terpenes, formylated phloroglucinol
compounds, flavanoids and the functional effects of
tannins. We discovered several significant trait
associations between allelic variants in the chloroplastic
MEP pathway and monoterpenes and between the
cytosolic MVA pathway and sesquiterpenes.
Systems genetics of wood formation in Eucalyptus
Mizrachi, E1, Van Dyk, MM1, Kullan, ARK1, Hefer,
CA2, Joubert, F2, Myburg, AA1
1
Dept of Genetics, Forestry and Agricultural
Biotechnology Institute (FABI), University of Pretoria,
2
Pretoria,
South
Africa;
Bioinformatics
and
Computational Biology Unit, Dept of Biochemistry,
University of Pretoria, Pretoria, South Africa
Advances in Eucalyptus genomics in the past two years
have enabled the use of new biological tools for studying
fibre and lignocellulosic biomass properties in this genus,
which represents one of the most important sources of
cellulose globally for pulp, paper, and potentially
biofuels. In collaboration with industry partners, we have
produced a high quality interspecific mapping pedigree
of Eucalyptus grandis and E. urophylla, using the same
F1 hybrid parent in a two-way pseudobackcross, which
has produced more than 1000 F2 progeny. These display
high levels of genomic and phenotypic segregation, and
99
provide a powerful statistical framework for associating
genes and markers with multiple traits in this population.
The availability of a high density genetic map for this
population constructed using SSR and DArT markers,
which have also been linked to the E. grandis reference
genome sequence (JGI, V1.0), has allowed the
construction of a high confidence framework map for
QTL mapping. In addition to profiling phenotypic traits
of interest in over 300 individuals from each backcross,
we have in collaboration with ORNL profiled 83
metabolites in the developing xylem of 192 individuals
from one of the backcrosses and sequenced the
developing xylem transcriptomes of the same 192 F2
individuals using Illumina RNA-Seq, for expression QTL
(eQTL) and metabolite QTL (mQTL) mapping purposes.
We present our strategy for data generation and
integration, as well as the applications of Eucalyptus
Systems Genetics in reconstructing transcriptional
networks and identifying pathways, candidate genes and
regulatory sequences that influence wood and fibre
properties of relevance to commercial end uses of wood
such as pulp and paper production.
Eucalypt comparative genomics identifies model
genes to study the effect of domestication or range
depletion on adaptive variation
Sexton, T1, Thomas, D2, Henry, R3, Henson, M2,
Shepherd, M1
1
Southern Cross University, CRC for Forestry, Lismore,
Australia; 2Forests NSW, Coffs Harbour Jetty, Australia;
3
Present address: Queensland Alliance for Agriculture
and Food Innovation, University of Queensland,
Brisbane, Australia
In plants, balancing selection may cause the retention of
adaptive polymorphism over long time spans, with genes
for biotic and abiotic stress responses among the best
known of those affected. In the past, the inadvertent
removal of polymorphism from domesticated populations
otherwise maintained by balancing selection, has
sometimes met with catastrophic consequences. e.g. Irish
potato famine. Similarly, the unintentional threats from
the loss of adaptive diversity and inbreeding to the fitness
of natural populations that undergo reductions in size or
fragmentation, are also widely documented. A better
understanding of the prevalence of balancing selection,
its modes of action (heterozygote advantage, frequencydependent selection and selection varying in time and
space), and the genes it affects, might reveal new ways to
manage and mitigate against the loss of adaptive
variation during domestication or range depletion. The
present study used comparative genome analysis to
identify genes under balancing selection. Thirty four
candidate genes for wood formation were screened for
SNP common to the Symphyomyrtus and Eucalyptus
subgenera of the genus Eucalyptus. These transsubgeneric SNP likely derive from ancestral
polymorphisms that are maintained in each lineage postspeciation by balancing selection. Genes containing
clusters of trans-specific SNP are good models for
monitoring the loss of adaptive variation because the
drivers of selection in these genes may be universal in
eucalypts. The study showed balancing selection was
more common among candidate genes for wood
formation than might be expected on average in a
100
genome, nonetheless, this high frequency was congruent
with potential pleiotropic roles for these genes in biotic
and abiotic stress responses. Strong evidence for
balancing selection was found in ten genes where there
was a prevalence of trans-subgeneric SNP clustered in
functional gene regions. Two of these genes were from
the pectin methylesterase gene family, key enzymes that
catalyse
the
de-methyl-esterification
of
homogalacturonan, the major constituent of pectin. This
gene family has pleiotropic functions in wood formation,
seed dormancy, fruit ripening and stress responses.
Association testing found both genes also influenced
physical and chemical wood phenotypes of interest for
tree improvement. Adaptive variation in one of these
genes was found to be maintained through a heterozygote
advantage. These genes may be useful models for
exploring the consequences of diversity reduction at
genes subject to balancing selection.
Genomic impacts
conservation
on
eucalypt
cultivation
and
Wright, J1
1
ArborGen Inc., Summerville, USA
The genus Eucalyptus includes species that comprise the
most important hardwood plantation resource in the
world. There are an estimated 100 eucalypt tree
improvement programmes utilizing seedling or clonal
propagation techniques with objectives as diverse as bioenergy to furniture grade lumber. These eucalypt
improvement programmes are making great advances in
productivity, industrial processing, improving rural
livelihoods and job creation. However, perhaps only a
handful of programmes are making use of recent
advances in eucalypt genomics. A concerted effort to
map the eucalypt genome would help immensely many
current and future eucalypt tree improvement
programmes as well as assist in gene conservation with
native eucalypts in Australia, Indonesia and Papua New
Guinea. Genomic advances, aided by the sequencing of
the euclaypt genome, could be used in marker aided
selection, directed species hybridization, overcoming
seed/clonal propagation difficulties, developing trees for
climate changes as well as developing the eucalypts for
more marginal sites including dry, marginal sites.
Sym038: Plant genomes: not just for models
anymore – 38A: 28 July, 38B: 28 July
Genomics of wild crop relatives
Henry, R1, 2
1
Queensland Alliance for Agriculture And Food
Innovation, University of Queensland, Australia; 2Centre
for Plant Science, Southern Cross University, Lismore,
Australia
Analysis of the genomes of wild crop relatives facilitates
their use as genetic resources expanding the available
gene pool to satisfy the needs of food security and
adaptation to climate change. Genome, transcriptome and
specific amplicon sequencing are all contributing to
accelerated knowledge of wild and domesticated plants
and revealing new approaches to plant improvement.
Genome sequences have provided genetic explanations
for traits selected by humans in domestication that would
be deleterious to the survival of plants in the wild.
Analysis of nuclear, mitochondrial and plastid genomes
can be achieved at the same time by sequencing of a
conventional total DNA extract from the plant. The
chloroplast is sequenced at high coverage in shot gun
sequencing of total DNA. This provides a whole
chloroplast genome sequence to use as a barcode for
identifying the plant and phylogenetic analysis. Wild rice
relatives from Australia and Asia have been sequenced to
determine their relationships. The Australian species
have been isolated from domestication in Asia and
represent a valuable and diverse resource for use in rice
improvement.
Transcriptome
sequencing
allows
discovery of biologically important or functionally useful
genes in plant populations. Extensive sequencing of the
transcriptomes of the developing wheat seed has
identified genes that may determine nutritional value and
food quality. Amplicon sequencing can be used to
characterize wild plant populations. Variation in genes in
wild populations found growing across environmental
gradients can allow analysis of the genetic differences
associated with adaptation to different environments and
indicate ways to adapt agricultural plant varieties to
climate change. This approach has shown that some
grasses have a greater diversity in biotic defense loci in
dryer environments. Large scale amplification and
sequencing of candidate wood property genes from
Eucalypts has revealed evidence for balancing selection
in these genes in wild populations. These insights explain
the complex genetics of these traits important for plant
performance in the wild and for human use.
Population genomics of non-model invasive species
Dlugosch, K1
1
University of Arizona, USA
Introduced and invasive species are major threats to plant
diversity, but they are also outstanding opportunities to
study the ecology and evolution of populations
colonizing novel environments. Large numbers of plants
species are being introduced to new habitats around the
globe, and most of these are non-model species.
Moreover, the genomic features that interest us in these
systems necessarily reside in wild, outbread individuals:
How have allele frequencies changed across populations?
Where do we seee evidence of selection? What is the
contribution of admixture and hybridization to
population expansion? Genomics can allow us to answer
these questions, but doing so, particularly without a full
reference genome, presents a variety of challenges. I will
report on several of these methodological issues for
which we have released freely-available public software,
including the editing and assembly of next-generation
transcriptome (EST) sequence data, and the comparison
of genetic variation among outbred (wild) individuals
with incomplete genomic information. I will also present
data from projects where I and my collaborators are
using genomic approaches to investigate the causes and
consequences of evolution in several species of invasive
plants. One major explanatory hypothesis for invasions is
that invaders have evolved along fitness trade-offs that
are common to all plants, gaining competitive advantages
at the expensive of other functions not selected in their
new environment (such as defenses). An alternative
(though not mutually exclusive) hypothesis is that
hybridization associated with species introductions
generates novel genetic benefits for invaders. We are
quantifying fitness levels in response to various biotic
and abiotic environments, comparing expression level
and genome-wide sequence variation among native and
invading genotypes, and mapping the genetic basis of
observed evolutionary increases in growth rate. Finally, I
also report on a new project to quantify changes in
mating system and elucidate the genetic basis of
associated losses of inbreeding depression in invading
populations.
Build a digital library of plant genomes
Yang, B1
1
BGI, Shenzhen, China
The application of second-generation sequencing
technology in genome sequencing has propelled us into a
new era. Using highly parallel processing in microfluidic
devices and imaging system, highly accurate sequencing
results are obtained. Orders of magnitude larger amounts
of data are generated at substantially decreased cost and
effort. This has made it possible to sequence plants
genomes not just for models. Up to the present, a number
of plant genomes have been sequenced. BGI-Shenzhen
has developed the cucumber (367Mb), Chinese cabbage
(500Mb) and potato (830Mb) genomes. Plant genomes
are essential to understanding how plants function and
how to develop desirable plant characteristics. For
example, the sequenced cucumber genome affords
insight into traits such as its sex expression, disease
resistance, biosynthesis of cucurbitacin and ®fresh green
odor. Due to the significant impact that knowledge of
genome sequence has shown, the genomes of more plants
are expected to be completed in the next few years. We
are taking a genomics approach to build a digital library
of plants. Obtaining the genome sequence of a plant will
generate vast amounts of informative datasets and enable
the comprehensive understanding of the plant. In
particular, we are developing de novo sequencing of
clade genomes, which will unveil the set of whole
genome sequences in the same family or genus (core
genome + variable genomes). Investigators of clade
genomes will provide unique insight into mechanisms of
the speciation process and functional elements of species
that drive diversity in these genomes. Functional
elements related to growth, architecture, productivity or
resistance can be further applied in plant molecular
breeding and benefit for farmers, the seed and processing
industries, the environment and the customer in both the
industrialized and the developing world.
Genomic footprints of hybridization
Barker, M1
1
University of Arizona, USA
Natural hybridization has long fascinated botanists as a
possible source of novelty and innovation, fueling a long
running debate concerning the ultimate role of
101
hybridization in plant evolution. One reason this debate
has persisted since Darwin is that detecting ancient
hybridization and introgression is difficult. Advances in
genetic and phylogenetic tools have permitted the
identification of a few homoploid hybrid species, but the
time and effort required to make these diagnoses is not
trivial. Here I present a novel and efficient method for
identifying ancient hybridization and introgression by
inferring intrologs (introgressed orthologs) in EST data
sets. Using a combination of simulations and data from
established hybrid species, I explore this new test and
demonstrate the type of data required. Application of this
novel test to the broadly available plant ESTs I find
evidence of many other, previously undocumented
examples of ancient hybridization. From this survey of
plant ESTs, I also use this new method to discriminate
allo- and autopolyploidy and provide an estimate of the
relative prevalence of these two forms of polyploid
speciation.
The milkweed genome project: sequencing and
characterization
of
the
Asclepias
syriaca
(Apocynaceae) genome based on illumina short read
sequences
Straub, SCK1, Fishbein, M2, Cronn, RC3, Liston, A1
1
Oregon State University, Corvallis, OR, USA;
Oklahoma State University, Stillwater, OK, USA;
3
USDA Forest Service, Forest Genetics, Pacific
Northwest Research Station, Corvallis, OR, USA
2
Milkweeds are important models for the evolutionary
ecology of plant reproduction, plant hybridization, and
plant-herbivore co-evolution. The common milkweed,
Asclepias syriaca L., is the most intensively studied
milkweed, and as such is an attractive target for the
development of genomic resources. The milkweed
genome project aims to sequence the 835 Mbp genome
of A. syriaca to a minimum of 25X coverage using the
Illumina platform for massively parallel DNA
sequencing. With a lower coverage preliminary data set,
most of the high copy fractions and some of the lowcopy fraction of the genome were assembled using a
combination of reference guided and de novo assembly
strategies. A complete 155 kbp plastome sequence was
obtained, revealing that Asclepias has a typical asterid
chloroplast genome, except that both accD and clpP are
pseudogenes. More than 400 kbp of the mitochondrial
genome was assembled and characterized for gene
content. A 7.5 kbp nuclear ribosomal DNA cistron was
assembled and ribosomal DNA copy number estimated
to be approximately 1500 based on sequencing depth.
Low-copy nuclear genes were assembled through a
comparative genomics approach utilizing data from other
asterids, including Coffea, Solanum, and Capsicum. The
repeats present in the milkweed genome were also
surveyed. This scan revealed a high number of
interspersed repeats associated with the long terminal
repeat retrotransposons (e.g., Ty1-copia, Ty3-gypsy). In
addition, numerous potential microsatellite loci were
identified and evaluated. The markers obtained through
this sequencing effort will be applied to milkweed
genetic map development and to estimate phylogenetic
relationships among the 135 species of Asclepias. This
project will provide the first insights into the genomic
basis of the incredible morphological and ecological
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diversity observed among milkweeds. The genome will
serve as a community resource for studies of plant-insect
co-evolution, floral developmental genetics, chemical
evolution, population genetics, and comparative
genomics. The results to date also demonstrate the
feasibility of extending genome sequencing to a wide
range of organisms of evolutionary and ecological
interest.
Amborella: an evolutionary reference genome for
plant biology
Soltis, PS1, Soltis, DE1, Barbazuk, WB1, Chamala, S1,
Walts, BM1
1
University of Florida, USA
The handful of angiosperm genomes that have been
sequenced to date represent phylogenetically derived
portions of the angiosperm Tree of Life and therefore
provide few insights into the characteristics of the
'ancestral angiosperm'. A complete understanding of any
gene or genomic feature requires a perspective based on
evolutionary lineages, one that can be obtained through
analysis of an appropriately broad sampling of genomes,
including ancient angiosperm lineages. Recent
phylogenetic analyses of the flowering plants have
identified Amborella trichopoda, a shrub known only
from the island of New Caledonia, as the single sister
species to all other living flowering plants. Amborella
therefore offers the unique ability to root analyses of all
angiosperm features, from gene families to genome
structure to morphology, and when coupled with
comparisons to non-flowering plants, to reconstruct the
features of the 'ancestral angiosperm'. Although the
genome structure of the 'ancestral angiosperm' is
currently debated, our recent data suggest that a wholegenome duplication predated or coincided with the origin
of angiosperms, perhaps catalyzing their success. The
'Amborella Genome Project' is designed to address the
fundamental question of genome structure and evolution
in the angiosperms, while providing genetic and genomic
resources for anyone studying any aspect of angiosperm
biology, from morphology to genomics. A better
understanding of the structure and evolution of flowering
plant genomes will also contribute enormously to society
through enhancements to agriculture and forestry.
Patterns of genetic diversity and selection in soybean
genome
Lam, H-M1, Xu, X2, Liu, X3, Song, C2, Shao, G3, Sun,
SS-M1
1
State Key Laboratory of Agrobiotechnology and School
of Life Sciences, The Chinese University of Hong Kong,
China; 2BGI-Shenzhen, China; 3Institute of Crop
Sciences, The Chinese Academic of Agricultural
Sciences, China
Soybean is an important crop for food. Understanding the
patterns of genetic diversity and selection in soybean
genome will help to locate regions associated to
important agronomic traits. To achieve this end, we resequencing 17 wild and 14 cultivated soybean genomes
(~5X depth and >90% coverage for each accession) and
generated a total of ~180 Gb sequencing data, using the
Illumina Genome Analyzer II platform. The genomic
variations between wild and cultivated soybeans were
mapped. The genome-wide re-sequencing data reveal
that there is an alarming loss of genetic diversity in
cultivated soybeans and that wild germplasms are
valuable sources of novel alleles and genes. The extreme
high linkage disequilibrium in the soybean genome
suggests that marker-assisted breeding will be far less
challenging than using map-based cloning with genetic
populations. A total of 205,614 single-nucleotide
polymorphism tags were identified to facilitate future
breeding and quantitative trait analysis. In addition, we
also performed de novo sequencing of one wild accession
(~80X coverage) and the genome assembly is now close
to completion. We also obtained transcriptome data to
enhance the accuracy of gene annotation of the wild
genome. By a detailed comparison between the wild
soybean genome and the reference cultivated soybean
genome using the de novo sequencing and the gene
expression data, we can identify expressed genes that are
unique to wild or cultivated soybeans. [This work was
partly supported by the Hong Kong RGC General
Research Fund 468610 (to H.-M.L.), Hong Kong UGC
AoE Center for Plant & Agricultural Biotechnology
Project AoE-B-07/09, and a special fund from the
Resource Allocation Committee, The Chinese University
of Hong Kong (to H.-M.L. and S.S.-M.S.). We also
acknowledge funding support from National Natural
Science Foundation of China (30725008), the Chinese
973 program (2007CB815703; 2007CB815705), Chinese
Ministry of Agriculture (948 program), Shenzhen
Municipal Government of China, from Shenzhen Bureau
of Science Technology & Information, China
(ZYC200903240077A; CXB200903110066A).]
Sequencing giant genomes: second generation
sequencing analysis of Fritillaria (Liliaceae)
Kelly, LJ1, 2, Leitch, AR2, Renny-Byfield, S2, Nichols,
RA2, Fay, MF1, Macas, J3, Novák, P3, Neumann, P3,
Leitch, IJ1
1
Royal Botanic Gardens Kew, Richmond, UK; 2Queen
Mary University of London, UK; 3Institute of Plant
Molecular Biology, Èeské Budìjovice, Czech Republic
The genus Fritillaria (Liliaceae) is characterized by an
exceptionally large range of genome sizes (c.30,000 to c.
80,000 Mb in the diploid species), and includes some of
the largest genomes ever recorded in plants. The range of
genome sizes in Fritillaria provides an outstanding
opportunity to study the processes involved in genome
size evolution. Moreover, the phylogenetic distribution
of Fritillaria species with large genomes indicates that
two independent shifts towards giant genomes have
occurred during the evolution of the genus, allowing
comparison of the processes involved in these separate
instances of genomic expansion. Studies of plants with
small (e.g. Arabidopsis thaliana, c. 157 Mb) and medium
(e.g. Hordeum vulgare, c. 5,500 Mb) sized genomes have
revealed that changes in genome size are largely
governed by the interplay between the amplification and
deletion of repetitive DNA. However, it is not clear
whether the same processes control the evolution of giant
genomes. Using data from second generation sequencing
technologies (e.g. 454 sequencing) we are analysing the
composition of the most highly represented sequences
within the genomes of multiple Fritillaria species in
order to gain insights into the evolutionary dynamics of
genomic obesity. We discuss the results of these
analyses, and their implications for our wider
understanding of how genomes evolve in plants.
Geraniaceae, a natural model system for examining
plastid genome evolution
Jansen, R1
1
University of Texas at Austin, USA
During the past decade there has been a rapid surge in
plastid genome sequencing of flowering plants with over
100 species now publicly available. The sampling of
species has increased in two important ways: all major
lineages of angiosperms are represented and several
highly rearranged genomes have been sequenced. Plastid
genome sequences have provided important data for
improving our understanding of patterns and rates of
genome evolution. Gene and intron content and gene
order are highly conserved among the early diverging
angiosperms and basal eudicots, but over 60 independent
gene and intron losses are present in more derived
monocot and eudicots clades. Furthermore, a lineagespecific correlation was identified between rates of
nucleotide substitutions and genomic rearrangements.
One of the most remarkable lineages is the geranium
family (Geraniaceae). Plastid genome sequencing of 27
species from all five genera in this family have revealed
several bizarre phenomena, including include multiple
and extreme contractions and expansions of the IR
resulting in plastomes with both the smallest (0 bp) and
largest (74,571 bp) inverted repeats among all land
plants, a remarkable accumulation of dispersed repeats
associated with changes in gene order, repeated losses
and duplications of genes, and unprecedented increases
in rates of nucleotide substitutions, especially in
ribosomal protein and RNA polymerase genes. Two
unusual changes involve putative gene losses of rpoA in
Pelargonium and all 11 ndh genes in one lineage of
Erodium. The implications of these data for
understanding mechanisms of plastid genome evolution
will be discussed.
Repetitive DNA and its evolution: genomic strategies
to understand the processes and exploit biodiversity
Heslop-Harrison, JS1, Schwarzacher, T1
1
University of Leicester, UK
Repetitive DNA is comprised of sequence motifs that are
repeated hundreds or thousands of times in the plant
genome, and includes microsatellites, longer tandem
repeats or satellite DNA, DNA transposons and
retrotransposons. It shows rapid evolution in copy
number, location and sequence, with diverse turnover
mechanisms which we will show in the talk. Repetitive
sequences often mark the major differences between
closely related genomes in, for example, crops and their
wild relatives in the same or related species, and hence
are critical to study in the context of phylogenetic studies
at the DNA level. Because of the repetitive nature, it is
hard to analyse by next generation or even wholegenome sequencing methods, leading to the numerous
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breaks in contigs. In this talk, we will discuss the nature
of repetitive DNA evolution, amplification and
distribution throughout the genomes and how in situ
hybridization, BAC analysis and paired-end strategies
can enable repetitive DNA diversity to be analysed.
Using a range of different eudicot and monocot species,
with and without reference genomes, we have been able
to exploit repetitive DNA to generate markers and
examine evolutionary diversification mechanisms in
crops, during domestication and that are essential to
exploit diversity in plant breeding strategies. Related
information, the talk, and references will be available
from www.molcyt.com
Organellar genome evolution in parasitic plants –
assessing patterns of genome reduction and rate
acceleration under relaxed selective pressure
Wicke, S1,3, Quandt, D2, Müller, K3, DePamphilis, C4,
Schneeweiss, GM1
1
occur much earlier during the evolution of parasitism
than previously assumed and strongly affects structural
integrity of distinct plastome fragments. It seems as if the
establishment of obligate parasitism can be viewed as the
major prior relaxing the selective pressure on plastome
integrity preceding the loss of photosynthesis. The
pattern of pseudogenization and rate acceleration is
highly lineage specific among different broomrapes.
However, there is a general trend towards the early loss
of subunits encoding an eubacterial-type polymerase, and
protein subunits involved in electron flow.
Orobanchaceae mitochondrial genes and genomes are
apparently not affected by different grades of
heterotrophy. They do not exhibit significant alterations
in structure and gene content compared to autotrophs,
although there is evidence that holoparasites evolve more
conservative than hemiparasites. Interestingly, however,
is that mitochondrial plastid-derived genes show
substitution rates similar to those of plastid genes in
holoparasitic lineages.
University of Vienna Rennweg, Austria; 2Rheinische
Friedrich-Wilhelms-Universitaet
Bonn,
Germany;
3
University of Muenster, Germany; 4Penn State
University, USA
Evolutionary genomics of diploid Fragaria species:
insights into the origin of the cultivated strawberry
Among land plants, plastidial and mitochondrial
chromosomes show highly divergent patterns in terms of
genome structure and substitution rates. While the
multipartite plant chondriome exhibits and extraordinary
variability regarding size, structure and gene content, the
quadripartite structure of the plastid chromosome and its
gene content and order is rather conserved. For example,
the transition from water to land of green plants is only
accompanied by few distinct changes in the plastid
genome including at least 8 inversions of plastid
chromosomal fractions, some gene transfers to the
nuclear genome as well as one gene gain. The present
study illustrates the evolution of plant plastomes and
chondriomes comparing genome structure and patterns of
molecular evolution, with a focus on rate heterogeneity
among distinguished gene classes, single genes and gene
operons. Reviewing the functions of proteins in the
plastid genomes shows that transmembrane proteins as
well as proteins required at high copy numbers are
retained in the plastid genome. Other genes, however,
might be substituted or bypassed by nuclear paralogues
which could contribute to the loss of all subunits of an
entire protein complex (e.g. genes for ndh-complex,
sulfur transporter genes) multiple times during land plant
evolution in independent lineages. As a group of plants
that exhibit major changes in plastid genome structure,
both semi- and non-autotrophic plants will be discussed
in order to explore and understand the subtle but
continuous reduction of genomes under relaxed
evolutionary constraints. The transition from a fully
autotrophic way of life towards a complete heterotrophic
lifestyle (i.e. complete loss of photosynthesis) via various
levels of semi-autotrophy severely affects plastome
stability and evolution. To this end, the organellar
genomes from several hemiparasitic and holoparasitic
representatives
from
the
broomrape
family
(Orobanchaceae) have been sequenced using different
sequencing strategies. Organellar genomes have been
reconstructed de novo and analyzed with respect to colinearity, gene content, pseudogenization and substitution
rates. Relaxation of evolutionary constraints appears to
1
104
Liston, A1, Govindarajulu, R2, Ashman, T-L2
2
Oregon State University, Corvallis, Oregon, USA;
University of Pittsburgh, Pittsburgh, Pennsylvania, USA
The domestication of strawberry (Fragaria ×ananassa)
in the 1700s is well documented, but we have a poor
understanding of the evolutionary history of the species
that contributed to this important crop. Fragaria
×ananassa originated in Europe from hybridization
between two octoploid species, the South American
Fragaria chiloensis and the eastern North American
Fragaria virginiana. Phylogenetic analysis based on
plastid genomes indicate that the octoploids are
monophyletic, and identify the northwest North
American diploid F. vesca subsp. bracteata as their
cytoplasmic donor. The 240 Mbp genome of the
European diploid Fragaria vesca subsp. vesca has been
recently published, and we have used this as a reference
to conduct low coverage genome sequencing of F. vesca
subsp. bracteata, and two East Asian diploids, F.
mandshurica and F. iinumae. Our phylogenomic
comparison of 21,563 genes in these four taxa revealed
genome-wide patterns of lineage sorting and identified
loci that have apparently undergone positive selection.
These results provide novel insights into the genes and
genomic regions that were involved in the origin of the
octoploid progenitors of the cultivated strawberry.
Sym039: Regulatory mechanisms and
evolution of apomixis – 26 July
Unravelling apomixis in aposporous Hieracium
Koltunow, AMG1, Johnson, SD1, Okada, T1, Hu, Y2, Ito,
K3, Suzuki, G3
1
Commonwealth Scientific and Industrial Research
Organization Plant Industry, Glen Osmond, Australia;
2
College of Life Science, Capital Normal University,
Beijing, China; 3Laboratory of Plant Molecular Genetics
Division of Natural Science, Osaka Kyoiku Universitya,
Osaka, Japan
In apomictic Hieracium subgenus Pilosella species,
asexual seed formation is the dominant reproductive
mode, however, rare sexual seed are also produced.
Sexual reproduction initiates first in apomicts as the
megaspore mother cell (MMC) undergoes meiosis in the
ovule. Somatic aposporous initial (AI) cells develop
nearby and the sexual pathway is terminated as AI cells
undergo mitotic embryo sac formation. Seed formation is
fertilization independent. Two dominant, independent
loci, LOSS OF APOMEIOSIS (LOA) and LOSS OF
PARTHENOGENESIS (LOP) control apomixis in
Hieracium praealtum. The functions of LOA and LOP
and their interaction with the sexual pathway were
examined using irradiation mutants, wild-type genetic
populations and transgenic analyses. Sexual initiation is
required for apomixis initiation because inhibition of
MMC function using a cytotoxic reporter inhibits AI cell
differentiation. LOA is sporophytic in action and
stimulates both AI formation and sexual suppression.
LOP is gametophytic in action, stimulates fertilizationindependent embryo and endosperm formation and these
determinants are tightly linked. Loss of function in either
LOA or LOP results in partial reversion to sexual
reproduction. Loss of function in both results in complete
reversion to sexual reproduction indicating it is the
default reproductive mode. Therefore, LOA and LOP are
not essential, mis-regulated elements of the sexual mode
of reproduction as some models propose. Sexual and
apomictic pathways co-exist, operating in parallel in H.
praealtum ovules. Incomplete functional penetrance of
these dominant apomixis alleles is likely to give rise to
the observed rare sexual progeny. We have identified the
genomic region containing the LOA locus and found it to
be located on a single chromosome. Transcriptomic
analyses are providing information concerning gene
expression in AI cells as they transition to aposporous
embryo sac formation. This and our progress towards
identification of the genes responsible for apomixis
initiation will be discussed.
Searching for elements of apomixis in Zea mays
Brunner, A1, Barrell, P1, Kessler, S1, Grossniklaus, U1
1
University of Zürich, Zürich, Switzerland
The introduction of apomixis into sexual crop plants
bears tremendous promise for agriculture. Most
flowering plants reproduce sexually and viable seed
formation depends on the fertilization of the egg and
central cell, and the coordinated development of the
embryo, the endosperm, and the maternal seed coat.
Apomictic plants employ a closely related, yet asexual
strategy, in which progeny of maternal origin are
produced in the absence of meiotic reduction and
fertilization. We proposed that this alternative approach
to seed production arose from the spatial and temporal
deregulation of ancestral sexual processes (Spillane et
al.). Thus, apomixis and sexual reproduction are closely
interrelated and tractable, sexual model systems can be
used to identify genes that play a role in apomixis. Using
maize as a model, we concentrate on two of the three
elements of apomixis: apomeiosis and parthenogenesis.
Using transposon-based, forward genetic screens have
identified genes that, if mutated, display aspects of
diplospory or parthenogenesis. Our progress in the
characterization of these maize mutants will be reported.
Targeted sequencing of a chromosome transmitting
apomixis
Ozias-Akins, P1, Conner, J1, Zeng, Y1
1
The University of Georgia, USA
Apomixis (asexual reproduction through seeds) in
Pennisetum results from aposporous embryo sac
development and parthenogenesis of the unreduced egg.
Fertilization of the central cell is required for seed
formation. In crosses between the apomictic wild species,
P. squamulatum, and cultivated pearl millet, P. glaucum,
a single chromosome is necessary and sufficient to
transmit apomixis. From mapping in interspecific F1
hybrids, results indicate that approximately ¼ of the
chromosome lacks recombination and is transmitted as a
linkage block. Various strategies are being pursued to
sequence the chromosome transmitting apomixis
including the non-recombining region. These are
sequencing of bacterial artificial chromosome (BAC)
clones mapping to the non-recombining region, DOPPCR products from the microdissected chromosome, and
transcriptomes from the apomictic parent and an
introgression line containing only the apomixistransmitting chromosome. Candidate genes such as
BABY BOOM have been discovered through sequence
analysis. Comparative analyses with sequenced genomes
and candidate genes in related species also have been
informative for understanding the evolution of this
genomic region.
Hybridization delays the sexual development and
triggers apomixis in the Ranunculus auricomus
complex
Hojsgaard, DH1, Pellino, M2, Vogel, H2, Sharbel, TF2,
Hoerandl, E1
1
Dept of Systematic and Evolutionary Botany, Faculty
Center of Biodiversity, University of Vienna, Vienna,
2
Austria;
Apomixis Research Group, Dept of
Cytogenetics and Genome Analysis, Leibniz Institute of
Plant Genetics and Crop Plant Research (IPK),
Gatersleben, Germany
Apomixis, the asexual pathway for seed formation,
involves a bypass of meiosis (apomeiosis) and formation
of an unreduced female gametophyte. The unreduced egg
cell develops parthenogenetically (by pseudogamy or
autonomously) into an embryo that is genetically
identical to the mother plant. The connection between
polyploidy to apomixis is frequently explained in terms
of hybridization. We hypothesize that hybridization of
different ecotypes and/or polyploidy cause asynchrony of
reproductive developmental steps to thus trigger
apomixis. In the Ranunculus auricomus complex, the
diploid R. carpaticola and tetraploid R. cassubicifolius
are the sexual parental species of the natural
allohexaploid apomictic nothotaxon R. carpaticola × R.
cassubicifolius. To understand and explore the origin and
functionality of apomixis we compare the sexual parents
with the natural hybrid. Furthermore, we have generated
105
laboratory crosses between the early flowering diploid
sexual species R. notabilis with the late flowering species
R. carpaticola and R. cassubicifolius. Embryological
analyses of the experimental diploid hybrids shows the
occurrence of aposporous initial cells as first step in
apomictic development, and asynchronous development
during megagametogenesis compared with the parental
species. The frequency of aposporous cells is lower in the
experimental hybrids than in the natural hybrids, and
according to flow cytometric seed screening (FCSS), the
aposporous pathway is only stable in the natural
allohexaploid hybrids since fully-developed apomictic
seeds were not recovered in the experimental hybrids.
However, in natural apomictic genotypes, precocious
apospory exists and outcompetes sexual development
when both pathways are expressed in the same ovule.
Alterations of gene expression and asynchrony in hybrid
genomes might be necessary for initiation of apospory,
while polyploidy could favour selection of efficient
apomictic development. We have thus performed
Illumina transcriptome sequencing in 3 sexual and 2
apomictic accessions to develop a Ranunculus-specific
expression microarray. Stage-specific expressionprofiling will inform us to what extent different patterns
in gene expression are correlated with asynchronous
development to make functional apomixis possible.
Molecular evolution and comparative genomics of
soybean orthologs of meiotic genes responsible for
gamete reduction
Sherman-Broyles, S1, Lee, M-J1, Mardonovich, S1,
Doyle, J1
1
Cornell University, USA
Two recently described mutants of the Arabidopsis genes
OMISSION OF SECOND DIVISION 1 (OSD1) and
PARALLEL SPINDLE 1 (PS1) result in unreduced
gametes. We have investigated the evolution of these
genes in the duplicated genomes of soybean and its
Australian wild relatives. Cell cycle and meiotic genes
have been described as two classes of duplication
resistant genes. The genus Glycine has experienced three
rounds of whole genome duplication (WGD), the rosiid
gamma event (130–240 million years ago (MYA)), the
legume event (59mya) and the Glycine event (13 mya).
Arabidopsis has also experienced three WGD events, the
rosiid gamma duplication, a beta duplication for which
the date is uncertain, and the alpha duplication that
occurred 20–100 mya. OSD1 and PS1 show different
patterns of retention in Arabidopsis. Arabidopsis retains
two homoeologs from the alpha duplication event that
show evidence of subfunctionalization, OSD1 is involved
in meiosis and UVI4 is involved in endoreduplication.
PS1 is single copy in Arabidopsis but retains two
homoeologs in soybean. We report on the sequence
diversity, gene phylogenies and expression of these two
genes in the genus Glycine represented by cultivated
soybean, G. sojae, the annual wild relative of soybean
and seven species of perennial Glycine.
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Sym040: Marchantia as a model for
evolutionary and developmental biology –
25 July
Marchantia as a model representing the earliest land
plants
Graham, L1, Graham, J2, Hanson, D2, Cook, M3,
Cardona-Correa, C1
1
University of Wisconsi, USA; 2University of New
Mexico, USA; 3Illinois State University, USA
The molecular phylogenetic literature indicates that
liverworts form a monophyletic group that is the earliestdiverging clade of modern land plants. The modern
paleontological literature provides evidence that
liverwort-like plants were present during the Ordovician,
a time when their spread could have been fostered by
warm, moist conditions that prevailed until the onset of
epoch-ending global glaciations. Recent fossil
discoveries, as well as structural and stable isotopic
comparisons of particular fossil remains to modern
Marchantia suggest that similar liverworts may have
been common in the Silurian and Devonian, possibly
occupying large areas of terrestrial surface prior to and
during the rise of tracheophytes. Liverwort-like early
land plants thus early acquired key terrestrial adaptations
– some likely inherited by descendent lineages – that
fostered clade persistence through stressful endOrdovician glaciations and other periods of dramatic
environmental change, to the present time. Identifying
such traits is not only useful in modeling the earliest
impacts of land plants on global biogeochemistry, but
also essential to predicting ways in which current and
future environmental change will influence vegetation.
To identify key traits and the order of their appearance,
we compared structural, reproductive, and physiological
features of Marchantia to those of earlier-diverging
liverworts, early-divergent mosses such as Sphagnum,
and charophycean green algae grown under subaerial
conditions. We have determined that Marchantia and
relatives are capable of mixotrophy – the uptake and
utilization of exogenous organic compounds such as
sugars – indicating that mixotrophy is an early-evolved
plant trait that may subsidize the production of increased
amounts of tissue that is resistant to microbial attack. By
this means, mixotrophy fosters both the ecological
persistence of modern Marchantia, and the formation of
fossil remains by Marchantia-like ancient bryophytes.
Our recent experimental advances include new evidence
that the direction of incident light is the primary
environmental signal determining the dorsiventral body
orientation of asexual gametophytes produced by
Marchantia and other liverworts, explaining the typical
downward growth of rhizoids from lower surfaces and
production of gemmae on upper surfaces. A major role
for gravitropism in body orientation was disproved by
the re-orientation of plant growth in response to light
provided only from below, with rhizoids produced from
plant surfaces facing away from both light and the
gravity vector. Light-directed reorientation allows
displaced plants to recover normal spatial orientation, a
trait that might have been particularly useful to
Ordovician plants growing on then globally-extensive,
but easily disturbed terrestrial quartz sand deposits. Other
new experimental results derived from comparative
analyses illuminate the evolutionary origin and past and
present ecological importance of asexual gemmae,
bacterial associations, desiccation tolerance, and
responses to combined thermal and UV stress, thereby
providing examples of ways in which Marchantia
models early land plant structure, reproduction, and
physiological ecology. Such information can be used to
build a conceptual foundation to aid studies focused on
the evolution of plant systems biology.
Mutualistic mycorrhiza-like symbiosis in Marchantia
Beerling, D1, Humphreys, C1, Bidartondo, M2, Leake, J1
1
University of Sheffield, UK; 2Royal Botanic Gardens,
Kew, UK
Over thirty five years ago it was hypothesized that
mutualistic symbiotic soil fungi assisted land plants in
their initial colonization of terrestrial environments. This
important idea has become increasingly established with
palaeobotanical and molecular investigations dating the
interactions between arbuscular mycorrhizal fungi
(AMF) and land plants to at least 400 Ma, but the
functioning of analogous partnerships in ‘lower’ land
plants remains unknown. Here, we show with multifactorial experiments that colonization of Marchantia, a
complex thalloid liverwort, with AMF significantly
promotes photosynthetic carbon uptake, growth and
asexual reproduction. Plant fitness increased through
fungal-enhanced acquisition of phosphorus and nitrogen
from soil, with each plant supporting 100-400 m of AMF
mycelia. A simulated CO2-rich atmosphere, similar to
that of the Palaeozoic when land plants originated,
significantly amplified the net benefits of AMF and
likely selection pressures for establishment of the
symbiosis. Our analyses provide essential missing
functional evidence supporting AMF symbionts as
drivers of plant terrestrialization in early Palaeozoic land
ecosystems.
The genome of Marchantia polymorpha L.
Yamato, KT1, Ishizaki, K2, Kohchi, T2, Floyd, S3,
Bowman, J3
1
Kinki University Faculty of Biology-Oriented
Technology and Science, Kinokawa, Japan; 2Kyoto
University Graduate School of Biostudies, Kyoto, Japan;
3
Monash University School of Biological Sciences,
Melbourne, Australia
The liverwort Marchantia polymorpha L. is one of extant
species of the first land plants that appeared about 450
Myr ago. The genomes of plastid, mitochondria and Y
chromosome in M. polymorpha were the first to be
published among all plant species, making significant
contributions to plant biology. M. polymorpha has now
become a fascinating model organism for plant biology,
because of its crucial position in the evolution of land
plants and molecular genetic tools that have been
recently developed. M. polymorpha is dioecious, and its
complete haploid set of chromosomes (approximately
280 Mb) consists of eight autosomes and a single sex
chromosome: an X chromosome for a female (n=8+X)
and a Y chromosome for a male (n=8+Y). A genetic map
has been constructed using >100 markers based on DNA
polymorphisms between our two laboratory lines, the
number of its linkage group is eight, which is consistent
with the number of autosomes. This map can be used for
arranging genomic sequences, as well as mapping
mutations. Since the Y chromosome has been sequenced,
a female standard line of M. polymorpha was selected for
whole-genome sequencing at the Joint Genome Institute
(JGI) in USA (PI: J.L. Bowman, Monash University,
Australia) (assembled data not available at the time of
abstract submission). To preview the M. polymorpha
genome, 30 genomic PAC clones which collectively
represent approximately 3 Mb of the genome were
sequenced and examined. Based on the obtained data, the
GC content of the M. polymorpha genome is
approximately 42%, and the frequency of known
transposable elements in the genome was roughly 1 in
100 kb, with an exception of one clone that contains a
much larger number of them. Similarity search and EST
mapping analyses revealed that the density of proteincoding genes is approximately one per 14 kb. Therefore,
the total number of genes in the M. polymorpha genome
was estimated to be around 20,000, which is consistent
with an estimate from EST analyses. An increasing
number of studies indicate the genetic redundancy in the
M. polymorpha genome is low. In angiosperms, many
regulatory genes are encoded by gene families, which
provides more elaborate regulatory systems. For
example, Arabidopsis has five phytochrome genes that
were generated by gene duplication and have
functionally differentiated. In contrast, M. polymorpha
appears to have a single phytochrome gene thus far. Our
preliminary data strongly suggest that M. polymorpha
has a minimum number of member genes for regulatory
systems, such as development and environmental
response. It should be also noted that species-specific
gene duplication observed in the moss Physcomitrella
patens does not appear to be common in M. polymorpha.
Its low genetic redundancy again makes M. polymorpha
an excellent model organism. In addition to genomic
sequence data, a large number of ESTs have been
generated (~300,000 of Sanger reads and >2,000,000 of
454 reads) and will be mapped on genomic data. Since
the genome project is ongoing, a more comprehensive set
of data is expected to be presented.
Transgenesis of the liverwort Marchantia polymorpha
and its application to developmental genetics
Ishizaki, K1, Masuda, A1, Saida, Y1, Ueda, M1,
Yamato,KT1, Kohchi, T1
1
Graduate School of Biostudies, Kyoto University,
Japan; 2Graduate School of Science, Kyoto University,
Japan
Transformation technique is an essential component of
functional genomics. We have recently developed a
simple and rapid Agrobacterium-mediated transformation
system for the liverwort Marchantia polymorpha.
Hundreds of stable transformants per sporangium were
obtained using immature thalli developed from spores. It
took only 3–4 weeks to establish individual transgenic
plants after starting liquid culture of spores. DNA
analyses verified random integration of 1–5 copies of
intact T-DNA between the right and the left borders into
the nuclear genome. To avoid potential chimerism, clonal
107
transgenics can be rapidly established by using gemmae
which arise asexually from single initial cells. Four kinds
of selectable markers and various reporters including
green fluorescent protein (GFP), β-glucuronidase (GUS),
and luciferase (LUC), have been successfully used for.
Therefore, it has become feasible to perform various
transgenic experiments using M. polymorpha; for
example, overexpression, promoter analysis, and
observation of subcellular protein localization.
Agrobacterium-mediated transformation is a powerful
tool not only for introduction of constructs of interest
into plants, but also for T-DNA insertional mutagenesis.
We have generated over 10,000 T-DNA tagged lines of
M. polymorpha using the binary vector pCAMBIA1300,
and screened them for abnormal morphological
phenotypes. Because of the haploidy of M. polymorpha,
their mutant phenotypes were detectable in the primary
generation of transformants. We have isolated 22 lines
that exhibited various morphological phenotypes, such as
formation of callus-like tissue, loss of air-chamber
development, and defect in gemma formation.
Characterization of these mutants is expected to reveal
both the common and divergent developmental programs
between gametophyte-dominant and sporophytedominant land plants. We will present our recent
progress in the genetic characterization of these M.
polymorpha morphological mutants.
The role of patterning genes in Marchantia:
implications for body plan evolution in land plants
Floyd, S1, Bowman, J1
1
Monash University, Vic, Australia
The availability of genetic and genomic resources and
tools for Marchantia polymorpha allow the analysis of
gene function in a representative of the earliest-diverging
land plant clade. Interpretation of mutant and transgenic
phenotypes and expression data indicate that in
Arabidopsis the Class III Homeodomain-leucine zipper
(Class III HD-Zip) family of transcription factors are
essential for SAM formation, patterning of vascular
tissues, adaxial/abaxial polarity in leaves and cotyledons,
and lateral root formation. With a role in most major
organs of the sporophyte, it is likely that this family of
transcription factors has been important in land plant
evolution. A survey of these genes in land plants
suggested that a role in vascular patterning and meristem
function is conserved in vascular plants but so far
functional data are lacking outside of flowering plants. I
will present data describing the role of the single Class
III HD-Zip gene in Marchantia. Our findings have
implications not only for the ancestral function for the
Class III Hd-Zip, but the significance of miRNA
regulation in embryophyte development and evolution.
Developmental gene regulation by chromatin
remodelling factors in basal land plant Marchantia
polymorpha
Dierschke, T1, Bowman, J1
1
School of Biological Sciences, Monash University, Vic,
Australia
108
Chromatin remodelling factors are master regulators of
gene expression in animals as well as in plants. Research
in Arabidopsis thaliana and Physcomitrella patens
indicate that these genes are responsible for major
transitions in developmental stages during the life cycle.
Arabidopsis thaliana CURLY LEAF (CLF), a
homologue of Drosophila ENHANCER OF ZESTE
(E(z)) and member of the Polycomb Repressive Complex
2 (PRC2), is necessary for stable repression of floral
homeotic genes. In Drosophila, TRITHORAX Group
proteins (TrxG) often oppose the action of Polycomb
group (PcG) proteins. Mutations in ATX1 (a TrxG gene)
suppress phenotypic defects of clf mutants, providing
evidence that PcG/TrxG factors have antagonistic
functions in plants by regulation of a shared gene locus.
Each of the three Arabidopsis E(z) homologues CURLY
LEAF (CLF), MEDEA (MEA) and SWINGER (SWN)
displays different spatio-temporal expression pattern
during plant development and all PRC2-like complexes
display variable compositions of the core proteins,
demonstrating that CLF, SWN and MEA act partially
redundant in A. thaliana. In P. patens the PcG proteins
FIE and PpCLF, both proteins being components of
PRC2 in Arabidopsis, play a key role in phase transitions
in the life cycle of P. patens, including the alternation of
generations. The basal land plant Marchantia
polymorpha is a good model as EST´s are available and
its genome has recently been sequenced. Unlike A.
thaliana, M. polymorpha shows no redundancy in PRC2
proteins, providing us with the opportunity to study the
ancestral role of these genes in land plants. We are
undertaking a combination of gene expression analysis
and phenotypic analyses of gain-and induced loss-offunction alleles that will provide insights in the roles of
the chromatin remodelling factors MpE(z), MpTRX and
MpGYM in the life cycle of M. polymorpha.
Sym041: Learning from the extremists: 21st
century approaches to understanding plant
stress tolerance – 30 July
Decoding plant environmental strategies with new
models for the 21st century
Cheeseman, J1, Dassanayak, M1, Oh, D-H1, Bohnert, H1
1
University of Illinois, USA
There is no doubt that for the last 20 years, a single major
model plant system such as Arabidopsis was well
justified: the technical limitations of the early molecular
era and first generation sequencing made it impossible to
maintain the taxonomic breadth previously characterizing
the field of plant physiology. Now, however, the key
obstacle to progress in understanding genetic
mechanisms by which plants tolerate and ameliorate
stress is the fact that all of the current major models are
plants adapted to and dependent on abundant resources.
Plants adapted to extreme conditions – those which
actually have successful environmental response
strategies – have been significantly under-utilized. It is,
therefore, opportune at this point to identify those
characters to be sought in defining the next generation of
plants for which serious genetic, proteomic, metabolomic
and physiological resources should be developed. This
contribution will address four major areas, including
those directly relate to stress tolerance, to genetic
tractability, to amenability to systems biology approaches
involving multiple –omics, and to those related to life
history strategies and life styles. The need for
multispecies breadth in the post arabidocentric universe
will be presented.
Cluster root molecular physiology: regulating the
development of an adaptation that mines phosphorus
from nutrient-impoverished soils
evolution of Pi responsiveness in the Proteaceae, and
may give insights into why H. prostrata is unable to
regulate its Pi responsiveness as effectively as other
plants, while at the same time displaying a very effective
Pi acquisition capability.
Evolution of salt tolerance: a phyloinformatic
approach to understanding the evolution of complex
traits to adapt to harsh environments
Bromham, L1, Bennett, T1, Flowers, T2
Finnegan, PM1, Jost, R1, Siddique, ABM1, Ludwig, M2,
Lambers, H1
1
1
Salt-affected land is a serious and increasing problem in
agriculture and land management, but the large amount
of effort directed at developing salt-tolerant crops has
produced disappointingly few successes. This is
perplexing, given that there are over 1500 plant species
that have some natural salt-tolerance. To resolve this
paradox, we need to understand why so many different
lineages have produced naturally salt-tolerant species, yet
why we have been limited in our ability to repeat this
success in artificial breeding and associated genetic
techniques. We take a comparative, biodiversity-based
approach to understanding the evolution of salt-tolerance,
surveying all halophytic flowering plant species and
asking what traits or preconditions underlie the evolution
of salt-tolerance.
School of Plant Biology, University of Western
2
School
of
Biomedical,
Australia,
Australia;
Biomolecular and Chemical Sciences, University of
Western Australia, Australia
Ancient, highly weathered soils, such as those found in
south-western Australia and the Cape region of South
Africa, contain relatively low phosphorus and are
extremely poor in plant-available inorganic phosphate
(Pi). Evolution has provided plants endemic to these
regions with structural and physiological adaptations to
maximise their capacity for acquiring Pi. One of these
adaptations is the cluster roots found among Proteaceae.
Cluster roots typically exude substantial quantities of
carboxylates that mobilise complexed or sorbed Pi into
the soil solution. Once liberated from soil particles, the Pi
must be taken across the plasmalemma of cells in contact
with the soil solution and redistributed throughout the
plant body. We are exploring the molecular physiology
of Pi acquisition by 'proteoid' cluster roots and the
underlying molecular genetic control of their
development in Hakea prostrata. Pi transport across
membranes is most likely through members of the PHT1
family of Pi transporters. In those species examined, the
steady-state transcript abundance of several members of
the PHT1 gene family, especially those expressed in
roots, respond to Pi in the soil solution such that
transcript accumulation is repressed by high Pi
availability. It is unknown if this down-regulation of Pi
transporters occurs in H. prostrata and is of interest
because previous work showed that this plant, unlike
most other plants investigated, seems unable to
effectively down-regulate Pi up-take in response to
excess Pi (M. W. Shane, M. E. McCully, H. Lambers
(2004). This situation can lead to Pi toxicity through the
accumulation of excess Pi in leaves, if Pi availability is
raised even slightly above the Pi levels found in this
species' natural habitat. The PHT1 gene family of H.
prostrata contains at least 13 members. Complementary
DNAs for four of the 13 HpPHT1 genes were isolated
from cDNA libraries derived from cluster roots,
indicating that these genes are expressed in this tissue.
We are continuing to characterise the PHT1 gene family
of H. prostrata to determine the tissue-dependent
transcript profiles and Pi responsiveness of its members.
The Pi responsiveness of PHT1 genes in model plants
relies on a complex regulatory network that involves
proteins and microRNAs. We are undertaking a
transcriptome sequencing approach to determine whether
the genetic functions known to be involved in regulating
Pi homeostasis in other model species are present in H.
prostrata. This analysis will give insights into the
2
Australian National University, Canberra, Australia;
University of Sussex, UK
Using Arabidopsis gene networks to
transcriptome dynamics and stress responses
study
Ma, S1, Bohnert, H2, Dinesh-Kumar, SP1, Oh, D-H1
1
University of California at Davis, USA; 2University of
Illinois at Urbana–Champaign, USA
Arabidopsis gene networks based on large scale gene
expression data have been constructed with various
methods, such as relevance network and graphical
Gaussian model. However, little is known about the
molecular mechanisms behind these networks. One
hypothesis is that the large network can be separated into
many coherent sub-networks whose genes’ expressions
are driven by various hub proteins, especially hub
transcription factors (TFs). To identify such hub TFs, we
developed an algorithm to identify promoter motifs
associated with the genes in the network, and identify the
motifs that would bind to the hub TFs, which we call
them hub motifs. Once the motifs are identified, a protein
array based method was used to identify the hub TFs that
bind to these hub motifs. Such methods are helpful to
elucidate the transcriptional modules Arabidopsis uses to
counteract various abiotic and biotic stresses.
The genome of an extremophile, Thellungiella parvula
(Brassicaceae)
Dassanayake, M1, Oh, D-H2, Haas, J1, Hernandez, A1,
Cheeseman, J1, Bohnert, H2
1
University of Illinois, Urbana–Champaign, Illinois,
USA; 24Gyeongsang National University and WCU
Program, Government of Korea, KR
109
A close relative of Arabidopsis thaliana, Thellungiella
parvula is adapted to an extremophile lifestyle. T.
parvula is, is notable for its tolerance of high salinity,
freezing temperatures, water deficit and resource-poor
environments. With a small nuclear genome of ~140Mb
in 7 chromosomes (N), T. parvula represents an
extremophile model species. We have determined its
genome sequence and the transcript profile with the
objective of comparing how the plant differs in genome
structure and expression characteristics from the model
Arabidopsis, which is a glycophyte. Arabidopsis and
Thellungiella ancestors are estimated to have separated
~15–20 MY ago. A comparison of their respective
genomes provides information that will allow for an
analysis of the evolutionary pressures that shaped the two
species leading to divergent lifestyles. Our sequencing
strategy was aimed to retrieve 50x coverage of the
estimated genome size by a hybrid sequencing approach
utilizing only next generation sequencing technologies:
454 Roche GS FLX Titanium and Illumina GA2. Our de
novo assembly of short read sequences provided a high
quality draft genome of T. parvula that shows extensive
microsynteny
with
Arabidopsis
and
Brassica
chromosomes. In many instances the observed
degenerate synteny with Arabidopsis is due to the
absence of close homologs of T. parvula in Arabidopsis.
However, over 70% Arabidopsis transcript models have
inferred homologs sharing more than 75% sequence
similarity with T. parvula transcripts. Functional
categories that are significantly differently represented in
T. parvula compared to Arabidopsis include genes for
transporters and receptor signaling functions. Examples
of genome structure, gene complement and gene
expression, and some obvious differences between T.
parvula and A. thaliana, will be further discussed. Our
results highlight differences between an extremphile and
glycophyte lifestyles at two key levels: first, copy
number variation in terms of gene copy number which
affect expression strength and second, allelic variation
that translates to changes in protein domain structure,
where stress-essential proteins show minute alterations
from their glycophytic homologs. On the level of future
crop breeding in the age of genomics, we argue for the
importance of selecting extremophile characters in crop
species that could even emerge from wild but stressadapted species.
Sym042: Developmental genetics and cell
biology of Marchantia polymorpha – 25 July
Auxin response and signaling factors in Marchantia
polymorpha
Kato, H1, Ishizaki, K1, Nonomura, M1, Yamato, KT1,
Kohchi, T1
1
Graduate School of Biostudies, Kyoto University, Japan
Phytohormone auxin regulates a variety of growth and
developmental processes in plants. Recent studies in
Arabidopsis have provided a scheme that F-box proteins,
TIR1/AFBs, function as auxin receptors and degrade
transcriptional repressors, AUX/IAAs, allowing ARFs to
regulate transcription of auxin-responsive genes. The
liverwort Marchantia polymorpha, which belongs to a
110
group of basal land plants, has low genetic redundancy
and undergoes simple developmental processes. We have
been investigating the mechanism of auxin signaling in
M. polymorpha to understand if the components of the
auxin signaling mechanism are conserved among land
plants.
Application
of
synthetic
auxin,
1naphthaleneacetic acid (NAA), induced development of
rhizoids from not only the ventral but also the dorsal side
of thallus at 1 µM. In addition, treatment with auxin
transport inhibitor, 2,3,5-triiodobenzoic acid (TIBA),
occasionally caused inversion of the dorsiventrality in
thallus. These results suggest that auxin gradient is
involved in formation of the dorsiventral axis in M.
polymorpha. Next, we examined the distribution of auxin
in M. polymorpha by monitoring an auxin-inducible
reporter gene fusion, GH3:GUS. Transgenic plants
carrying GH3:GUS showed elevated GUS activity in
response specifically to auxin treatment, indicating the
GH3:GUS reporter system can measure auxin
distribution in M. polymorpha. Histological GUSstaining was observed at the bottom of gemma cups and
in developing sporophytes without exogenous auxin,
suggesting a role of auxin in gemma and sporophyte
development. To investigate the molecular mechanism of
the auxin signaling in M. polymorpha, we searched for
key genes in auxin signaling. We identified one
AUX/IAA (MpIAA), three ARFs (MpARF1, MpARF2,
and MpARF3) and one TIR1/AFB (MpTIR1) genes in
the M. polymorpha genome. MpARF1 has a putative
target sequence for microRNA167 as in ARF6 and ARF8
of Arabidopsis. MpIAA has a glutamine-rich region in
addition to the four known functional domains conserved
among AUX/IAAs. In Arabidopsis, it is known that
mutation in domain II of AUX/IAA confers dominant
auxin-resistant phenotype. The expression of MpIAA
that has the mutation in domain II conferred reduced
sensitivity to auxin. Our results suggest that the
molecular mechanism of auxin signaling is conserved
among land plants through the evolutionary shift from
gametophyte-dominant to sporophyte-dominant life cycle
Auxin signaling factors in Marchantia polymorpha II
Flores-Sandoval, E
1
Monash University, Australia
Auxin is involved in establishing key developmental
processes in flowering plants but the role of this hormone
is not well understood in the earliest diverging lineages
of land plants. We test the morphogenetic effect of lossof-function Auxin Response Factors of Marchantia
polymorpha by experiments using the TOPLESS corepressor fused to protein-protein interaction domains of
AUX/IAA and ARF proteins. Dominant negative
mutations of TOPLESS were also performed to asses
gain-of-function ARF phenotypes. The function of
individual ARF lineages was assessed in the context of
conserved miRNAs 160 and 390 in liverworts. Our work
contributes in understanding land plant evolution by
comparing morphogenetic effects of auxin signaling
disruption between Arabidopsis and Marchantia, which
has a haploid dominant thallus with potentially several
ancestral characteristics.
Molecular conservation of MIKC*-type MADS-box
proteins in the gametophytic generation of land
plants: insights gained from studying bryophytes
Functional analysis of MpLFY, the homolog of
LEAFY in Marchantia polymorpha
Zobell, O1,2, Faigl, W2, Muenster, T2, Zachgo, S1
Sakai, Y1, Araki, T1
1
University of Osnabrueck, Osnabrueck, Germany; 2Max
Planck Institute for Plant Breeding Research, Cologne,
Germany
1
Dept of Responses to Environmental Signals and
Stresses, Division of Integrated Life Science, Graduate
School of Biostudies, Kyoto University, Japan
Land plants are characterized by an alternation of two
generations, the haploid gametophyte and the diploid
sporophyte. The development of the small and simple
male gametophyte of the flowering plant Arabidopsis
thaliana critically depends on the action of five MADSbox proteins of the so-called MIKC* subclade. These
MADS-box genes were isolated from land plants with
relatively large and complex gametophyte bodies,
namely the bryophytes. We found that the gene family
expanded in the mosses Sphagnum subsecundum,
Physcomitrella patens, and Funaria hygrometrica, just as
it did in any vascular plant analyzed till date. However,
only a single homologue, Marchantia polymorpha
MADS-box gene 1 (MpMADS1), has been retained in
the liverwort M. polymorpha. Liverworts are the earliest
diverging land plants, and so a comparison of
MpMADS1 with its angiosperm homologues addresses
the molecular evolution of a land plant-specific
transcription factor over the widest phylogenetic
distance. MpMADS1 was found to form a homodimeric
DNA-binding complex, which is in contrast to the
Arabidopsis proteins that are functional only as
heterodimeric complexes. The M. polymorpha
homodimer, nevertheless, recognizes the same DNA
sequences as its angiosperm counterparts and can
functionally replace endogenous MIKC* complexes to a
significant extent when heterologously expressed in
Arabidopsis pollen. The 11 MIKC* homologues from the
moss F. hygrometrica are highly and almost exclusively
expressed in the gametophytic generation. Taken
together, these findings suggest that MIKC* MADS-box
proteins have largely preserved molecular roles in the
gametophytic generation of land plants. Currently, we are
focusing on elucidating the specific role of MpMADS1
in M. polymorpha.
LEAFY (LFY) encodes a plant-specific transcription
factor that plays a key role in the formation of flowers in
angiosperms. LFY orthologs have been found also in
gymnosperms, ferns, fern allies, mosses, and liverworts.
In most cases, LFY is a single-copy gene. In Arabidopsis
thaliana, transcriptional networks downstream and
upstream of LFY are well studied. Floral homeotic genes
encoding MADS-box transcription factors, such as AG,
AP3, PI, AP1 and CAL, have been identified as direct
targets of LFY. On the other hand, several transcription
factors including AGL24, SOC1 and SPL3 are involved
in regulation of LFY expression. Recently, function of
the LFY orthologs from non-flowering plants was
analyzed in detail in Physcomitrella patens. It was
demonstrated that Physcomitrella LFYs (PpLFY1 and
PpLFY2) are involved in the cell division of the
sporophyte. Although PpLFYs are expressed not only in
the sporophyte (diploid) but also in gametophyte
(haploid), their functions in gametophyte are unknown.
We isolated the LFY ortholog, MpLFY, from Marchantia
polymorpha, expecting that the study of function of
MpLFY should provide important information to
understand the origin, ancestral functions, and evolution
of LFY. Where and how does MpLFY function in M.
polymorpha? Whether does LFY function in
gametophyte? Furthermore, which kinds of genes are
directly regulated by MpLFY? To answer these questions,
we have performed the expression analysis of MpLFY in
various tissues throughout the life cycle. Transgenic
plants, in which the expression levels of MpLFY are
altered, were produced and analyzed. To better
understand the phenotypes of these transgenic plants,
developmental processes of wild-type plants were
observed in organ-, tissue- and cellular-levels, using live
imaging. In addition, by microarray expression analysis,
using the EST-based custom-made array and a
glucocorticoid receptor (GR)-fusion protein system, it
was shown that hundreds of genes were up-regulated in
haploid gametophyte by activation of MpLFY-GR
protein. To identify the direct targets among these
candidate genes, their induction plofiles in the transgenic
plants expressing MpLFY-GR are investigated in the
presence or absence of cychloheximide. Results of these
studies will be discussed.
The role of CLE in Marchantia development
Sawa, S1, Tabata, R1
1
Kumamoto University, Japan
CLV3/ESR related (CLE) is supposed to function as
peptide hormone to regulate various developmental steps
in plants. Marchantia has only one CLE gene, MpCLE1.
In order to examine their developmental function, we
produced over expression and knock down transgenic
Marchantia plants. MpCLE1 OX plants fail to develop
epidermal cell. Air pore like structure was produced.
However, inside of air pore structure can be observed
directly from out side. Interestingly, air pore like
structure was produced both of abaxial and adaxial side
in the MpCLE1 OX plants. In the case of knock down
transgenic plants, excess cell division of epidermal cells
was observed. Here we introduce our opinion about
conservation and difference of CLE signaling molecular
mechanisms and functions during plant evolution.
Diversification of post-Golgi trafficking pathways
among land plants
Ueda, T1
1
The University of Tokyo, Japan
Membrane trafficking plays integral parts in various cell
activities in all eukaryotic cells. RAB GTPase and
SNARE are evolutionary conserved regulatory molecules
for membrane trafficking. In general, RAB GTPase
promotes tethering of transport vesicles/organelles to
111
target membranes, which is followed by membrane
fusion executed by assembly of specific combinations of
three Q-SNAREs (Qa-, Qb-, and Qc-SNAREs) and one
R-SNARE into a stable complex. Recent comparative
genomics suggests that the diversification of membrane
trafficking pathways was, at least partly, achieved by
paralogous gene expansion of organelle identity
molecules such as the RABs and SNAREs. However, it
remains completely unknown how newly acquired
molecules pioneered a new trafficking route. Plants have
acquired several endocytic Rab and SNARE molecules
unique to plants during evolution, which strongly
suggests that endocytic and/or post-Golgi trafficking
pathways have been diversified in a plant-unique way.
ARA6 is a plant-unique RAB5-like GTPase of
Arabidopsis thaliana with several unique structural
features. Recently, we have found that ARA6 regulates a
novel trafficking pathway from endosomes, which also
involves a plant-unique longin-type R-SNARE with a
characteristic insertion in its N-terminal longin domain.
Plants also harbor orthologs of animal RAB5, which
regulate traffic to the vacuole via endosomes. To
understand when and how plants acquired the unique
endosomal trafficking system, we are studying structures
and functions of endosomal RAB and SNARE molecules
in the basal land plant Marchantia polymorpha. We
isolated homologs of ARA6 and conventional RAB5 in
M. polymorpha, and compared localization and function
of their products. As we expected, these two RAB5
groups act in different trafficking pathways in M.
polymorpha and, intriguingly, functions of ARA6-type
RAB5s seem to be diversified between A. thaliana and
M. polymorpha.
Sym045: Crassulacean acid metabolism:
functional and comparative genomics –
25 July
Developmental and environmental control of CAM
expression in Bromeliads: the role of phytohormones
and other signaling molecules
Freschi, L1, Rodrigues, MA1, Mioto, PT1, Pereira, PN1,
Hamachi, L1, López, AM1, Mercier, H1
1
University of São Paulo, Brazil
The extent to which the biochemical and physiological
traits of CAM are expressed can greatly vary both within
and between species. The so-called C3–CAM facultative
plants are probably the best examples of intraspecific
plasticity in the expression of CAM while, in contrast,
constitutive CAM plants are believed to exhibit a more
limited flexibility in the proportion of CO2 uptake over
the day and night. Regardless of these differences in
classification, the degree of CAM expression in both
facultative and constitutive CAM species has been shown
to be strongly dependent on the photosynthetic maturity
of the tissues. In this study, we have demonstrated that
even pineapple (Ananas comosus), an archetypical CAM
constitutive bromeliad, displays a remarkable flexibility
in the expression of CAM during the initial phases of
development. In fact, when challenged by a reduction in
the water availability, young individuals of this
bromeliad are able to respond with an intense, rapid, and
112
completely reversible up-regulation in nocturnal malate
accumulation and in the expression and activity of
important CAM enzymes, indicating that the expression
of CAM represents an adjustable response rather than a
predetermined state during the early ontogeny of this
species. Similarly, Vrisea gigantea and Guzmania
monostachia, two epiphytic tank bromeliads, also
showed a high degree of flexibility in CAM expression,
which was strongly dependent on both plant and leaf age.
In these species, most of the up-regulation of CAM under
water deficit conditions occurred specifically in the upper
leaf portion, which is the more mature and light-exposed
region of tank-forming leaves. Taking advantage of the
photosynthetic plasticity exhibited by these three
bromeliad species, we have characterized the hormonal
signals associated not only with the intensification of
CAM but also with the attenuation of this photosynthetic
pathway in response to changes in environmental factors
such as water, light and nutrient availability. This
approach allowed us to identify a substantial
correspondence between the signals involved in both upand down-regulation of the CAM expression,
characterizing ABA and cytokinins as the main hormonal
components of the signal transduction pathways
controlling the levels of CAM activity. For instance,
during both up- and down-regulation of CAM in
pineapple, the degree of CAM expression was positively
and negatively correlated with the endogenous levels of
abscisic acid (ABA) and cytokinins, respectively.
Moreover, when exogenously applied, ABA stimulated
and cytokinins repressed the expression of CAM.
However, inhibition of water-deficit-induced ABA
accumulation did not block the up-regulation of CAM,
suggesting that a parallel, non-ABA-dependent signaling
route was also operating. The involvement of both nitric
oxide (NO) and cytosolic calcium during CAM signaling
was also demonstrated, revealing that changes in
cytosolic calcium represent a convergence point among
water stress, ABA and NO during the signaling cascade
controlling CAM expression. Finally, the signaling
events modulating the degree of CAM expression during
the ontogeny of these bromeliad species will be also
discussed.
Lending colour to the CAM story…
Ceusters, J1, Borland, AM2, Taybi, T2, Godts, C1,
Calcoen, J1, De Proft, MP1
1
KULeuven, Heverlee, Belgium; 2Newcastle University,
Newcastle Upon Tyne, UK
The correct functioning of
Crassulacean acid
metabolism (CAM) hinges on effective temporal
coordination of the metabolic processes that determine
the supply and demand for carbon over the day/night
CAM cycle. In general, light is considered a crucial input
factor in sustaining the circadian rhythms of CO2 uptake
and release in CAM plants, probably by triggering
different light sensitive sensors such as the red/far red
absorbing phytochromes and the blue/UV-A absorbing
cryptochromes. Moreover, light is considered essential
for the daytime processing of nocturnally accumulated
malic acid, as plants in continuous darkness maintain
high levels of malic acid for several days. However, the
interplay of the different components of the light
spectrum (i.e. different wavelengths of light) with the key
components of CAM, i.e. stomatal aperture, gas
exchange, malic acid processing and carbohydrate
partitioning is largely unknown. A 24 h experiment was
conducted with the CAM plant Aechmea ‘Maya’ under
an 18 h photoperiod but with 4 different wavelengths
illuminated by LED, i.e. 470 (blue), 530 (green), 630
(orange – red) and 660 (red) nm administered at 10 µmol
m-2 s-1. Control treatments consisted of an 18 h
photoperiod under white light (100 µmol m-2 s-1) and
continuous dark for 24 h. For each regime, gas exchange
was monitored by IRGA and leaf samples were taken
every 4 hours for the determination of organic acids,
sugars and starch. The data was complemented with
activity measurements in vitro of the key CAM enzymes
PEPC and PEPCK, along with measurements of protein
and transcript abundance of both enzymes over the diel
cycle. By integrating measurements of the key
components of CAM at the molecular, biochemical and
physiological levels, a picture emerges of the complex
interplay between light quality and the functioning of this
photosynthetic specialization.
Integrated functional genomics of crassulacean acid
metabolism
in
the
Common
Ice
Plant
(Mesembryanthemum crystallinum L.)
Cushman, JC1, Albion, RL1, Gulle, B1, Covington, M2,
Schlauch, KA1
1
1Dept of Biochemistry and Molecular Biology, MS200,
University of Nevada, Reno, USA; 22Dept of
Biochemistry and Cell Biology, Rice University,
Houston, USA
Crassulacean acid metabolism (CAM) is a specialized
mode of photosynthesis that improves atmospheric CO2
assimilation in water-limited terrestrial and epiphytic
habitats and in CO2-limited aquatic environments by
taking up CO2 from the atmosphere partially or
predominantly at night. Temporal separation of nocturnal
CO2 uptake and fixation by phosphoenolpyruvate
carboxylase (PEPC) and daytime formation of C4 organic
acids (i.e., malic acid), reciprocal fluxes in storage
carbohydrates, and inverse stomatal behavior is predicted
to be under circadian clock control, however, the
molecular genetic mechanisms that underlie the control
of these processes remain largely unknown. In order to
investigate circadian clock control of CAM, we have
initiated an integrated functional genomics program to
simultaneously investigate transcriptomic, proteomic,
and metabolomic profiling along with metabolic pathway
reconstruction to integrate these diverse data sets in the
stress-inducible CAM species Mesembryanthemum
crystallinum. To date, we have used a combination of
Sanger sequencing and Roche/454 Life Sciences
pyrosequencing to generate over 2.3 million EST reads
resulting in 765 MB of cDNA sequence data. These data
have been used to generate microarray mRNA expression
profiles or to serve as a reference transcriptome for high
throughput RNA sequencing to characterize circadian
clock control of mRNA transcript changes over a 48 or
72-hour period with sampling every 4 hours (under
constant light and temperature conditions) in wild type
plants performing either C3 photosynthesis or CAM. A
parallel study was also performed with a CAM-defective
mutant in order to discern CAM-specific changes from
those adaptive responses arising directly from either
salinity or drought stress. In addition to mRNA
expression studies, we are performing concomitant
protein and metabolite profiling studies to identify
potential regulatory hierarchies and interactions that
might mediate posttranscriptional and posttranslational
modes of circadian clock regulation.
Using RNA-seq to dissect the molecular basis for
circadian optimisation of crassulacean acid
metabolism
Boxall, SF1, Dever, LV1, Gregory, R1, Knerova, J1, Hall,
N1, Hartwell, J1
1
Dept of Plant Sciences, Institute of Integrative Biology,
University of Liverpool, Liverpool, UK
The goal of our research is to identify all the genes
involved in the establishment and circadian coordination
of crassulacean acid metabolism (CAM) in the obligate
CAM species, Kalanchoë fedtschenkoi. K. fedtschenkoi is
an excellent model for the study of CAM photosynthesis
for a number of key reasons. Firstly, extensive
biochemical and physiological characterization of CAM
has previously been performed with this species.
Secondly, we have developed a simple, rapid and
efficient stable transformation system. Thirdly, it is
readily amenable to molecular, biochemical and
physiological analysis permitting detailed phenotypic
characterization of transgenic lines. Finally, it performs a
clear developmental progression from C3 to CAM during
leaf ontogeny. By performing RNA-seq experiments
using
both
the
Roche
454
and
Applied
BiosystemsSOLiD second generation sequencing
systems, we have compared the transcriptome of C3 and
CAM leaves from K. fedtschenkoi over a diurnal cycle.
Detailed bioinformatic analysis of the RNA-seq data has
permitted us to identify thousands of known and
unknown genes with potential roles in either the
biochemical steps or the circadian coordination and
optimization of CAM. We are focusing downstream
analysis on genes encoding regulatory proteins that could
play a role in the circadian coordination of CAM;
undertaking detailed RT-PCR studies to corroborate the
RNA-seq data, and then manipulating putative circadianregulated CAM genes in transgenic lines using both
silencing with RNAi, and constitutive over-expression.
In addition, we have also silenced and over-expressed
many of the known major metabolic steps of the CAM
pathway (PEPc, PPDK, NAD(P)-ME etc), and have
begun detailed phenotypic analysis of these transgenic
lines. Some of our preliminary phenotypic analysis of the
transgenic lines will be presented, along with an
overview of the discoveries achieved through the RNAseq analysis of the diurnal and circadian control of the
CAM transcriptome.
Molecular basis of crassulacean acid metabolism
(CAM) evolution inferred from gene family structures
in Neotropical orchids (Subtribe Oncidiinae)
Gulle, B1, Albion, BL1, Silvera, K2, Cushman, JC1
1
Dept of Biochemistry and Molecular Biology, University
of Nevada, Reno, NV, USA; 2Dept of Botany & Plant
Sciences, University of California, Riverside, CA, USA
113
Crassulacean acid metabolism (CAM) is an important
water-conserving photosynthetic pathway present in
approximately 7% of vascular plant species from at least
35 families. The Orchidaceae is arguably the largest
family of vascular plants with about 30,000 species of
which approximately 40% are likely to exhibit some
degree of weak or strong CAM. Phylogenetic analysis
from 1,103 species native to Panama and Costa Rica
revealed that CAM has evolved independently several
times within the Orchidaceae. The Oncidiinae, which is
the second largest orchid subtribe, was selected for
evolutionary analysis, because it has one of the most well
established molecular phylogenies available and has been
sampled by leaf tissue carbon isotope composition. To
better understand the CAM evolution, molecular changes
were observed using microarray analysis. Roche/454
pyrosequencing for the strong CAM orchid species
Rossioglossum ampliatum resulted in a total of 189 Mb
of data with more than 41,000 contigs and 100,000
singletons. More than 39,000 probe sets were used to
design Nimblegen oligonucleotide microarray to detect
the expression differences among three closely related
orchid species performing photosynthesis in a range of
C3 to weak CAM to strong CAM. In order to test the
hypothesis that CAM evolution is accompanied by gene
duplication events and recruitment of discrete isogenes
with enhanced mRNA expression, we have investigated
gene family structures for phosphoenolpyruvate
carboxylase (PEPC), carbonic anhydrase (CAH) and
glucose-6-phosphate/Pi translocator (GPT). We have
sampled over 2000 cDNA products using a degenerate
RT-PCR strategy to recover an average of five PEPC,
four CAH and two GPT isogenes within each family
across ten orchid species. Ana24-hour gas exchange
analysis showed that weak CAM species exhibit limited
amounts of nocturnal CO2 uptake when compared to
strong CAM species. Our current results indicate that the
evolutionary progression from the ancestral C3 state to
the derived CAM state is accompanied by selective
recruitment of discrete isogenes that show increased
mRNA expression in order to fulfill the enhanced
metabolic demands of CAM to perform nocturnal CO2
fixation.
crop species such as sugar cane and maize, and thus
compete with food security for available land. With all of
these major mounting pressures, there is a growing
acceptance that 21st century agriculture needs to think
outside the box in order to respond to the challenges and
balance food security with the production of crop
feedstocks for biofuels. Crassulacean acid metabolism
(CAM) is a metabolic adaptation of photosynthesis that
increases water use efficiency relative to C3
photosynthesis by between 6 and 20-fold. Thus, CAM
plants are able to thrive on arid and semi-arid land where
major crops such as rice and wheat will not grow
productively. Certain CAM crops can achieve very
respectable yields of up to ~ 45 tonnes per hectare per
year on seasonally-dry land. In particular, high
productivity species of the monocot CAM genus Agave,
such as Agave tequilana, Agave fourcroydes, and Agave
sisalana, have been proposed as excellent biofuels
feedstocks crops suited to seasonally-dry lands. A key
reason why Agaves are believed to have great potential is
their high content of the fructan sugars which can very
readily be fermented into ethanol. In addition, they have
a high percentage of low lignin cellulose (e.g. sisal fibre),
which could be exploited with second-generation
biofuels technology aimed at the conversion of cellulose
to ethanol. Despite the urgent and pressing need to
optimize the exploitation of certain CAM plants for
human good, they remain one of the most poorly
understood photosynthetic types and little scientific
research or breeding has been done to enhance the
productivity of CAM crops. Our goal is to develop and
exploit genomic resources for CAM species. In
particular, we are using second-generation high
throughput DNA sequencing to decode the
transcriptomes and genomes of CAM species as a basis
for discovering all of the genes required for efficient
CAM. We focus on genes involved in the optimisation of
the biochemical steps of CAM over the light dark cycle,
particularly on components of the circadian clock
signalling pathway linking CAM biochemistry to the
central molecular circadian clock. This talk will present
an overview of our recent progress in understanding the
functional genomics of CAM in our chosen biofuels
feedstock crop, Agave sisalana.
Functional genomics of CAM in the monocot biofuel
feedstock crop Agave sisalana
Boxall, SF1, Waller, JL1, Gregory, R1, Hall, N1,
Hartwell, J1
1
Dept of Plant Sciences, Institute of Integrative Biology,
University of Liverpool, Liverpool, UK
Climate change predictions based on a variety of models
suggest that the land area covered by arid and semi-arid
regions will expand this century as the climate warms
and extreme weather events become more frequent.
Furthermore, there is a growing realisation that the
human population will grow to 9 billion by 2050 and that
the yield of the world's major food crops has reached a
plateau. There are thus grave concerns about the ability
of the world's farmers to generate sufficient food to
sustain the predicted population. At the same time,
concerns that global warming is being driven by CO2
released by the burning of fossil fuels are driving a push
to develop sustainable, carbon-neutral liquid biofuels
from crop biomass. Current biofuels largely rely on food
114
Sym046: Using molecular genetics and
bioinformatics to elucidate cell wall proteins
and their biosynthesis – 28 July
cis-Golgi localization mechanism of type 2 prolyl 4hydroxylases; targeting domain and possible partner
Matsuoka, K1,2, Moriguchi, R1, Ohsawa, Y2, Suyama, A1
1
Laboratory of Plant Nutrition, Faculty of Agriculture,
Kyushu University, Fukuoka, Japan; 2RIKEN Plant
Science Center, Yokohama, Japan
Peptidyl prolyl 4-oxigenase, which is also called prolyl
4-hydroxylase (P4H), catalyzes the formation of
hydroxyproline residues in proteins. Two classes of
P4Hs, type1 P4H that contain N-terminal signal anchor
and type 2 P4H that contain both N-terminal signal
peptide and C-terminal toxin homology domain (tox1
domain) has been found in plants. We cloned two full-
length cDNAs for type 2 P4H (NtP4H2.1, NtP4H2.2)
from tobacco and analyzed the encoded proteins. Cell
fractionation study using NtP4H2.2-specific antibody
and the GFP fusion study indicated that NtP4H2.2 is
localized predominantly in the cis-Golgi. Biochemical
analysis revealed that NtP4H2.2 is a peripheral
membrane protein tightly associated to the luminal side
of microsoms. Expression of GFP-tox1 domain into the
luminal part of the secretory pathway directed the GFP to
cis-Golgi in both tobacco BY-2 cells and Arabidopsis
leaf epidermal cells. Membrane fractionation analysis
and brefeldin A treatment of tobacco cells expressing
GFP-tox1 also demonstrated that tox1 domain directs
GFP to the cis-Golgi. In addition, membrane association
of GFP was enhanced by the fusion with tox1 domain.
Tox1 domains from both Arabidopsis and rice also
directed GFP to the cis-Golgi in tobacco BY-2 cells.
These results indicate that tox1 domain is a novel cisGolgi targeting domain and its function is conserved in
higher plants. In a separate experiment we searched
interacting partner of NtP4H2.2 to address the
localization mechanisms of this protein. Cross-linking
experiment allowed us to identify a couple of possible
partners. One of them corresponds to a tobacco ortholog
of proteins that are involved in GPI-anchor remodeling.
This protein is of particular interest as many of the
precursors to arabinogalactan protein contain GPIanchor. The tobacco cDNA for this protein was cloned
and the characterization of this protein is under way. We
observed that expression of this protein in yeast mutant
complemented the phenotype and HA-tagged this protein
in tobacco BY-2 cells was predominantly localized to the
cis-Golgi. These observations raise a possibility that
proline hydroxylation and subsequent glycosylation are
somehow coupled with the remodeling of GPI-anchor
during the biosynthesis of arabinogalactan proteins. This
work was supported by a grant from Ministry of
Economy, Trade and Industry, Japan. We thank Drs.
Yoshifumi Jigami and Takehiko Yoko-o in National
Institute of Advanced Industrial Sciences and
Technology for yeast strains and expression vectors.
Identification
and
characterization
of
fucosyltransferases
and
galactosyltransferases
involved in the biosynthesis of arabinogalactanproteins
Showalter, A1, Wu, Y1, Williams, M1, Liang, Y1,
Kieliszewski, M2, Faik, A1
1
Ohio University, Dept of Environmental & Plant
Biology, Molecular and Cellular Biology Program,
Athens, USA; 2Ohio University, Dept of Chemistry and
Biochemistry, Molecular and Cellular Biology Program,
Athens, USA
Arabinogalactan-proteins (AGPs) are highly glycosylated
hydroxyproline-rich glycoproteins (HRGPs) located at
the cell surface and function in various aspects of plant
growth and development. Arabinogalactan (AG)
polysaccharides are attached to hydroxyproline (Hyp)
residues in the protein backbone via a Hyp-Gal linkage
and contain arabinose, galactose (Gal), rhamnose,
glucuronic acid, galacturonic acid, and occasionally
fucose (Fuc). Each protein backbone is decorated with
numerous AG polysaccharides which are likely added in
the endoplasmic reticulum and Golgi by specific
glycosyltransferases. This presentation reports on two
non-redundant Arabidopsis fucosyltransferases, FUT4
and FUT6, which add Fuc to AG polysaccharides and on
the isolation and characterization of AGP-specific
galactosyltransferase (GalT) activities. Multiple lines of
evidence indicate that the AtFUT4 and AtFUT6 genes,
members of the glycosyltransferase 37 family, encode
alpha (1,2)fucosyltransferases (FUTs) for AGPs. First,
overexpression of the two genes in tobacco BY2 cells,
known to contain nonfucosylated AGPs, resulted in a
staining of transgenic cells with eel lectin, which
specifically binds to terminal alpha-linked fucose.
Second, monosaccharide analysis by high pH anion
exchange chromatography and mass spectrometry
indicated the presence of Fuc in AGPs from transgenic
cell lines but not in AGPs from wild type cells. Third,
detergent extracts from microsomal membranes prepared
from transgenic lines were able to fucosylate purified
AGPs from BY2 wild type cells. Susceptibility of
[14C]fucosylated AGPs to alpha (1,2)fucosidase, and not
to alpha (1,3/4)fucosidase, indicated that an alpha (1,2)
linkage is formed. Furthermore, dearabinosylated AGPs
were not substrate acceptors for these enzymes,
indicating that arabinosyl residues represent fucosylation
sites on these molecules. Testing of several
polysaccharides, oligosaccharides, and glycoproteins as
potential substrate acceptors in the fucosyl transfer
reactions indicated that the two enzymes are specific for
AGPs but are not functionally redundant because they
differentially fucosylate certain AGPs. AtFUT4 and
AtFUT6 are the first enzymes to be characterized for
AGP glycosylation. In addition, AGP GalT activities in
tobacco and Arabidopsis microsomal membranes were
studied with an in vitro GalT reaction system, which
utilized acceptor substrates composed of [AO] repetitive
units, specifically, a chemically synthesized [AO]7
acceptor and a transgenically produced and
deglycosylated d[AO]51 acceptor. Incorporation of
[14C]Gal from UDP-[14C]Gal into the [AO]7 and
d[AO]51 acceptors was observed following HPLC
fractionation of the reaction products. Hyp-[14C]Gal
monosaccharide and Hyp-[14C]Gal disaccharide were
identified in the base hydrolysates of the GalT reaction
products, indicating the presence of two distinct GalT
activities for the addition of the first and second Gal
residues to the [AO] peptide. Examination of the
Arabidopsis Hyp:GalT activity using various acceptor
substrates, including two extensin sequences containing
SO4 modules and a [AP]7 peptide, indicated this activity
was specific for peptidyl Hyp in AGP sequences. Mass
spectrometry analysis demonstrated that only one Gal
was added per peptide molecule to the C-terminal or
pentultimate Hyp residue of the [AO]7 peptide. In
addition, [AO]7:GalT and d[AO]51:GalT activities were
localized to the endomembrane system of Arabidopsis
suspension cultured cells following sucrose density
gradient centrifugation. This in vitro GalT assay provides
a useful tool for the identification and verification of
AGP-specific GalT proteins/genes.
Enzymes of CAZy GT-family-31: towards unravelling
the function(s) of the candidate glycosyltransferase
family members in Arabidopsis thaliana
Egelund, J1, Ellis, M2, Doblin, M2, Fangel, JU1, Schultz,
C3, Willats, WGT1, Bacic, A2
115
1
University of Copenhagen, Faculty of Life Sciences,
Section for Plant Glycobiology, Denmark; 2Plant Cell
Biology Research Centre, School of Botany, The
University of Melbourne, Australia;
3
School of Agriculture, Food and Wine, The University of
Adelaide, Glen Osmond, Australia
Arabinogalactan-proteins (AGPs) are highly glycosylated
macromolecules
usually
comprising
90-98%
carbohydrate and 2-10% protein. They belong to a large
family of plant cell wall (CW) glycoproteins, the
hydroxyproline-rich glycoproteins (HRGPs), that are
ubiquitous throughout the plant kingdom. AGP
backbones are typically rich in hydroxyproline (Hyp),
which are usually substituted by type II ArabinoGalactan
(AG) chains. AGP protein backbones are extensively
modified in the endoplasmic reticulum/Golgi apparatus
prior to secretion to the cell surface. This includes Oglycosylation by GTs (i.e. the addition of type II AG
chains),
and
the
addition
of
a
glycosylphosphatidylinositol (GPI) anchor, that enables
the attachment of AGPs to the plasma membrane. In
addition to the important roles in plant growth and
development, AGPs have numerous applications as
functional food ingredients and are increasingly
recognized as having health benefits. However, the
biosynthetic machinery involved in the synthesis of the
glycan component of AGPs is poorly understood. We
will present an overview of the Arabidopsis thaliana
members of CAZy GT-family-31 using our recent
research as a working paradigm (Egelund et al., 2011;
Ellis et al., 2010; Qu et al., 2008). In addition, we will
reveal the latest biochemical analysis of some of these
putative galactosyltransferase (GalT) candidate genes
responsible for synthesizing the beta(1,3)-Gal linkages of
the type II AG chains.– a step in revealing the catalytic
specificity of the Arabidopsis thaliana members of
CAZy GT-family-31.
Mutants with altered O-glycosylation levels of the cell
wall protein extensin reveal a role in lateral root
development
Gille, S1, Roycewicz, P2, Malamy, J2, Pauley, M1
1
University of California, Berkeley, Plant and Microbial
Biology Dept, Berkeley, CA, USA; 2The University of
Chicago, Molecular Genetics and Cell Biology, Chicago,
IL, USA
Plant cells are encased in a cell wall that plays multiple
roles in the life cycle of a plant including the
maintenance of structural integrity and a conduit for
environment to cell signals. Cell walls consist of various
polymer networks mainly polysaccharides (cellulose,
various hemicelluloses, and pectins) and the polyphenol
lignin, but also a glycoprotein network. One major
component of this proteinaceous network is extensin, a
protein containing a large abundance of hydroxyprolineresidues, which are O-glycosylated with arabinosyl- and
to a lesser extend galcatosyl-residues. Proper
glycosylation of extensin has been shown to be important
for its conformation and polymerization capability, but
the physiological role of extensin glycosylation remained
elusive. In a forward genetic screen we have identified an
Arabidopsis mutant with a lack of a transcript encoding
XEG113, a CAZy family 77 glycosyltransferase protein.
116
Analysis of the cell wall of the mutant revealed a severe
reduction in extensin glycosylation suggesting that
XEG113 represents an extensin:arabinosyltransferase. As
a result of extensin underglycosylation mutant plants
have a larger appearance and elongated hypocotyls. In
addition, under certain conditions lateral roots appeare in
the mutants, while wildtype plants lack those. We
hypothesize that underglycosylation of extensins lead to
a disruption of the wall glycoprotein network, which in
turn facilitates the emergence of the lateral roots through
the root cortex tissue. Moreover, we identified a knockout mutant of a close homolog, XEG113-like.
Characterization of this mutant and the double mutant
XEG113/ XEG113-like suggests that XEG113-like also
represents an arabinosyltransferase and acts additive to
XEG113. The physiological role of XEG113-like is
currently investigated and will be discussed including its
synergies with XEG113.
Identification of a novel glycosyltranseferase gene
family in plants
Shimma, Y-I1, Saito, F1, Suyama, A2, Oka, T3, Yoko-o,
T1, Matsuoka, K2, Jigami, Y1
1
Research Center for Medical Glycoscience, National
Institute of Advanced Industrial Science and Technology
(AIST), AIST Tsukuba Central 6, Tsukuba, Japan;
2
Laboratory of Plant Nutrition, Faculty of Agriculture,
Kyushu University, Fukuoka, Japan; 3Dept of Applied
Microbial Technology, Sojo University, Kumamoto,
Japan
Plant glycoproteins such as extensin and arabinogalactan
proteins are modified with plant specific O-linked
galactosylation on serine and hydroxyproline (Hyp)
residues. An assay system for peptidyl serine Ogalactosyltransferase (SGT) activity was established,
using UDP-galactose as a donor, and chemically
synthesized peptides of extensin-like amino acid
sequences as an acceptor. The neighboring Hyp residues
adjacent to serine in the acceptor peptide were required
for SGT activity. SGT protein was purified from cell
extracts of C. reinhardtii, and subjected to Mascot
analysis of proteins to determine the amino acid
sequences by mass spectrometry. The analyzed peptide
sequences were completely matched with an ORF in the
C. reinhardtii genome database. A corresponding DNA
fragment was cloned from C. reinhardtii cDNA library.
The SGT activity was confirmed through the cell surface
expression system in yeast Saccharomyces cerevisiae,
therefore, designated as CrSGT1. Highly homologous
ORFs were found in various plant genomes, such as
Arabidopsis thaliana, Nicotiana tabacum, Oryza sativa,
etc. The AtSGT1 and NtSGT1 also showed SGT activity
when expressed in yeasts. The SGT proteins contained a
conserved DXD motif and showed a type I membrane
topology,
but
no
homology
with
known
glycosyltransferases, indicating that SGT1 is a novel
glycosyltransferase gene family, existing only in plant
kingdom.
Complexity and coordination of root growth under
water deficit: recent advances from transcriptomic
and cell wall proteomic analyses
Sharp, RE1, Voothuluru, P1, Yamaguchi, M1, Zhu, J1,
Byro-Jilek, M2, Garnett, JS1, Cho, I-J3, Oliver, MJ3,
Bunzel, M2, Simmonds, J4, Wu, Y5
1
University of Missouri, Columbia, USA; 2University of
Minnesota, St Paul, USA; 3USDA-ARS, Columbia,
Missouri, USA; 4Agriculture and Agri-Food Canada,
Ottawa, Canada; 5South Dakota State University,
Brookings, USA
Previous work on maize primary root adaptation to water
deficit showed that the response of cell elongation varies
at different positions within the growth zone. In the
apical 3 mm (region 1), elongation is maintained at wellwatered rates even under severe stress (water potential of
-1.6 MPa), whereas in the 3–7 mm region (region 2),
which exhibits maximum elongation in well-watered
roots, elongation is progressively inhibited in stressed
roots. In association with these responses, cell wall
extensibility is enhanced in the apical region but
decreased in the basal region. This presentation will
focus on recent advances in understanding of these
responses from transcriptomic and cell wall proteomic
analyses. Cell wall proteomic analysis (Zhu et al. 2007)
revealed region-specific changes in protein profiles
between well-watered and water-stressed roots. In
particular, several proteins related to reactive oxygen
species (ROS) generation increased in abundance
particularly in region 1, prominent among them being
putative oxalate oxidases (OxO), which produce
hydrogen peroxide. To investigate the role of
OxO/apoplastic ROS in root elongation, we have
characterized transgenic maize lines constitutively
expressing a wheat OxO gene. Results show that OxO
activity is increased in a region-specific manner with
different profiles in well-watered and water-stressed
roots, and that these changes are associated with
differential effects on growth and growth-related
processes. Interestingly, the results indicate that cell
production rather than cell expansion processes are
altered in the OxO transgenic lines. Previous work
showed that in both regions 1 and 2, the activity of wallloosening expansin proteins is enhanced in water-stressed
compared with well-watered roots. In region 1, the wall
susceptibility to expansins is also increased, whereas in
region 2, expansin-induced wall extension is inhibited.
Ferulates are abundant in the cell walls of
monocotyledonous plants and have a role in cross-linking
wall polysaccharides and other components. Microarray
analysis suggested that differential regulation of ferulate
metabolism between the apical and basal regions of the
root growth zone could contribute to the different
changes in wall extensibility and expansin susceptibility
under water stress. To test this hypothesis, the spatial
distribution of wall-bound ferulates was determined by
histochemical and HPLC analyses. The results show that
ferulate content decreases and increases, respectively, in
regions 1 and 2 of water-stressed compared with wellwatered roots. To evaluate whether the accumulation of
ferulates in region 2 prohibits the ability of expansins to
extend the cell walls, root segments were treated with
feruloyl esterase (FE), which can release ferulates from a
range of esterified substrates. An extensometer system
was used to show that FE treatment completely restores
expansin-induced wall extension in region 2 of waterstressed roots, while having a minimal effect in the same
region of well-watered roots. These studies provide novel
insights into the complexity and coordination of root
growth regulation and adaptation under water deficit
conditions. This research was supported in part by a grant
to R.E.S. from Monsanto.
Sym048: Bio-ontologies for plant science –
28 July
The Plant Ontology: an updated tool for all plant
biologists
Walls, RL1, Cooper, L2, Elser, J2, Gandolfo, MA3,
Mungall, C4, Justin, P2, Smith, B5, Stevenson, DW1,
Jaiswal, P2
1
New York Botanical Garden, USA; 2Oregon State
University, USA; 3Cornell University, USA; 4Lawrence
Berkeley National Lab, USA; 5University at Buffalo, USA
The Plant Ontology (PO: http://plantontology.org) is a
structured vocabulary and database resource for plant
researchers that links plant anatomy and development to
the rapidly expanding field of genomics in the domain of
all green plants. The PO contains interrelated concepts or
terms, organized in a hierarchical tree, that describe plant
anatomy and morphology, as well as plant growth and
development stages. Like all ontologies, the PO
facilitates data sharing and automated analyses through
the consistent use of vocabulary with explicit, logical
definitions and defined relationships among terms.
Originally designed to span the monocot-dicot divide in
flowering plants (based on the model angiosperms Zea
mays, Oryza sativa, and Arabidopsis thaliana), the PO
has been redesigned to encompass all angiosperm species
and to include terms and annotations from non-flowering
plants such as gymnosperms, pteridophytes, and
bryophytes. This is the first ontology designed to
encompass anatomical structures as well as growth and
developmental stages across such a broad taxonomic
range. Over the past 18 months, upper level parent terms
have been added, renamed, or revised to ensure
applicability to the entire plant kingdom, allowing
comparative studies across distantly related taxa. At the
same time, many new clade-specific terms have been
introduced at lower levels, allowing precise annotation of
genomic and genetic datasets for individual species.
Throughout the revision process, curators worked to
incorporate advances in ontology design and
construction. These included the use of logical text and
relational definitions and references to external
ontologies where appropriate. An essential, powerful
feature of the PO is the links through terms to associated
structure or growth stage specific genes, proteins, and
phenotypes from numerous genomics datasets. One of
the main goals of the PO is to facilitate cross-database
querying and to foster consistent use of vocabularies in
annotation. To this end, the PO is developing annotation
tools for the plant science community. Outreach activities
include annotation workshops and outreach booths and
symposia at international conferences. Currently, the PO
includes over 500,000 annotations associated with over
117
1,100 terms. In this capacity, it is widely applicable to
plant genomic and evolutionary developmental studies.
In addition, image libraries are being created through
PlantSystematics.org and linked to terms to provide
reference images for plant structures, along with the
definitions. This makes the PO a valuable resource for
research and teaching that can be used as a guide to plant
structures and the common growth and developmental
landmarks in lifecycles of plants across taxa. This
presentation will provide an overview of the Plant
Ontology and the annotation database, as well as
potential applications of the PO. The PO is publicly
available and collaboration with diverse user groups is
encouraged. Information will be available for research
groups that wish to provide annotations or use the PO in
novel applications.
Unraveling Darwin’s ‘abominable mystery’: using
phylogenomics to identify proteins of importance in
plant evolution
Cibrian, A1, Martienssen, R2, Stevenson, D3, Coruzzi,
G4, Desalle, R5
1
Center for Genomics and Systems Biology, New York
University, USA; 2Cold Spring Harbor Laboratory, USA;
3
The New York Botanical Garden, USA; 4Center for
Genomics and Systems Biology, New York University,
USA; 5American Museum of Natural History, USA
Darwin was famously concerned that the sudden
appearance and rapid diversification of flowering plants
in the mid-Cretaceous could not have occurred by
gradual change. Here I present a phylogeny among the
major seed plant groups, i.e. cycads, ginkgo, conifers,
gnetophytes, and flowering plants based on complete
genomes and unigenes from 150 plant species. This is the
largest plant phylogenomic matrix to date. I provide a
bioinformatic pipeline in which these phylogenetic
relationships can be used as a platform for identifying
genes of functional importance in plant diversification.
Genes with positive partitioned Bremer support at major
nodes were used to identify overrepresented gene
ontology (GO) terms. This is a novel method in which
phylogenomic tools are used to postulate hypotheses of
gene function in the evolution of major taxa. Although I
focus on plants, it can be applied to any group of species
with ESTs or genomes available. We provide support for
one of the long-standing, most controversial hypothesis
of gymnosperm evolution. We also found that genes
involved in PTGS (post-transcriptional gene silencing)
provide support for the divergence of the monocots in
early angiosperm evolution. One of these genes, RNAdependent RNA polymerase 6, is required for the
biogenesis of trans-acting small interfering RNA
(tasiRNA), confers heteroblasty and organ polarity, and
restricts maternal specification of the germline.
Functional hypotheses such as the role of these genes for
plant diversification can be further coupled with
expression and genetic data but their phylogenetic
importance is identified with our approach first. This can
lead to better gene searches, annotations, and functional
analysis of genome level studies. This phylogenomic
approach and those genes identified here guide plant
ecological genomics studies and help understand the
precise
evolutionary
mechanisms
driving
the
118
diversification of plant species, gradually unraveling
Darwin’s abiding and perplexing mystery.
Investigating trait ontologies to facilitate integrating
phenotype and genome sequence level information in
wheat
Appels, R1
1
Centre for Comparative Genomics, Murdoch University,
Perth, WA, Australia
Commercially important crops such as wheat (Triticum
aestivum L.) have an extensive history of data collection,
relating phenotype to genetic information. The catalogue
of
gene
symbols
for
wheat
(http://www.shigen.nig.ac.jp/wheat/komugi/genes/symbo
lClassList.jsp, edited by R.A. McIntosh), provides a
well- (meaning manually) curated assessment of the
genetic studies carried out to map traits of interest to
genetic maps. These traits are assigned symbols, and an
example of an entry is: Pre-harvest sprouting QTL:
Several QTL for falling number and alpha-amylase
activity, two indicators for pre-harvest sprouting
resistance, were identified in {0169}. The most
significant were associated with Xglk699-2A and
Xsfr4(NBS)-2A,
Xglk80-3A
and
Xpsr1054-3A,
Xpsr1194-5A and Xpsr918-5A, Xpsr644-5A and
Xpsr945-5A, Xpsr8(Cxp3)-6A and Xpsr563-6A, and
Xpsr350-7B and Xbzh232(Tha)-7B {0169}. Typically, a
trait such as pre-harvest sprouting will have several
synonyms, such as sprouting index (QSi.crc-5D),
dormancy (Q.SD1), or pre-harvest sprouting (Qphs.ocs3A.2), which need to be captured for an effective
analysis of published information. In order to crossreference
genome
sequence
information
to
trait/phenotype studies, the available information in
wheat is now cross-referenced to detailed consensus
molecular
genetic
maps
(http://ccg.murdoch.edu.au/cmap/ccg-live/cgibin/cmap/viewer) in the CMap software utilized by
GRAMENE
(http://www.gramene.org/). In this
presentation, the experience of developing trait
ontologies for wheat, using the information established
for rice, will be discussed in the context of relating the
CMap-based information that locates published QTL for
traits to the genome sequence of wheat. The sequence of
a complex genome such as wheat has been challenging to
develop, but several new technologies are now
converging to establish draft sequence-level definitions
of the gene-space.
The past, present and future: ontologies for plant
biology
Jaiswal, P1, Cooper, L1, Elser, J1
1
Oregon State University, USA
As a result of current developments in sequencing
technology, the number of sequenced plant genomes is
rapidly increasing. Along with the deluge of information
on nucleotide and amino acid sequences from a
genetically diverse set of species, large quantities of data
are also being generated on genes, alleles, their
polymorphism, protein functions, transcriptome,
proteome and metabolomics experiments, mutants and
their phenotypes, metabolic and regulatory interaction
networks, and literature references. In the midst of this
influx of data, we also realize that few species are being
studied in sufficient detail to understand how plants
develop, adapt, and diversify. Therefore, experimental
annotations generated for a set of well-studied species are
being increasingly used to project annotations for lesserstudied species. This demands that the annotations from
the well-studied species be generated meeting current
genomics/genetics standards and remain up to date all the
times. It is, however, time-consuming and laborious for
individual researchers to collect information from
multiple original data sets and to rearrange it for their
own purposes. The concept of ontology has been
introduced to biology to support and encourage
researchers to share and reuse information among
biological databases to foster consistency and use of
common vocabulary. Ontology is a kind of glossary that
has a built-in hierarchical structure, logical definitions,
and relationships among concepts, and is used to define
biological processes, functions and environments from
the cellular to the organismal level. In the presentation, I
will introduce ontology-based annotation strategies being
adopted by the new generation of plant genomics and
phenomics projects and their role in the discovery
environment.
PODD: an ontology driven architecture for extensible
phenomics data management
Kennedy, G1,2, Li, Y-F2, Davies, F2, Hunter, J1, Furbank,
B1
1
The Australian Plant Phenomics Facility, High
Resolution Plant Phenomics Centre, CSIRO, Canberra,
Australia; 2School of ITEE, The University of
Queensland, Brisbane, Australia
Ontologies have found increasing favour in the plant
sciences because they can deliver a set of terminologies
and understandings about biological concepts that are
agreed between researchers. Typically ontologies are
used to annotate data on the web, but the notion of a
common vocabulary with formally defined semantics
makes ontologies the vehicles for representing data and
knowledge in the Semantic Web. Ontologies provide
unambiguous classifiers and descriptors that are made
available in a format other computers can autonomously
discover and interrogate, and thus may be linked across
disparate databases and repositories. In the Phenomics
Ontology Driven Data repository (PODD) we have taken
the notion of classification of experimental concepts
using ontologies one step further by using an ontology,
the PODD ontology, as the schema of our data
management system. We utilise the Semantic Web
ontology languages OWL and RDFS to do this because
they provide the extensibility and the semantic rigour
required. In this ontology-driven architecture the
behaviours of domain concepts and objects are captured
entirely by ontological entities, around which all data
management tasks are carried out. An ideal domain for
applying these principles is plant phenomics, the
systematic study of the phenotypes of model and crop
plants that are a consequence of the individual plant's
genome and environment. Phenomics research generates
high volumes of heterogeneous data through the use of
emerging imaging and measurement technologies and
processes. This data is combined with metadata to form
complex digital objects and then further associated with
provenance metadata on the experimental process. In this
context, we describe the development of a phenomics
experimental process ontology, and how we have applied
the principles of ontology-driven architecture in the
development of PODD, a data management system for
phenomics based research. Keywords: Phenomics,
Semantic Web, Ontologies, OWL, data management,
PODD
Predicted protein–protein interactions in the moss
Physcomitrella patens: a new bioinformatic resource
Schuette, S1, Corley, A1, Lang, D2, Geisler, M1
1
Dept of Plant Biology, Southern Illinois University,
Carbondale IL, USA; 2Plant Biotechnology, University of
Freiburg, Freiburg, Germany
Physcomitrella patens, the model moss for plant biology,
has a protein-coding genome similar in size to
Arabidopsis, but is similar to yeast in efficiency of gene
targeting experiments and has a haploid dominant form
making an interesting and useful molecular genetic tool
for plants. The availability of the moss genome has made
possible the exploration of plant diversity at the
molecular level. The model moss is fast becoming a tool
for bioinformatic and molecular work due to its key
phylogenetic position as sister to land plant lineages. We
present here the first predicted protein-protein PPI for a
bryophyte based on the interolog method. Whole genome
sequences from reference species including yeast,
nematode worm, fruitfly, mouse, rat, human, bacteria and
Arabidopsis were compared to the genome of
Physcomitrella patens in a pairwise fashion using
reciprocal blasts to separate inparalogs from orthologs
and outparalogs with INPARANOID software package.
A reference interaction database was assembled using
MySQL by compiling BioGrid, BIND, DIP, and Intact
databases. The reference database was queried for which
moss orthologs existed for both interacting partners. We
predicted more than 60 000 total interactions from
different predicting references including 41,936 unique
interactions from 4062 different P. patens proteins that
were visualized in Cytoscape, a Java-based software
package. The twenty most interactive proteins represent
strongly conserved pathways that have not altered
significantly during eukaryotic evolution. Analysis of
gene ontology revealed the most significant categories
represented include metabolic processes, intracellular and
cytoplasmic likely due to their conserved nature, and
protein binding due to physical interaction requirement
for inclusion, and catalytic activities. The utility of
predicted interactomes lies in the 'guilt-by-association'
model of predicting proteins in a pathway under the
assumption that orthologous proteins have similar
functions. For example, we constructed a Calvin Cycle
network to determine the number of proteins associated
with this all-important process and discovered an
uncharacterized protein with phosphoglycerate kinase
activity that interacts directly with NADP-ME, an
enzyme involved in C4 photosynthesis. The addition of
moss, a plant representative 200 million years diverged
from Arabidopsis, to interactomic research greatly
expands the possibility of conducting comparative
analyses thus giving tremendous insight into network
119
evolution
of
land
plants.
Sym123: The role of heritable epigenetic
variation in plant evolution – 29 July
Exploring natural epigenetic variation and its
implications for plant evolution
Paun, O1, Stuessy, TF1, Chase, MW2
1
Dept of Systematics and Evolutionary Botany,
University of Vienna, Austria; 2Jodrell Laboratory,
Royal Botanic Gardens Kew, UK
Without altering the underlying DNA sequence,
epigenetic information influences the identity of cells and
their response to the external and internal environment by
modulating gene expression and regulating repetitive
elements. Epigenetic changes can be transient, being
reset between generations. However, several spontaneous
or induced epigenetic variants were shown to be stably
inherited across multiple generations. Our laboratorybased mechanistic understanding of epigenetics in model
organisms is expanding rapidly. These exciting new
findings indicate that divergent epialleles influence
phenotypic features and have the potential to affect
adaptation and divergence, even in the absence of genetic
variability. We have now the first evidence that natural
selection acts on epigenetic variation in a similar way as
on genetic components and results in novel adaptations.
Epialleles, like random genetic mutations, can alter
development and metabolism and therefore have
evolutionary implications. However, epigenetic variation
is often under direct environmental influence and may be
generated at a much higher rate than genetic diversity,
especially in rapidly changing environmental conditions.
Different degrees of epigenetic silencing or activation
can further produce continuous variation in phenotypes
rather than discrete phenotypic classes. Environmentally
stimulated disruption of epigenetic control may also
simultaneously induce several new epimutations in the
same individual, in marked contrast with random
spontaneous genetic changes. The tools necessary for
epigenetic investigations are already available even for
non-model organisms, but so far they have been
insufficiently explored to study this level of natural
variation. In order to improve the general understanding
of natural phenotypic variation and organismic adaptive
strategies, we need to complement the gene- and
genome-centered view, currently dominating our
evolutionary perspective about variability, heritability
and adaptation, with a substantial consideration of
epigenetic factors.
Trans-generational inheritance in flax – association
with genomic re-arrangements and small RNAs
Cullis, C1, Johnson, C1, Moss, T1
1
Case Western Reserve University,USA
Flax (Linum usitatissimum) can undergo heritable
changes in phenotype and genotype in response to the
growth environment. These changes can be stable over
many generations or be reversible following alterations
120
in the growth environment in subsequent generations.
The responses have the characteristics of epigenetic
modifications. They are also associated with reversible
genomic reorganization events including the novel
insertion event, named LIS-1, which can arise in flax in
response to particular growth conditions. LIS-1 was
observed to always become both homozygous and
inherited in subsequent generations under a particular
growth environment, sporadically appeared but was
never transmitted to the progeny under another growth
environment, while has not been observed either during
growth or in the next generation under a third growth
environment. In some flax varieties that did not produce
stable genotrophs, LIS-1 was subsequently lost unless the
appropriate growth environment was maintained. Thus
appearance and subsequent inheritance of LIS-1 is
specific to particular growth environments and is not part
of the normal developmental program of flax. Stable
lines (genotrophs) resulting from the initial growth under
each of these conditions appear to grow better when
grown under the same conditions in subsequent
generations suggesting that adaptive changes have taken
place. The ability of flax to respond to the environmental
conditions (as assayed by the appearance of LIS-1) is
genetically controlled. The loci controlling the ability to
respond to the growth environment have been mapped in
F2 populations of crosses between responsive and stable
lines. and candidate genes being identified.
Responsiveness is dominant over stability. LIS-1 is the
result of a precise programmed set of events in response
to the growth environment although its origins remain
unclear. The element is not present in an intact form in
responsive lines prior to its appearance. However,
primers spanning putative small RNA encoding segments
within LIS-1 can be used to amplify, from DNA isolated
from varieties lacking LIS-1, stretches of sequences
similar to, and sometimes identical to, the final LIS-1
element. One possible analogy to this novel molecular
restructuring process in flax is the series of molecular
events that accompany the ciliate macronuclear
development which are facilitated by guiding by micro
RNAs. Although it is accepted that small RNAs are
capable of causing epigenetic regulation of genes through
modulation of chromatin, this system in flax offers the
opportunity to determine the involvement of small RNAs
in reversible, physical genomic rearrangements induced
by environmental stress that may also affect gene
expression and possible adaptation. The specificity of the
appearance and subsequent inheritance of LIS-1 and
associated phenotypes to particular growth environments
demonstrates that the environment can act as both the
inducer of targeted genetic variation and as the selective
agent for advantageous mutations. The evolutionary
implications of this mechanism for any organism in
which the germline is not set aside very early in
development is that a selectable, coordinated set of
variations can arise under particular environmental
stresses resulting rapid adaptive evolutionary responses.
Epigenetic and genetic variation in imprinted genes
between Arabidopsis thaliana and Arabidopsis lyrata
Fujimoto, R1, Sasaki, T2, Dennis, E1
1
CSIRO Plant Industry, Canberra, Australia; 2Gregor
Mendel Institute of Molecular Plant Biology, Vienna,
Austria
DNA methylation is one of the epigenetic marks
associated with transposable element silencing and parent
of origin-specific gene expression (imprinting) in plants
and mammals. In plants, imprinted gene expression
occurs in the endosperm by cytosine demethylation of the
maternal genome mediated by the DNA demethylase
DEMETER. In Arabidopsis thaliana, imprinted genes
often contain invading sequences such as transposons in
their flanking regions, and it has been suggested that
imprinting evolved from targeted methylation of
transposable element. FWA gene is an imprinted genes
and silencing of FWA in vegetative tissues is dependent
on cytosine methylation in the region of a SINE
retroelement. We examined the critical region for DNA
methylation in both A. thaliana and A. lyrata using
double stranded RNA to direct DNA methylation to
target regions. DNA methylation in the region upstream
from the transcription start site plays a role in FWA
silencing in both species, while DNA methylation in the
region downstream from the transcription start site is
important for the FWA silencing only in A. thaliana.
Large tandem repeats are present in this region including
the transcription start site only in A. thaliana. These
results indicate that the acquisition of the large tandem
repeats enlarged the critical methylated region in A.
thaliana. We also examined DNA methylation of the
promoter region of other genes in A. lyrata which are
imprinted in A. thaliana. We found both conservation
and variation of the methylated regions of these genes
between A. lyrata and A. thaliana.
Chromatin in signaling of plant development and
response to environmental stress
Dong, A1, Zhu, Y1, Yu, Y1, Berr, A1, Ménard, R1, Shen,
W-H1
1
State Key Laboratory of Genetic Engineering, Dept of
Biochemistry, Institute of Plant Biology, School of Life
Sciences, Fudan University, Shanghai, China; Institut de
Biologie Moléculaire des Plantes du CNRS, Université
de Strasbourg, France
Chromatin represents the physiological template of
genetic information in all eukaryotes. The basic unit of
chromatin is the nucleosome, which is composed of 146
base pairs of DNA wrapped around an octamer of two
molecules of each of the histones H2A, H2B, H3, and
H4. Nucleosome assembly/disassembly is mediated by
histone chaperones and occurs during DNA replication as
well as during gene transcription, DNA repair, and
recombination. Our work on Arabidopsis histone
chaperones has demonstrated that proper nucleosome
assembly is crucial for maintenance of genome integrity,
cell proliferation and plant response to genotoxic stresses
(1–3). Histone methylation is one type of the epigenetic
marks that play essential regulatory functions in
chromatin structure organization and genome function.
Our work on Arabidopsis SET-domain histonemethyltransferases has shown that histone H3 lysine 4
(H3K4) and H3K36 methylations are critical for
transcriptional activation of several key regulatory genes
involved in flowering time control or plant reproduction
(4–7). Remarkably, H3K36 methylation is also
dynamically involved in plant defense against fungal
pathogens (8). We found that the Arabidopsis PRC1-like
ring-finger proteins, which likely read the H3K27
trimethylation, are necessary for repression of embryonic
traits and for maintenance of proper stem cell activity
during plant vegetative growth (9, 10). We will present
and discuss our most recent progress in understanding of
nucleosome assembly and histone code as epigenetic
mechanisms in signaling of plant development and in
plant response to environmental cues. (1) Zhu et al. 2006.
(2) Liu et al. 2009. (3) Liu et al. 2009. (4) Zhao et al.
2005. (5) Xu et al. 2008. (6) Berr et al. 2009. (7) Berr et
al. 2010. (8) Berr et al. 2010. (9) Xu and Shen 2008. (10)
Chen et al. 2010.
Epigenetic regulation of pollinator syndromes
Baumberger, R1,2, Grossniklaus, U1
1
Institute of Plant Sciences & Zürich-Basel Plant Science
Center, University of Zürich, Zürich, Switzerland;
2
Pädagogische Hochschule Zürich, Zürich, Switzerland
Until recently, epigenetic variation was not thought to
play any significant role in evolution and most text books
on evolutionary biology lack any reference to epigenetic
processes. Indeed, many biologists have difficulties to
see how epigenetic variation could contribute to
evolutionary change, as exemplified by the statement:
‘… it is hard to see its [epigenetics] possible evolutionary
significance, …’ (1). Nevertheless, over the last few
years epigenetic research has taken centre stage and
several scientists have argued for a role of epigenetic
variation in evolution (2–4). A few years ago, we
proposed that apomixis, the asexual reproduction through
seeds, may have evolved through epigenetic changes
caused
by
inter-specific
hybridization
and
polyploidization (5, 6), but apomictic systems proved
difficult to study in this respect. Here, we present a new
model system that may allow us to analyze epigenetic
changes and their possible role in evolution at the genetic
and molecular level. We will provide evidence that
different taxa of Mimulus spp. with distinct pollinator
syndromes are in fact epigenetic variants. An insectpollinated plant with yellow flowers can change, over the
course of several years, into a plant with bird-pollinated,
red flowers. Moreover, this epigenetic state is heritable
and behaves like an epimutation. Since the acquired
epigenetic state affects the morphology, colour, and scent
of the flower and leads to reproductive isolation, it is
expected to have a strong effect on population structure
and eventually the evolutionary trajectory of this taxon.
(1) Wolpert L 1998. (2) Jablonka E, Lamb MJ 1995. (3)
Rapp RA, Wendel JF 2005. (4) Richards EJ 2006. (5)
Grossniklaus U et al. 1998. (6) Spillane C et al. U 2001.
Sym157: The genetic and genomic
consequences of polyploidy – 29 July
Genomic consequences
polyploidy in Senecio
of
hybridisation
and
Hegarty, M1, Barker, G2, Brennan, A3, Batstone, T2,
Abbott, R3, Edwards, K2, Hiscock, S2
1
2
Aberystwyth University, IBERS, Aberystwyth, UK;
University of Bristol, School of Biological Sciences,
121
Bristol, UK; 3University of St Andrews, School of
Biology, St Andrews, UK
Interspecific hybridisation (often involving a change in
ploidy) is an important mechanism by which speciation
can occur in plants. To better understand the impact of
merging two divergent genomes within a single hybrid
nucleus, we conducted a comparative transcriptomics
assay in the genus Senecio, which provides examples of
both diploid and allopolyploid hybrids formed within the
last 300 years. These hybrids are recognised as examples
of hybrid speciation, forming either in allopatry or
sympatry. Using a custom microarray platform, we
identified widespread non-additive changes to gene
expression in both types of hybrid, and demonstrated that
hybridisation and genome duplication have separate,
distinct effects on gene expression. Subsequent research
has focussed on investigating the epigenetic factors
underpinning these expression changes and has shown
that hybrids can display global modifications to DNA
methylation in a nonadditive manner similar to that
observed for gene expression. Allopolyploid Senecio
hybrids have also been demonstrated to display biased
expression of parental homoeologues. Current efforts are
focused on the development of a draft reference genome
for the diploid hybrid Senecio squalidus and the
application of comparative genomics techniques to
address outstanding questions about the consequences of
genomic mergers.
Genetic, karyotypic and genomic
Tragopogon allotetraploids
evolution
in
Soltis, DE1, Soltis, PS1, Buggs, RJA2, Viccini, LF3,
Chester, M1, Jordon-Thaden, IE1, Veruska Cruz da Silva
Muniz, A1, J. A. Tate4, Symonds, VV4, Wu W5,
Schnable, PS5, Chamala, S1, Davenport, R1, Barbazuk,
WB1
1
University of Florida, USA; 2Queen Mary University of
London, UK; 3Universidade Federal de Juiz de Fora,
Brazil; 4Massey University, New Zealand; 5Iowa State
University, USA
Understanding polyploid evolution is central to
understanding the origin and diversification of most
lineages of life, particularly flowering plants. However,
despite the prevalence and importance of polyploidy in
plants, most of what we know about the genetic and
genomic consequences of genome doubling is derived
from synthetic polyploids, crops, and model organisms
that are ancient polyploids (e.g., Arabidopsis). To
understand better how polyploidy shapes genome
evolution and gene function, we have been investigating
naturally occurring polyploids in the genus Tragopogon
(Asteraceae). Tragopogon provides two well-known
examples of recent allopolyploid speciation and a unique
opportunity to investigate the genetic and genomic
changes that occur across a continuum from F1 hybrids,
synthetic polyploids, and recently and recurrently formed
natural populations of allopolyploids (T. mirus and T.
miscellus, each of which formed fewer than 80 years ago;
i.e., 40 generations in these biennial plants). Also, this
system provides the unusual opportunity to determine
whether genome evolution follows a program and if
underlying 'rules' govern genomic interactions in
polyploids. We report patterns of extensive homeolog
122
loss, karyotypic variation, and shifts in gene expression
across populations of both allotetraploid species. Recent
advances in high-throughput sequencing technology
provide a rapid and cost-effective means of generating
sequence data. Given that Tragopogon is an excellent
natural model for polyploid evolution, and our ready
access to state-of-the-art sequencing technologies, we
have assembled a draft genome sequence of the diploid,
Tragopogon dubius, which will provide a foundation for
further analysis of the genetic and genomic consequences
of allopolyploidy in Tragopogon.
The impact of paleopolyploidy on network evolution
in the Brassicales
Edger, P1, Bekaert, M1, Conant, G1, Hudson, C1, Barker,
M2, Jiao, Y3, dePamphilis, C3, Schranz, E4, Pires, JC1
1
University of Missouri – Columbia, USA; 2University of
Arizona, USA; 3Penn State University, USA; 4University
of Amsterdam, The Netherlands
Ancient whole genome duplications (WGDs), inferred
from analyzed genomes and transcriptomes, are prevalent
and recurring throughout the evolutionary history of
higher eukaryotic lineages. The impact of these events on
gene networks (e.g. metabolic, regulatory, signaling, and
protein-protein interaction) remains unclear. Despite its
small size (157Mb), the Arabidopsis thaliana genome
shares the remnants of at least three ancient WGDs. We
have constructed a phylogenomic framework, which
includes having localized the two most recent WGD
events (At-α and At-β), to investigate patterns of
duplicate gene retention (i.e. gene family size evolution),
innovation of novel gene functions, and the origin of
novel pathways. In addition, we analyzed patterns of
surviving duplicates from both At-α and At-β across the
entire Arabidopsis metabolic network. These results has
provided insights into the selective constraints that retain
specific functional genes in duplicate post-WGD over
millions of years, which over longer time periods (once
constraints are lifted) may sub- or neo-functionalize.
Allopolyploid genome divergence is associated with
genome downsizing and elimination of paternally
derived repetitive DNA sequences in tobacco
Leitch, AR1, Renny-Byfield, S1, Chester, M0, Kovarík,
A3, Le Comber, SC1, Grandbastien, M-A4, Deloger, M4,
Nicholas, RA1, Macas, J5, Novak, P5, Chase, MW6
1
Queen Mary University of London, School of Biological
and Chemical Sciences, London, UK; 2Laboratory of
Molecular Systematics and Evolutionary Genetics,
Florida Museum of Natural History, University of
Florida, Gainesville, FL, USA; 3Institute of Biophysics,
Academy of Sciences of The Czech Republic, Brno, Czech
Republic; 4Institute Jean-Pierre Bourgin, INRAVersailles, France; 5Biology Centre ASCR, Institute of
Plant Molecular Biology, Czech Republic; 6Jodrell Lab,
Royal Botanic Gardens, Kew, Richmond, Surrey, UK
Angiosperm evolution is heavily impacted by polyploidy,
which has occurred in the ancestry of all, or most,
species. Interspecific hybridisation combined with
genome multiplication (allopolyploidy) provides a
natural experiment in genome perturbation. Genetic
changes, subsequent to polyploid formation, can be
inferred by studying the descendants of the two
progenitor species and the allopolyploid offspring. In
1984 McClintock first proposed that these changes might
be distinctive: that allopolyploidy can induce 'genomic
shock', which may produce rapid alteration at the DNA
sequence level in addition to significant structural,
transcriptional, epigenetic and karyotypic changes.
Moreover such dynamism has been observed to occur
extraordinarily rapidly in some model species, occurring
after only a few generations. This has led many to
envisage a 'genome revolution' where perturbation of
progenitor genomes is induced by their unification. To
investigate this phenomenon we used next generation
sequencing to characterise and compare the genomes of
the recently derived allotetraploid, Nicotiana tabacum
(tobacco, < 200,000 years old), with its diploid
progenitors, N. sylvestris and N. tomentosiformis. We
show that all major types of retroelements found in
angiosperms
are
present.
Sequence
similarity
comparisons and estimates of repetitive DNA abundance
all suggest that the three genomes have experienced
different evolutionary histories. The diploid N. sylvestris
genome exhibits evidence of recent bursts of sequence
amplification and/or homogenisation, whilst the genome
of N. tomentosiformis reveals only hints of such a
pattern. In contrast, the genome of tobacco shows
evidence of sequence loss, particularly evident among the
Ty3-gypsy retroelements, but also involving tandem
repeats and 35S ribosomal DNA. Moreover the
paternally (N. tomentosiformis) derived T-genome of
tobacco shows evidence of erosion, while the maternal
(N. sylvestris) S-genome appears materially unchanged,
indicating the possibility of preferential loss of paternally
derived repetitive DNAs. These observations together are
in-line with the genome downsizing and nuclear
cytoplasmic interaction hypotheses. In a broad sense, we
can consider the genomes of N. sylvestris, N.
tomentosiformis and N. tabacum to be dynamic, stable
and decaying, respectively.
Reconstruction of the chloroplast genome of Spartina
maritima, and molecular dating of the divergence
between the two genomes reunited in the recent
allopolyploid S. anglica
Bellott, S1,2, Ainouche, K1, Chelaifa, H1, Coudouel, S1,
Lima, O1, Naquin, D1, Ainouche, M1
1
Ecosystems, Biodiversity and Evolution, University of
Rennes, France; 2Systematic Botany and Mycology,
University of Munich (LMU), Germany
The genus Spartina (Poaceae, Chloridoideae) is an
important system for analyzing reticulate evolution and
recurrent polyploid speciation. Eight of the 14 species are
tetraploid (4x) and five are hexaploid (6x), among them
some give rise to further allopolyploids (7x, 8x, 9x, 12x).
The birth of S. anglica c. 1890 by such hybridization and
genome duplication is among the best-known examples
of a recent allopolyploid speciation. Most Spartina
naturally colonize intertidal zones of the American and
European Atlantic coasts, and the especially effective
sand-fixer S. anglica has been widely introduced, often
with massive colonization episodes and marshes silting.
We are developing genomic resources for Spartina in an
effort to better understand the changes accompanying
hybridization and polyploidy, focusing on S. anglica and
its parents. 454 GS FLX pyrosequencing data were used
to reconstruct the plastid sequence of the Euro-African
hexaploid S. maritima, one of the parents. The 993,229
obtained reads were BLAST-searched against chloroplast
genomes of other Poaceae, yielding 25,568 reads
corresponding to plastid DNA. The assembled plastid
genome was then annotated using Saccharum
officinarum as a reference. Results confirm the conserved
gene order of grass plastid genomes. A relaxed molecular
clock (assuming uncorrelated rates) applied to coding
(rbcL, matK, ndhF) and non-coding (introns and
intergenic spacers) regions of 12 of the 13 species
yielded a divergence time between the tetraploid and
hexaploid clade of <5 million years (Ma). Because of the
uniparental inheritance of plastid genomes, these
estimates depend on depends on whether the hexaploid
species (S. maritima and S. alterniflora) inherited their
plastids from their tetraploid ancestor or from their
diploid ancestor. Our best estimate is that S. maritima
and the American S. alterniflora the parents of S.
anglica, diverged around 3 my ago. These results provide
a temporal framework for our ongoing work on the
evolution of the transcriptomes of S. anglica and other
allopolyploid Spartina.
THEME 04: PHYSIOLOGY AND
BIOCHEMISTRY
Sym049: Plant hydraulic systems: structure
and function – A: 25 July, B: 25 July
The functional role of intervessel and intertracheid
pit structure on cavitation resistance in angiosperm
wood
Lens, F1, Sperry, JS2, Christman, M3, Rabaey, D4, Smets,
E5, Jansen, S6
1
National Herbarium of The Netherlands, Leiden
University, Leiden, The Netherlands; 2Biology Dept,
University of Utah, Utah, USA; 3Biology Dept,
University of Utah, USA
4
Laboratory of Plant Systematics, K.U.Leuven, Leuven,
Belgium; 5National Herbarium of The Netherlands,
Leiden University, Leiden, The Netherlands; 6Institute
for Systematic Botany and Ecology, Ulm University,
Ulm, Germany
Fine-scale anatomical observations of the pit structure in
28 species belonging to several nonrelated lineages,
including Acer, Artemisia, Ceanothus–Rhamnus, Lycium
and Rosaceae, were carried out using the same native
populations that were previously collected to perform
hydraulic measurements. All species were observed
using transmission electron microscopy to link
ultrastructural pit characters with mean cavitation
resistance (MCP). The 28 species were selected based on
their differences in wood anatomy: seven contain a
considerable number of tracheids that are associated near
vessels (vasicentric tracheids in Ceanothus, Rhamnus and
Lycium) and nine show true tracheids throughout the
ground tissue (Rosaceae), while the other species studied
123
are characterized by non-conducting fibres. Preliminary
observations show that intervessel pit membrane
thickness is the most tightly correlated pit character with
MCP when all species are taken into account. Within
specific clades, the pit characters correlated with MCP
vary, as does the strength of individual correlations. This
suggests that most pit correlations are clade-specific
implying that resistance to cavitation can be achieved in
many different ways. For instance, Ap (= mean pit area
per vessel) is most tightly correlated with MCP in
Rosaceae, but not in the other clades studied. Likewise,
the strong correlation between pit chamber depth and
MCP in Acer is weak or absent in the other clades. An
exception to this clade-specificity is pit aperture fraction
(= pit aperture area per pit membrane area), which is
linked with MCP in all but one clade. Among the species
having vessels as well as true or vasicentric tracheids, the
intervessel pit characters generally show higher tradeoffs with MCP than the intertracheid pit features. When
vessel and tracheid pits are compared at the species level,
however, there is a general trend for intertracheid pit
membranes to be thicker than vessel-tracheid pit
membranes, which are in turn thicker than intervessel pit
membranes. These preliminary observations support the
idea that tracheids act as a safe subsidiary transport
mechanism in case too many vessels embolise due to
prolonged drought stress.
Formation of freeze/thaw-induced embolism
Ball, M1
1
Australian National University, Canberra, Australia
While much progress has been made on understanding
the mechanisms underlying formation of freeze/thawinduced embolism, many questions remain. CryoScanning Electron Microscopy (CSEM) was combined
with conventional hydraulic techniques to explore the
occurrence of freeze/thaw induced embolism in the snow
gum, Eucalyptus pauciflora. Measurements were made
on detached leaves, detached stems with leaves, and
intact plants, and compared with characteristics of
samples collected from field-grown plants during natural
frost events. Freezing typically initiated in the midvein
near the petiole and spread throughout the leaf in
approximately 10 s at -4˚C. Exotherms measured on
attached, intact leaves show that temperatures remain
elevated due to latent heat released during freezing for
over 30 min following nucleation events. Such prolonged
heating requires movement of water to sites of freezing
and raises the possibility that the freezing of leaves may
withdraw water from unfrozen stems. Detached leaves
supplied with water showed a rapid increase in uptake
once freezing began, with average uptake rates of 20 mg
per hour sustained with cooling of leaves at 2˚C per hour
to -8˚C, declining sharply to undetectable levels with
further cooling from -10 to -14˚C. Using dyes to follow
the path of water, we found that the uptake of water into
freezing leaves occurred via unfrozen vessels. The
decline in uptake as freezing progressed was associated
with decrease in the number and size of unfrozen vessels.
When flow through stems was blocked, uptake of water
by freezing leaves induced cavitation of stem xylem.
Similar measurements were made on intact plants that
were either well watered or drought stressed. Drought
stress induced loss of stem hydraulic conductance due to
124
embolism. During freezing of these droughted plants,
however, the embolized vessels filled with ice as liquid
water was drawn into the vessels through their walls.
Vessels remained filled with water and hydraulic
conductance was restored following thawing from a
moderate freezing temperature of -6˚C, whereas the
fraction of embolized vessels was greater after thawing
from -12˚C, apparently due to greater tension exerted by
greater tissue dehydration at the lower nadir temperature.
The results show that vessels freeze independently and
that the probability of freezing depends on vessel
diameter and the extent of supercooling, with far
reaching consequences for understanding the importance
of freeze-induced redistribution of water within whole
plants to understanding freeze/thaw-induced embolism.
Aquaporins and control of water flow
Tyerman, SD1, Vandeleur, RK1, Bramley, H2, Shelden,
MC2, Dayod, M1, Tataranni, G4, Gilliham, M1, Mayo, G5,
Kaiser, BN1
1
School of Agriculture Food and Wine, University of
Adelaide, Waite Campus, Australia; 2Institute of
Agriculture, The University of Western Australia,
Crawley, Australia; 3Australian Centre for Plant
Functional Genomics, School of Botany, University of
Melbourne, Parkville, Australia; 4Dipartimento Di
Scienze Dei Sistemi Colturali, Forestali E Dell'Ambiente
Università Degli Studi Della Basilicata Viale Dell'
Ateneo Lucano, Potenza, Italy; 5Australian Centre for
Plant Functional Genomics, School of Agriculture, Food,
and Wine, University of Adelaide, Waite Campus,
Australia
In the biosphere plants may conduct huge amounts of
water through aquaporins, but there are unanswered
questions about how aquaporins work and how they link
to other nutrient transport such as nitrogen and Ca2+.
There are a variety of mechanisms controlling aquaporin
activity in plant membranes, notably cytosolic pH and
Ca2+ concentration. The effect of Ca2+ is additionally
interesting because its transport in the plant is largely
coupled to water flow. These enable rapid responses to
sudden environmental changes. Abiotic stresses such as
drought and hypoxia have interesting effects on
aquaporin mediated water transport that differ between
species and cultivars within a species. Root anatomy and
morphology are linked with the role of aquaporins in
these abiotic stresses. The differences between cultivars
in their water transport physiology present an opportunity
to correlate the physiology with differences in gene
expression. Root hydraulic conductance, which is linked
with the expression of a PIP aquaporin in grapevine, is
correlated with leaf transpiration indicating that long
distance signalling is occurring. This can be observed in
a variety of species as a correlation between root
hydraulic conductance and leaf conductance or
transpiration. This ultimately allows regulation to
achieve maximum extraction of water from the soil.
Understanding these signals will be as important as is our
understanding of the long distance signalling involved in
stomatal regulation.
Biology of xylem refilling
Zwieniecki, M1, Secchi, F1
1
Arnold Arboretum of Harvard University, USA
The process of xylem refilling requires coordinated
action of stem parenchyma cells adjacent to the
embolized vessels. Such coordination must rely on the
plant ability to detect embolism which is temporally and
spatially localized. We suggest that continuous
transpiration in functional vessels removes signal
molecules (sugars) released from parenchyma cells
preventing their accumulation in conduit walls. If
transpirational stream ceases following cavitation,
signaling molecules will accumulate in the xylem walls
allowing for localized detection of embolism. This
detection has to be followed by a biological response that
provides energy and facilitates water transport to the site
of refilling. Here we present an overview of the Populus
trichocarpa transcriptome response to embolism
formation. This response includes changes in the
expression pattern of genes belonging to diverse gene
families including aquaporins, sugar transporters and
sugar metabolic pathways. We discuss the transcriptome
activity for its consistency with formerly proposed
models of xylem refilling process.
Embolism resistance and refilling in plants: new
insights using novel imaging techniques
Choat, B1, McElrone, A2, Brodersen, C3
1
The Australian National University, USA; 2United States
Dept of Agriculture, USA; 3University of California,
Santa Cruz, USA
Plants are capable of rapidly transporting water to heights
in excess of 100 m, and of extracting water from
extremely dry or saline substrates. To achieve this, plants
have evolved a transport system that relies on water
sustaining a tensile force, such that the xylem sap is at
negative absolute pressures. However, this transport
mechanism comes with its own set of problems, most
notably that water under tension is prone to cavitation,
which results in the formation of a gas bubble
(embolism). Embolism reduces the capacity of the xylem
tissue to deliver water to sites of gas exchange and can
therefore impact the ability of the plant to maintain a net
positive carbon balance. In the extreme, xylem embolism
can reach lethal levels causing branch die back and
ultimately plant death. Resistance to embolism is now
recognised as a key trait determining the extent of woody
plant mortality during drought and the limits of plant
distribution with regards to water availability. Hydraulic
constraints on plant growth and survival also clearly play
a role in declining productivity in natural and agricultural
systems during prolonged and severe droughts. Plants
can avoid extensive build up of embolism in two ways.
First, by refilling conduits after they have cavitated, and
second, by achieving hydraulic design that reduces the
risk of embolism spreading throughout the xylem as
water stress increases. The basic principles of water
transport in plants are regarded as well known and there
is a general consensus that the cohesion-tension
mechanism is the driving force of water movement
through the xylem. However, discoveries in the last two
decades demonstrate that there are still fundamental gaps
in our knowledge of long distance water transport in
plants. I will address two outstanding questions to how
plants transport water, (a) the ability to plants to refill
embolised conduits during active transpiration and, (b)
the factors that control the relative resistance to drought
induced embolism in plants. Recent insights into
embolism formation and refilling gained by x-ray
microtomography and magnetic resonance imaging will
be presented in the context of structure-function
relationships.
Nighttime transpiration and xylem embolism repair
in plants: two mysteries explain each other
Schenk, HJ1, Espino, S1, Martínez-Cabrera, H2, Jones,
CS2
1
California State University Fullerton, USA; 2University
of Connecticut, USA
Two enduring mysteries of plant physiology are the
function of nighttime transpiration and the nature of the
mechanism that allows removal of xylem embolisms
while a plant’s hydraulic system is functioning under
negative pressure. Nighttime transpiration is particularly
common in plants from dry environments, which would
appear to be least able to afford wasteful water loss.
Refilling of air-filled conduits while the remaining
hydraulic system is under negative pressure has been
thought to be physically impossible, yet is commonly
observed. Here it is shown that the two mysteries can
explain each other. The North American desert shrub
Encelia farinosa (Asteraceae) was used as the study
system for this research. In this species embolism repair
under negative pressure occurs usually at night while the
stomata are open and while water potentials are below
those potentially generated by root pressure.
Experimental inhibition of nighttime transpiration by
bagging of leaves inhibits embolism repair. These
findings show that, at least in this species, a transpiration
stream is required for embolism repair under negative
pressure. Measurements of air flow into artificially
created embolisms in the wood revealed that air from
these embolisms dissolves into the transpiration stream
of functioning conduits. It is hypothesized that air from
refilling xylem conduits diffuses through pit membranes
into the transpiration stream of functioning conduits.
This happens while temperatures decline during the
night, causing gas solubility in xylem sap to increase.
Nighttime transpiration appears to be required to move
air-saturated sap towards the leaves before temperatures
increase again during the next morning, which would
cause gas solubility to decrease and air to come out of
solution. Thus xylem appears to operate as a liquid-gas
membrane contactor, which is an engineered device that
efficiently moves gas via diffusion through large gaspermeable membranes that separate a gas and a liquid
phase. Measurements of dissolved gas in xylem sap in
woody roots and stems of Encelia farinosa fully
supported this theory. The findings should help to put to
rest enduring criticisms of the tension cohesion theory of
water transport, which are largely based on the false
assumption that negative-pressure hydraulic systems
cannot self-repair after suffering embolism formation.
Nighttime transpiration, an important flux in the water
balance of many ecosystems, is explained at least in part
125
as playing a vital role in the nocturnal recovery from
drought-stress experienced during the day.
Are hygroscopic particles on the leaf surface part of
the plant hydraulic system?
Burkhardt, J1, Hunsche, M1, Pariyar, S1
1
University of Bonn, Germany
The hydraulic system of plants is generally assumed to
end near the leaf surface but always still within the leaf.
It is assumed that all liquid water will evaporate there
and that only water vapor will exit the plant via the
stomata or the cuticle. The establishment of thin liquid
water connections along stomatal walls might extend the
hydraulic system to the leaf surface and intensify its
coupling to the atmosphere, which would support earlier
studies pointing to high frequency coupling between
atmospheric turbulence and sap flow. In this
contribution, we investigate how this 'hydraulic
activation of stomata' (HAS) may establish, using
environmental scanning electron microscopy to observe
drying/wetting cycles of a range of different salts on
hydrophobic leaf cuticles. We also investigate the
response of stomatal conductance and transpiration to
changes in relative humidity. The water vapor absorption
to hygroscopic salts is a direct function of relative
humidity, and together with HAS this is able to explain
the stomatal humidity reaction. This includes the
'feedforward' effect (i.e. decreasing transpiration caused
by decreasing relative humidity), which is interpreted as
an emergent reaction of a stomatal patch. For this part of
the study we use plants grown in particle free
environment, in comparison with plants from normal air,
and plants treated with different salt solutions. Different
salts, placed on hydrophobic tomato cuticles, responded
differently to humidity changes around their
deliquescence point, but usually the salts expanded after
several drying/wetting cycles, sometimes in dentritic
form. This shows the capacity to overcome the
hydrophobicity of leaf cuticles under conditions of high
ionic strength, and further confirms the recently observed
capability of thin water films to extend into the stomata.
The humidity reaction of stomata and plant transpiration
differed between plants from the particle free
environment and plants with different kinds and amounts
of particles on their leaf surface. This supports the idea
that leaf surface particles are an important part of
plant/atmosphere interactions, and may eventually form
the end of the plant hydraulic system. Coupling to the
atmosphere is intensified by the degree of HAS and may
be beneficial at moderate HAS, when acting as ‘humidity
sensor’. Strong HAS (e.g. caused by air pollution) may
affect plant water relations by wicking of liquid water out
of the stomata, with hygroscopic leaf surface particles
acting as desiccants.
Coordinated development of veins and stomata
matches hydraulic supply with potential transpiration
Brodribb, T1, Jordan, G1, Lam, V1, Biffin, E1, Rai, H1,
Chang, Y1, Brodribb, T1, Graham, SW1
1
University of Tasmania, Hobart, Australia
126
Higher leaf vein density enables higher rates of
photosynthesis because enhanced water transport allows
higher leaf conductances to CO2 and water. However the
total cost of leaf venation rises in proportion to the
density of minor veins, meaning that efficient investment
in leaf xylem requires minor vein synthesis to match
potential transpirational demand. Under conditions where
maximum photosynthesis and stomatal conductance are
limited by light intensity, optimal allocation of carbon for
vein production should occur if variation in vein density
(Dv) is coordinated with variation in stomatal density.
Here we examined leaves of the evergreen tree
Nothofagus cunninghamii to determine whether this was
the case. Sun and shade-grown leaves were compared
across five populations ranging in altitude and rainfall,
and a very strong correlation between Dv and stomatal
density was found at all levels of comparison ranging
from within-trees to among-populations. Calculated leaf
conductances to liquid and vapour-phase water were
strongly correlated over a two-fold range in Dv and
stomatal density. Our results provide strong evidence that
the development of veins and stomata are coordinated in
such a way as to produce a highly efficient use of carbon
investment in leaf venation. The developmental
mechanisms that may integrate veins and stomata are
discussed.
Hydraulic properties and photosynthesis in six
deciduous and six evergreen tree species in a tropical
limestone forest in southern Yunnan, China
Fu, P1, Jiang, Y1, Wang, A1, Cao, K1
1
Key Laboratory of Tropical Forest Ecology,
Xishuangbanna Tropical Botanical Garden, Chinese
Academy of Sciences, Yunnan, China; 2Graduate
University of Chinese Academy of Sciences, Beijing,
China
Trees growing on limestone will face frequent drought
because of the low water retention capacity of the
shallow soil, especially in the 6-month long dry seasons
in SW China. And the evergreen and deciduous tree
species growing in limestone may use different strategies
to adapt to the seasonal drought. In the present study, we
compared the stem hydraulic conductivity, leaf gas
exchange rates, leaf pressure volume (P-V) curves traits,
and leaf water status of six evergreen and deciduous tree
species both in dry and wet seasons in a tropical
limestone forest in Southern Yunnan, China. We also
compared stem vulnerability curves and xylem anatomy
of the 12 tree species. Our results showed that the leaf
specific hydraulic conductivity, sapwood specific
conductivity (KS), and maximum leaf mass based net
photosynthesis rate (Am) were much higher in the six
deciduous tree species than those of the six evergreen
tree species. And the deciduous tree species had much
wider vessel diameter than that of the evergreen tree
species. The evergreen tree species had lower xylem
water potential at 50% loss of hydraulic conductivity
than that of the deciduous tree species. The difference of
KS between the wet and dry season were not significantly
different in most of the 12 species. However the KS of
one deciduous species Bauhinia variegata (L.) in the dry
season was significantly lower than that of the wet
season, which might be caused by xylem embolism; and
the KS of another deciduous tree species Millettia cubitti
(Dunn) in the dry season was higher than that in the wet
season, which might be due to the newly growing
sapwood in the dry season. The turgor loss point (TLP)
that calculated from the P-V curves for leaves or terminal
shoots of the evergreen species were more negative than
those of the deciduous tree species in dry season, which
means the evergreen tree species have greater ability to
maintain their leaf turgor than the deciduous tree species.
Our results indicate that there is a trade-off between
hydraulic efficiency and safety: the evergreen species
exhibit greater ability of drought-resistant with lower P50
while the deciduous tree species show greater water
transporting efficiency and photosynthesis rate in the
rainy season. The seasonal exchange of KS shows that the
declining of hydraulic conductivity of the stem may not
be responsible for the leaf shedding of the deciduous tree
species.
Linkages among diel carbon and water fluxes in six
Eucalyptus species
Lewis, JD1, 2, Phillips, NG3, Logan, BA4, Tissue, DT2
1
Fordham University, USA; 2University of Western
Sydney, Australia; 3Boston University, USA; 4Bowdoin
College, USA
Nocturnal water loss via transpiration is substantial in
many plant species. While nocturnal transpiration may
increase total daily carbohydrate production by
increasing early-morning net photosynthetic rates and
nutrient uptake, it may also reduce production by
increasing water stress. However, the relationships
between diel carbon and water fluxes in leaves are poorly
understood. In this study, we examined leaf-level carbon
and water fluxes of six Eucalyptus species, differing in
drought sensitivity, during two 24-hour cycles in a
common garden experiment at the University of Western
Sydney in Richmond, NSW. Drought-sensitive species
generally exhibited lower net photosynthetic rates (A)
and stomatal conductances (gs) at sunrise and midday,
and A and gs values peaked earlier in the day than in
drought-tolerant species. Variation in light-saturated net
photosynthetic rates (Asat) reflected gs and starch
accumulation during the day, and the relationship
between Asat and gs did not vary among species.
Nocturnal respiration rates varied with leaf N
concentration and the rate of soluble sugar loss at night.
As a result, there were no clear relationships between
daytime and nocturnal carbon and water fluxes. These
results suggest that drought-tolerant Eucalyptus species
may maintain higher photosynthetic rates for longer
periods of the day than drought-sensitive species.
Water-use of Eucalyptus species originating from
differing climates: is canopy conductance modulated
by species?
Bourne, A1, Haigh, A1, Ellsworth, D1
1
Hawkesbury Institute for the Environment and School of
Natural Sciences, Australia
Transpiration by plants controls a major portion of water
loss from land surfaces as mediated by stomata and the
environmental conditions in which they function. There
is currently limited information on species comparisons
of transpirational water use for ecologically contrasting
Eucalyptus species despite the predominance of this
genus on the Australian continent and in tropical and
subtropical plantations world-wide. We asked whether
there are differences in canopy conductance and its
relationship to the environment among species adapted to
contrasting climates. We investigated canopy scaled
stomatal conductance (Gc) to determine how tree canopy
conductance responded to climate variation amongst sub
humid (SH) and humid (H) zone Eucalyptus species
across a year. Measurements were made on four tree
species from contrasting climate zones, namely E. crebra
(SH), E. dunnii (H), E. melliodora (SH), E. saligna (H),
and E. tereticornis (H). Sap flow techniques were used
for the measurements, which were then scaled to canopy
conductance by inverting the Penman Monteith formula.
Species originally from contrasting climate zones had
different maximal Gc values, as well as different Gc
responses to vapour pressure deficit (D). From different
maximal Gc's at low D, different species converged on
the same minimum Gc at high D. Sub humid Eucalyptus
species showed a shallower response of Gc to D than did
humid zone Eucalyptus species. This response to
increasing D meant that sub humid species used larger
amounts of water during dry and hot conditions, whereas
humid zone species used larger amounts of water during
humid and hot conditions, corresponding to the
prevailing conditions in their climates of origin. Thus
differences in Gc and the total water use response to
changing environmental conditions were attributed to the
original climate of the species. Understanding how
Eucalyptus water-use is regulated by stomata and how
native species differ in this regard is critical for
managing water resources.
Sym050: Evolution and ecophysiology of C4
grasses – 30 July
The evolution of C4 photosynthesis in the eudicots:
lessons for understanding C4 evolution in grasses and
other monocots
Sage, R1, Sage, T1
1
University of Toronto, Canada
There are currently 62 lineages of C4 photosynthesis in
the plant kingdom, of which 36 are in the eudicots and 18
are in the Poaceae. The C4 grass lineages have proven
difficult for addressing hypothesis of C4 origin, because
their taxonomy and phylogenetics are currently in flux,
many lineages lack close C3 relatives, and there are few
C3–C4 intermediate species. A major exception is the
small Australian genus Neurachne, which has numerous
C3 species, one C4 species and a C3–C4 intermediate
species. While the anatomy and physiology of Neurachne
are well studied, its phylogenetics remain vague, limiting
its value for evolutionary work. By contrast, the lineages
of C4 dicots have been valuable for addressing hypothesis
regarding C4 evolution. Multiple species level
phylogenies exist in the C4 clades, there are numerous
C3–C4 intermediates, and closely related C3 and C4
species have been identified. Thus, early work on C4
evolution in Flaveria has been built upon by comparative
127
studies of eudicot genera such as Heliotropium, Cleome,
Chamaesyce, Portulaca and Mollugo. These studies
demonstrate conclusively that C4 photosynthesis arose
via the evolution of a photorespiratory CO2 concentrating
mechanism, which appeared in C3 species of very hot,
monsoon-affected climates where photorespiration is
high. C3 species with high vein density and enlarged
bundle sheath cells appear predisposed to evolve C4
photosynthesis. Our working hypothesis is that high vein
density in C4 ancestors occurred in order to transport
water to the mesophyll cells in hot, low humidity
environments where transpiration is extreme. With high
vein density there are often high numbers of bundle
sheath (BS) cells, which are fully incorporated into the
leaf photosynthetic apparatus by an increase in
chloroplast number along the BS periphery. To partially
offset high photorespiration, it is possible that a
photorespiratory loop is established along the length of
the BS cells, with photorespiratory metabolites diffusing
from the outer BS periphery to the inner cell region
where mitochondria and glycine decarboxylase (GDC)
are localized. Here, release of photorespired CO2 can be
efficiently refixed by adjacent chloroplasts. This
possibility is supported by close studies of the immediate
C3 relatives of the C4 lineages in Heliotropium and
Flaveria, where mitochondria and glycine decarboxylase
only occur along the inner BS wall. The establishment of
a BS photorespiratory loop could enable the subsequent
establishment of a mesophyll to BS photorespiratory
cycle via a mutation that eliminates mesophyll GDC
expression. By establishing high numbers of
photosynthetic BS cells, and localizing the BS
mitochondria to the inner wall, C3 species are
predisposed to survive a loss of mesophyll GDC, thereby
allowing evolutionary optimization of an efficient
photorespiratory CO2 concentrating mechanism.
The evolution of beta carbonic anhydrases in C4
plants
Ludwig, Martha1
1
University of Western Australia, Crawley, Australia
Both C3 and C4 plants contain multiple isoforms of the
enzyme β-carbonic anhydrase (CA), which catalyse the
interconversion of CO2 and bicarbonate. In C3 plants,
most CA activity localizes to the chloroplasts of the
mesophyll cells. C3 plastidial β-CAs have diverse roles,
including the facilitation of CO2 diffusion across the
chloroplast envelope, lipid biosynthesis, disease
resistance, and stomatal closure. By contrast, high levels
of CA activity localize to the cytosol of C4 mesophyll
cells where it catalyzes the hydration of atmospheric
CO2, producing bicarbonate, the substrate for
phosphoenolpyruvate carboxylase (PEPC), the primary
carboxylating enzyme of C4 plants. Most of our current
understanding of the molecular changes responsible for
the differences in CA expression patterns between C3 and
C4 plants has been gained through examination of the
CAs in species within the dicot genus Flaveria. This
group of plants contains species that do either C3 or
NADP-malic enzyme-type C4 photosynthesis, as well as
other species that carry out C3–C4 intermediate types of
photosynthesis. Results from immunocytochemistry,
chloroplast import studies, quantitative reverse
transcription polymerase chain reaction assays and
128
sequence analyses indicate that the gene coding for an
ancestral C3 chloroplastic CA was the evolutionary
template for the C4 cytosolic form of the enzyme in
Flaveria, with the loss of the sequence encoding the
chloroplast transit peptide from the C3 CA gene leading
to the retention and operation of the C4 CA in the
mesophyll cytosol. Analysis of the upstream region of
the C4 CA gene identified a sequence similar to that of
the mesophyll expression module 1 (Mem1) that directs
mesophyll cell-specific expression of the PEPC gene in
C4 Flaveria species. When this CA gene upstream region
was used in a promoter/reporter gene construct to
transform F. bidentis plants, reporter gene expression
was detected specifically in the mesophyll cells of this C4
species. With respect to the Flaveria intermediate
species, cDNA sequence analyses indicated that the C4like species F. brownii expresses an ancestral
chloroplastic C3 form of the CA gene while in another
C4-like species, F. vaginata, a cytosolic C4 form of the
CA3 gene is transcribed. These results indicate that
different biochemistries and/or gene expression patterns
can result in similar photosynthetic physiologies, and that
different molecular evolutionary paths may have been
taken to achieve C4-ness in Flaveria . Recent work on the
molecular evolution of the β-CAs in Cleome, another
dicot genus that contains C3 and NAD-malic enzymetype C4 species, as well as insights into the molecular
evolution of β-CA gained from studies focusing on
grasses, will also be discussed.
Efficiency of the CO2 concentrating mechanism
during C4 photosynthesis: response to changes in light
availability and potential of the single-cell C4 plants
Cousins, A1, King, J1, Ubierna Lopez, N1, Sun, W1
1
Washington State University, USA
Of the total solar energy reaching the Earth’s surface,
only a portion is used by higher plants to convert
inorganic carbon to organic carbon. This is in part
because under current atmospheric CO2 concentrations,
photorespiration in C3 plants decreases the theoretical
maximal efficiency of converting solar energy into
chemical energy. In response, some species have evolved
C4 photosynthesis, which reduces photorespiration rates
by capturing atmospheric CO2 in the C4 cycle and
concentrating it around the compartmentalized Rubisco
and the C3 cycle. The efficiency of the C4 photosynthetic
CO2-concentrating mechanism is defined in part by the
fraction of CO2 fixed by the C4-cycle that subsequently
leaks out of the compartmentalized C3-cycle and is not
assimilated by Rubisco. Both the relative biochemical
capacities of the C4 and C3 cycles and the conductance of
CO2 from the compartmentalized Rubisco determine the
amount of CO2 ‘leakiness’. The use of leaf-level models
and measurements of 13CO2 isotope discrimination (δ13C)
are powerful tools to estimate the efficiency of the CO2concentrating mechanism (Farquhar, 1983). The goal of
our research is to use modeled and measured values of
δ13C to determine how the efficiency of the CO2concentrating mechanism during C4 photosynthesis is
influenced by changes in light quantity and quality, and
by variations in anatomical structures used to facilitate C4
photosynthesis. Light availability, quantity and quality,
are expected to impact the coordination of the C4 and C3
cycles, especially if there is unequal distribution and
absorption of light energy within a leaf. Indeed, the rate
of C4 photosynthesis decreases and CO2 leakiness
appears to increase in response to low light availability.
Additionally, CO2 leakiness changes when illumination
shifts from red to blue and blue to red light. Data will be
presented describing the response of leakiness and
potential mechanisms influencing leakiness in response
to changes in light quantity and quality. In addition to the
coordination of the C4 and C3 cycle, the conductance of
CO2 diffusion between the compartmentalized C4 and C3
cycles is required for efficient C4 photosynthesis. To
maintain a low conductance most terrestrial C4 plants
utilize two distinct photosynthetic cells (Kranz anatomy)
to concentrate CO2 around Rubisco and minimize rates of
photorespiration. However, the Chenopodiaceae species
Bienertia sinuspersici uses central and peripheral
cytoplasmic compartments and Suaeda aralocaspica
utilizes distal and proximal compartments, each within a
single-cell, to facilitate C4 photosynthesis. There is
strong evidence that these plants perform C4
photosynthesis; however, questions remain regarding the
photosynthetic capacity and efficiency of these singlecell CO2 concentrating mechanisms. Data will be
presented demonstrating that the rates of photosynthesis
and the efficiency of the CO2 concentrating mechanisms
of the single-cell C4 plants B. sinuspersici and S.
aralocaspica are similar to those of the more common
Kranz-type C4 plants.
Global environmental change and the future of C4
crops for food and fuel
Leakey, ADB1, Markelz, RJC1, Strellner, RS1
1
University of Illinois At Urbana–Champaign, USA
Crops with the C4 photosynthetic pathway are vital to
global food supply, particularly in the Americas and
Africa. While rising atmospheric [CO2] is the driving
force behind the greater temperatures and water stress
which threaten to reduce future crop yields, it also has
the potential to directly benefit crop physiology. The
nature of C4 plant responses to global environmental
change has been controversial. Recent evidence from
Free-Air Concentration Enrichment experiments suggests
that elevated [CO2] does not directly stimulate C4
photosynthesis. Nonetheless, drought stress can be
ameliorated at elevated [CO2] as a result of lower
stomatal conductance and greater intercellular [CO2].
Therefore, unlike C3 crops for which there is a direct
enhancement of photosynthesis by elevated [CO2], C4
crops will only benefit from elevated [CO2] in times and
places of drought stress. This talk reviews the results
from recent field experiments investigating the response
of maize to the CO2 x drought interaction, as well as a
new project aiming to resolve a key remaining
knowledge gap - whether rising temperatures will
directly sensitize C4 photosynthesis to elevated [CO2].
Ecophysiology of C4 grasses: a comparative approach
Osborne, C1, Taylor, S2, Ripley, B3, Woodward, I1
1
University of Sheffield, Sheffield, UK; 2University of
Texas, Austin, USA; 3Rhodes University, Grahamstown,
South Africa
C4 photosynthesis ranks among the most important
evolutionary innovations in plants, and the assembly of
ecosystems dominated by C4 grasses has transformed the
terrestrial biosphere. The rapid accumulation of
phylogenetic evidence over the past decade has revealed
multiple evolutionary origins of the C4 pathway spanning
a diverse range of grass lineages. This accumulated
knowledge brings new opportunities for understanding
the functional significance of the C4 syndrome within its
evolutionary context. In this talk, we will consider the
question: what changes in plant water relations and
nitrogen-use have been associated with the evolution of
C4 photosynthesis in grasses? First, a comparative
screening experiment used a total of 34 grass species to
sample five independent C4 origins, including three
groups of C3 sister taxa. Data supported the a priori
expectations of lower stomatal conductance, and greater
water- and nitrogen-use efficiency in C4 than C3 species.
Further data showed that the soil-leaf water potential
gradient was greater in C3 than C4 species. However,
differences in photosynthetic rate and leaf nitrogen
concentration were smaller than expected. A second
comparative screening experiment compared the
physiological responses to drought in a phylogenetically
structured sample of 14 C3 and C4 grass species, covering
seven independent C4 origins. Under mesic conditions,
the C4 grasses had higher photosynthetic rates, but lower
stomatal conductance, and a smaller soil-leaf water
potential gradient than their C3 counterparts. Under
drought, stomatal conductance declined more
dramatically in the C3 than C4 species, and
photosynthetic water-use and nitrogen-use efficiency
advantages held by C4 species under control conditions
were each diminished by 40%. Again, there was only a
small effect of photosynthetic pathway on leaf nitrogen
concentration. Accounting for the phylogenetic diversity
of C4 grass species has therefore provided new insights
into the evolutionary links between photosynthetic
pathway and leaf water- and nitrogen-use. A modelling
framework for drought mortality is used to interpret these
results in the context of ecological selection for C4
photosynthesis.
A phylogenetic perspective on the responses of C3 and
C4 grasses to fire
Ripley, B1, Martin, T1, Osborne, C2
1
Botany Dept, Rhodes University, South Africa; 2Dept of
Animal and Plant Sciences, University of Sheffield, UK
C4 grasses possess characteristics that potentially
advantage growth in fire-prone environments, including
high photosynthetic productivity, efficient light and
nutrient use and significant allocation to below-ground
reserves. Such characteristics allow fast regeneration
after fire, and may be the consequence of photosynthetic
physiology, phylogenetic ancestry or may have been
acquired as adaptations to frequently burnt environments.
The aim of this study was to examine the role of
photosynthetic pathway by comparing the fire ecology of
14 species of C3 and C4 grasses belonging to the
subfamilies Panicoideae (Panicoid), Aristidoideae and
Danthonioideae (non-Panicoid), and drawn from the
same regional flora in the Eastern Cape of South Africa.
Its focus was on aboveground characteristics that would
contribute to a fire fuel load and the re-growth responses
129
of plants subsequent to a controlled experimental burn
during the natural winter fire season. Prior to the burn,
but after frost, a greater proportion of the aboveground
biomass of C4 species was dead, and had a lower
moisture content, and higher flammability than that of
the C3 plants. These characteristics would all potentially
contribute to a greater fuel load and meant that C3 plants
lost a larger proportion of living tissue in the
experimental burn. However, these patterns were equally
strongly determined by phylogeny, and leaf mortality
was greater in the Panicoid than the non-Panicoid
grasses. Similarly, re-growth subsequent to burning was
more rapid and complete relative to controls in Panicoid
than non-Panicoid grasses, and did not differ between C3
and C4 grasses within each of these phylogenetic groups.
The re-growth of Panicoid grasses was supported by a
stronger re-allocation of larger belowground reserves
than was apparent for non-Panicoid grasses and again
was not different between photosynthetic types. Results
suggest that Panicoid grasses are tolerant of fire and
would explain why the number of species is positively
correlated to fire frequency. What is not evident is why
C4 Panicoid grasses dominate frequently burnt
ecosystems, as their performance after fire was not
significantly superior to that of C3 Panicoid grasses.
Sym051: Plant-rhizosphere interactions –
28 July
The biophysics of the rhizosphere
Young, IM1
1
School of Environmental & Rural Science, University of
New England, Armidale, NSW, Australia
Much is know about life in and near the rhizosphere.
Relatively little is known of the consequences of this life
in the context of the dark opaque and heterogeneous
geohabitats of the rhizosphere, which is their home, as
opposed to simple agar blocks. This talk will focus on
these heterogeneous habitats and how the soil-microbe
interactions within the rhizosphere are defined in many
ways by the physical micro-architecture of the soil, and
how in turn microbes define their habitats. Using high
resolution micro-tomography the talk will explore the life
of microbes in soil and what makes them what they are.
Bioactive root exudates: a novel
allelochemicals and plant protectants
source
of
Weston, L1
1
Charles Sturt University, Wagga Wagga, Australia
Plant root exudates are known to play an important role
in community structure and are involved in complex
rhizospheric interactions. Our past work with Sorghum
spp. has elucidated the role of the allelochemical
sorgoleone, a potent inhibitor of plant growth that is
released in sorghum root exudates. Graminaecous species
including fine fescue (Festuca rubra) also produce large
amounts of novel secondary products and can selectively
inhibit weeds in both field and laboratory conditions.
These constituents are known to play important roles in
plant defense against herbivores, insects, pathogens and
130
microbes as well as competing plants. In Australia,
Paterson's curse (Echium plantagineum) also produces
unique root exudates from two types of root hairs, which
are involved in active exudation processes in the plant.
We have discovered that the periderm of both its younger
lateral roots and older taproots produce unusual, redcolored chemical constituents which are localized in the
outer layers of cells. We have determined the structure of
these novel anthroquinones and discovered that they are
potent inhibitors of certain microbes and pathogens.
Further analyses on their localization, mode of action,
and biosynthesis are underway.
Measurement of allelochemical dynamics in the
rhizosphere
Weidenhamer, J1, Mohney, B1
1
Ashland University, USA
Plants produce a wide variety of highly phytotoxic
chemicals, some of which have activities comparable to
synthetic herbicides. The possibility that plants exert
direct chemical, or allelopathic, effects on neighboring
plants as well as on soil microflora has attracted
considerable research interest. The success of certain
invasive plants has been attributed to phytotoxic root
exudates. However, the difficulties of monitoring
allelochemical concentrations in soil and their dynamics
over time have been a major barrier to testing hypotheses
of allelopathic effects. We have used diffusive sampling
strategies employing polydimethylsiloxane (PDMS)
microtubing to map the spatial distribution and temporal
dynamics of root-exuded thiophenes from the African
marigold (Tagetes erecta) and French marigold (Tagetes
patula). Solid phase root zone extraction (SPRE) probes
were constructed by inserting stainless steel wire into
PDMS tubing. Alternately, 1 m lengths of PDMS
microtubing have been placed in marigold soil with the
two ends of the tubing remaining out of the soil so that
solvent could be washed through the tubing to collect
samples for HPLC analysis. This silicone tube
microextraction (STME) method gave a linear response
for á-terthienyl when maintained in soils spiked with 010 ppm of this thiophene. These PDMS-based techniques
are experimentally simple and use inexpensive materials,
and should be broadly applicable to the measurement of
non-polar root exudates. By allowing repeated sampling
with minimal disturbance of the soil, these methods
provide a means to test hypotheses about the role of root
exudates in plant–plant and other interactions.
The evolution and functioning of fungal symbiosis
from liverworts to higher plants
Field, K1, Tille, S1, Cameron, D1, Leake, J1, Beerling, D1
1
University of Sheffield, UK
It was first hypothesised over 30 years ago that symbiotic
soil fungi assisted plants in ‘greening the Earth’ over 400
million years ago, by forming mutualistic arbuscular
‘mycorrhizal associations’ through which the fungus
gains photosynthate in return for supplying host plants
with mineral nutrients and water (Pirozynski & Malloch
1975). Crucial new evidence revealed that liverworts not
only occupy the most basal node on the land plant
phylogenetic tree, but were probably the first plants to
establish symbiotic partnerships with arbuscular
mycorrhizal fungi (AMF) upon land colonisation (Wang
et al. 2010). Essential genes required for mycorrhization
in liverworts have been vertically inherited through to all
the other major groups of land plants (Wang et al. 2010).
These advances in phylogenetics have exposed that
virtually nothing is known about mycorrhizal functioning
in lower land plants occupying major nodes on the land
plant evolutionary tree. The remaining key to
understanding the role of plant–AMF symbioses in the
‘greening of the Earth’ is now to resolve their functional
relationships in lower plants. We measured carbon-formineral nutrient exchanges in plant–AMF associations in
Pressia quadrata, a thalloid liverwort, Osmunda regalis,
a ‘lower’ tracheophyte fern and Plantago lanceolata, a
modern ‘higher’ plant. Plants were grown at modern-day
ambient (440 ppm) and under simulated Palaeozoic
(1500 ppm) atmospheric CO2 concentrations.
Carbohydrate allocation from plant to AMF was
determined by 14CO2 pulse-labelling of thallus or shoots
and measurement of 14C in external mycorrhizal
mycelium growing into nylon mesh cores that exclude
rhizoids and roots. Transfer of phosphorus absorbed by
the fungi from within the cores into plant tissues was
assessed by addition of 33P-labelled H2PO4 tracer. The
length of mycorrhizal mycelium in the soil supported by
each plant provides a measure of surface area available
for nutrient absorption and fungal biomass. In the
liverwort and fern significant 14C transfer from plant
photosynthates to AMF was detected, but at rates that
were more than two orders of magnitude lower than in
the higher plant. Phosphorus uptake via the fungal
partner showed a similar pattern of greater transfer in the
higher plant than the lower plants. However, carbon cost
per unit phosphous gained from the mycorrhizal
symbiosis was lowest in Pressia and rose progressively
through Osmunda to Plantago. This decrease in
efficiency was in linear proportion to the hyphal lengths
that increased from the liverwort through to the higher
plant. Although net P uptake increased dramatically
under elevated CO2, the carbon costs rose even more
sharply resulting in loss of efficiency of the symbiosis
compared to ambient CO2, and this corresponded with
greatly increased hyphal lengths. Our results establish
that AMF associations in lower land plants can function
in the same mutualistic manner as in higher plants, both
in early Palaeozoic and current CO2 atmospheres. The
carbon cost of AMF in the ‘lower’ plants is less than in
the higher plants and has decreased with decreasing
atmospheric CO2 concentrations. These findings provide
important new insights into the evolution and functioning
of fungal symbiosis from liverworts to higher plants.
Competition for N in the rhizosphere of European
beech forests
Simon, J1, Rennenberg, H1
1
University of Freiburg, Institute of Forest Botany and
Tree Physiology, Germany
Beech-dominated deciduous forests constitute the
potential natural vegetation in Central Europe. Like other
forests, they developed on marginal soils characterised
by N limitation. Thus, different biota in these forests
have to share and, therefore, compete for the N resources.
For example, plant and microbial N fluxes are closely
linked in terrestrial ecosystems. Plants may affect
microbial N turnover by root exudation, whereas
microorganisms may influence plant N fluxes by
mineralisation of decaying biomass. When N is limiting
in the soil, plants and microorganisms may compete for
the same inorganic or organic N sources. This
competition may even be enhanced under the
prognosticated
climate
changes
(i.e.
elevated
temperature, enhanced frequency and duration of
summer droughts), particularly in tree species susceptible
to strong and prolonged periods of drought. Such species
(e.g. European beech) may be negatively affected in their
physiological performance and growth. To optimize the
exploitation of limited soil N resources, trees have
developed several mechanisms. However, the complex
interactions between different components of vegetation,
mycorrhizal fungi, and soil microorganisms in the
competition for N and the regulation of these interactions
are currently far from being understood. Therefore, the
main objectives of this study were (1) to characterize and
quantify the significance of vegetation components and
soil microorganisms in the competition for N in Nlimited beech-dominated deciduous forests, and (2) to
analyse the factors regulating this competition.
Sym052: Regulation of phosphate
acquisition and phosphorus homeostasis in
plants – 26 July
Molecular dissection of local and systemic responses
to phosphate starvation in Arabidopsis thaliana
Nussaume, L1, Desnos, T1, Clement, M1, Thibaud, MC1,
Arrighi, J-F2, Bayle, V3, Paz Ares, X4, Kanno, S5,
Nakanishi, T6
1
LBDP,UMR 6191 CNRS-CEA, Aix-Marseille II, CEN
Cadarach, St Paul lez Durance,France; 2LIPM UMR
441/2594 INRA,CNRS, Castanet-Tolosan, France;
3
LRDP, ENS Lyon, France; 4CNB, CSIC,Campus de
Cantoblanco, Madrid, Spain; 5Graduate School of
Agricultural and Life Sciences,University of Tokyo,
Japan
Phosphate (pi) is a crucial and often limiting nutrient for
plant growth. Ìt is also a very insoluble ion
heterogeneously distributed in soil. to cope with such a
situation, plants have evolved a complex network of
morphological and biochemical processes (1) controlled
by various regulatory systems. these signalling pathways
are triggered either by pi concentration in the growth
medium (external pi; 2,3,4), or by plant cells internal Pi.
A split-root assay performed to mimic an heterogeneous
environment combined with a transcriptomic analysis
was used to identify clusters of genes locally or
systemically regulated by P i starvation (5). The
combination of genetic tools and physiological analysis
revealed distinct regulatory roles for the internal and the
external Pi. They also pointed out a central role of the
transcription factor phr1 for genes systemically
controlled by low Pi. In addition, results obtained with a
set of tools including chemical genetics and
manipulations of the entire family of the high affinity P i
transporters will be presented. These tools offer novel
131
powerful approaches to dissect Pi perception pathways.
(1) Misson et al. 2005. (2) Reymond et al. 2006. (3)
Svistoonoff et al. 2007. (4) Ticconi et al. 2009. (5)
Thibaud et al. 2010.
Translocation of miRNAs in phloem in response to
phosphorus deficiency
Rodriguez-Medina, C1, Ho, A2, Loughlin, P3, Atkins,
CA4, Smith, PMC3
1
Institut National de la Recherche Agronomique (INRA),
France; 2Dept of Molecular Biosciences, University of
Oslo, Norway; 3School of Biological Sciences, The
University of Sydney, Australia; 4School of Plant
Biology, The University of Western Australia, Australia
The phloem long-distance translocation system functions
as a nutrient delivery system and as a signalling pathway
through which molecules such as growth-regulators or
bioactive peptides, proteins and RNAs are disseminated
throughout the plant. This translocation of signals is
involved in coordinating development and allowing the
plant to respond to environmental conditions. However,
the mechanisms controlling macromolecular trafficking
and information flow are not well described. Small RNA
molecules like small interfering RNAs (siRNAs),
microRNAs (miRNAs) and noncoding RNAs that play
an important role in the regulation of gene expression,
have been detected in phloem exudate. We have
identified 11 different miRNAs in L. albus phloem
exudate through hybridisation and cloning. In
Arabidopsis we are investigating whether these miRNAs
are translocated in response to nutrient stress using a
grafting assay where wild-type tissue is grafted onto a
hen1 mutant that is disrupted in miRNA biogenesis. The
accumulation of miRNAs in scions and rootstocks was
assessed by real-time quantitative PCR. In phosphorus
deficient conditions miR399 was translocated as well as
two other miRNAs known to respond to P deficiency in
phloem. We are currently using small RNA sequencing
to identify other miRNAs that are translocated. We are
using a GFP sensor construct in Arabidopsis to study the
process of translocation of miRNAs.
Phosphate signaling and homeostasis in plants
Pant, BD1, Scheible, WR1
1
Max-Planck Institute of Molecular Plant Physiology,
Germany
Phosphate (Pi) is often limited in majority of the world
soils for plant growth and development. To supplement
the Pi-deficiency, phosphate is supplied to the soil as a
fertilizer. The main source of phosphate fertilizer is
phosphate rock which is a limited resource and will be
finished in the near future. On the other hand, using
excessive fertilizer is not eco-friendly. To cope with low
Pi availability, plants develop a number of adaptive
features at morphological, physiological and molecular
level. We have identified that a large number of genes
are induced in response of Pi-deficiency using ATH1
array and real-time RT-PCR. Developing a real-time RTPCR based platform to quantify the primary transcript
(PTs) of all known Arabidopsis miRNAs, we identified
many nutrient responsive miRNAs. Among those are
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miR399s, miR827, miR778, miR156, miR169s,
miR399* and miR778*. In addition, by small RNA
library sequencing, we identified some additional Pistarvation inducible miRNAs including miR2111.
miR399 is induced specifically during Pi-limitation and
goes down with Pi-resupply to Pi-starved plants. miR399
negatively regulates an ubiquitin conjugating enzyme
(UBC24/PHO2) by transcript degradation as well as by
translational inhibition. Therefore, overexpressor of
miR399 (miR399OX) or loss-of-function PHO2 mutant
(pho2) leads to the same biochemical and molecular
phenotype. miR399OX or pho2 leads to the
accumulation of 2–4 fold high Pi in the shoot. Some Pistarvation inducible (PSI) genes including high affinity
Pi-transporter PHT1; 8 remain induced in miR399Ox or
pho2 even under high Pi condition. This explains the high
Pi-accumulation phenotype of miR399OX or pho2 and
shows that miR399/PHO2 module is involved in
signaling Pi-limitation and allocation of Pi between shoot
and root. We identified that PHR1 (a Myb-related
transcription factor) is an upstream regulator of miR399.
PHR1 regulates a large number of PSI genes in addition
to miR399. During Pi-deficient condition, different plant
organs need to communicate and co-ordinate among each
other. We identified that miR399 PT is induced to Pilimitation to a greater extent in shoot. The miR399
moves from shoot to the root via phloem stream and in
down-regulates PHO2. Consequently, higher Pi is
supplied to the shoot to meet its Pi-demand. To our
knowledge, this is the first example of a miRNA shown
to be a systemic signal. Recently, we have identified a
number of new plant miRNAs in Arabidopsis and
Brassica by small RNA sequencing. We are
characterizing some of these Pi-responsive miRNAs to
reveal their role in Pi-signaling and homeostasis.
Furthermore, being a component of protein degradation
pathway, the proteins that PHO2 will target for
degradation are unknown and we are doing some
experiments to find out its target proteins and its
interacting partners.
Genetic and genomic evidence that sucrose is a global
regulator of plant responses to phosphate starvation
in Arabidopsis
Lei, M1, Liu, Y1, Zhang, B2, Zhou, Y2, Zhao, Y-T2,
Wang, X-J2, Raghothama, KG3, Liu, D1
1
Protein Science Laboratory of The Ministry of
Education, School of Life Sciences, Tsinghua University,
Beijing, China; 2State Key Laboratory of Plant
Genomics, Institute of Genetics and Developmental
Biology, Chinese Academy of Sciences, Beijing, China;
3
Dept of Horticulture and Landscape Architecture,
Purdue University, West Lafayette, USA
Plants respond to phosphate (Pi) starvation by exhibiting
a suite of developmental, biochemical, and physiological
changes to cope with this nutritional stress. To
understand the molecular mechanism underlying these
responses, we isolated an Arabidopsis mutant, hps1
(hypersensitive to Pi starvation 1), which has enhanced
sensitivity in almost all the aspects of plant responses to
Pi starvation. Molecular and genetic analyses indicated
that the mutant phenotype is caused by overexpression of
SUCROSE TRANSPORTER 2 (SUC2) gene. As a
consequence, the hps1 has a high level of sucrose in both
its shoot and roots tissues. Overexpression of the SUC2
or its closely related family members SUC1 and SUC5 in
wild type plants recapitulate the phenotype of hps1. In
contrast, the disruption of SUC2 functions greatly
inhibits plant responses to Pi starvation. The microarray
analysis further indicated that 73% of the genes that are
induced by Pi starvation in wild type plants can be
directly induced by elevated level of sucrose in hps1
mutants, even when they are grown under Pi sufficient
condition. These genes include several important Pi
signaling components and those that are directly involved
in Pi transport and mobilization. Interestingly sucrose and
low Pi signals appear interact with each other both
synergistically and antagonistically in regulating gene
expression. Genetic and genomic studies provided strong
evidence that sucrose is a global regulator of plant
responses to Pi starvation. Keywords: Pi starvation
response, hps1 mutant, sucrose, global regulator
by supplying Phi instead of Pi to P-starved plants. This
could be an indication for altered shoot Pi reallocation
patterns in those plants. We show that Phi evokes a set of
distinct physiological and molecular reactions that
distinguish it from well characterised Pi-induced changes
and therefore make it an excellent tool to study P-sensing
and -signal-transduction pathways. This will also provide
new insights into how Phi alters plant defence responses
to boost their resistance against parasitic oomycetes.
Is the phosphate analogue phosphite interfering with
plant phosphorus homeostasis and signalling?
Blomstedt, C1, Neale, A1, O'Donnell, N1, Møller, B2,
Stuart, P3, Hamill, J1, Gleadow, R1
Jost, R1, Pharmawati, M2, Berkowitz, O3, Pearse, SJ1,
Lambers, H1, Finnegan, PM1
1
1
Forage sorghum is an important pasture grass with high
growth rates, providing good feed stock, and it is drought
and heat tolerant. Thus, it is widely grown in dry, tropical
regions worldwide. Sorghum plants produce a stable,
non-toxic tyrosine-derived cyanogenic glycoside
compound known as dhurrin. Dhurrin is a natural
defence product that liberates prussic acid (HCN) when
the leaf tissue is consumed. Young plants or those
experiencing abiotic stresses, particularly drought, can be
highly toxic, accumulating dhurrin to high levels. In
Australia alone there is loss of approximately $20 million
a year from fields of sorghum that cannot be grazed, due
to fears of toxic poisoning. We are using TILLING
(Targeted Induced Local Lesions in Genomes) to identify
induced point mutations in a number of key genes in the
cyanogenesis pathway of sorghum. These mutant lines
are currently being characterised for growth rate,
nitrogen use efficiency and stress tolerance. The aim of
our research is to produce novel sorghum lines with
reduced prussic acid levels.
School of Plant Biology, The University of Western
Australia, Crawley, WA, Australia; 2Biology Dept,
Faculty of Mathematics and Natural Sciences, Udayana
University Campus Bukit, Jimbaran, Bali, Indonesia;
3
School of Biological Sciences and Biotechnology /
Centre for Phytophthora Science and Management,
Murdoch University, Murdoch, WA, Australia
Phosphorus (P) is a macronutrient that is essential for
plant growth, but often has a low availability due to a
low solution P pool and sorption to soil minerals. P is
taken up by the roots of plants in the form of inorganic
phosphate (Pi) and plants feature complex regulatory
networks to maintain P homeostasis and optimise their P i
uptake and storage capacities to meet metabolic and
developmental demand. Phosphite (Phi, HPO32-) is a
more reduced form of P that is used as a biostat to
enhance plant resistance against Phytophthora species.
These pathogenic oomycetes are a major threat to both
food security (Phytophthora infestans caused the Irish
potato famine in the mid 19th century) and natural
diversity (Phytophthora cinnamomi has been termed the
‘biological bulldozer’ due to its devastating effect on
plant communities in many biodiversity hotspots around
the globe). However, despite its successful marketing as
a ‘fungicide’ relatively little is known about its longerterm impact on plant growth and development. Phi is
believed to mimic P i in suppressing the plant’s Pistarvation response and severely inhibits growth of plants
with a low P status. Its uptake most likely proceeds via
transporters of the PHT1 family and is highly sensitive to
competitive inhibition by Pi. Here we show that Phi is not
a perfect mimetic of P i in suppressing Pi-starvation
responses. While it does suppress root-hair formation and
attenuate the expression of many P i-starvation-induced
genes, it does not reduce the expression of many other
well known Pi-signalling genes. In contrast to Pi
resupply, Phi addition actually leads to a severe
inhibition of primary and secondary root elongation and
an increase in lateral root density that is much more
pronounced than under Pi starvation itself. Anthocyanin
accumulation in older leaves is not completely reversed
Sym053: Regulation and genetic
manipulation of nitrogen-based secondary
metabolism in plants – 26 July
Tilling identifies mutations in key genes involved in
the cyanogenesis pathway in sorghum
Monash University, Australia; 2University of
Copenhagen, Denmark; 3Pacific Seeds, Qld, Australia
Smoking out the masters: clustered transcription
factors regulating nicotine biosynthesis in tobacco
Shoji, T1, Kajikawa, M1, Hashimoto, T1
1
Nara Institute of Science And Technology, Japan
Alkaloids are one of the most diverse families of natural
products derived from plants; over 12,000 different
chemical structures have been discovered and some of
them exploited as important pharmaceutical agents.
Tobacco (Nicotiana tabacum) synthesizes nicotine and
related pyridine alkaloids in the root, and their synthesis
increases upon herbivory on the leaf via a jasmonatemediated signaling cascade. Regulatory NIC loci that
positively regulate nicotine biosynthesis have been
genetically identified, and their mutant alleles have been
used to breed low-nicotine tobacco varieties. Here, we
report that the NIC2 locus, originally called locus B,
comprises clustered transcription factor genes of an
ethylene response factor (ERF) subfamily; in the nic2
133
mutant, at least seven ERF genes are deleted altogether.
Overexpression, suppression, and dominant repression
experiments using transgenic tobacco roots showed both
functional redundancy and divergence among the NIC2locus ERF genes. These transcription factors recognized
a GCC-box element in the promoter of a nicotine
pathway gene and specifically activated all known
structural genes in the pathway. The NIC2-locus ERF
genes are expressed in the root and upregulated by
jasmonate with kinetics that are distinct among the
members. Thus, gene duplication events generated a
cluster of highly homologous transcription factor genes
with transcriptional and functional diversity. The NIC2locus ERFs are close homologs of ORCA3, a jasmonateresponsive transcriptional activator of indole alkaloid
biosynthesis in Catharanthus roseus, indicating that the
NIC2/ORCA3
ERF
subfamily
was
recruited
independently to regulate jasmonate-inducible secondary
metabolism in distinct plant lineages. Possible
applications with this class of transcription factors for
desired metabolic engineering of medicinal plants will be
discussed.
Gene-mediated alterations in Nicotiana alkaloid
metabolism and effects on primary and secondary
metabolism in response to stress
Dalton, HL1, Edwards, A1, DeBoer, K1, Neale, A1,
Hamill, J1
1
Monash University, Australia
Increasingly, alkaloids are recognised as important
nitrogen-containing defensive compounds, the synthesis
of which may increase in response to wounding in order
to provide protection from predators in native habitats. A
good example is the production of toxic pyridine
alkaloids, which are a feature of all species in the genus
Nicotiana and some other genera in the Solanaceae
family. Wound- or jasmonate-induced alkaloid synthesis
in Nicotiana species involves an increasingly well
understood cascade of regulatory genes/proteins leading
to elevated transcript and enhanced activity of a number
of key alkaloid biosynthetic enzymes such as ornithine
decarboxylase (ODC), arginine decarboxylase (ADC),
putrescine methyltransferase (PMT) and quinolinate
phosphoribosyltransferase (QPT) and an isoflavone
reductase-like protein (A622) which is associated with
the final stage of pyridine alkaloid biosynthesis.
Production of alkaloids in plants places demands upon
vital resources, particularly nitrogen, and thus requires
close co-ordination between primary and secondary
metabolism. Using various Nicotiana species as
experimental models, the present study focuses on the
regulation of polyamine and pyridine nucleotide (1°)
metabolism and alkaloid (2°) metabolism and the
regulatory control mechanisms that operate under normal
and stressed conditions. Antisense and RNAi-mediated
down-regulation of genes involved in Nicotiana alkaloid
biosynthesis allows not only quantitative and qualitative
effects upon alkaloid metabolism to be determined, but
also effects on activity of related genes and enzymes in
primary and secondary metabolism. The capacity of such
transgenic Nicotiana tissues to redirect nitrogen into
primary metabolism and growth is of particular interest –
particularly after exposure to abiotic and environmental
stresses such as apex removal, leaf wounding, exposure
134
of plants to drought, elevated temperatures and high
light. Recent results show that RNAi-mediated down
regulation of ODC transcript levels in N. tabacum,
causes a substantial change in the overall alkaloid
spectrum of transgenic tissues. These alterations are
particularly evident after wound-associated stress with
diminished levels of nicotine and an increase in
concentrations of anatabine – normally a minor alkaloid.
In separate experiments, RNAi-mediated down
regulation of A622 led to plants with scarcely any
alkaloids in leaf and young shoot tissues – even when
growth is stimulated by apex removal which normally
results in a large increase in alkaloid accumulation in
newly formed young tissues. These plants were
morphologically normal but showed slower growth rates
and reduced capacity to recover from damage to aerial
tissues. They also showed enhanced photosensitivity
which may be associated with alterations in pyridine
cycle metabolism.
The diverse roles of cyanogenic glucosides in plants
Jørgensen, K1,3, Kannangara, R1,
Sánchez-Perez, R2, Møllel, BL1
Bjarnholt,
N1,
1
University of Copenhagen, Plant Biochemistry
Laboratory, Denmark; 2Departamento de Mejora
Vegetal, Centro de Edafoloia y Biologia Aplicada del
Segura-Consejo Superior de Investigaciones Cientificas,
Spain; 33VKR Research Centre 'Pro-Active Plants',
University of Copenhagen, Denmark
Cyanogenic glucosides are ancient bioactive plant
constituents which upon cellular disruption of the plant
tissue in which they are present release toxic hydrogen
cyanide to deter herbivorous insects and pests.
Cyanogenic glucosides are produced from one of the
amino acids valine, isoleucine, leucine, phenylalanine,
tyrosine and cyclopentenyl glycine with alsoximes and
cyanohydrins as key intermediates. The pathway is
catalyzed by two membrane bound cytochromes P450,
belonging to the CYP79 and CYP71 family and a soluble
UDPG-glucosyltransferase. During evolution cyanogenic
glucosides have been recruited for additional function
such as scavengers of reactive oxygen species,
transporters of reduced nitrogen and as buffer
compounds to balance primary metabolism. Cassava
(Manihot esculenta) is a vegetatively propagated tropical
crop with starch rich tubers which serve as a key stable
food in Africa. Major deficits of cassava are low protein
content in the tubers, rapid post-harvest tuber
deterioration and high content of cyanogenic glucosides.
Careful processing of cassava roots is required to avoid
the risk of acute or chronic cyanide intoxication.
Unfortunately, processing to remove the toxins typically
results in loss of protein, minerals, and vitamins. Cassava
produces the cyanogenic glucosides linamarin and
lotaustralin from the amino acids valine and isoleucin,
respectively. Young leaves are the main site of synthesis.
These cyanogenic glucosides are then transported and
stored in the root tubers. Besides serving a protective
role, the cyanogenic glucosides may also function as a
source of reduced nitrogen. In transgenic cassava where
expression of the genes encoding the first step in the
synthesis are blocked using RNAi technology, the lines
with the lowest content of cyanogenic glucosides exhibit
a specific phenotype in vitro showing elongated
seedlings and poor leaf development . When grown in
media with extra nitrogen the phenotypic difference is
minor and the nearly acyanogenic plants show wild type
phenotype when grown in greenhouse. These
observations indicate a role for cyanogenic glucosides
during the early developmental phase of cassava. In
cassava and sorghum (Sorghum bicolor), the seedling
synthesises the cyanogenic compounds during the first
days of germination. In Sorghum the cyanogic glucoside
content per plant peaks 3-4 days after germination and
the diminishes due to endogenous turn-over without
release of hydrogen cyanide. In contrast to cassava, bitter
almonds (Prunus dulcis) store the cyanogenic glucoside
amygdalin in the seed. When the seed germinate the
content of cyanogenic glucosides are turned over and is
used by the developing plant. Cyanogenic glucosides
have in addition to being defence compunds important
roles during plant development and in the interaction
between plants and herbivorous insects and pathogens.
Sym054: Desiccation tolerance; molecular
mechanisms for surviving severe waterdeficit – 26 July
Introducing 'Resurrection Plants'
Don F. Gaff1
Plants respond to drought by adjusting gene expression
and metabolite composition in order to cope with stress.
We have recently reported that a sulfur-related
metabolite, PAP (3'-phosphoadenosine 5'-phosphate),
increases during drought stress in Arabidopsis. PAP is an
inhibitor of RNA processing enzymes and can alter gene
nuclear gene expression. The Arabidopsis mutant alx8
presents altered drought response, and increased PAP
levels, which regulate a novel ABA-dependent pathway
to control stomatal closure. Using a combination of
genetic and biochemical approaches, we investigated the
role of PAP during drought, its interaction with ABA and
how the subcellular pools of this metabolite could
contribute stress responses. Preliminary results suggest
that PAP levels are regulated by both ABA-dependent
and independent mechanisms. Also, the subcellular
location of this metabolite is also important in regulating
the drought response. Additionally, using double and
revertant mutants with altered levels of both PAP,
putrescine and leaf morphology, we investigated the
causes of the drought tolerant phenotype of the alx8
mutant. Our preliminary results indicate that polyamines,
originally thought to be required for the drought
response, are not essential in alx8, and that its leaf
morphology is not the main contributing factor of its
drought tolerance. This research sheds new light into the
roles of metabolites, gene regulation and physiology of
drought in plants.
1
School of Biological Sciences, Monash University,
Clayton, Australia
Functional analysis of dehydration responsive genes
in the resurrection grass Sporobolus stapfianus
Most vascular plants succumb to drought when their
water potential falls below –15MPa. Resurrection plants
have desiccation-tolerant foliage that survives –300MPa
or, in many species, even below –600MPa. Rehydration
of their airdry leaves brings rapid recovery – usually
within 24h. They can survive the airdry state for 6
months to 2 years, depending on the species and on the
ambient relative humidity. Resurrection plants occur over
a wide range of climates, latitudes, altitudes, insolations,
topography, soils and rock substrates. The hydrated
foliage of most resurrection plants is not desiccationtolerant: desiccation tolerance is induced by moderate
water deficits – a process accompanied by changes in
protein composition and an accumulation of protective
substances. Desiccation tolerance exists in only a small
proportion of monocot species and in a much lower
proportion of dicot species in several unrelated families.
Desiccation-tolerant seed and/or pollen are found in
almost all non-resurrection angiosperm species. It seems
most likely that desiccation-tolerant foliage has evolved
separately in several angiosperm families when extreme
selection for improved protoplasmic drought tolerance
acted on plants in shallow soils by producing expression
of their seed/pollen desiccation tolerance mechanism in
buds, then in young leaves and finally in mature leaves
(but never in senescent leaf tissue).
Griffiths, C1, Blomstedt, C1, Hamill, J1, Neale, A1
New insights into the role of nucleotides and
polyamines during drought stress in Arabidopsis
mutants
Estavillo, G1, Chan, K1, Phua, SY1, Pornsiriwong, W1,
Crisp, P1, Pogson, B1
1
The Australian National University, Canberra, Australia
1
Monash University, Australia
Plant drought tolerance is an increasingly important issue
in the current global climate and will remain an issue as
global temperatures rise. The aim of this project is to
identify the functions of two novel genes that are being
transcribed during the dehydration of the resurrection
grass S. stapfianus which exhibits extreme drought
tolerance. The transcripts from these two genes, SDG3i
and SDG4i, accumulate during dehydration particularly
at relative water contents (RWC) of 59-40% and 39-20%
respectively. This project looks at the phenotypic
changes in transgenic Arabidopsis over-expressing these
genes, intracellular localisation of the genes, and
hormone regulation of the genes in S. stapfianus. Motifs
present in the putative protein encoded by SDG3i suggest
it may be a membrane channel protein associated with
the peroxisome while the motifs in the protein encoded
by SDG4i suggest it may have a function associated with
chromatin remodelling. The creation of homozygous
Arabidopsis and rice over-expressing these genes is
being used to provide clues on how SDG3i and SDG4i
function. GFP fusion constructs indicate that SDG4i is
localised to the nucleus. The over-expression of SDG4i
in Arabidopsis has significantly increased osmotic stress
tolerance in comparison to the wild type suggesting that
SDG4i may have a role in regulating desiccation
tolerance in S. stapfianus. Furthermore the SDG4i
transgenic Arabidopsis also appear to germinate and
grow in the cold suggesting at SDG4i is aiding in the
regulation of other stress responses. By looking at these
genes it is hoped that the information gained on the
desiccation tolerance of S. stapfianus can be applied to
135
agriculturally important crop species such as rice, corn
and sorghum and ultimately render a desiccationsensitive plant desiccation-tolerant.
Sym055: Structural basis of function of
plant proteins – 28 July
The evolutionary and biosynthetic origin of cyclic
peptides in sunflower seeds
Mylne, J1
1
Institute for Molecular Bioscience, University of
Queensland, Australia
Sunflowers have universal appeal. Their seeds are
popular in many countries both as confectionary and a
source of high quality oil. Perhaps less well known is that
they contain head-to-tail cyclised peptides that are braced
by an internal disulfide bond. One of these, called SFTI,
is 14-residues in size and an extremely potent inhibitor of
trypsin (1). SFTI has promise as a drug lead in its own
right with drug-like inhibition of the oncogenic protease
matriptase (2) and has been proposed as an ultra-stable
protein engineering scaffold (3). Its structure, ideal for
protease inhibition, is used as a starting point for the
design of serine protease inhibitors and recently a
modified version was shown to specifically inhibit the
protease KLK4, which is involved in prostate cancer (4).
In this talk I will describe the unusual biosynthetic route
for SFTI, and an even smaller cyclic peptide SFT-L1.
They are not encoded by dedicated precursors, rather
they arise as ‘extra’, unrelated products from much larger
proteins as these get proteolytically matured. We have
been using the model plant Arabidopsis to study this
biosynthesis using modified precursor protein transgenes
combined with endogenous gene knockouts. Analysis of
the sequences for the SFTI and SFT-L1 precursor
proteins suggests a conserved processing mechanism
requiring the enzyme asparaginyl-endopeptidase, has
been converged upon at least thrice by plants to generate
cyclic peptides. Upon close inspection, the precursor
DNA sequences also provide some tantalising clues as to
the genetic event that gave rise to these sunflower cyclic
peptides. (1) Luckett, S. et al. 1999. (2) Long, Y.Q. et al.
2001. (3) Daly, N.L. et al. 2006. (4) Swedberg, J.E. et al.
2009.
Directed evolution and rational design of immune
receptor proteins in the flax–flax rust pathosystem
Ravensdale, M1, Thrall, PH1, Ellis, JG1, Dodds, PN1
1
CSIRO, Plant Industry, Canberra, Australia
Disease resistance in the flax–flax rust pathosystem is
determined by a gene-for-gene recognition where flax
immune receptors interact with rust effector proteins. In
one such example, members of the AvrL567 effector
protein family in flax rust interact with members of the L
receptor protein family (L5, L6, and L7) in flax. The
physical nature of these direct protein interactions has
resulted in a co-evolutionary 'arms race' between these
organisms. Mutational analysis of amino acid
polymorphisms occurring between AvrL567 variants has
136
revealed a number of solvent exposed surfaces that
contribute to recognition specificity, suggesting the
presence of multiple interacting surfaces on the
corresponding L receptor proteins. Directed evolution
and rational design strategies have been applied in
attempts to understand, and possibly improve, the
recognition specificities of L receptor proteins. Chimeric
and randomly mutagenized L proteins have been
constructed via overlap PCR and error-prone PCR,
respectively. Evaluation of these modified L proteins in
the yeast-2-hybrid assay has identified specific regions
within the leucine-rich repeat domain that mediate
interactions with specific polymorphic residues found in
AvrL567 variants, and has also revealed evidence of
extensive co-variation between domains and residues
within L proteins.
Structural basis of R-protein mediated disease
resistance in flax against flax rust
Williams, S1, Ve, T1, Bernoux, M2, Anderson, P3,
Dodds, P2, Kobe, B1
1
School of Chemistry and Molecular Biosciences,
University of Queensland, Brisbane, Australia; 2CSIRO
Plant Industry, Canberra, Australia; 3School of
Biological Sciences, Flinders University, Adelaide,
Australia
A plant’s ability to detect an invading pathogen and
circumvent a subsequent disease state is essential for its
survival. The pioneering work of Harold Flor, using the
interaction between flax and flax rust, demonstrated that
this ability to detect and resist the infection of a specific
pathogen rests with two critical genes; a resistance (R)
gene in the plant and a corresponding avirulence
(effector) gene in the pathogen (1). This, so called ‘genefor-gene’ model, has subsequently been shown to apply
in many other plant-pathogen interactions and has
spawned considerable research efforts directed towards
understanding R protein-effector interactions and the
consequential disease resistance response. Using the
flax/flax rust pathosystem our research aims to further
understand the molecular basis of R protein-effector
interactions utilising structural and biochemical
approaches. Flax R proteins encoding tri-domain proteins
with a central nucleotide-binding domain (NB), a Cterminal leucine rich repeat (LRR) and a Toll-interleukin
1 receptor-like (TIR) domain at the N-terminus. We have
previously shown that the flax R proteins, M and L6,
interact directly with the flax-rust effectors AvrL567 and
AvrM, respectively (2,3) and have defined the structure
of the AvrL567 effector protein (4). Here we report the
crystal structure of the TIR domain from the flax R
protein, L6, at 2.3 Å resolution. The structure reveals
important differences from the structures of mammalian
TIR domains, and highlights three separate functionally
important protein surfaces, involved in dimerisation,
interaction with a downstream signalling partner, and
regulatory intramolecular interactions, respectively. We
have also determined the structure of the flax rust
effector protein, AvrM, at 2.7 Å resolution. AvrM, which
has no significant sequence similarity with proteins of
known structure, has a novel L-shaped helical fold, with
two chains forming a dimmer that create an unusual nonglobular shape. Furthermore, using a combined
phenotypic and biochemical analysis of mutants made
within the NB domain of the flax M protein, we further
define the molecular requirements for R protein
activation. Collectively, these results bring us closer to
understanding the molecular basis of R protein mediated
plant disease resistance, a perquisite to the future
engineering of novel resistance specificities in important
crop species. (1) Flor 1971. (2) Dodds et al. 2006. (3)
Catanzariti et al. 2010. (4) Wang et al 2007.
Structural basis of function of plant proteins
Bond, C1, Fujii, S2, Stanley, W3, Small, I1
1
School of Biomedical, Biomolecular and Chemical
Sciences, The University of Western Australia, Crawley,
Australia; 2Centre of Excellence in Computational
Systems Biology, The University of Western Australia,
Australia; 3ARC Centre of Excellence in Plant Energy
Biology, The University of Western Australia, Australia
Organelle gene expression involves a series of more or
less coupled processes from transcription through
transcript processing to translation. Many of the events
that occur during these processes require sequence
recognition by RNA processing factors. In plants,
pentatricopeptide repeat (PPR) proteins are the most
numerous of these factors, with a bewildering array of
450+ family members in all flowering plants studied to
date (1,2,3). PPR proteins are found in lesser numbers in
all eukaryotes with a mitochondrial genome, and
probably play a similar role in organelle gene expression
in plants, animals, fungi and protists (4). The sequencespecific RNA binding ability of these proteins is
remarkable, given the wide range of different targets
bound by different family members, but the molecular
basis for target recognition is almost completely
unknown (5). Research is hampered by the lack of any
experimental data on the detailed structure of these
proteins due to the difficulty of producing the proteins in
large quantities in a soluble form. However, there is a
huge amount of sequence information available from
many fully sequenced plant genomes. We show that this
sequence data is sufficient to construct a plausible
structural model of the PPR motif, and of a tandem array
of PPR motifs, using contact site prediction from covarying amino acid pairs. The methods we employed
should work similarly well on similar protein families
containing tandem repeats for which many sequences are
available. Furthermore, the patterns of selection on one
particular class of PPR proteins give strong indications
about which amino acid residues within the PPR motifs
determine RNA binding specificity (6). Based on this, we
propose a model for how PPR proteins bind RNA. (1)
Small, ID, & N Peeters 2000. (2) Lurin, C, et al. 2004.
(3) O'Toole, N, et al. 2008. (4) Schmitz-Linneweber, C,
& I Small 2008. (5) Delannoy, E et al. 2007. (6) Fujii, S
et al. (in press).
screened for mutants with enhanced growth relative to
their dwarf siblings, but which still retained the original
dwarfing mutation. Many such ‘overgrowth’ mutants
were isolated and characterised, the vast majority being
due to new mutations in the principal DELLA genes of
these species (Sln1 and Rht-1 for barley and wheat
respectively). More than 30 new DELLA alleles have
been identified, and this number will increase as more
mutants are sequenced. Overgrowth mutants grow faster
than their dwarf parent because they have enhanced GA
signalling. We investigated whether GA responses other
than growth are also affected in such lines. á-Amylase
production by endosperm half-grains of barley is
normally seen only in the presence of an active GA.
Overgrowth lines showed clear examples where the
original parental response was maintained, but also other
examples of moderate and of high á-amylase production
in the absence of active GAs. Some lines with only a
partial restoration of growth showed high levels of áamylase production. Analogous results were found in
wheat, with a poor correlation between mature plant
height and the maximum extent of coleoptile elongation.
Both sets of results indicate a considerable degree of
specificity in the extent to which different overgrowth
alleles influence different GA responses. In barley we
have observed novel phenotypes associated with some
overgrowth alleles. Several new alleles are associated
with an increase in grain size of approximately 25%,
averaged over several greenhouse generations. This
effect has also been observed in back-crossed material in
a commercial barley cultivar. A combination of two
different overgrowth mutations results in barley lines that
grow much better in the presence of exogenous abscisic
acid (ABA) than either single mutants or the parental
line. Such lines also had faster growth than either single
mutants or the wild type when subjected to water deficit.
DELLA proteins contain several conserved amino acid
sequence motifs, and the functions of these regions,
which include interactions with other proteins such as the
GA receptor, an F box subunit involved in targeting
DELLA for degradation, and PIF (phytochrome
interacting factor) transcription factors, are being actively
studied in rice and Arabidopsis. The phenotypes of
different barley and wheat overgrowth alleles will allow
specific changes in DELLA motifs to be related to
different roles of this protein in influencing phenotype.
These are likely to involve differences in binding to
interacting proteins. In one case, different mutations of
the same amino acid residue of the SLN1 protein in
barley lead to clearly different phenotypes. DELLA
semidwarfs formed the basis of the ‘Green Revolution’ in
wheat, and are still used in the vast majority of wheat
varieties. By generating many new semi-dwarfing alleles,
potentially associated with other useful traits (early
vigour, high grain dormancy, rapid á-amylase
production), we hope to extend the range of semidwarfing alleles available for wheat and barley breeding.
Overgrowth mutants of barley and wheat: new
insights into the functions of DELLA proteins
Chandler, P1
1
CSIRO Plant Industry, Canberra, Australia
Defined dwarf mutants of barley and wheat were treated
with a mutagen, sown in the field, and the M2 generation
137
Sym124: Mycoheterotrophic plants –
29 July
Diversification and mycorrhizal specificity of
flowering plants living on arbuscular mycorrhizal
fungi
Merckx, V1, Smets, EF1,2
1
Netherlands Centre of Biodiversity Naturalis (section
NHN), Leiden University, The Netherlands; 2Laboratory
of Plant Systematics, K.U.Leuven, Belgium
Fully mycoheterotrophic plants are achlorophyllous
during their entire development and obtain all of their
carbon from root-associated fungi. Most fully
mycoheterotrophic flowering plants are growing in the
leaf litter of dense tropical rain forest and associate with
arbuscular mycorrhizal fungi (Glomeromycota). Due to
the rarity and ephemeral occurrence of tropical
mycoheterotrophic plants we know little about the
evolution and ecology of the intimate interaction between
these plants and their fungi. We use nuclear and
mitochondrial DNA data to construct diversification
hypotheses for mycoheterotrophic Burmanniaceae,
Thismiaceae, Triuridaceae, and Gentianaceae. Molecular
clock inferences allow us to compare the timing of the
shifts towards mycoheterotrophy in these different
clades. Our results indicate that in some clades a fully
mycoheterotrophic mode of life evolved relatively
recently, while other clades share an ancient origin. Older
mycoheterotrohic clades consist of considerable more
species than more recent clades. This demonstrates that
mycoheterotrophic lineages are able to persist and
diversify over considerable periods of time. In addition,
we sampled roots of a subset of mycoheterotrophic
species from each clade and analyzed the small subunit
ribosomal DNA gene amplified from root DNA extracts
using primers specific for arbuscular mycorrhizal fungi.
The results indicate that certain clades of arbuscular
mycorrhizal mycoheterotrophs consist of specialized
species, that associate with very narrow lineages of fungi.
Other clades contain generalist species, that are able to
associate with a broad range of fungi. Generalist
mycoheterotrophic species seem to have broader
distribution ranges than specialists.
Factors driving the mycoheterotrophic
autotrophic carbon gain by green orchids
versus
Gebauer, G1, Stöckel, M1, Preiss, K1, Adam, I1, Liebel,
H1
1
BayCEER, Laboratory of Isotope Biogeochemistry,
University of Bayreuth, Bayreuth, Germany
In the mycorrhizal symbiosis plants usually exchange
photosynthates for mineral nutrients acquired by fungi
from the soil. This mutualistic arrangement has been
subverted by a few hundreds of fully mycoheterotrophic
plant species that lack the ability to photosynthesize. The
most numerous examples of this behaviour are found in
the orchid family. Non-photosynthetic orchids are known
to be highly specialized exploiters either of the
ectomycorrhizal symbiosis of trees or of wood-rotting
saprotrophic fungi. These fully mycoheterotrophic
138
orchids are characteristically distinguished in their C and
N stable isotope natural abundance from co-occurring
autotrophic plants in a similar way as various functional
types of fungi are characteristically distinguished in their
isotope signature from co-occurring plants (Gebauer &
Meyer 2003). Also among the numerous green orchid
species more and more representatives, specifically from
the subfamily Epidendroideae, turn out to possess isotope
signatures positioned between fully autotrophic and fully
mycoheterotrophic plants. These orchids live obviously
partially at the cost of their fungal partners. Therefore,
their type of nutrition is called partial mycoheterotrophy
(Gebauer & Meyer 2003). Here we present evidence that
the proportional carbon gains from photosynthesis or
from the fungal source by these partially
mycoheterotrophic orchids are not constant. They are
rather related to a couple of biotic and environmental
factors. Of specific importance are (1) the functional
types of fungal partners, (2) the light climate at the
orchid habitat and (3) the leaf chlorophyll concentration.
Orchids associated with fungi simultaneously forming
ectomycorrhizae with neighbouring trees gain
considerably more carbon from the fungal source than
closely related orchids associated with saprotrophic fungi
of the polyphyletic Rhizoctonia group (Liebel et al.
2010). Even within orchid species the proportional
carbon gain from either source can vary considerably.
Cephalanthera damasonium individuals living in the
deepest shade of beech forests and individuals of the
same species with variegated leaves and therefore having
considerably less leaf chlorophyll concentrations tap
considerably more on the fungal carbon source than
individuals living in more sunny forest gaps and having
fully green leaves (Preiss et al. 2010; Stöckel et al. 2010).
Our results document furthermore that the orchids’
change in proportional reliance on fungi as a carbon
source affects leaf carbon and nitrogen concentrations.
Parallel evolution of mycoheterotrophy in land
plants: a different story in the tropics vs temperate
regions?
Selosse, M-A1, Martos, F1, Walder, F2, Courty, P-E2
1
Centre d'Ecologie Fonctionnelle et Evolutive, CNRS
Montpellier, France; 2Botanical Institute, University of
Basel, Switzerland
The evolution of the land flora has provided repeated
emergences of the mycoheterotrophic habit, where
achlorophyllous plants exploit carbon from fungi
mycorrhizal in their roots. This condition, suggested to
be an adaptation to forest environments where little light
is available, was mainly studied through two tools:
fungal molecular barcoding allowed identification of the
(often uncultivable) fungi from the roots; natural isotopic
abundances in mycoheterotrophs were instrumental in
supporting that a given fungal guild was providing
carbon to the plant. Most classical works investigated
temperate and Mediterranean species that proved to have
specific basidiomycetes fungal partners, forming the socalled ectomycorrhizae with surrounding trees. Recently,
the research interest somewhat shifted to subtropical and
tropical forests, where most mycoheterotrophic species
are growing, including many species that connect to
arbuscular-mycorrhizal (AM) fungi. Studies by our team
and others have shown that high specificity for
mycorrhizal fungi is not the rule among tropical
mycoheterotrophs. Although some species are specific,
other species associated with basidiomycetes or AM
fungi show less specificity, even if they remain selective
(i.e. have preferenda among the whole diversity of the
targeted fungal guild). Secondly, especially in forest
devoid of ectomycorrhizal basidiomycetes, other fungal
guilds were targeted: some orchids from unrelated genera
receive carbon from saprotrophic, wood-decaying or
litter-decaying fungi, as supported by their isotopic
abundances. At the same time and even in same forests,
AM fungi were used by other mycoheterotrophs, as
stated above, e.g. in the Gentianaceae and
Burmanniaceae families. Our ongoing works suggest
that, in the later case, the isotopic properties of the
continuum between green plant (providing carbon) – AM
fungi – mycoheterotrophic plant shows differences as
compared
to
the
analogous
continuum
for
mycoheterotrophs associated with saprotrophic or
ectomycorrhizal basidiomycetes. Moreover, C/N values,
that are often low in mycoheterotrophs associated to
basidiomycetes, are unexpectedly higher in AM
associated mycoheterotrophs. Based on our recent data
and several published ones, we hypothesize here that
different factors contribute to the features recorded for
tropical mycoheterotrophs. First, the ability of
saprotrophs to support growth of mycoheterotrophs may
simply be a question of water availability and duration of
activity over the year. Indeed, in every biomes,
saprotrophic fungi support a mycoheterotrophic growth
during underground germination of orchid seeds, but this
stops when plant enlarge and emerge from the soil, into a
more desiccant environment. Second, AM-associated
mycoheterotrophy may have evolved purely to support
carbon need of the mycoheterotrophs, especially in the
framework of shaded, but not N-limited tropical forests;
at the opposite, the evolution of basidiomycetesassociated mycoheterotrophs may be linked to N
acquisition in N-limited, but not always dark, temperate
forests. Thus, we discuss that, beyond apparent
similarities, the parallel evolution of mycoheterotrophy
in land plants followed evolutionary pathways that are
linked to the ecology of the respective plant lineages
involved, thus differing from one biome to another.
Australian obligate myco-heterotrophic orchids and
their fungal associations
Dearnaley, JDW1, Le Brocque, AF2, Bougoure, JJ
1
Australian Centre for Sustainable Catchments and
Faculty of Sciences, The University of Southern
Queensland, Australia; 2Lawrence Livermore National
Laboratory, USA
All orchids rely on mycorrhizal fungi for provision of
carbon compounds during seed germination and uptake
of inorganic nutrients and water throughout the life cycle.
For adult green orchids, the flow of carbon appears to be
reversed with photosynthate provided to fungal partners
in exchange for their services. A small proportion of the
approximately 30,000 orchid species worldwide are not
photosynthetically active at adulthood. These obligate
myco-heterotrophic orchids rely on mycorrhizal fungi to
provide carbon compounds as well as inorganic nutrients
and water throughout their life cycles. Our research has
been focused on understanding the mycorrhizal biology
of four Australian obligate myco-heterotrophic orchids,
namely Dipodium variegatum, Dipodium hamiltonianum,
Erythrorchis cassythoides and Gastrodia sesamoides.
Identifying the mycorrhizal fungi of obligate mycoheterotrophic orchids is complicated as the fungi
involved are usually impossible to isolate into pure
culture. We have circumvented this problem by
extracting DNA from whole orchid roots and separating
fungal from plant DNA via PCR with fungal specific ITS
primers. Amplicons have been cloned and sequenced and
GeneBank BLAST searches used to identify the fungal
partners of the four orchid species. To support our
interpretations of the results of these molecular analyses,
we have used mass spectrometry to study natural carbon
and nitrogen stable isotope abundances within orchid
tissues. Fungal ITS sequencing suggested that the fungal
community of Dipodium variegatum included Russula,
Trichoderma and Verticillium spp. The fungal
community of Dipodium hamiltonianum consisted of
Gymnomyces, Russula and Penicillium spp. Analysis of
the fungal endophytes of Erythrorchis cassythoides
suggests that the orchid is colonized by both
ectomycorrhizal fungi such as Russula and Coltricia as
well as the saprotrophic Gymnopus. In Gastrodia
sesamoides, the main fungal partner revealed by ITS
sequencing was a member of the wood-rotting
Campanella genus. This finding was reinforced by stable
isotope data which suggested that the orchid receives
carbon from saprotrophic fungi. These results suggest
that like North American and European obligate mycoheterotrophic orchids, some Australian obligate mycoheterotrophic orchids are colonised by members of the
Russulaceae. As these fungi are ectomycorrhizal and
Dipodium species typically grow at the base of
Eucalyptus, the orchids may be indirect parasites on the
trees but this remains to be proven. The involvement of
Gymnomyces spp. as mycobionts in D. hamiltonianum
may be one reason why this orchid is becoming rare as
the fruiting bodies of this species are much sort after food
of fungivorous marsupials which may act as dispersal
agents for fungal spores. The occurrence of both
ectomycorrhizal and saprotrophic fungi as mycobionts in
Erythrorchis cassythoides suggests that the orchid may
be able to survive the death of its host tree by switching
from a parasitic mode of nutrition to a saprophytic one.
Gastrodia sesamoides is exceptional among the four
orchids studied in that it appears to exclusively receive
its carbon from a wood-rotting saprotrophic fungus.
Investigation of the mycorrhizal biology of these
Australian obligate myco-heterotrophic orchids has thus
revealed some novel orchid-fungal associations as well
as provided insight into the multiple nutritional modes of
these unusual plants.
Comparative
plastid
genome
mycoheterotrophic Ericaeae
study
in
Stefanovic, S1, Braukmann, T1
1
University of Toronto,Mississauga, Canada
Heterotrophic plants show a wide range of evolutionary
degradation of photosynthetic capability and rely entirely
or partially on their host autotrophic plants to supply
water and nutrients. These plants are usually divided into
two morphologically distinct yet evolutionary artificial
groups, parasitic plants and mycotrophic plants,
139
depending on whether they derive all or part of their
nutrients via direct connection with the host plant tissue
(haustorium), or via symbiotic relationship with
mycorrhizal fungi, respectively. Haustorial parasitism
has evolved at least 11 times independently within
flowering plants and there are at least 10 independent
origins of mycoheterotrophy in angiosperms plus one in
conifers. Each of those lineages of heterotrophs
represents an independent natural genetic experiment
whose plastids and genes have evolved under relaxed
functional constraints and therefore, each represents a
unique opportunity to dissect plastome function and
evolution. While several of haustorial parasitic groups
have been moderately- to well-studied (e.g., Epifagus,
Orobanchaceae; Cuscuta, Convolvulaceae), very few of
mycoheterotrophic lineages were subjects of any
significant plastid genome study to date. Hence, little is
known about their plastid genome size, content, gene
order, and expression. Ericaceae, the heather family, is a
large and diverse group of plants known to have
elaborate
symbiotic
relationships
with
fungi
(mycorrhizae). Grounded in an improved phylogenetic
framework and a broad taxonomic sampling, a
comparative investigation of plastid genomes was
conducted in this family using a Southern hybridization
approach. This survey encompassed lineages within
Ericaceae that have quite different life histories and
trophic levels, including multiple representatives of
hemi-mycoheterotrophs
(pyroloids)
and
holomycoheterotrophs (monotropoids). Also, a number of
fully photosynthetic taxa, carefully chosen to best
represent the other major clades within the family, were
included. More than 50 probes, derived from all
categories of protein-coding genes usually found in
plastomes of fully photosynthetic plants, were used.
Comparative analyses of the plastomes of plants along
the full trophic spectrum, from autotrophy to hemiheterotrophy to full heterotrophy, allow us to assess the
degree to which genomic changes take place in hemiheterotrophs prior to complete loss of photosynthesis and
to dissect the evolutionary pressures on plastomes
exerted by other plastid metabolic functions. Also,
comparisons with well-studied parasitic systems provide
us with an opportunity to assess whether haustorial
parasitism and mycoheterotrophy have different genomic
consequences.
Pylogenetics of mycoheterotrophic monocots and
gymnosperms using plastid loci
Lam, V1, Biffin, E2, Rai, H3, Chang, Y1, Graham, SW1
1
University of British Columbia, Canada; 2University of
Adelaide, Australia; 3Utah State University, USA
Mycoheterotrophic plants obtain their carbon budget
from fungi involved in mycorrhizal networks, and thus
indirectly from green plants. Full mycoheterotrophs are
not photosynthetic and they often have reduced, scalelike leaves and unusual floral biology. Mycoheterotrophy
has arisen multiple times in plant evolution, most
abundantly in the monocots (i.e., in Burmanniaceae,
Corsiaceae, Iridaceae, Orchidaceae, Petrosaviaceae,
Thismiaceae and Triuridaceae); this nutritional mode is
known only sporadically in other land plants, including
the only heterotrophic conifer, Parasitaxus usta.
Genomic consequences of the transition from an
140
autotrophic to fully heterotrophic lifestyle are evident in
the loss or degradation of photosynthesis-related plastid
genes, such as the Rubisco large subunit (rbcL).
Therefore, phylogenetic studies of these plants have
tended to focus on mitochondrial or nuclear markers,
either to study relationships within taxa, or to place them
in overall plant phylogeny. Some of these placements,
based in part on retained plastid genes, are now
uncontroversial. For example, Petrosavia is now
recognized as one of two genera of Petrosaviales, one of
the deepest diverging lineages in monocot phylogeny.
However, the local phylogenetic placement of other
mycoheterotrophic taxa is less clearly resolved, and in
general these plants remain poorly integrated with
mainstream plant phylogenetic studies, which continue to
focus on plastid markers. Essential, non-photosynthetic
genes in the plastid genome may be retained regardless
of trophic lifestyle, and represent potentially useful
sources of phylogenetic markers. They may also provide
insights into plastid genome evolution and function in
heterotrophic plants. Here we report on our attempts to
recover plastid genes involved in different aspects of
plastid function: accD (acetyl-CoA carboxylase, involved
in fatty-acid biosynthesis), matK (the plastid Group II
intron maturase) and clpP (serine protease involved in
hydrolysis of peptide bonds). We surveyed these genes in
a broad range of monocots, including the major
mycoheterotrophic lineages outside Orchidaceae. We
recovered at least one of these genes from the
mycoheterotrophic families, including the first plastid
sequences reported from Corsiaceae (for Arachnitis
uniflora) and Triuridaceae (Sciaphila spp.). Phylogenetic
analyses were complicated in some cases by long
branches subtending sequences from mycoheterotrophs,
but in most cases the gene products were open reading
frames. Our data are consistent with placements of
Burmanniaceae and Thismiaceae in Dioscoreales, and
indicate a (tentative) placement of Corsiaceae in Liliales.
Sequences recovered from Sciaphila are both diverse and
divergent, but some of them place this taxon within
Stemonaceae (Pandanales). We also surveyed a broad
range of plastid genes in the mycoheterotrophic (and
hemiparasitic) conifer Parasitaxus, to place it better in
conifer phylogeny. We recovered open-reading frame
sequences from plastid genetic apparatus genes (accD,
ribosomal protein genes, RNA polymerase subunit genes
and matK). Most photosynthesis-related genes
(photosystem II subunit genes) had interrupted reading
frames and are present as multiple recent and divergent
copies, but atpB and atpE are present as open reading
frames, hinting at possible retention of function. We were
able to obtain a preliminary estimate of its divergence of
Parasitaxus from two conifers (Manoao and
Lagarostrobos) that we were also able to confirm as its
closest relatives in Podocarpaceae.
Sym145: Evolution of plant secondary
metabolites – phylogeny and
chemoinformatics – 29 July
Evolutionary footprints of higher plants in chemical
space
Backlund, A1
1
Uppsala University, Sweden
Natural compounds and their biosynthesis machinery are
developed and honed under evolutionary pressure,
displaying a unique diversity of chemical properties and
corresponding biological activities. The width of their
chemical diversity when compared to various
combinatorial chemistry compund libraries, have in the
last few years fostered a renewed interest in natural
compounds also from e.g. the pharmaceutical industry.
Of utmost importance for a rational characterization of
the observed diversity of plant secondary compounds are
two aspects: one the identification and charting of the
biologically relevant chemical space, the other a similar
charting of the corresponding evolutionary space (1, 2
pro parte). The first key to achieve such a goal would be
to explore evolutionary space by elucidating and utilising
robust phylogenies for the organisms under study. From
this basis reflecting the evolutionary history and hence
biosynthesis development, further conclusions can be
drawn (e.g. 3). The second key would consequently be
the coverage of secondary metabolites' chemical space.
For this purpose we introduced ChemGPS-NP (4, 5),
with the aim to provide a tool for more efficient and
stringent compound comparison, to identify parts of
chemical space related to particular biological activities,
and to track changes in chemical properties due to e.g.
evolutionary traits and modifications in biosynthesis.
Physical-chemical properties not immediately discernible
from structural data can be compared. Based on these
initial assumptions, the intersection of chemical and
evolutionary space have been explored. With regard to
e.g. compound classes such as iridoids, betalains, and
sesquiterpene lactones, evolutionary patterns of changes
in physical-chemical properties are observed and
compared. For eight major classes of plant defence
peptides analyses of structure base alignments provide
arguments for rational classification. References: (1)
Bohlin, L et al. 2007. (2) Bohlin, L et al. 2010. (3) elSeedi, H et al. 2005. (4) Larsson, J et al. 2005. (5)
Larsson, J et al. 2007.
The suitability of various classes of natural products
as chemosystematic markers: case studies from the
Cichorieae and Gnaphalieae (both Asteraceae)
Zidorn, C1
1
University of Innsbruck, Austria
Chemosystematics is an interdisciplinary field of natural
sciences investigating the distribution of natural products
within all groups of living organisms (archaea, bacteria,
fungi, plants, and animals). Many primary metabolites
are shared by most forms of life (with the notable
exception of many archaea) and studies in
chemosystematics aiming at the elucidation of
relationships between taxa are therefore usually focused
on secondary metabolites. Recently, the systematics of
the Hypochaeridinae subtribe (Asteraceae, Cichorieae)
was re-evaluated based on a combination of published
and new molecular data as well as on a combination of
these data with phytochemical data. The results required
major changes in the systematics of the subtribe. The
overall satisfactory level of knowledge of the
phytochemistry of the various genera of the
Hypochaeridinae (and the Cichorieae in general) together
with the good coverage of molecular data gave the
opportunity to systematically compare the degree of
systematic information extractable from the distribution
patterns of plant secondary metabolites from different
classes of natural products. Three classes of secondary
metabolites were analyzed, caffeic acid derivatives,
flavonoids, and sesquiterpene lactones. Flavonoids are
due to the facts that they are easily detectable by simple
means, occur ubiquitously in higher plants, and show a
high degree of structural variations, one of the favorite
classes of secondary metabolites for phytochemical
investigations. However, the erratic distribution of some
groups of flavonoids, e.g. isoetin derivatives, makes
flavonoids suitable systematic markers only at low levels
like species and intra-specific level. Sesquiterpene
lactones on the other hand are especially in the
Asteraceae excellent chemosystematic markers at the
level of tribes, subtribes, and genera. These patterns were
also verified for the Hypochaeridinae. In recent studies,
the formerly overlooked suitability of caffeic acid
derivatives as excellent chemosystematic markers was
established for some genera of the Cichorieae, e.g. the
morphologically similar genera Crepis and Hieracium
are characterized by the presence and absence,
respectively, of the caffeoyl tartaric acid derivatives. The
alpine Leontopodium alpinum (Edelweiss) features
unique caffeoyl glucaric acid derivatives. A
phytochemical investigation of European members of the
closely related genus Gnaphalium revealed that caffeoyl
glucaric acid derivatives currently known only from
Leontopodium are also present in Gnaphalium.
Interestingly, Gnaphalium species ecologically restricted
to high alpine environments contain much higher
concentrations of these radical scavenging compounds
than their lowland relatives. This hints to a major caveat
of all chemosystematic studies, the level of many natural
products is directly linked to ecological stressors and the
analytical absence of a certain secondary metabolite does
not necessary imply the inability of the investigated plant
taxon to synthesize these compounds, if need be. Taking
other related studies into account, a picture emerges,
where chemical characters are in their suitability as
systematic markers as well as in their dependency from
ecological factors similar to morphological characters.
The applicability of various kinds of these morphological
markers, too, differs depending on the group
investigated; one or the other set of characters might be
better suited to characterize taxa at different systematic
levels and in different systematic groups.
Shionone synthase, an oxidosqualene cyclase of an
Asteraceae plant that yields a unique tetracyclic
triterpene ketone: molecular cloning and evolutionary
view
Ayabe, S-I1, Sawai, S1, Uchiyama, H1, Mizuno, S1, Aoki,
T1, Akashi, T1, Takahashi, T1
141
1
Dept of Applied Biological Sciences, Nihon University,
Japan
Biosynthesis and
Gelsemiaceae
Plant triterpenoids contain both primary metabolites, i.e.,
the precursors of membrane sterols and steroid
hormones,
and
secondary
metabolites
like
pharmaceutically
important
saponins
and
ecophysiologically active chemicals. They display a
remarkable variety with about 100 mono- to penta-cyclic
skeletons, but structures most frequently found are
6/6/6/5 tetracycles and both 6/6/6/6/6 and 6/6/6/6/5
pentacycles. The skeletal variety is attributed to both the
diversity of oxidosqualene cyclase (OSC) enzymes
(genes) and multiple products from single OSC reactions.
Molecular phylogenetic analysis indicates that plant
OSCs belong to four families: lanosterol synthase (LAS),
cycloartenol synthase (CAS), lupeol synthase (LUP) and
the most divergent β-amyrin synthase (BAS) families.
Shionone, the major triterpenoid of the roots of Aster
tataricus, an Asteraceae plant used in traditional Oriental
medicine, has a unique 6/6/6/6 tetracyclic skeleton with a
3-oxo-4-monomethyl partial structure. The A-C ring part
of shionone is identical to the same part of a 6/6/6/6/6
pentacyclic triterpene, friedelin. The occurrence of
shionone is very limited, whereas friedelin is widely
distributed in land plants. While the biogenetic
consideration was useful in the structural determination
of shionone in the 1960s (1), no actual biosynthetic
studies have been performed, and whether a single OSC
carries out the construction of the rare skeleton and
extensive methyl and hydride shifts to yield shionone or
more than one enzymes are involved in its biosynthesis
remains unclear. Only two OSCs have so far been
reported to yield the 6/6/6/6 tetracycles; Arabidopsis
thaliana baruol synthase (2) and Stevia rebaudiana
baccharis oxide synthase (BOS; 3). In 2010, the first
friedelin synthase cDNA was cloned from Kalanchoe
daigremontiana (4), which should catalyze up to 10
rearrangement steps from 2,3-oxidosqualene. These
OSCs are all multiproduct enzymes, but shionone has
never been documented as a product from their reactions.
In the present study, we have identified the cDNA of an
OSC that yields shionone for the first time. An OSC
cDNA isolated from A. tataricus by PCR techniques was
expressed in the LAS-deficient yeast, and the OSC
reaction products accumulated in the yeast were
identified. The enzyme yielded ca. 90% shionone and
small amounts of byproducts, and was designated
shionone synthase (SHS). The presence of 4-epishionone
among the byproducts indicates that SHS catalyzes the
production of the enol form of shionone, and
subsequently the major product shionone and minor 4epishionone should be formed non-enzymatically.
Phylogenetic analysis and comparison of reaction
specificity of SHS and other OSCs showed that SHS and
BOS have evolved in the Asteraceae from BAS lineages,
and SHS must have acquired a high product-specificity
and unique species-specificity in A. tataricus. The
evolutionary
and
chemotaxonomic
discussion
incorporating recently reported plant OSCs yielding
shionone-related triterpenes will be presented. (1)
Takahashi T et al. 1967. (2) Lodeiro S et al. 2007. (3)
Shibuya M et al. 2008. (4) Wang Z et al. 2010.
Backlund, M1, Larsson, S2, Backlund, A3
142
the
systematic
placement
of
1
Swedish Museum of Natural History, Stockholm,
Sweden; 2Royal Botanical Gardens, Kew, UK; 3Uppsala
University, Uppsala, Sweden
The order Gentianales has during the last decade been the
target for a number of major systematic endeavours, most
based on molecular data from DNA sequences. Although
a number of achievements have been made, including the
interfamilial systematics of Rubiaceae (1, 2), the
reduction of Asclepiadaceae as a subfamily of
Apocynaceae (3), and the re-circumscription of
Loganiaceae (4). Among the remaining interfamilial
issues remaining to be addressed in the Gentianales, we
find the question of the systematic rank and affinities of
the family Gelsemiaceae (5). The small family
Gelsemiaceae, comprised of only the two genera
Gelsemium and Mostuea, and their 17 species, exhibit
morphological similarities with both Loganiaceae s.str.
and Apocynaceae. Also from phylogenetic analyses of
DNA sequence data have no conclusive results yet been
reached, with only weak affinities indicated. There is,
however, additional information derived from analyses of
alkaloid biosynthesis which may shed further light on
this situation. From the Gelsemiaceae a set of unique
alkaloids have been described. Comparing core structural
elements from these, with known biosynthetic reactions
and alkaloids from the neighbouring families
Apocynaceae and Loganiaceae provide a plausible
explanation for the ancestry of the Gelsemiaceae
alkaloids. This demonstrates yet another example of how
interpretations of natural products biosynthesis may aid
in systematic classifications or circumscriptions.
References: (1) Bremer, B 1996. (2) Bremer, B et al.
1995. (3) Sennblad, B & Bremer, B 1996. (4) Oxelman,
B et al. 1999. (5) Backlund, M et al. 2000.
Can phylogenies help bioscreening? A comparative
analysis of the medicinal floras of Nepal, New
Zealand and the Cape of South Africa
Saslis-Lagoudakis, CH1,2, Savolainen, V2, Hawkins, JA1
1
Dept of Biological Sciences, The University of Reading,
Reading, UK; 2Dept of Life Sciences, Imperial College,
London, Silwood Park Campus, Ascot, UK
Several ethnomedicinal studies have aimed to reveal
relationships between ethnomedicinal floras of different
peoples. Traditionally, such efforts have been impeded
due to the fact that different peoples are exposed to
different local floras, limiting comparability between
dissimilar floras. However, the advent of molecular
phylogenetics in recent decades has revolutionised our
knowledge of plant relationships and has provided a
framework where for a number of plants a phylogenetic
distance can be calculated. This allows us to calculate
relatedness of ethnomedicinal species that are used in
different parts of the globe, in order to quantify how
‘phylogenetically different’ ethnofloras from different
cultures are. In this study, the phylogenetic relationships
of the floras from three distant regions from biodiversity
hotspots (Nepal, New Zealand, and the Cape of South
Africa) were reconstructed. Trees were constructed for
individual floras as well as for the three floras combined.
Ethnomedicinal usage from each region was
superimposed on the phylogenetic trees. We applied
techniques initially designed for community ecology to
calculate phylogenetic distance of the ethnofloras and to
highlight lineages that are more heavily used than others.
We found significant phylogenetic clumping for
medicinal plants in the phylogeny in most cases in the
individual trees and in some cases in the combined tree,
suggesting that i) certain lineages are richer in medicinal
properties than others and ii) close relatives are used in
different regions to treat similar conditions. Usage of
closely related taxa globally would indicate that these
taxa are the most promising in delivering new medicines,
as they have been selected independently for similar
uses. We are proposing that these techniques can be
applied to guide bioscreening from phylogenetic data and
the same phylogenetic manipulations can be used at the
interface of phylogeny and phytochemistry. This study
provides a methodological and conceptual framework of
how phylogenies, combined with ethnomedicinal data,
can help bioscreening programmes and reveals that
ethnomedicinal floras around the globe might not be as
distantly related as previously thought.
The predictive power of phylogenies for traditional
medicine and lead discovery in Amaryllidaceae
Rønsted, N1, Stafford, G1, Meerow, A2, van Staden, J4,
Jäger, A1
1
University of Copenhagen, Denmark; 2United States
Dept of Agriculture, Miami, Florida, USA; 3Fairchild
Tropical Garden, Miami, Florida, USA; 4University of
KwaZulu-Natal, Pietermaritzburg, South Africa
Plant secondary metabolites are produced and selected by
evolution for their biological activity. Such natural
products have always played a major role in traditional
medicine and as leads for modern medicine. Only a small
fraction of the world’s biodiversity has been explored for
chemical and biological activity. A correlation between
phylogeny and biosynthetic pathways is often assumed
and could offer a predictive approach enabling more
efficient selection of plants for traditional medicine lead
discovery. However, formal tests of correlations between
phylogeny and chemistry are rare, and the potential
predictive power is consequently unknown. As a case in
point, we are exploring the Amaryllidaceae subfamily
Amaryllidoideae sensu APG, which is known for
subfamily specific alkaloids with activity in the central
nervous system (CNS). Galanthamine registered for
treatment of Alzheimers disease was first isolated from
the Caucasian snowdrop Galanthus woronowii. We
present a phylogenetic hypothesis of the Amaryllidaceae
subfamily Amaryllidoideae based on nuclear and plastid
DNA sequences of 120 of the circa 850 species,
representing all tribes and geographical regions. All
major lineages are now well supported and the extended
sampling uncovered several genera as non-monophyletic,
emphasizing the importance of using phylogenetic rather
than classical classification for interpretation of character
distribution. Alkaloid profiles and CNS-related
bioactivity profiles are significantly correlated with
phylogeny using formal tests. Relationships between
phylogenetic and chemical diversity are further explored.
The predictive power is used to select candidate taxa for
lead discovery and to make recommendations for
traditional use.
Sym151: Plants as concept generators for
biomimetic materials and structures with
hierarchical organisation – 28 July
Plants as concept generators for biomimetic materials
and structures with hierarchical organisation
Speck, T1
1
Plant Biomechanics Group Freiburg, Botanic Garden,
Faculty of Biology, University of Freiburg, Germany
In the course of evolution, plants have developed a
hierarchically organisation on at least five levels: in the
stem, the tissues, the cells, the cell wall structure and the
biochemical level. These hierarchies are also expressed
by gradients in the tissues and the presence of sublevels
(e.g. groups of fibrous bundles-fibrous bundles-fibres)
and hold responsible for beneficial mechanical properties
like a benign fracture behavior, an optimized vibration
damping or impact damping, high bending stiffness, heat
insulation, avoidance of notch stresses and delamination
as well as actuation and self-adaptation properties.
Therefore, analysing the hierarchical organisation in
plants is a major key toward understanding the
morphological-mechanical relationships in the natural
structures and for assessing the potential for technical
implementation. Over the last few years, it has been
shown in a multitude of biomimetic projects that such a
translation into technical products is feasible. However,
the hierarchical organisation that is found in the
biological concept generators has only been incorporated
in a small part of technical materials and structures. As a
result, (1) the identification of the biomimetic potential
by functional morphology and biomechanics and (2) the
abstraction of the identified principles remains one of the
future challenges for developing innovative products.
Development of optimised biomimetic shells and
branchings based on biological concept generators
Masselter, T1, Seidel, R1, Haushahn, T1, Thielen, M1,
Speck, T1
1
Plant Biomechanics Group Freiburg, Botanic Garden,
Faculty of Biology, University of Freiburg, Germany
Hierarchical organisation is present in most plants on at
least five hierarchical levels: stem, tissue, cell,
ultrastructural and molecular level. This morphological
structuring has important implications on the mechanical
properties of these plants, e.g. lightweight, optimised
stiffness, damping and benign fracture behaviour.
Furthermore, it could also be shown that the
morphological and mechanical optimisations present in
biological organisms can be abstracted and be used to
develop optimised bio-inspired technical products. Two
recent biomimetic projects of the Plant Biomechanics
Group in Freiburg are dealing with the damping
behaviour of nuts and drupes resp. the branchings of
arborescent monocotyledons and arborescent cacti and
143
their potential for the development of biomimetic
products. In the first project, the damping properties of
the Macadamia nut, the Pumello and the coconut are
investigated to gain a better understanding of the
morphological-mechanical relationships in these fruits.
The tough seed coat of the Macadamia nut serves as an
excellent biological role model for puncture resistant
materials. The hierarchically organised, thick and spongy
fruit wall of the pummelo, Citrus maxima, allows for
high dissipation of the initial potential energy during
impact. The coconut, Cocos nucifera, combines both
hierarchical structures in a sandwich with an outer
fibrous layer capable of high energy dissipation by large
deformation together with a tough hard inner shell.
Implementing the hierarchical structuring of the
protection layer and the use of gradients together with
fiber reinforcement is intended to lead to the
development of biomimetic impact resistant composite
materials for helmets, containers with high shock
absorbance as well as space station protection against
meteoroid impact and protection of vehicles. In the other
project, the potential of hierarchically structured plant
ramifications as concept generators for innovative,
biomimetic branched fibre-reinforced composites was
assessed by morphological and biomechanical analyses.
Promising biological role models were found within
monocotyledons, i.e. Dracaena and Freycinetia as well
as within columnar cacti like Cereus and Myrtillocactus.
These plants possess ramifications with a pronounced
fibre matrix structure and a special hierarchical stem
organization, which markedly differs from that of other
woody plants by consisting of isolated fibres and/or
wood strands running in a partially lignified ground
tissue matrix. The angles of the Y- and T-shaped
ramifications in the plants resemble those of the branched
technical structures. Our preliminary investigations
confirm that the ramifications possess mechanical
properties interesting for technical applications, such as a
benign fracture behaviour, a good oscillation damping
caused by high energy absorption, and a high potential
for lightweight construction. Potential technical
applications are hubs of wind-power plants, branch
points of framework constructions in building industry,
aerospace, ramified vein prostheses in medical
technology or the connecting nodes of axel carriers. The
results within the two projects demonstrate the high
potential for a successful technical transfer and has led to
the development of concepts for producing demonstrators
in lab-bench scale that already incorporate ‘solutions
inspired by nature’.
Biomechanical diversity of tropical rain forests as a
basis for bio-inspired materials and structures
Rowe, N1, Paul-Victor, C1, Gueroult, M1
1
Botany and Computational Plant Architecture, AMAP,
CNRS, University of Montpellier 2, France
Tropical rain forests are probably the most structurally
complex ecosystems in the world and comprise a vast
range of plant life forms and growth forms. Herbs,
shrubs, trees, vines, lianas, epiphytes and hemi-epiphytes
may all live in close physical contact and have adapted a
wide range of biomechanical strategies for life in the
forest. Two main factors potentially underline many of
the mechanical strategies adopted by plants in the
144
tropical forest; first the need to reach light but at the
same time survive in a mechanically perturbed
environment with frequent tree-falls and debris-falls.
Second, the fact that different plant groups have different
basic developmental constraints: such as woody dicots
and non-woody monocots. Different growth forms have
different mechanical constraints and have adapted many
ways of producing stiffness, flexibility and resistance to
failure that can offer a rich source for bio-inspired
technologies. We survey some of the biomechanical
strategies of climbing plants that are relevant to
developing bio-inspired materials and structures. Woody
lianas can develop what can be viewed as super gradient
materials with extreme transitions in stiffness and
resistance to failure. Monocotyledonous climbers such as
the Ischnosiphon centricifolius (Marantaceae) develop
high stiffness of cane-like internodes but also highly
compliant branch points at the nodes that ensure high
flexibility and resistance to failure in the event of
mechanical perturbation. Attachment devices of nonwoody and woody climbers provide a wealth of
mechanical strategies for bio-inspired applications
including 'dumb-hooks' of climbing palms that need
tension, friction or sharpness to remain attached to the
support and 'smart hooks' of woody climbing species of
Bauhinia (Caesalpiniaceae) and Strychnos (Loganiaceae)
that can eventually develop strong permanent tendrillike attachments but can first develop flexible 'clip on –
clip off' hooks in mechanically perturbed environments.
Self-irrigation by fog collection: lessons from plant
structures
Roth-Nebelsick, A1, Ebner, M2, Voigt, D3, Gottschalk,
V4, Konrad, W2
1
State Museum of Natural History Stuttgart, Germany;
University of Tübingen, Institute for Geology, Tübingen,
Germany; 3Functional Morphology and Biomechanics,
Zoological Institute, Christian-Albrechts University,
Kiel, Germany; 4Institute for Textile Technology and
Process Engineering Denkendorf, Dept of Technical
Textiles, Denkendorf, Germany
2
Fog and dew collection as a substantial water source has
gained increasing attention and there are ongoing efforts
to optimize technical harvesting systems. Since many
plants (and animals) benefit from fog and dew collection,
the analysis of these biological systems can provide
important information about useful strategies for
obtaining water in arid environments. One important
aspect in this respect is the role of surface properties.
Usually, a surface is characterized with respect to its
interaction with liquids by the contact angle and/or water
repellency which itself depends on the minimum drop
size. Fog and dew, however, involve very small droplets
in the range of a few tens of micrometers diameter. Since
parameters such as contact angle and shape of the drop
contact line depend in the case of rough surfaces on the
ratio between drop size and size of the surface
irregularities, surface structures can affect fog and dew
collection
via
microdroplet
behavior,
the
sticking/detachment of these drops and by directed water
flow. A particular example is provided by the fogcollecting grass species Stipagrostis sabulicola that
occurs exclusively on sand dunes of the Central Namib
Desert. S. sabulicola is able to harvest 4–5 liters per
nocturnal fog event and subsequently conducts the water
almost entirely towards the plant base. In this manner,
local soil moisture is concentrated and becomes available
for the roots. The directed water conduction is due to a
combination of various leaf surface traits. The natural
system of S. sabulicola and its transfer into a technical
fibre is described.
Biomechanics and functional morphology of suction
traps
in
aquatic
carnivorous
bladderworts
(Utricularia spp.) as concept generator for biomimetic
products
Poppinga, S1,2, Weisskopf, C1, Vincent, Olivier3,
Quilliet, Catherine3, Joyeux, M3, Marmottant, P3,
Masselter, T3, Speck, T1,2
1
Plant Biomechanics Group Freiburg, Botanic Garden,
Faculty of Biology, University of Freiburg, Germany;
2
Competence Network Biomimetics, Baden-Württemberg,
Germany, and BIOKON International-The Biomimetics
Association; 3Laboratoire de Spectrométrie Physique,
University of Grenoble, France
For nutrient supply, aquatic carnivorous bladderworts
(Utricularia spp., Lentibulariaceae) catch small prey
animals with suction traps. These traps, also called
bladders, are considered as one of the most complex
plant structures and show one of the fastest movements
generally known from plants, which is particularly
intriguing as it functions underwater. In collaboration
between physicists from Grenoble and biologists from
Freiburg three species have been analysed as to their
functional morphology, the biomechanics of trap and trap
door, and the hydrodynamics involved. The bladders
contain water which is pumped out by special glands,
hence generating negative pressure und allowing elastic
energy to be stored in the trap walls. A door with four
protruding trigger hairs provides a watertight closure of
the trap. When these hairs are touched by prey, the door
opens and closes in a fraction of a second, and relaxation
of the trap walls leads to the sucking in of water and
prey. Prey animals are sucked in with an acceleration of
up to 600 times that of gravity, leaving them no chance to
escape. The door deformation involves a complete
inversion of curvature which runs in several
distinguishable intermediate steps. This ultra-fast,
complex and at the same time precise and highly
repetitive movement is enabled by certain functionalmorphological adaptations. Based on quantitative
analyses of functional morphology and biomechanics of
bladderwort traps, a transfer into innovative biomimetic
products including micro-pipettes and microfluidic
devices is intended.
The plant cuticle: multifunctional interface and
model for innovations in engineering
1
2
3
Neinhuis, C , Bargel, H , Koch, K
1
Technische Universität Dresden, Germany; 2Universität
Bayreuth, Germany; 3Hochschule Rhein-Waal, Germany
A thin extracellular membrane, called the cuticle, covers
the aerial surfaces of plants. It serves as the outermost
border of plants and represents a composite consisting of
three major components: the biopolyester cutin, soluble
lipids of various chain lengths (waxes), and cellulose
fibrils. The latter tightly connect the cuticle to the cell
wall resulting in a gradient of material properties. The
cuticle is a multifunctional interface that primarily
prevents the plant from uncontrolled water loss, but also
serves as a protective layer against biotic and abiotic
environmental influences. In virtually all species of land
plants, waxes cover the cuticle either as defined
crystalline structures, thin films or thick layers. These
layers or three-dimensional structures may grow up to
several micrometers. The transport of lipids through the
cuticle as well as the formation of epicuticular wax
crystals based on self-assembly upon the surface is
studied by atomic force microscopy, which allows
observing the regeneration of defects of the outer surface
wax coverage in situ. After removing the existing
epicuticular waxes from leaves of different species, most
plants instantaneously regenerate a multi-layered wax
film as well as wax crystals. Considerable differences
were found in the intensity of regeneration, as well as in
the growth mechanisms. Based on AFM examinations
we demonstrate that wax regeneration is a highly
dynamic and rather fast process, indicating an overall
importance of a continuous outer hydrophobic coverage.
These studies of the dynamic processes on the molecular
level on the living plant surfaces may generate valuable
insight in self-assembly processes that eventually can be
applied in creating self-assembled structures in situ. Selfassembly processes should be preferred since structures
are formed in a highly parallel manner independent of the
surface geometry. Applications have been demonstrated
earlier since products with biomimetic self-cleaning
surfaces such as facade paints, polymers or textiles are
already introduced. However the contribution of
structures of different length scales on adhesion in
various aspects still have a great potential for
development and further technical applications. In
addition the polymer exhibits promising features that
might have impact on the development of future
polymers. These features include the ability to grow, to
adapt to environmental requirements and to adjust
mechanical properties and will be highlighted on selected
examples.
Sym153: Strigolactones, new signals and
crosstalk – 28 July
Strigolactone mixtures determine host specificity of
root parasitic weeds
Yoneyama, K1, Xie, X1, Yoneyama, K2
1
2
Weed Science Center, Utsunomiya University, Japan;
Dept of Biosciences, Teikyo University, Japan
Strigolactones (SLs) were originally isolated from plant
root exudates as germination stimulants for root parasitic
plants of the family Orobanchaceae, including
witchweeds (Striga spp.), broomrapes (Orobanche and
Phelipanche spp.), and Alectra spp., and so were
regarded as detrimental to the producing plants. Most of
these root parasites cause devastating damages to
agricultural production, in particular, in developing
countries, and their effective and economically feasible
control measures have not yet been established. These
145
root parasites have evolved special strategies to ensure
their survival; the seeds germinate only when they are
within the host rhizosphere so that after germination the
seedlings can reach and parasitize the host roots. To
locate host roots, root parasites exploit SLs that are
released by host plants for symbiotic arbuscular
mycorrhizal (AM) fungi. In addition to these functions in
the rhizosphere, SLs act as a novel class of plant
hormones regulating shoot branching. Among the weedy
root parasites, some of them attack various plant species,
but the others parasitize only their specific hosts. Such
specificity can be observed in germination stimulation by
SLs. For example, seeds of S. hermonthica can be
induced to germinate by most of SLs including the
synthetic analogue GR24, but GR24 cannot elicit seed
germination of S. gesnerioides. Furthermore, when
parasite seeds are treated with a mixture of SLs, additive,
synergistic, and even antagonistic effects are observed in
seed germination stimulation. Since plants release their
own mixtures of SLs, some root parasitic weeds with
strict host specificity appear to detect quantitative and
qualitative differences of SLs in the mixtures. By
contrast, AM fungi may be able to reach their hosts by
detecting any mixtures of SLs, as they can establish
symbiotic relations with more than 80% of land plants.
signal host root proximity during symbiotic and parasitic
interactions. To gain a better understanding of the origin
of strigolactone functions, we characterised a moss
mutant strongly affected in strigolactone biosynthesis
following deletion of the CAROTENOID CLEAVAGE
DIOXYGENASE 8 (CCD8) gene. Here we show that
wild type P. patens produces and releases strigolactones
into the medium where they control branching of
protonemal filaments and colony extension. We further
show that Ppccd8 mutant colonies fail to sense the
proximity of neighbouring colonies, which in wild type
plants causes the arrest of colony extension. The mutant
phenotype is rescued when grown in the proximity of
wild type colonies, by exogenous supply of synthetic
strigolactones or by ectopic expression of seed plant
CCD8. Thus our data demonstrate for the first time that
bryophytes (P. patens) produce strigolactones which act
as signalling factors controlling developmental and
potentially ecophysiological processes. We propose that,
in Physcomitrella patens, strigolactones are reminiscent
of quorum-sensing molecules used by bacteria to
communicate with one another
Strigolactones and plant development
Nelson, DC1, Flematti, GR1, Scaffidi, A1, Waters, M1,
Dixon, KW1, Ghisalberti, EL1, Smith, SM1
Brewer, PB1, Dunn, E1, Mason, M1, Meyers, E1,
Beveridge, C1
1
The University of Queensland, School of Biological
Sciences, St Lucia, Qld, Australia
One of the incredible features of plants is their ability to
completely change their shape and structure according to
environmental conditions. The ability for plants to
change their fate is due to persistent meristems. These
meristems are controlled by long-distance hormones that
enable communication and homeostasis within the plant.
The recently discovered plant hormone, strigolactone
affects meristematic processes including shoot branching,
adventitious rooting and lateral root development. In
addition to identifying new genetic tools aiming to tease
out the biosynthetic and response pathway for this new
plant hormone, our research has now expanded to
understanding how this signal can regulate diverse
aspects of development and is testing the hypothesis that
strigolactone plays a fundamental role in diverse
suppressed meristems.
Strigolactones regulate protonema branching and act
as a quorum sensing-like signal in the moss
Physcomitrella patens
Proust, H1, Hoffmann, B1, Xie, X2, Schaefer, D3,
Yoneyama, K2, Nogué, F1, Rameau, C1
1
Institut Jean-Pierre Bourgin, UMR1318 INRAAgroParisTech, Centre De Versailles-Grignon, France;
2
Weed Science Centre, Utsunomiya University,
Utsunomiya, Japan; 3Institute of Biology, Laboratory of
Cell and Molecular Biology, University of Neuchatel,
Switzerland
Strigolactones are a novel class of plant hormones
controlling shoot branching in seed plants. They also
146
Karrikin signalling, interaction with light and
relationships with strigolactones
1
University of Western Australia, Australia
Karrikins are a new family of naturally-occurring plant
growth regulators discovered in smoke from wildfires.
They were discovered for their ability to break seed
dormancy and stimulate seed germination. While they are
active upon species that respond to fire, they are also
active in species not normally associated with fire,
implying a broader significance. Arabidopsis thaliana
responds sensitively to karrikins, providing a means to
investigate their mode of action. Recent research has
shown that karrikins can change the sensitivity of seeds
and seedlings to light, and influence seedling
photomorphogenesis. Karrikin-insensitive mutants have
been isolated and characterised, leading to the discovery
that karrikin action depends on the F-box protein
MAX2/ORE9/PPS. This is the same protein that is
required for response to strigolactones. Karrikins have
some structural similarity with strigolactones, which are
known to stimulate seed germination in some parasitic
plants. However, whereas strigolactones interact with
auxins to control lateral shoot development, karrikins do
not have this activity. Therefore, while karrikins and
strigolactones both act through MAX2, the plant can
distinguish these two signalling molecules. The transport,
metabolism and mode of action of karrikins will be
discussed.
Can signalling crosstalk happen within the receptor
molecule?
Irving, HR1, Kwezi, L, Donaldson, L3, Ruzvidzo, O4,
Wheeler, JI1, Wang, YH1, Freihat, L1, Meier, S3,
Gehring, C3
1
Monash University, Australia; 2University of the
Western Cape, South Africa; 3King Abdullah University
of Science and Technology, Saudi Arabia; 4North West
University, South Africa
Guanosine 3’5’-cyclic monophosphate (cGMP) has been
identified as an important molecule involved in
regulating a wide variety of physiological effects ranging
from plant hormone dependent responses to induction of
plant defence responses although the guanylate cyclase
(GC) enzymes responsible for cGMP synthesis remain
elusive. We hypothesised that at least one, if not several
different, functional GCs exist in higher plants.
Consequently, we designed and tested a search motif
based on several functionally assigned amino acids in the
catalytic domain of known GCs from lower eukaryotes
and animals. The search returned over 40 putative GCs,
the majority of which are annotated as receptor-like
kinases (RLKs). Surprisingly, the GC catalytic centre is
embedded in the kinase domain which is distinct from
animal GCs where the two domains are separated. The
large family of RLKs with both GC and kinase domains
implies that these dual functionalities have coevolved
due to the importance of both enzyme activities in plant
development and stress response. These include several
RLKs known for their role in plant development and
stress responses such as BRASSINOSTEROID
INSENSITIVE 1 (BRI1), WALL ASSOCIATED
KINASE LIKE 10 (WAKL10), PHYTOSULFOKINE
RECEPTOR 1 (PSKR1) and PEP1 RECEPTOR 1
(PEPR1). We have shown that these RLKs contain both
kinase and GC activity in vitro. Moreover, the natural
ligands of BRI1 and PSKR1 stimulate increases in cGMP
in planta. Hence it is possible that the plant receptors
could switch between downstream cGMP-mediated or
kinase-mediated signaling cascades to elicit desired
outputs to particular stimuli. The challenge now lies in
understanding the interaction between the GC and kinase
domains at the molecular level and how these receptors
capitalize on their dual functionality in planta.
A spatio-temporal sequence of cross-regulatory events
in root meristem growth
Hardtke, C1, Scacchi, E1, Salinas, P1, Gujas, B1,
1
Santuari, L1, Ragni, L
1
University of Lausanne, Switzerland
A central question in developmental biology is how
multi-cellular organisms coordinate cell division and
differentiation to determine organ size. In Arabidopsis
roots, this balance is controlled by cytokinin-induced
expression of SHORT HYPOCOTYL 2 (SHY2) in the
so-called transition zone of the meristem, where SHY2
negatively regulates auxin response factors (ARFs) by
protein-protein interaction. The resulting downregulation of PIN-FORMED (PIN) auxin efflux carriers
is considered the key event in promoting differentiation
of meristematic cells. Here we show that this regulation
involves additional, intermediary factors and is spatiotemporally constrained. We found that the described
cytokinin-auxin crosstalk antagonizes BREVIS RADIX
(BRX) activity in the developing protophloem. BRX is
an auxin-responsive target of the prototypical ARF
MONOPTEROS (MP), a key promoter of vascular
development, and transiently enhances PIN3 expression
to promote meristem growth in young roots. At later
stages, cytokinin-induction of SHY2 in the vascular
transition zone restricts BRX expression to downregulate PIN3 and thus limit meristem growth. A novel
network modeling approach extending the SQUAD
software that takes into account experimentally identified
regulatory constraints predicted a direct involvement of
BRX in auxin signal transduction. Indeed, in vitro
interaction and yeast two hybrid assays confirmed that
BRX directly interacts with MP. Interestingly, proper
SHY2 expression requires BRX, which could reflect
feedback on the auxin-responsiveness of SHY2 because
BRX protein could act as a co-factor of MP. Thus, crossregulatory antagonism between BRX and SHY2 could
determine ARF activity in the protophloem. Our data
suggest a model in which the regulatory interactions
favor BRX expression in the early, proximal meristem,
while SHY2 prevails because of supplementary
cytokinin-induction in the later, distal meristem. The
complex equilibrium of this regulatory module might
represent a universal switch in the transition towards
differentiation in various developmental contexts.
Sym156: Respiration – 28 July
Molecular
and
systems
thermoregulation in plants
elucidation
of
Ito, K1, Ogata, T1, Kakizaki, Y1, Elliott, C2, Albury, M2,
Moore, A2
1
Cryobiofrontier Research Centre, Faculty of
Agriculture, Iwate University, Japan; 2Dept of
Biochemistry & Molecular Biology, School of Life
Sciences, University of Sussex, UK
Heat production in thermogenic plants has been
attributed to a large increase in the expression of the
alternative oxidase (AOX). AOX acts as alternative
terminal oxidase in the electron transfer chain, reducing
molecular oxygen to water. However, in contrast to the
mitochondrial terminal oxidase, cytochrome c oxidase,
AOX is non-protonmotive which allows the dramatic
drop in free energy between ubiquinol and oxygen to be
dissipated as heat. In addition to AOX, cDNAs for
uncoupling protein (UCP) have been isolated for several
plants, and although some tissues have been shown to coexpress UCPs with AOX, their role in promoting
thermogenesis still remains unclear. In the present study,
we identified cDNAs for AOX and UCP and examined
their mRNA expression profiles in Arum maculatum.
RT-PCR based cloning using RNAs from the appendices
of intact thermogenic inflorescences revealed that at least
six cDNAs for AOX (AmAOX1a, 1b, 1c, 1d, 1e, and 1f)
and one for UCP (AmUCPa) are co-expressed, but organ
and developmental regulation is evident. In particular,
the expression of AmAOX1e appears to be dominant in
thermogenic appendices among six AmAOXs, while the
expression level of AmUCPa was ubiquitous in the
various tissues examined. Interestingly, predicted amino
acid sequences of AmAOX1e shows that the E/DNV
element found in almost all other AOX sequences,
including AmAOX1a, 1b, 1c, 1d and 1f, was substituted
by QNT. This is in contrast with SgAOX from
thermogenic species S. guttatum in which E/DNV
element is present as QDC. Further functional analyses
with mitochondria isolated from yeast heterologous
147
expression system revealed that AmAOX1e is less
sensitive to stimulation by pyruvate. These data, together
with our comparative studies on temperature and
proteomic analyses of A. maculatum and S. renifolius, are
interpreted in terms of the possible mechanism for
thermoregulation in plants.
Alternative oxidases of non-angiosperm plants
McDonald, A1
1
Wilfrid Laurier University, Waterloo, Canada
Biological electron transport chains (ETCs) power life on
this planet. In most eukaryotic organisms, ETCs in
mitochondria
generate
energy
via
oxidative
phosphorylation. This ‘classic’ ETC is present in
mammals, but it does not accurately reflect respiration in
most prokaryotes and eukaryotes. Typically, linear ETCs
are depicted in textbooks, however, this is misleading, as
most organisms have additional protein complexes that
increase the points of entry and/or exit of electrons,
resulting in a branched chain. Alternative oxidase (AOX)
is a terminal ubiquinol oxidase present in mitochondrial
electron transport chains that introduces a branch-point in
respiration and can bypass two of the three proton
pumping complexes (Complexes III and IV). This leads
to a decrease in the amount of ATP that can potentially
be generated by ATP synthase. Plant AOX research to
date has focused on angiosperms such as Arabidopsis
thaliana, tobacco, soybean, and rice, where a good deal
is known about its multigene family, gene expression,
and the post-translational regulation of AOX activity. In
contrast, little is known about AOX in other plant groups.
We utilized a bioinformatics approach to investigate the
taxonomic distribution of AOX in non-angiosperm
members of the Viridiplantae (green plants) and used
multiple sequence alignments of AOX proteins to
investigate the distribution of the AOX multigene family,
the AOX1 and AOX2 subtypes, and amino acid residues
involved in the catalytic function and post-translational
regulation of the enzyme. AOX sequences were found in
many members of the Viridiplantae, in both
Chlorophytes and Streptophytes, including liverworts, a
moss, a lycopod, ferns, and several gymnosperms. We
are employing reverse transcriptase PCR using
degenerate primers as a strategy to amplify novel AOX
sequences from plant phyla for which molecular data are
not yet available (e.g. Psilotophyta, Equisetophyta,
Ginkophyta, and Cycadophyta). A comparison of AOX
sequences at the amino acid level from angiosperms and
non-angiosperms reveals similarities and differences
which have direct implications for the evolutionary
history of AOX, AOX catalytic function, and the posttranslational mechanisms that regulate AOX activity in
plants.
Elucidating the mechanism of thermogenesis in
Philodendron bipinnatifidum – elevated oxygen
concentrations overcome diffusional limitations to
isotope discrimination during respiration in dense
thermogenic tissues
Miller, R1,2,3, Grant, N2, Giles, L4, Ribas-Carbo, M5,
Berry, J4, Watling, J3, Robinson, S2
148
1
School of Biological Sciences, Monash University,
Clayton, Australia; 2Institute for Conservation Biology
and Environmental Management, The University of
Wollongong, Wollongong, Australia; 3Ecology &
Evolutionary Biology, School of Earth and
Environmental Sciences, The University of Adelaide,
Adelaide, Australia; 4Dept of Global Ecology, Carnegie
Institution of Washington, Stanford, USA; 5Universitat de
les Illes Balears, Departament de Biologia, Unitat de
Fisiologia Vegetal, Illes Balears, Spain
The thermogenic inflorescences of Philodendron
bipinnatifidum heat up to 34ºC above ambient
temperature by achieving high mass specific respiratory
rates, equivalent to those in some animals, yet the
mechanism of heating in this and other arums has not
been definitively characterised. Transcripts for both the
alternative oxidase (AOX) and plant uncoupling protein
(pUCP) – the two possible pathways for heat generation
in plants – have been found in thermogenic tissues of P.
bipinnatifidum. The only means to definitively
demonstrate the mechanism of heat production in vivo is
to quantify respiratory pathway fluxes using stable O2
isotope discrimination techniques; however these
measurements have not been possible in thermogenic
Araceae to date because of the high diffusional
resistances in these structurally dense tissues. We aimed
to investigate the contribution of the alternative oxidase
(AOX) and uncoupling proteins (pUCPs) to heating, in
both fertile (FM) and sterile (SM) male florets of P.
bipinnatifidum using oxygen isotope discrimination.
Specifically we aimed to investigate whether isotopic
discrimination was affected by diffusion during peak
respiration in SM florets, by conducting measurements
under different O2 partial pressures. We also
characterised heating patterns and mechanisms in the
little studied fertile male (FM) florets. We found that FM
florets heat independently of SM florets, and both heat
for up to 30 hours after removal from the plant. In FM
florets, heat production was strongly correlated with both
total respiration and AOX pathway flux. In contrast,
whilst heating was also strongly correlated with total
respiration in SM florets, AOX flux was not. To
determine whether this was a function of pUCP activity
or an artefact of diffusional limitations in SM tissues, we
measured isotope discrimination under elevated O2
partial pressures in the most strongly heating tissues.
These measurements confirmed that diffusional
limitations were responsible for the low AOX fluxes
observed in SM florets in air. Under increased O2, AOX
contributed up to 92% of total flux in peak heating SM
florets. Elevated O2 can thus be used to measure
respiratory pathway flux in dense tissues. Protein data
support the substantial role for AOX in thermogenesis in
P. bipinnatifidum. Both pUCP and AOX proteins were
present in thermogenic tissues; however, AOX protein
increased 5-fold with the onset of thermogenesis in both
floret types whereas pUCP remained low throughout
development. No relationship between AOX protein
content and heating was found, suggesting that fine scale
regulation of AOX is post-translational.
Flux distributions within the heterotrophic plant
TCA cycle
Ratcliffe, RG1, Beard, KFM1, Kruger, NJ1, Masakapalli,
SK1, Sweetlove, JL1, Williams, TCR2
1
University of Oxford, Oxford, UK;
Federal de Vicosa, Vicosa, Brazil
2
Iniversidade
The input of acetyl CoA into the tricarboxylic acid
(TCA) cycle allows the cycle to maintain a cyclic flux
that lies at the heart of mitochondrial respiratory
metabolism. This flux supports the oxidation of a series
of carboxylic acids, generating the reducing equivalents –
NADH and FADH2 – that fuel the synthesis of ATP by
oxidative phosphorylation. The TCA cycle is embedded
in a wider metabolic network, allowing it to support both
cyclic and non-cyclic flux modes, and the observed flux
distribution is dependent on the metabolic and
physiological demands of the cell (1). Labelling
experiments and metabolic modelling provide the key to
analysing the flux distribution in the TCA cycle, and
several groups have harnessed the power of steady-state
metabolic flux analysis (MFA) to analyse the cycle in
heterotrophic tissues. Steady-state MFA is used to
generate flux maps of the core network of central carbon
metabolism and the TCA cycle fluxes are often well
defined (2). Flux maps are based on observations of the
redistribution of an isotope, typically 13C, in labelling
experiments and robust protocols have been developed to
allow the method to be applied to the extensively
compartmented network of heterotrophic metabolism in
plant cells. Applications to Arabidopsis cell cultures have
revealed physiologically important features of the
network, such as its robustness (3) and the balance
between cytosolic and plastidic metabolism (4).
Moreover a comparison between MFA and constraintsbased stoichiometric modeling has shown that the latter
approach is capable of accurately predicting some of the
responses of central metabolism to the imposition of
stress conditions (5). The results of several steady-state
MFA analyses of the TCA cycle in a heterotrophic
Arabdiopsis cell culture will be discussed, including
current investigations of the impact of phosphorus and
nitrogen nutrition on central carbon metabolism and
carbon use efficiency. The extent to which flux maps
capture the expected features of highly compartmented
metabolic networks is variable, and a further
complication that has rarely been considered, and which
might be significant for the TCA cycle, is the potential
existence of metabolite channelling. This process can
have a significant impact on the redistribution of isotopic
label – indeed evidence for channelling is frequently
obtained from isotope dilution experiments – but this
aspect of metabolism has been largely ignored in the
development of steady-state MFA for plants. Theoretical
analysis of simple networks, and re-analysis of GCMS/NMR datasets obtained for Arabidopsis cell cultures,
suggests that the effects of channelling are detectable in
parts of the network and in parallel with this in silico
approach, isotope dilution experiments are being
conducted on isolated mitochondria to test the extent to
which channelling occurs between intermediates in the
TCA cycle. (1) L.J. Sweetlove et al. 2010. (2) N.J.
Kruger & R.G. Ratcliffe 2009. (3) T.C.R. Williams et al.
2008. (4) S.K. Masakapalli et al. 2010. (5) T.C.R.
Williams et al. 2010.
Gene expression and metabolite signatures associated
with global change treatments that engage or
disengage mechanisms maintaining homeostasis
between respiration and photosynthesis
Leakey, ADB1, Richter, K1, Gillespie, KM1, Ainsworth,
EA1
1
University of Illinois At Urbana–Champaign, USA
Understanding and modeling of plant and ecosystem
carbon balance has long been challenged by uncertainty
about how and when homeostasis is maintained between
photosynthetic and respiratory fluxes. We present a case
study of how gene expression and metabolite signatures
can reveal the metabolic and biosynthetic responses in
leaves distinguishing: (a) enhanced dark respiration
coupled with greater photosynthesis and productivity at
elevated [CO2] from (b) enhanced dark respiration
coupled with impaired photosynthesis and productivity at
elevated [O3]. Soybean was grown over its entire
lifecycle under ambient atmospheric conditions, elevated
[CO2] and elevated [O3] treatments using free-air
concentration enrichment (FACE) at a field site in the
Midwest U.S.. Stimulated foliar respiration at night
under elevated [CO2] was associated with enhanced
photosynthetic carbon gain, larger pools of sugar and
starch substrates, and greater abundance of transcripts
encoding the respiratory machinery. This is consistent
with transcriptional reprogramming of metabolism to
increase respiratory capacity in response to: (1) greater
substrate availability from photosynthesis and, (2) greater
demand for energy from phloem loading associated with
additional photoassimilate export to support enhanced
whole-plant growth. Stimulated foliar respiration at night
under elevated [O3] was associated with reduced
photosynthetic carbon gain, but greater antioxidant
capacity, ascorbate content and greater abundance of
transcripts encoding respiratory, anti-oxidant and
chlorophyll synthesis pathways. This is consistent with
transcriptional reprogramming of metabolism in response
to the necessity for energy and carbon skeletons from
respiration to support detoxification and repair processes
associated with oxidative stress, despite reduced
substrate availability. The decoupling of respiration from
photosynthesis under elevated [O3] greatly exacerbated
the negative consequences for carbon balance at the leaf
and whole-plant scales. These results suggest that both
sugar status and stress signals can drive modulation of
respiratory capacity in leaves. Further analysis of
transcription factors and other regulatory elements
displaying altered gene expression in these experiments
presents an opportunity to determine how sugar and
stress signals are integrated to engage or disengage
mechanisms
maintaining
homeostasis
between
respiration and photosynthesis.
Unraveling the acclimation of the mitochondrial
proteome to changing environments
Taylor, N1,2, Huang, S2, Jacoby, R2, Shingaki-Wells, R2,
Tan, Y-F2, Millar, H2
1
ARC Centre of Excellence In Plant Energy Biology,
Australia; 2Centre for Comparative Analysis of
Biomolecular Networks, Australia
149
Changes in the environment in which a plant grows can
have dramatic affects on the metabolic processes of
photosynthesis and respiration. This in turn can have
major implications on biosynthesis, cellular maintenance
and biomass allocation. Analysing the network of
changes under different environments is essential to
understand the plasticity of this acclimation system as a
whole. Here we investigate three examples of the effects
of a changing environment on mitochondrial function
and protein content. 1. Plants can acclimate to the
extremes of temperature following a pre-exposure to a
lower sub-lethal increase/decrease in temperature that
allows them to adjust their metabolism and to survive.
The respiratory and photosynthetic rates of these plants
remain similar to plants grown at optimal temperatures
and plants that have a greater thermal tolerance tend to
more quickly adjust their metabolism and restore
respiration to pre-thermal change levels. Using both
Arabidopsis whole plants and cell culture we have
produced data that suggests a remodeling of proteins in
the mitochondrial electron transfer chain allows
respiratory homeostasis to be achieved during
acclimation. Also changes in other mitochondrial
membrane and soluble proteins have been measured
quantitatively at the proteome level following chilling. 2.
While rice is cultivated on flooded/anaerobic soils many
other dry-land crop species suffer when encountering
waterlogging leading to O2 deficiency. Rice is an ideal
model species with an available genome sequence for
elucidating the mechanisms of anoxia tolerance in plants
and because it can survive under prolonged anoxia.
Without O2, the glycolytic pathway that is linked with
ethanolic fermentation is the predominant mechanism of
energy production in plants. However, much less energy
is produced during anoxia and the synthesis rate of
proteins will decrease well below that of what is seen in
aerated tissues. Even so, rice coleoptiles still exhibit a
complex pattern of newly synthesized proteins. Along
with classical anaerobic proteins, anoxic rice coleoptiles
also synthesize some proteins with unknown functions
and mitochondria initiate specific anaerobic metabolic
functions. 3. Salinity is a severe impediment to
agricultural productivity and with the increased use of
marginal land, breeders will need to produce crop and
fodder plants that exhibit high salinity tolerance. Salinity
is an acute problem in the Australian wheat growing
regions. We have found quantitative differences in the
shoot mitochondrial proteomes of v.Wyalkatchem and
v.Janz, two commercially important wheat varieties that
are known from a range of experiments to have differing
salinity tolerance. These proteins included Mnsuperoxide dismutase (Mn-SOD) and the alternative
oxidase (AOX), both of which have previously linked to
reduced ROS formation from the electron transport chain
and salt tolerance in Arabidopsis. Together, the data
presented here suggest that changes in mitochondrial
ROS defense pathways in the mitochondrial proteomes
of key Australian wheat varieties correlate with wholeplant salinity tolerance. As plant biomass accumulation is
governed by the equation of assimilation of CO2 minus
respiratory CO2 loss, the rate, degree and timing of
changes in respiratory function is a critical component in
plant growth and provides an insight to the dynamic
nature of the mitochondrial proteome.
150
THEME 05: STRUCTURE,
DEVELOPMENT AND
CELLULAR BIOLOGY
Sym056: Evolution, development and
function of the leaf venation architecture –
28 July
Fern venation as a possible evolution from tree-like to
net-like vein architecture
Douady, S1
1
MSC Laboratory, CNRS-Paris Diderot University,
France
Following the evolution, the leaf venation has come
roughly from dichotomous tree-like for the ferns, to
reticulate in the dicotyledons, back to parallel veins with
small cross connections in the monocotyledons. When
looked at the tree-like pattern of the first ferns, it is
difficult to understand how such a dramatic change in
pattern could have led to the net-like fully reticulated
patterns of the dicotyledons. However, a detailed study of
the pattern of veins in neotropical ferns can reveal a
complete variety of patterns, from the full dichotomous
tree-like pattern, to the full reticulation, even in a simple
genus such as Adiantum, or Thelypteris. It can indeed be
observed the first connection of only two veins at he
bottom of two leaflets, to the common connection of all
the third order veins at the middle line, creating an
intermediary line and a continuous leaf, to more
intermediary connections to finally the full reticulation.
These intermediary patterns are particularly interesting as
they could reveal how and why the transition happened.
All these patterns can be analyzed with tools developed
for studying other reticulate patterns like porcelain cracks
and street network. It is interesting to classify all these
patterns, to see if it is possible to organize them along a
single line of evolution, to see if there is a unique path,
and to compare the result with what is know from the
evolution of these ferns.
The evolution of maple leaf size, shape, composition,
stomata and venation architecture
Sack, L1,2, Scoffoni, C2, Barron, R3, Frole, K4, Zanne, A5
1
Corresponding Author; 2University of California, Los
Angeles, Dept of Ecology and Evolutionary Biology,
USA; 3Harvard University, Dept of Organismic and
Evolutionary
Biology,
Biological
Laboratories,
Cambridge, USA; 4University of Hawaii, Botany Dept,
Honolulu, USA; 5University of Missouri St Louis,
Biology Dept, St Louis, USA
Species of maple (Acer, Sapindaceae) are highly variable
in leaf form, e.g., ranging from compound to simple
leaves and in shape from entire to 11 lobes. We
determined the variation, phylogenetic signal and
evolutionary coordination of over 50 traits relating to
size, shape, nutrient composition, venation architecture
and stomatal anatomy, for well-illuminated leaves of 30
maple tree species of North America, Europe and Asia,
grown in a common garden (Arnold Arboretum of
Harvard University). We also determined intra-canopy
plasticity for key leaf traits. We comprehensively tested
expectations for how traits should correlate with shadetolerance and drought tolerance based on previous
studies of species variation within and across
communities. We found evidence of strong traitenvironment linkages, but that these held only in the
minority of expected cases, indicating that trait
adaptation to habitat is not direct or predictable in the
simplest ways, and we must consider simultaneous
adaptation to multiple environmental axes, and evolution
of multi-trait clusters rather than single traits. Indeed, we
found novel, tight relationships among traits within
clusters related to leaf size, or shape, or composition, or
venation, or stomatal anatomy, and also within clusters
as defined by function (e.g., flux-related traits and leaf
economics traits). However, we found impressive
evolutionary independence among these trait clusters.
The independence of leaf trait clusters results in the
possibility of many trait configurations in leaf form even
among species similar in habitat and successional stage
(e.g., pioneer or shade-establishing). Across the maple
species, we observed strong variation among traits in
their phylogenetic signal across the lineage. Across the
traits considered, trait phylogenetic lability was
independent of trait diversification (i.e., the degree the
trait varied across extant species). Thus, strong trait
diversification can arise equally frequently from multiple
trait shifts among closely-related species as from few
shifts deeply nested in the tree, and trait similarity across
the genus can arise equally from phylogenetic
conservatism as from frequent shifts within narrow
bounds. Such multiple pathways to trait similarity and
divergence highlight how evolutionary flexibility
potentiated the rich total diversity in maple leaf form.
Finally, across the traits we found a correlation of a trait's
developmental plasticity within the canopies of
individual trees with both its phylogenetic lability and
diversification across species in the genus. This work
provides insights into the genetic basis for leaf traits, and
highlights the necessity for mechanistic understanding of
how multiple leaf traits contribute to integrated function,
during adaptation within and across habitats. Key words:
leaf traits, stomata, scaling, phylogeny, venation
architecture, leaf morphology.
Leaf hydraulic vulnerability is related to conduit
dimensions and drought resistance across a diverse
range of woody angiosperms
Blackman, C1, Brodribb, T1, Jordan, G1
1
School of Plant Science, University of Tasmania,
Australia
Hydraulic dysfunction in leaves determines key aspects
of whole-plant responses to water stress, however, our
understanding of the physiology of hydraulic dysfunction
and its relationships to leaf structure and ecological
strategy remain incomplete. Here, we studied a
morphologically and ecologically diverse sample of
angiosperms to test whether the water potential inducing
a 50% loss in leaf hydraulic conductance (P50leaf) is
predicted by properties of leaf xylem relating to water
tension-induced conduit collapse. We also assessed the
relationships between P50leaf and other traits considered
to reflect drought resistance and ecological strategy.
Across species, P50leaf was strongly correlated with a
theoretical predictor of vulnerability to cell-collapse in
minor veins (the cubed ratio of conduit wall thickness to
conduit lumen breadth). P50leaf was also correlated with
mesophyll traits known to be related to drought
resistance, but unrelated to traits associated with carboneconomy. Our data indicate a link between the structural
mechanics of leaf xylem and hydraulic function under
water stress. Although it is possible that collapse may
directly contribute to dysfunction, this relationship may
also be a secondary product of vascular economics,
suggesting that leaf xylem is dimensioned to avoid wall
collapse.
Decline of leaf hydraulic conductance during
desiccation: relationships to leaf size and venation
architecture in species varying strongly in drought
tolerance
Scoffoni, C1, Rawls, M1, McKown, A1, Sack, L1
1
University of California, Los Angeles, USA
Leaves vary greatly in their size and venation
architecture. Leaf veins deliver water to replace that lost
to transpiration, allowing stomata to remain open for
photosynthesis. Previous studies have shown that the leaf
hydraulic conductance (Kleaf) is influenced by venation
architecture. Severing the midrib caused a decline in
Kleaf and gas exchange to a degree that depended on
venation architecture: leaves of higher major vein density
(length/area) had greater tolerance of hydraulic
disruption due to additional pathways for water flow
around the severed vein. Because desiccation-induced
vein embolism also reduces Kleaf, we hypothesized that
leaves with higher major vein density and thus greater
redundancy of flow paths would have a lower hydraulic
vulnerability. Further, smaller leaves, which tend to have
intrinsically higher major vein densities, should tend to
have lower hydraulic vulnerability. For ten species
ranging strongly in drought sensitivity, we determined
the relationships among leaf hydraulic responses to
desiccation and rehydration, venation architecture, gross
morphology, and other drought tolerance traits. We
quantified Kleaf using the evaporative flux method for
leaves of a range of water potentials (Øleaf). Hydraulic
vulnerability, calculated as the Øleaf at 50% and 80%
loss of Kleaf, correlated negatively with major vein
density and positively with leaf size (|r |= 0.85 to 0.93; P
= 0.01-0.002). These relationships were independent of
other aspects of drought tolerance. Hydraulic
vulnerability was independent of minor vein density,
consistent with computer simulations showing the
importance of the hierarchical arrangement of veins.
These findings suggest a new functional importance of
high major vein density and small leaf size in drought
tolerance and ecological specialization, potentially
important in as a determinant of biogeographic patterns
in leaf size.
151
Sym057: Orchid-pollination: The PostDarwinian revolution – 28 July
The ghosts that Darwin missed: pollination of
Caladenia by sexually deceived wasps … and others
Petit, S1
1
University of South Australia, Australia
The complexity of Caladenia (syn. Arachnorchis)
species’ reproductive success remains shrouded in
mystery. I will unravel some of the mystery surrounding
the pollination of spider orchids (leaving plenty for
others to unravel). By mimicking the pheromone of a
wingless female insect, an orchid tricks the sexually
aroused winged male. Are the pollinators simply silly
thynnid wasps? What makes an effective pollinator?
What makes an orchid a successful temptress?
Pollinators are difficult to study in species with relatively
low pollination rates, but their ghostly behaviours can be
derived from examining plant characteristics in relation
to pollination success. The orchid masters the art of
treachery, but will it be its demise?
Pollination systems of Angraecoid orchids: from
Darwin to the present day
Micheneau, C1, 2, Fournel, J2, Warren, B2, Hugel, S3,
Gauvin-Bialecki, A2, Pailler, T2, Strasberg, D2, Chase,
M4
1
Université Libre de Bruxelles, Brussels, Belgium;
Université de La Réunion, Saint-Denis, La Réunion;
3
CNRS – Université de Strasbourg, Strasbourg, France;
4
Royal Botanic Gardens, Kew, Richmond, UK
2
Since the famous prediction of Darwin, the spectacularly
long nectar spurs of Madagascan Angraecum orchids
have represented a classic example of floral adaptation to
long-tongued
hawkmoth
pollination.
Although
specialisations for a specific group of pollinators can be
viewed as a key innovation that has been responsible for
the evolutionary success of a lineage, extreme
specialisations in turn can be linked with loss of
evolutionary potential, decreasing the ability of species to
adapt to future environmental change. Here we report a
surprising pollinator shift in the orchid genus Angraecum
from hawkmoth to bird and raspy-cricket pollination (in
the insect order Orthoptera). This evolutionary shift
occurred after this group of orchids dispersed to a new
insular habitat that harboured both different
environmental conditions and groups of pollinators than
were present in their native island, Madagascar. This
specialised plant-pollinator interaction further represents
the first clear case of orthopteran-mediated pollination in
flowering plants.
Total evidence phylogenetic analysis of the orchid
tribe Diurideae and what it tells us about the
evolution of pollination systems
Weston, PH1, Indsto, JO2, Perkins, AJ1, Clements, MA3,
Peakall, R4
152
1
National Herbarium of New South Wales, Australia; 234
Loftus Road, Pennant Hills, Australia; 3Centre for
Australian National Biodiversity Research, CSIRO Plant
Industry, Australia;4Research School of Biology, The
Australian National University, Australia
The tribe Diurideae is a clade of terrestrial orchids that
has its centre of diversity in Australia, but some of its
sub-clades extend into the south-western Pacific and
southern and eastern Asia. Most species are perennial
deciduous herbs that die back to dormant tubers at the
beginning of summer, renewing active growth the
following autumn. Annual growth in most species
involves the replacement of the old tuber with a single
new one and growth of a single-leaved shoot subtending
a multi-flowered raceme. The Diurideae includes taxa
that offer nectar to their pollinators (e.g. Prasophyllum)
as well as those that lure pollinators by mimicking: 1.
food sources (e.g. some species of Diuris) or 2. female
hymenopteran insects (e.g. Drakaeinae) or 3. brood-sites
of female flies (e.g. Corybas) and it also includes a
diverse assemblage of self-pollinating and apomictic
taxa. The fruits of the underground orchids, Rhizanthella,
are berries enclosing large, crustose, presumably animaldispersed seeds but those of all other taxa are capsules
that release dust-like, wind-dispersed seeds. The
phylogeny of the orchid tribe Diurideae will be
reconstructed down to the level of species groups using a
combined matrix of morphological and anatomical
characters and alignments for 4 genes (matK, trnL-F,
rbcL, psbA), plus the intergenic spacer ITS. The data will
be phylogenetically analysed using parsimony and
Bayesian methods. The molecular partition of the dataset
will also be subjected to molecular dating analyses using
Bayesian relaxed clock methods, calibrated using a
recently described orchid fossil as well as secondary
calibrations based on non-orchid monocot fossils and the
known ages of some biogeographic disjunctions.
Preliminary analyses suggest the following:
• The crown group of Diurideae diversified in Australia
after final separation of the continent from Antarctica
about 35 mya and several lineages subsequently
dispersed to south western Pacific islands and into Asia
across ocean gaps
• Deciduousness, annual production of a single
replacement tuber, a multi-flowered raceme and capsular
fruit are ancestral character states relative to evergreen
habit, absence of tubers, production of multiple
replacement tubers, single-flowered inflorescence and
baccate fruit
• Food source mimicry is ancestral relative to both sexual
mimicry and nectar production
• Sexual deception of male Hymenoptera has evolved
independently in at least 6 different lineages
(Cryptostylis, Calochilus, Leporella, Drakaeinae, at least
two distinct clades in Caladenia)
• Nectar production has evolved multiple times (in
Prasophyllinae,
Acianthinae,
Diuris,
Eriochilus,
Caladenia)
• Several clades of closely related species include both
nectar-producing and nectarless species (Diuris,
Caladenia, Eriochilus) and multiple, possibly
bidirectional transformations between these states have
occurred in these clades
• Autogamous and apomictic lineages have evolved
numerous times from food source mimicking, sexually
deceptive and nectar-producing ancestors What selective
pressures have facilitated the evolution of sexually
deceptive
lineages
from
food-source-mimicking
ancestors? Pollinator reliability seems the best answer.
Explaining the evolution of nectar-producing lineages
from food-source-mimicking ancestors and vice versa
seems a much more complex problem. Species groups
such as Diuris section Purpureo-albae that include both
nectar-producing species and food-source mimics offer
useful model systems for exploring this problem.
Pollinator-driven evolution of orchids in southern
Africa
Johnson, S1
1
University of KwaZulu-Natal, South Africa
The orchid diversity in southern Africa is largely the
outcome of radiation in a single terrestrial clade. There is
now overwhelming evidence that much of the
diversification of the larger genera in this clade, such as
Disa and Satyrium, is the consequence of evolutionary
shifts between different pollinators. Orchids generally
form part of broader pollination guilds, and frequently
exploit other guild members through floral mimicry. This
is particularly evident in Disa where many members of
non-rewarding clades have been identified as Batesian
food mimics. Species-level phylogenies are now
available for most of the larger orchid genera in southern
Africa, allowing both the direction and frequency of
pollinator shifts to be estimated. In addition, these
phylogenies allow the degree of lability and covariation
in key floral traits, such as nectar, colour, shape and
scent, to be assessed for the first time.
rewarding model flowering plant species, although
convergent evolution is a potentially confounding factor.
The function of colour polymorphism is less clear in food
deceptive orchid species exhibiting more generalised
mimicry without a specific model species. Although
some studies suggest colour polymorphism is due to
frequency dependent selection by pollinators, several
other abiotic and environmental explanations may be
more influential. New technologies and devices provide
affordable means to measure spectral wavelengths
reflected by orchids, but how are these colours seen by
pollinators? Competing models of insect vision mean
interpreting pollinator perception of orchid spectral
reflectivity remains controversial. Here I review and
evaluate the most common methods of modelling
spectral reflectance and trichromatic hymenopteran
pollinator vision: hexagonal colour opponency (as
proposed by Chittka) and triangular non-colour
opponency (as proposed by Vorobyev and Brandt). I
discuss suggested methods and techniques for data
collection, and performing calculations manually and
with software. I also present new data on floral colours of
sexually deceptive and putatively brood-site deceptive
orchid species from Australia and New Zealand. Broodsite deception involves mimicry of typical oviposition
sites and therefore pollination by female rather than male
insects. Brood-site mimicry by orchids has received less
attention than other forms of deceptive pollination,
although anecdotal evidence is strong. If deception
imposes different costs on the reproduction of female
insects than on male insects, each form of deceptive
pollination may involve distinct selective pressures.
Consequently, the functions and roles of visual versus
olfactory signals may vary between these pollination
systems.
Orchid colour and pollination by deception
Gaskett, AC1
1
The University of Auckland, New Zealand
Visual signals such as floral colour are primary pollinator
attractants. Orchids have long been thought to use colour
in pollinator attraction and deception, but colour is likely
to function quite differently in rewarding than in
nectarless or deceptive pollination systems. Darwin
supported Sprengel's then-controversial hypothesis that
showy floral colours were pollinator attractants.
Consequently, Darwin noted that he had few
explanations for why pollinators were attracted by
orchids with drab green or inconspicuous flowers, many
of which had hinged labellae. These non-traditional floral
features are now strongly associated with sexually
deceptive pollination systems in which orchids mimic
female insects and pollination occurs when male insects
are fooled into sexual behaviour with flowers. Although
sexual deception primarily relies on attracting pollinators
with olfactory signals, floral colour can still play a role.
Orchids may mimic the colour of female insects, or more
intriguingly, exploit pollinators’ sensory biases or innate
preferences for certain wavelengths and colour contrasts.
Research into the functions of colour in deceptive
pollination systems has focussed largely on fooddeceptive orchid species that are nectarless but
nonetheless still pollinated by foraging male and female
insects. In food deceptive orchid species, colour can
function in Batesian floral mimicry of specific, nearby,
Impacts of extreme weather on flowering phenology
of wild orchids in southwestern China
Liu, H1, Feng, C-L2, Luo, Y-B3, Deng, Z-H4
1
Florida International University, Fairchild Tropical
Botanic Garden, USA, and Guangxi University, China;
2
Experimental Center of Troical Forestry, Chinese
Academy of Forestry Sciences, China; 3State Key
Laboratory of Systematic and Evolutionary Botany,
Institute of Botany, Chinese Academy of Sciences, China;
4
Yachang National Orchid Nature Reserve, Guangxi,
China
Impacts of unusual weather on orchid reproduction was
mentioned by Darwin in his 2nd edition of the book On
the various contrivances by which orchids are fertilised
by insects. However, rare weather events as drivers of
temporal variations in reproduction of orchids were not
emphasized by him or other researchers. Yet, among the
predictions of on-going climate change, is increased
frequency of extreme weather events. Therefore, it is of
paramount importance to understand the impacts of
extreme weather events on orchid reproduction. Here we
explored the effects of an extreme cold event during
early spring of 2008 on flowering phenology of 50
species in 21 genera of wild orchids in the Yachang
Orchid Nature Reserve in southwestern China. We found
that 23 species (46%) delayed their flowering time
compared to the previous year that had average spring
weather, while 27 species (54%) did not delay. We
153
related these phenological responses to various
ecological traits, include flowering season (spring vs.
non-spring), habit (terrestrial vs. epiphytic/lithophytic),
endemicity (narrow endemic vs. non-narrow endemic),
population size (small vs. large population), and range
position (southern-most population or non-southern-most
population). We found that only population size had
significant impacts on whether the species had a
phenological response to the extreme low spring
temperature. Specifically, 60% of the species with
relatively large populations responded with a flowering
delay while only 25% of the species with very small
populations did. While terrestrial, spring flowering
orchids and species with a wide global distribution range
were more likely to delay flowering than epiphytic,
summer or fall flowering, and narrow endemic orchids,
these differences were not statistically significant. A
comprehensive logistic regression analysis (backward
stepping), which incorporated all the explanatory
variables also confirmed that population size was the
only significant factor. Since species that were not
sensitive to environmental cues were more likely to go
extinct during the past climate change events, orchids
with small populations in southwestern China may be
more vulnerable to the current and projected climate
change than orchids with large populations due to lack of
responses to environmental changes of the former group.
Sym058: Nectar: function, ecology and
evolution – 29 July
Biochemical evolution of pollination drops in seed
plants
von Aderkas, P1
1
Graduate Centre for Forest Biology, University of
Victoria, Canada
During the evolution of seed plants, in particular from
pteridosperms through gymnosperms, pollen was
captured by pollination drops. This is still the case for
almost all modern gymnosperms. A small number of
angiosperms have homologous ovular secretions. In
gymnosperms, these drops are secreted from the
nucellus, filling pollen chambers and/or micropylar
canals. Spheres of extruded liquid form at the outer
entrance to ovules. The drops are a component of
pollination mechanisms that have evolved to deliver
pollen into the ovule. The drops also induce pollen
germination. In species in which pollen is captured by
physical means, e.g. Douglas-fir and larch, drop secretion
and, consequently, pollen germination are delayed by
many weeks. Although some podocarps have pollination
drops that are able to scavenge for pollen, most
pollination drops indiscriminately accept whichever
pollen species land. Some evolutionary innovations exist,
such as sacci, that improve the chances for the ovule of
selecting homospecific pollen. Intergeneric crosses reveal
some chemically based selective mechanisms for
prezygotic seclusion of undesirable pollen. In some
species, pollination drops are secreted once only, in
others they are repeatedly secreted. In addition, there is
some evidence that pollen capture may be followed
almost immediately by drop resorption. With such a
154
diversity in behaviour and phenology, it is also not
surprising that the biochemical composition should show
evolutionary differences. Most drops include sugars,
amino acids, a limited number of secondary compounds
and calcium, as well as many proteins. Concentrations of
components, in particular sugars, show broad differences
associated with types of pollination. Gymnosperms
include species that are wind-pollinated and/or insectpollinated. The latter share compositional similarities
with nectar. Each gymnosperm pollination type has a
characteristic type of pollination drop, both in terms of
chemical composition and volume range. Windpollinated species tend to have lower volumes and lower
concentrations of sugars than insect-pollinated species.
We have molecular biological evidence that compounds
in the drops originate from the sporophyte, not the
megagametophyte. Proteins have a variety of roles
including alteration of carbohydrate composition (e.g.
invertases, xylosidases, galactosidases), defense against
microbes (e.g. chitinases, peroxidases, glucanases), and
prevention of ice damage (TLPs). A number of elements
are not yet understood. Work continues on surveying
proteins in the gymnsoperm clade. The mechanism that
regulates quick retraction of pollination drops is not
known. Genomics approaches to reproduction will likely
prove very rewarding in elucidating the evolution of
pollination drops in seed plants.
‘Toxic nectar’: the responses of pollinators to nicotine
in artificial nectar
Nicolson, S1, Koehler, A1
1
University of Pretoria, South Africa
The presence of secondary metabolites (SM) in floral
nectar seems paradoxical, in view of the reward function
of nectar, and little is known of their role in mediating
interactions between plants and pollinators. Nectar SM
may have multiple ecological functions, including
protection from microbial infection and unwanted
visitors, and attraction of specialised pollinators. We are
investigating the response of various pollinators to
nicotine, as a model alkaloid, in their nectar diets.
Nicotine, best known from the Solanaceae, is one of the
best-studied SM in terms of defence against herbivory. It
is highly toxic to most herbivores through its action on
acetylcholine receptors. Nectar is chemically diverse, and
the attractive or deterrent effects of SM such as nicotine
may depend on other nectar attributes. The most obvious
of these is nectar concentration. Using preference tests
with two very different pollinators – the whitebellied
sunbird Cinnyris talatala and the honeybee Apis
mellifera – we have shown that the dose-dependent
deterrent effect of nicotine is stronger in more dilute
nectars. Modulation of the deterrent effect of nectar
alkaloids by nectar sugar concentration is consistent with
SM in nectar acting as partial deterrents that keep
pollinators moving between plants and ensure crosspollination. Short visits by pollinators are not a
disadvantage in terms of plant fitness. From the animal
point of view, stronger deterrence in dilute nectars may
be considered beneficial when compensatory feeding, as
in nectar-feeding birds, potentially increases the alkaloid
intake. In coping with SM in nectar, pollinators must
achieve a balance between energetic gains and
palatability. We have also investigated the response to
nectar nicotine of the giant day gecko Phelsuma
madagascariensis grandis: these animals are attracted by
0.5 µM nicotine, repelled by 1000 µM, and indifferent to
intermediate concentrations. Pollinator declines are
currently of great concern internationally, and the
contributing factors are thought to include pesticides
such as neonicotinoids. These act at the nicotinic
acetylcholine receptors, and may have adverse effects on
nontarget insects and especially honeybees. We are
therefore interested in the physiological consequences of
ingesting nicotine in honeybees. When newly emerged
workers were caged in incubators and fed varying
concentrations of nicotine in sucrose solution for 21
days, consumption did not depend on nicotine levels in
the diet. Survival of the bees decreased on high nicotine,
but was unaffected by low and medium nicotine
concentrations. However, in three weak colonies nicotine
increased survival. It is possible that low levels of SM in
nectar may provide protection against disease, as already
shown for bumblebees. In future studies, we will
investigate how sublethal levels of nectar SM affect
honeybee foraging behaviour and trophallactic exchanges
among bees, and how toxin levels are changed by the
processing of nectar into honey. Sublethal effects of SM
may be more subtle but still detrimental for pollinators.
The role of scent compounds in attraction of rodent
pollinators to flowers of the South African Pineapple
Lily, Eucomis regia (Hyacinthaceae)
Wester, P1, 2, Pauw, A2, Johnson, S1
1
School of Biological and Conservation Sciences,
University
of
KwaZulu-Natal,
Scottsville,
Pietermaritzburg, South Africa; 2Dept of Botany and
Zoology, University of Stellenbosch, Stellenbosch, South
Africa
Plants adapted to rodent pollination show characters like
visually inconspicuous, bowl-shaped flowers near ground
level, stiff stamens, easily accessible nectar and often
characteristic scent. The South African Pineapple lily
Eucomis regia (Hyacinthaceae) is hypothesised to be
rodent-pollinated on the basis of sharing these characters
and as it differs from insect-pollinated Eucomis species
mainly in scent chemistry. Under natural conditions and
in the laboratory mice were observed to become dusted
with pollen as they licked nectar in the flowers. Pollen
and dye was transferred to stigmas. Live-trapped mice
had large amounts of E. regia pollen in the fur around the
snouts and in the faeces. Selective exclusion of
vertebrates, but not insects, led to significant reductions
in seed set. Controlled pollination experiments showed
that E. regia is self-incompatible and thus entirely
dependent on pollinator visits for seed production.
Spectral reflectance of floral tepals is very similar to the
green bracts and leaves, rendering flowers inconspicuous
to insects. The scent of flowers and nectar is reminiscent
of cooked potatoes due to the presence of the sulphur
compound methional. Choice experiments showed that
mice are strongly attracted to this compound.
Phloem at the epidermis – development of the
vascular supply within floral nectaries of Asteraceae
Davis, A1, Zhang, X1, Wist, TJ2, Sawhney, VK1
1
Dept of Biology, University of Saskatchewan,
Saskatoon, Canada; 2Dept of Biological Sciences,
University of Alberta, Edmonton, Canada
We are examining the development and role of vascular
tissue within floral nectaries. The comprehensive surveys
by Frei (1955) and Kartashova (1965) have demonstrated
that floral nectaries of dicotyledonous angiosperms either
are supplied by phloem alone, by both phloem and
xylem, or lack any direct vasculature into the glandular
tissue. We have found that in the floral nectaries of
Echinacea purpurea and Helianthus annuus, sieve tubes
of phloem in the nectary interior connect continuously to
sieve elements located within the subepidermal layer.
Moreover, evidence obtained by light and transmission
electron microscopy suggests that phloem in the
subepidermis of E. purpurea can originate from
periclinal divisions of nectary epidermal cells, thus
signifying a rare role of the epidermis in the formation of
specialized vascular tissue. Companion cells are the only
transfer cells found to exist within the nectaries of E.
purpurea, and the presence of these wall ingrowths
should assist determination of phloem-cell fate in the
subepidermal layer. We seek to determine stimuli and
patterns of actual formation of sieve elements and
companion cells, plus a prospective role for invertase at
the epidermis, to account for the hexose-richness of the
floral nectar secreted through stomata on the nectary
surface.
A role for auxin and PIN6 in the regulation of
quantitative nectar secretion in the Brassicaceae
Bender, R1, Fekete, M1, Bauer, B1, Lindgren, K2, Maki,
J2, Carter, C1
1
University of Minnesota Duluth, USA; 2College of St
Scholastica, Duluth, USA
To date, a mechanistic understanding of nectar synthesis
and secretion at the molecular level is lacking. In order to
identify genes mediating nectary form and function,
microarray analyses were used to identify nectaryenriched genes in Arabidopsis thaliana. One such gene,
PIN6, a polar auxin transporter, was confirmed to have
extreme enrichment in nectaries by both RT-PCR and
promoter:GUS fusion analyses. To identify a biological
role for PIN6, three independent T-DNA mutant alleles
were identified. Homozygous mutants were subsequently
examined for altered expression level via quantitative
reverse transcription polymerase chain reaction (qRTPCR). pin6-1, pin6-2 and pin6-3 mutants were identified
as knock-up, knock-out, and knock-down mutants
respectively. To link a role between PIN6 and nectary
function, mutant flowers were analyzed for total nectar
sugar, a measure of nectar production. Significantly,
PIN6 expression level was positively correlated to total
nectar sugar, with pin6-1 flowers (knock-up mutant)
displaying a 30% increase in nectar sugar over wild-type,
and pin6-2 (knock-out) and pin6-3 (knock-down) having
significant decreases in total nectar sugar. Interestingly,
pin6-1 and pin6-3 flowers displayed no visible
differences in morphology or nectary size from wild-type
plants; however, pin6-2 flowers had petals that failed to
fully expand, had reduced nectary size, and routinely
lacked one or both short stamen. The flowers of pin6-2
plants complemented with a PIN6 expression construct
155
were fully restored to a wild-type phenotype, including
total nectar sugar. In addition to the above, multiple TDNA mutants for other nectary-enriched genes, such as
MYB57 and gibberellin-2-oxidase 6 (GA-2-OX6),
displayed reduced total nectar sugar. RT PCR analyses of
these mutant lines also showed greatly reduced PIN6
expression level. Preliminary results indicated that
MYB57 directly binds to the PIN6 promoter and
regulates its expression. Finally, to link auxin to
quantitative nectar secretion, flowers treated with
exogenous auxin displayed significant increases in total
nectar sugar, whereas those treated with the auxin
transport inhibitors TIBA and NPA produced little or no
nectar. The findings described above are not unique to
Arabidopsis, as each has also been confirmed to occur in
Brassica rapa. A proposed mechanistic role for auxin
and PIN6 in nectar production will be presented.
Protein profiles in floral nectar: beyond a simple
reward
Nepi, M1, Guarnieri, M1, Pacini, E1
1
University of Siena, Dept of Environmental Sciences,
Italy
Nectar is considered a common floral reward that can be
utilized by a very large variety of animals. Sugars are the
more abundant solutes present in nectar and they have
been identified in a large number of species. Sucrose and
its monomers fructose an glucose are almost ubiquitous
as nectar sugars. Being simple molecules with a high
energy content, easy to digest and absorb, they are
considered the main alimentary reward of nectar. Other
solutes, such as amino acids, vitamins, organic acids
contribute to the alimentary value of nectar. Secondary
compounds such as alkaloids and volatiles are involved
in managing the insects behavior, being able to attract or
repel them. Protein also have been detected in floral
nectar since the early years of the last century but it is
only more recently that nectar protein profiles have been
better characterized. Apparently proteins are not involved
in attracting or repelling animals but rather their role is
related to two main functions: modifying the nectar sugar
profile and protecting the nectar from microorganism
invasion. Invertase is the enzyme responsible for the
hydrolysis of sucrose into fructose and glucose and thus
it is most involved in shaping the sugar profile of nectar.
It was the first enzyme known in nectar but its function
was little characterized. Nectar is an excellent media in
which fungi and bacteria can grow, especially when it is
openly exposed to the environment. Thus the plant must
defend this secretion and one way is the production of
nectar defense proteins. Few studies demonstrated a large
heterogeneity of nectar defense proteins in related and
unrelated species. Both types of enzymes have recently
been identified in the floral nectar of Cucurbita pepo: an
invertase with a very low activity and four iso-forms of a
β-D xylosidase for which a defense-related function can
only be hypothesized for the moment. Although nectar of
C. pepo contains hydrogen peroxide up to 0.2 mM, a
concentration that can be active against microrganisms, it
was not ascertained if the nectar redox cycle is operating
in this species. At present the study of nectar proteins by
means of the modern techniques of sequencing and
biochemical characterization is at its beginning but
revealed already complex and heterogeneous functions
156
that could not be hypothesized before. The biochemical
complexity of nectar demonstrate that this secretion,
dynamically modulated by the nectary itself, is much
more than a simple sugary reward for pollinators. This
complexity opens new perspectives for future research.
Sym059: Biosynthesis of plant cell walls –
29 July
Identification of new genes involved in Arabidopsis
cell wall expansion using activation tag screening
Somerville, C1, Anderson, C1
1
University of California Berkeley, USA
Cell wall expansion, in which the wall must increase in
surface area while retaining its ability to withstand turgor
pressure, is essential for plant growth and development.
The expected early lethality of null mutations in genes
required for cell wall expansion and the potential for
redundancy to mask the phenotypes of mutations in gene
family members limit conventional screening methods
for mutants in this process. To circumvent these issues,
we performed a screen to identify genes whose
overexpression causes enhanced cell expansion. As an
experimental system we chose etiolated Arabidopsis
seedlings, in which hypocotyl elongation is driven
primarily by cell expansion. From a population of
~30,000 lines transformed with an activation tag
construct containing four tandem CaMV 35S enhancers,
we identified putative single insertion lines with a
heritable elongated hypocotyl phenotype. Identification
of the insertion sites for these lines has allowed us to
generate a list of candidate genes with potential functions
in cell wall expansion. Characterization of these genes,
many of which are of unknown function, should enhance
our understanding of the molecular events of cell wall
expansion and has the potential to inform efforts to more
efficiently use plant cell walls for the production of
biofuels and renewable materials.
Xyloglucan and glucomannan biosynthesis
Keegstra, K1, Cavalier, D1, Danhof, L1, Davis, J1, Reca,
B1, Wang, Y1, Wilkerson, C1
1
Michigan State University, USA
Plant biomass is a major renewable resource that can be
used in the production of biofuels and other chemicals. It
consists mainly of plant cell wall polymers including
cellulose, hemicellulose and lignin. In spite of their
abundance in nature and their importance in the emerging
biofuels industry, too little is known about the
biosynthesis
of
these
cell-wall
components.
Hemicellulosic polysaccharides are known to be
synthesized in the Golgi before their delivery to the cell
surface. Identification and characterization of the
enzymes require for the synthesis of hemicellulosic
polysaccharides, such as xyloglucan or glucomannan,
have been difficult because they are low abundance,
integral membrane proteins. Consequently, we have
pursued a functional genomics strategy, taking advantage
of the genome sequence information that is available for
many plant species, including Arabidopsis. The proteins
needed for the synthesis of xyloglucan or glucomannan
from the various sugar nucleotides have been identified
and partially characterized. However, many important
questions regarding the molecular details of
polysaccharide biosynthesis remain to be determined.
The lecture will review the work leading to the
identification of the enzymes needed for xyloglucan and
glucomannan biosynthesis and present current efforts to
resolve some of the remaining unsolved problems. This
research was supported with funding from the US Dept
of Energy (DOE) Great Lakes Bioenergy Research
Center (DOE BER Office of Science DE-FC0207ER64494) and from the Chemical Sciences,
Geosciences and Biosciences Division, Office of Basic
Energy Sciences, Office of Science, U.S. Dept of Energy
(award no. DE-FG02-91ER20021).
Using forward genetic approach to study the monocot
cell wall biosynthesis
Zhang, B1, Xiong, G1, Li, R1, Liu, L1, Zhou, Y1
1
Institute of Genetics And Developmental Biology,
Chinese
Academy
of
Sciences,
China
Rice is a model organism for studying the mechanism of
cell wall biosynthesis and remolding in Gramineae.
Mechanical strength and plant height are important
agronomy traits of rice plants (Oryza sativa L.) that
affect crop lodging and grain yield. As the prominent
physical property of cell walls, mechanical strength and
plant height reflect upon the structure of different wall
polymers and how they interact. Studies on the
mechanisms that regulate these traits are therefore
helpful for uncovering the functions of corresponding
genes in cell wall biosynthesis and remodeling. Our
group focuses on systematical isolation of mutants that
have altered mechanical strength and/or plant height and
functional characterization of their corresponding genes.
The identified genes cover several pathways of cell wall
biosynthesis, including cellulose biosynthesis and
deposition, membrane trafficking, matrix polysaccharides
formation, and substrate supply. All of those have
revealed many secrets of monocot cell wall biosynthesis
and remodeling, which are of great benefit to harnessing
the waste rice straws for biofuel production.
Insights into the synthesis, structure and function of
the plant cell wall polysaccharide (1,3;1,4)-β-D-glucan
Doblin, M1, Burton, R2, Jobling, S3, Wilson, S1, Walsh,
C1, Collins, H2, Kibble, N2, Fincher, G2, 4, Bacic, A1, 5
1
ARC Centre of Excellence in Plant Cell Walls, School of
Botany, University of Melbourne, Australia; 2ARC
Centre of Excellence in Plant Cell Walls, School of
Agriculture, Food and Wine, University of Adelaide,
Waite Campus, Glen Osmond, Australia; 3CSIRO
Division of Plant Industry, Canberra, Australia;
4
Australian Centre for Plant Functional Genomics,
School of Agriculture, Food and Wine, University of
Adelaide, Waite Campus, Australia; 5Australian Centre
for Plant Functional Genomics, School of Botany,
University of Melbourne, Australia
Plant cell walls are of central importance to plants during
growth and development, providing mechanical support,
a reservoir of cell–cell communication and signaling
molecules, and as a physical barrier to pathogen attack.
The non-cellulosic polysaccharide (1,3;1,4)-β-D-glucan,
or β-glucan, is a plant cell wall polysaccharide found
almost exclusively within the Poaceae and related
families of the commelinoid clade of the Poales in higher
plants. The walls of the Poaceae have been extensively
studied because of the economic importance of grasses
and cereals. In plants, β-glucans have been implicated in
the control of cell expansion, acting as a structural
element and as a carbon storage reserve. In the human
diet, they are believed to lead to positive health benefits
by lowering serum cholesterol and attenuating blood
glucose levels. Soluble fibre is known to reduce the risk
and occurrence of coronary heart disease, colorectal
cancer, obesity and Type II diabetes. In contrast, because
of the ability of β-glucans to form highly viscous
solutions, they have a negative impact on the production
and quality of beer by interfering with the filtration
process and are also the cause of ‘sticky’ faeces in the
feedstock industry. Hence, there is widespread interest in
identifying the genes responsible for the synthesis,
regulation and modification of β-glucan with the aim of
being able to effectively produce cereals with high and
low β-glucan levels for different end uses. We have
identified two cellulose synthase-like gene families, CslF
and CslH, as encoding the likely catalytic components of
the (1,3;1,4)- β-D-glucan synthase enzyme (Burton et al.
2006, Doblin et al. 2009). We present our recent work in
determining the other component/s and of the β-glucan
synthesis machinery, the mechanism of enzyme action
and the control of β-glucan fine structure as well as the
regulation of its synthesis. This work was supported by
funding from the Commonwealth Scientific and Research
Organization Flagship Collaborative Research Program,
provided to the High Fibre Grains Cluster via the Food
Futures Flagship.
The biosynthesis of (1,3;1,4)-beta-D-glucan in the
Oryzeae tribe
Burton, R1, 2, Fabrizio, J1, Collins, H2, Lahnstein, J2,
Cosse, M1, Little, A2, Henderson, M1, Fincher, G1,2
1
ARC Centre of Excellence In Plant Cell Walls,
University of Adelaide, Australia; 2CSIRO Food Futures
National Research Flagship, University of Adelaide,
Australia
(1,3;1,4)-β-D-glucan is a non-cellulosic cell wall
polysaccharide found in many cereal crops where it is an
important source of dietary fibre for human nutrition
providing substantial health benefits. It is found in high
levels in certain cereals such as oats and barley but
currently very little is known about the amount and
distribution in rice, which is one of the world¡¦s most
important cereal crops. Currently only data from grain at
the very early stages of development, 3 to 5 days after
pollination (DAP), has been published (Brown et al.
1997). Therefore, we have examined the amount and
structure of (1,3;1,4)-β-D-glucan within economically
important rice cultivars (Oryza sativa), and in a number
of other Oryza species, in both developing grain samples
(6 to 28 DAP) and in various vegetative tissues using a
sensitive high performance chromatography method. The
157
physical distribution of this polysaccharide was also
determined using microscopic analyses and the BG1
monoclonal antibody specific for (1,3;1,4)-β-D-glucan.
Transcript levels of (1,3;1,4)-β-D-glucan synthase genes,
namely those in the CslF (Burton et al., 2006) and CslH
(Doblin et al., 2009) gene families, were analysed by
real-time quantitative PCR using cDNA templates
derived from vegetative tissues at various growth stages
and from developing grain 6 to 28 DAP. Transcripts of
OsCslF6 predominated during mid grain development,
which is consistent with the pattern previously reported
for the direct barley and wheat orthologues (Burton et al.
2008, Nemeth et al. 2010). However, the detection of
aberrant cDNAs in many rice tissues has led to an
investigation into splicing patterns of particular CslF
genes and the downstream effects this may have on
protein function.
Genetics of cell wall polysaccharide synthesis in the
grasses
Fincher, G1, Schwerdt, J1, Harvey, A1, Marshall, D2,
Russell, J2, Waugh, R2
1
ARC Centre of Excellence In Plant Cell Walls,
Australia; 2Scottish Crops Research Institute,
Invergowrie, Dundee, Scotland, UK
The CsIF genes of barley and rice mediate the
biosynthesis of (1,3;1,4)-β-glucans, which are noncellulosic cell wall polysaccharides found almost
exclusively in the Poaceae. Six of the eight rice OsCsIF
genes cluster on rice chromosome 7 within an interval of
approximately 100 kilobases, while four of seven
HvCslF genes of barley, eight of the 11 sorghum SbCsIF
genes and five of the seven BdCsIF genes from
Brachypodium map to a single locus in syntenic regions
of these other species. Further, the CsIF gene clusters are
components of ‘super clusters’ of genes that include
groups of genes involved in plant responses to biotic
stress. Within the clusters, individual CsIF genes exhibit
65–75% sequence identity, which suggests that the
clusters have been conserved over a considerable time
period. Thus, the CsIF gene clusters appear to be
taxonomically conserved within the grasses but are
nevertheless dynamic insofar as relatively recent
expansions and contractions of cluster size can be
detected. The conservation of the cluster might be
attributable to selection pressure that allows the grasses
to rapidly synthesise (1,3;1,4)-β-glucans during certain
stages of development or in response to environmental
stimuli.
Sym060: Intracellular and intercellular
RNA signalling – A: 25 July, B: 25 July
MiR159 regulation of gene expression in Arabidopsis;
specificity, mechanism and biological requirement
Li, J1,2, Lin, L1, Lin, Y1, Alonso-Peral, MM1, Allen, RS2,
White, RG2, Gubler, F2, Millar, AA1
1
Research School of Biology, Australian National
University, Australia; 2Plant Industry, CSIRO, Australia
158
MicroRNAs (miRNAs) are a class of small RNAs that
have been shown to control many critical aspects of plant
biology. We are examining the miR159 class of miRNAs
in Arabidopsis in order to understand general principles
of the specificity and mechanism of miRNA-mediated
gene silencing in plants. Firstly, bioinformatic and
molecular analyses predicts miR159 to regulate over 20
genes in Arabidopsis, including eight MYB genes that
contain a highly conserved miR159 binding site. Despite
this, genetic analysis demonstrated that miR159 is
functionally specific for only two target genes, MYB33
and MYB65, which have strong overlapping
transcriptional domains with the two major miR159
members, miR159a and miR159b. Many of the other
target genes have an overlapping transcriptional domain
with the remaining family member, miR159c. However
miR159c appears quiescent in nature, explaining the lack
of functional impact of miR159 regulation of these
predicted target genes. Secondly, with regards to
mechanism,
plant
miRNAs
have
extensive
complementarity and perfect matches around the
cleavage site and so they are thought to act
predominantly through mRNA cleavage, and to a lesser
extent translational repression. However, using
transgenic systems we show that that the steady-state
levels of MYB33 do not correlate with silencing, despite
the detection of miR159-guided cleavage products.
Moreover, artificial miR159 variants with mismatches
around the cleavage site (both positions 10,11) can still
fully silence MYB33. Together this suggests that
miR159 repression of gene expression can work
predominantly at the translational level. Finally we will
speculate on the biological requirement of miR159
regulation, and the novel aspects that this type of posttranscriptional regulation can give, compared to
regulation at a transcriptional level.
MicroRNAs in the shoot apical meristem of soybean
Wong, CE1, Zhao, Y-T0, Wang, X-J2, Croft, L0, Wang,
Z-H0, Haerizadeh, F1, Mattick, JS0, Singh, MB1, Carroll,
BJ4,5, Bhalla, PL1
1
ARC Centre of Excellence for Integrative Legume
Research, Faculty of Land and Food Resources, The
University of Melbourne, Australia; 2State Key
Laboratory of Plant Genomics, Institute of Genetics and
Developmental Biology, Chinese Academy of Sciences,
Beijing, China; 3Graduate University of The Chinese
Academy of Sciences, Beijing, China; 4ARC Centre of
Excellence for Integrative Legume Research, Australia;
5
School of Chemistry and Molecular Biosciences,
Australia; 6Institute for Molecular Bioscience, University
of Queensland, Brisbane, Australia
Plant microRNAs (miRNAs) play crucial regulatory
roles in various developmental processes. In this study,
we characterize the miRNA profile of the shoot apical
meristem (SAM) of an important legume crop, soybean,
by integrating high-throughput sequencing data with
miRNA microarray analysis. A total of 8,423 nonredundant sRNAs were obtained from two libraries
derived from micro-dissected SAM or mature leaf tissue.
Sequence analysis allowed the identification of 32
conserved miRNA families as well as eight putative
novel miRNAs. Subsequent miRNA profiling with
microarrays verified the expression of a majority of these
conserved and novel miRNAs. It is noteworthy that
several miRNAs* were expressed at a level similar to or
higher than their corresponding mature miRNAs in SAM
or mature leaf, suggesting a possible biological function
for the star species. In situ hybridization analysis
revealed a distinct spatial localization pattern for a
conserved miRNA, miR166, and its star species
suggesting they serve different roles in regulating leaf
development. Further, localization studies showed that a
novel soybean miRNA, miR4422a, was nuclearlocalized. This study also indicated novel expression
pattern of miR390 in soybean. Our approach identified
potential key regulators and provided vital spatial
information towards understanding the regulatory circuits
in the SAM of soybean during shoot development.
Defective embryo and meristems interacts with
conserved Ras-like nuclear protein, and mutants
display multiple epigenetic defects
Peters, J1,2, Gursanscky, N0, Lonhienne, T0, Matthew,
L0, Reyes, M.E.C0, Ngo, Q3, Hawker, N3, Sundaresan,
V3, Kobe, B1, Bowman, J.L3,4, Carroll, B.J1,2
1
1School of Chemistry and Molecular Biosciences The
University of Queensland, Australia; 2ARC Centre of
Excellence for Integrative Legume Research, The
University of Queensland, Australia; 3Section of Plant
Biology, University of California at Davis, Davis, USA;
4
School of Biological Sciences, Monash University,
Clayton Campus, Australia
Coordinated cell proliferation and cell differentiation
directs the shape and form of multicellular organisms.
The tomato defective embryo and meristems (dem)
mutant fails to develop beyond the seedling stage of
development. Somatically mutagenesis and modification
of DEM expression, demonstrated that DEM directs both
cell division and cell differentiation in tomato.
Arabidopsis has two DEM-like genes, DEM1 and
DEM2, and unlike dem in tomato, the single mutants,
dem1 and dem2, remain viable. However, the dem1dem2
double mutant is a gametophytic lethal. DEM is specific
to multicellular plants, and is not homologous to any
protein of known biochemical function. However, a twohybrid screen identified Ras-like nuclear protein (RAN)
as a potential interaction partner. E. coli-expressed
proteins confirmed that DEM interacts with RAN in
vitro. E. coli-expressed RAN proteins can also pull down
DEM from crude plant extracts. RAN is a guanine
nucleotide binding protein that is highly conserved
between plants and animals, and in animals has been
shown to play key roles in: i) nucleo-cytoplasmic protein
transport, ii) assembly of the spindle during mitosis, iii)
formation of the nuclear envelop following mitosis, and
iv) export of microRNAs (miRNA) from the nucleus.
Our recent work has demonstrated that Arabidopsis dem1
mutants have lower steady state levels of miRNAs. dem1
and dem2 mutants are also defective in transgene
silencing. GFP fusions to the N- or C-terminus of DEM1
indicated that DEM is present in the cytoplasm, but
restricted to the periphery of the nucleus. Our data are
consistent with the hypothesis that the role of DEM in
cell division and cell differentiation in multicellular
plants is directed through its interaction with RAN, and
its involvement in regulatory RNA pathways in the cell.
Introns protect
Arabidopsis
transgenes
from
silencing
in
Christie, M1, Carroll, BJ
1
School of Chemistry and Molecular Biosciences, The
University of Queensland, Australia
Transgene silencing is a major limitation on the
expression of introduced genes in plants. The problem is
exacerbated in applications that require expression of
multiple transgenes in a stable and predictable fashion.
Here we show that introns can greatly reduce the
frequency of transgene silencing in Arabidopsis.
Transformation of wild-type Arabidopsis with an
intronless green fluorescence protein (GFP) transgene
resulted in 85% of independent T1 transformants
showing GFP silencing. Silencing was RDR6-dependent
as 100% of independent rdr6 mutant transformants
showed GFP expression. Initially, we tested four
Arabidopsis introns and found that three were able to
significantly decrease the incidence of transgene
silencing in primary transformants by up to five-fold.
Molecular characterization of these transgenic lines and
others carrying additional modified introns showed that
efficient splicing was required to provide protection
against silencing. These results suggest that intron
splicing protects a transcript from becoming a substrate
for RDR6, and thereby protects it from gene silencing.
We have also shown that intron-mediated protection
against silencing is dependent on ABH1, the Arabidopsis
homologue of the human cap-binding protein 80
(CBP80). The mechanism of intron-mediated
suppression of transgene silencing will be discussed.
A genome-wide survey of imprinted genes in rice
seeds
Luo, M1, Taylor, J1, Zhang, H2, Spriggs, A1, Wu, X2,
Russell, S3, Singh, M4, Koltunowe, A5
1
CSIRO Plant Industry, Canberra, Australia; 2Rice
Research Institute of Sichuan Agricultural University,
Chengdu, Sichuan, P.R. China; 3Dept of Botany and
Microbiology, University of Oklahoma, Norman, USA;
4
Plant
Molecular
Biology
and
Biotechnology
Laboratory, The University of Melbourne, Parkville,
Australia; 5CSIRO Plant Industry, South Australia,
Australia
Imprinting is a mechanism resulting in the biased
expression of one allelic copy of a gene in a parent-oforigin specific manner. A few imprinted Arabidopsis
genes are involved in regulating seed development. Only
17 imprinted genes have been confirmed in plants to
date, therefore, we conducted a genome-wide survey of
parent-of-origin-specific gene expression in rice seed, an
important food crop. Transcriptomes of endosperm and
embryos isolated from reciprocal crosses between two
sequenced subspecies (Nipponbare and Chinese Indica
93-11) were profiled. Single Nucleotide Polymorphisms
(SNPs) enabled assignment of expressed sequences to the
parental genome of origin. In the endosperm, 165
expression-biased genes were identified in addition to 35
expression-biased intergenic regions. 104 genes showed
>90% expression bias from a parental allele, of which 62
were maternally expressed and 42 paternally expressed.
159
Most of these genes are expressed lowly or show no
evidence of imprinting in the embryo. Only one
maternally expressed gene was found in the embryo and
it was also maternally expressed in the endosperm. Rice
imprinted genes show low conservation with known
plant imprinted genes and they are not physically
clustered or significantly associated with transposons and
repeats relative to non-imprinted genes. Two cases of
novel parent-of-origin alternative polyadenylation were
identified in the endosperm. Four genes that were either
biallelically expressed or partially imprinted early in
endosperm development became uniparentally expressed,
suggesting mechanisms operate in rice to establish
imprinting after fertilization. We will discuss the putative
mechanisms regulating imprinting in rice endosperm and
their potential linkage to the small RNA pathway.
Do non-coding RNAs function in the Arabidopsis
vernalization response?
Helliwell, C1, Finnegan, J1, Robertson, M1, Dennis, L1
1
CSIRO Plant Industry, Canberra, Australia
Expression of the Arabidopsis flowering repressor, FLC,
is responsible for conferring vernalization responsive
flowering in many late-flowering ecotypes. The
repression of FLC by vernalization has the hallmarks of
an epigenetically regulated response; FLC expression is
repressed during cold and this repression is maintained
once plants are returned to warm conditions. This
repression of FLC requires the function of a PHD-PRC2
(Plant Homeodomain-Polycomb Repressive Complex 2)
protein complex which adds the repressive H3K27me3
mark to FLC chromatin. A number of non-coding RNA
transcripts have been identified at the FLC locus that
show altered expression during the cold. These
transcripts have been suggested to function in various
aspects of the vernalization response. We will present the
results of our investigations into the functions of these
non-coding RNAs.
Mechanisms of mobile
counterdefence in plants
antiviral
defence
and
Waterhouse, P1, Correa, R2, Fusaro, A1, Liang, D3,
White, R3, Anderssen, B3, Carroll, B4, Kawchuk, L6
1
2
University of Sydney, NSW, Australia; Depto De
Virologia, IMPPG, UFRJ, Brazil; 3CSIRO Plant
Industry, Canberra, ACT, Australia; 4University of
Queensland, Brisbane, QLD, Australia; 5Agriculture and
Agri-Food Canada, Alberta, Canada
RNAi-like pathways are present in almost all eukaryotes
and rely on small RNAs directing sequence specific RNA
degradation, translational repression or epigenetic
modifications within the cell. One of the RNAi pathways
in plants mediates an adaptive mobile viral defense that
has many parallels with the mammalian immune system.
Details of the mechanism by which the plant mobilizes
and enhances its defense, and how members of one
family of viruses, the Luteoviridae, have developed
elegant, but different, counter-defence mechanisms, will
be described.
160
Small RNAs in disease induction or symptom
attenuation by viral satellite RNAs in plants
Smith, NA1, Eamens, AL1, Shen, W1, Zhou, C1, Wang,
M-B1
1
CSIRO Plant Industry, Canberra, ACT, Australia
Plant viruses are often accompanied by small, 200–400nt parasitic RNAs termed satellite RNAs. These RNAs
do not encode proteins and depend on the associated
virus (helper virus) for their propagation and systemic
spread. While the replication of many satellite RNAs
attenuates the symptoms caused by their helper virus,
some satellite RNAs, such as the cucumber mosaic virus
Y-satellite (Y-Sat), can itself induce disease symptoms in
the host that are distinct to those of the helper virus. How
these non-protein-coding RNA pathogens induce disease
symptoms has been a long-standing question. We have
previously reported that the yellowing symptoms induced
by Y-Sat in tobacco was inhibited by the expression of a
viral RNA silencing suppressor, which led us to suggest
that pathogenic satellite RNAs might have sequence
homology to a host gene, and that disease symptoms are
due to satellite small interfering RNA (siRNA)-directed
silencing of that host gene. No such host gene has been
identified, leaving the satellite RNA-induced disease
mechanism unsolved. Here we will present our recent
finding that Y-Sat-induced yellowing symptoms in
tobacco are caused by Y-Sat siRNA-directed silencing of
a magnesium chelatase gene essential for chlorophyll
biosynthesis. We also demonstrate that Y-Sat-induced
disease symptoms can be prevented by the presence of a
naturally evolved, or artificially introduced, silencingresistant sequence variant of the magnesium chelatase
gene. These findings provide the first evidence of small
RNA-mediated viral disease symptom production, offer
an explanation for the previously observed species
specificity of satellite RNA-induced diseases, as well as
providing a potential strategy to prevent such diseases.
We will also discuss our findings concerning the
involvement of satellite RNA-derived siRNAs in the
attenuation of helper virus-induced symptoms in plants.
Transgenic RNA silencing-mediated plant disease
control strategies
Mitter, N1
1
The University of Queensland, Australia
RNA silencing is an innate defence response of plants to
protect them against virus infections. Transgene-induced
RNA silencing is triggered by sequence-specific doublestranded RNA which can be derived from sense,
antisense, hairpin RNA or artificial microRNA
transgenes. Viral silencing suppressors have been shown
to affect RNA silencing based transgenic virus resistance.
However, durable resistance has been achieved by
targeting genes that encode viral RNA silencing
suppressors, selection of homozygous plants or plants
with multiple transgene copies, and pyramiding of target
sequences from different viruses which may infect a
particular crop. We have shown efficiency and stability
of hpRNA-induced virus resistance in tobacco involving
cucumber mosaic cucumovirus (CMV) and potato virus
Y potyvirus (PVY). We have shown that RNA silencing
mediated immunity against PVY in transgenic tobacco
can be overcome by infection with CMV, making the
plant susceptible to the virus it was engineered to resist.
A single hpRNA construct of converging sequences
provided dual immunity to both CMV and PVY.
However, the location of the viral sequences in the
construct affected effectiveness, with sequences flanking
the intron acting as most efficient silencing inducers. In
addition to viruses we are also investigating the use of
plant-delivered hpRNAs to control fungal infections
targeting Phytophthora root rot of avocado . The
validation for the efficacy of dsRNA constructs targeting
P. cinnamomi has been obtained in Arabidopsis. We are
also developing artificial microRNAs (amiRNAs) for
introducing resistance to plant viruses. We have modified
an Arabidopsis thaliana miR159 precursor to amiRNAs
targeting viral mRNA sequences encoding the
nucleocapsid protein (N) and the silencing suppressor
(NSs) genes of Tomato spotted wilt virus. Transient
expression of amiRNAs in Nicotiana benthamiana has
confirmed expression of virus-specific amiRNAs as well
as the ability of the amiRNA constructs to confer
resistance. The amiRNA-based resistance has been
shown to be active even at lower temperatures, unlike
siRNA-based resistance, and offers an effective approach
to prevent breakdown of resistance in the field by
expressing two to three amiRNAs targeting different
essential regions of a virus. In addition, broad spectrum
resistance to several viruses may also be achieved by coexpression of appropriately designed amiRNAs.
Identification of epigenetic components required for
cell-to-cell movement of an RNA silencing signal in
Arabidopsis
Searle, IR1, Smith, L2, Baulcombe, DC2
1
1Research School of Biology, ANU, Canberra,
Australia; 2Dept of Plant Sciences, University of
Cambridge, UK
RNA silencing is a sequence-specific RNA degradation
process conserved in fungi, animals and plants that is
associated with cell-to-cell movement of a mobile
silencing signal. We developed a cell-to-cell movement
of RNA silencing system in Arabidopsis using an
inverted repeat transgene under the control of a phloemspecific promoter such that the spread of RNA silencing
was manifested in regions around veins. We have
previously identified epigenetic components, Polymerase
IV, RNA-Dependent-RNA-polmyerase 2, and CLSY (a
SNF2chromatin remodelling factor) that are required for
mobile RNA silencing. In addition we also identified a
putative histone H3 lysine 4 trimethyl demethylase,
JMJ14, that is required for mobile RNA silencing. In
addition to an effect on mobile silencing the jmj14
mutants also had reduced CHH DNA methylation,
increased abundance of endogenous transposon
transcripts and they flowered earlier than wild type. We
placed the activity of JMJ14 at a downstream point in
RNA silencing pathways because the subcellular
locations of upstream components RNA-dependent RNA
polymerase (RDR2) and Argonaute (AGO4) were not
perturbed in jmj14 mutants. These results illustrate the
potential for a link between RNA silencing and
demethylation of histone H3 trimethylysine. We will also
discuss our progress in identifying new mutants required
for the spread of RNA silencing.
Genetic determinants involved in graft-transmissible
gene silencing in Arabidopsis
Gursanscky, N1, Brosnan, C1, Bowman, J L2, Carroll, B
J1
1
School of Chemistry and Molecular Biosciences, and
ARC Centre of Excellence for Integrative Legume
Research, The University of Queensland, Brisbane,
Australia; 2Section of Plant Biology, University of
California at Davis, California, USA, and School of
Biological Sciences, Monash University, Clayton
Campus, Australia
We have been using Green Florescent Protein (GFP) as a
reporter to study the mechanisms of graft-transmissible
gene silencing in Arabidopsis. Recently, we developed a
transgenic parent line for use in a forward genetic screen
to identify additional genes involved in systemic gene
silencing. This parent line carries a transgene expressing
GFP-specific dsRNA from a root tip-specific promoter
along with a linked 35S:GFP transgene target. The GFP
silencing phenotype of ungrafted plants of this line
resembles the grafted plants described by Brosnan et al.
(2007), and rootstocks of this line transmit silencing to
scions expressing GFP. Following mutagenesis, over 40
independent systemic silencing mutants were identified.
Several of these have been shown to be allelic to rdr6 and
are deficient in both receiving the silencing signal in
newly formed shoot tissue and in transmission of the
mobile silencing signal from grafted rootstocks. RDR6 is
part of the trans-acting siRNA pathway, and additional
components of this pathway are being tested for
involvement in transmission of silencing signals from
rootstocks. We are using map-based gene cloning to
identify another mutant gene that does not appear to be
linked to any genes known to be required for grafttransmissible gene silencing.
Sym061: Cellular dynamics – 26 July
MIDD1: a novel membrane-associated
regulating secondary wall patterns
MAP
Fukuda, H1, Oda, Y1
1
University of Tokyo, Japan
To analyze cellular events visually underlying xylem
formation, we have established an Arabidopsis culture
system in which a master transcription factor, VND6, is
induced by a steroid hormone. In these systems, approx.
80% of cells differentiate to metaxylem vessel-like cells,
within 3 days. Using this culture, we performed
transcriptome analysis and found a number of genes
whose function is not understood yet. The VND6inducive culture also allowed us to follow cellular events
as live images in differentiating xylem cells under a
microscope. With advantages of our newly established in
vitro xylem cell differentiation system, we analyzed the
function of products of unknown genes and discovered a
novel microtubule end-tracking protein, designated
161
MIDD1 (Microtubule Depletion Domain 1). This protein
was anchored to distinct plasma membrane domains and
promoted local microtubule disassembly, resulting in pits
on walls of metaxylem vessel cells. The introduction of
RNAi for MIDD1 resulted in failure of local microtubule
depletion and the formation of secondary walls without
pits. Conversely, the overexpression of MIDD1 reduced
microtubule density. MIDD1 has two coiled-coil
domains; the first domain associates with microtubules
and the second domain is required for the anchorage of
MIDD1 to distinct plasma membrane domains.
Combination of the two coils caused end-tracking during
shrinkage and promoted microtubule disassembly. Our
results indicate that plants use a distinctive protein that
integrates spatial information in the plasma membrane
with cortical microtubule dynamics, for determining
xylem cell wall pattern.
Turning over tracks: dynamics of actin filaments and
cables in the cortical array of Arabidopsis epidermal
cells
Staiger, C1, Henty, J1, Sheahan, M2, Khurana, P1,
McCurdy, D2, Blanchoin, L3
1
Purdue University, USA; 2Newcastle University,
Australia; 3CEA/CNRS/UJF, Grenoble, France
Eukaryotic cells harness the power of actin dynamics to
create cytoskeletal arrays that stimulate protrusions and
drive intracellular organelle movements. In plants, the
actin cytoskeleton is generally understood to participate
in cell elongation and responses to biotic and abiotic
stimuli; however, a detailed description and molecular
mechanism(s) underpinning filament nucleation, growth
and turnover are lacking. We have used variable-angle
epifluorescence microscopy (VAEM) to examine the
organization and dynamics of the cortical cytoskeleton in
growing and non-growing epidermal cells from
Arabidopsis hypocotyls. Actin in the cortical array exists
as individual actin filaments that are short-lived, as well
as longer-lived actin filament bundles. Collectively, the
single actin filaments are randomly oriented and
surprisingly dynamic. Single actin filaments grow at
rates of 1.7 µm/s. Instead of depolymerization at their
ends, actin filaments are disassembled by prominent
severing activity. Incessant remodeling of the cortical
actin array also features filament buckling and
straightening events. We consider several mechanisms
for the control of actin dynamics, including rapid
polymerization from a large pool of profilin–actin,
specific severing and capping activities, and myosindriven filament-filament interactions. Aspects of this
model have been tested with pharmacological agents and
with
reverse-genetics.
Specifically,
we
have
demonstrated a role for ADF4 in severing actin filaments
in vivo. And, we find that myosin XI contributes to actin
dynamics. Our observations, the first to describe single
actin filament behavior in plant cells, indicate a
mechanism inconsistent with treadmilling, instead
resembling the stochastic dynamics of a recently
described biomimetic system for actin assembly in vitro.
162
Myosin XI drives endoplasmic reticulum motility and
organizes F-actin orientations
Ueda, H1, Yokota, E2, Kutsuna, N3, Shimada, T1, Dolja,
VV4, Hara-Nishimura, I1
1
Kyoto University, Japan; 2University of Hyogo, Japan;
The University of Tokyo, Japan; 4Oregon State
University, USA
3
Plants exhibit an ultimate case of the intracellular
motility involving rapid organelle trafficking and
continuous streaming of the endoplasmic reticulum (ER).
Although it was long assumed that the ER dynamics is
actomyosin-driven, the responsible myosins were not
identified, and the ER streaming was not characterized
quantitatively. Here we developed software to generate a
detailed velocity distribution map for the GFP-labeled
ER. This map revealed that the ER in the most peripheral
plane was relatively static, whereas the ER in the inner
plane was rapidly streaming with the velocities of up to
~3.5 µm/sec. Similar patterns were observed when the
cytosolic GFP was used to evaluate the cytoplasmic
streaming. Using gene knockouts, we demonstrate that
the ER dynamics is driven primarily by the ERassociated myosin XI-K, a member of a plant-specific
myosin class XI. Furthermore, we show that the myosin
XI deficiency affects organization of the ER network and
orientation of the actin filament bundles. Collectively,
our findings suggest a model whereby dynamic threeway interactions between ER, F-actin, and myosins
determine the architecture and movement patterns of the
ER strands, and cause cytosol hauling traditionally
defined as cytoplasmic streaming. (Ueda et al. 2010).
Auxin regulation of cytoskeletal organization,
endomembrane trafficking and cell morphogenesis in
Arabidopsis
Yang, Z1, Nagawa, S1, Xu, T1, Lin, D1
1
University of California, Riverside, USA
Auxin is a universal morphogenetic signal that regulates
the formation of various developmental and
morphogenetic patterns in plants, but the molecular and
cellular mechanisms for the auxin action remain poorly
understood. We investigate these mechanisms using
Arabidopsis leaf epidermal pavement cells as a model
system, which form the jigsaw puzzle cell pattern with
interdigitated lobes and indentation. We have shown that
pavement cell interdigitation is controlled by localized
ROP GTPase signaling, which impinges on the
organization of cortical actin microfilaments and
microtubules to generate interdigitating lobes and
indentations (1, 2). Our studies indicate that auxin is a
signal that activates pavement cell polarization to form
lobes and coordinates lobe formation with indentation
formation by activating ROP GTPase signaling through
an Auxin-Binding Protein 1 (ABP1)-dependent and cell
surface-based auxin perception system (3). This is a new
cytoplasmic auxin signaling mechanism distinct from the
well-established TIR1-dependent nuclear auxin signaling
system that regulates gene transcription. This new auxin
signaling mechanism regulates the interdigitated cell
pattern through its modulation of PIN1 localization to
lobe tips (3). Our recent results suggest that ABP1/ROP
signaling regulates PIN1 localization by affecting PIN1
endocytosis ad its recycling. These findings may provide
new insights into the molecular and cellular mechanisms
for auxin action as well as the first glimpse at how
cellular signaling links the cytoskeleton with
endomembrane trafficking in plant cells. References: (1)
Fu, Y et al. 2005. (2) Fu, Y et al. 2009. (3) Xu T et al.
2010.
An Arabidopsis formin tracks microtubule dynamics
and is involved in cell division
Ren, H1, Li, Y1, Shen, Y1, Cai, C1
1
Beijing Normal University, China
Formins have long been known to regulate
microfilaments, but have also recently been shown to
associate with microtubules. We have previously studied
a type II formin from Arabidopsis thaliana –AtFH14 –
and found it regulated both microtubule and
microfilament arrays. AtFH14-GFP expressed in BY-2
cells was shown to decorate preprophase band (PPB),
spindle, and phragmoplast, and to induce co-alignment of
microtubules with microfilaments. Pharmacological
experiments with cytoskeleton disrupting drugs showed
that AtFH14 bound preferentially to microtubules.
Knockdown of AtFH14 in mitotic cells altered
interactions between microtubules and microfilaments,
resulting in the formation of an abnormal mitotic
apparatus. To find out which domain is important for the
localization of AtFH14, we expressed its N-terminal Pten
domain and FH1FH2 domain in BY-2 cell and found
both of them could target to PPB, spindle and
phragmoplast, indicating that the location and function of
AtFH14 was determined by both Pten and FH1FH2
domains. To explore the function and localization of
AFH14 in non-dividing cells, we expressed FH1FH2RFP in onion epidermal cells, and found a fluorescence
labeled filamentous network. The results of double
labeling with different cytoskeleton reporter proteins
indicated that FH1FH2-RFP co-localized with cortical
microtubules. Treatment of cells expressing FH1FH2RFP with cytoskeleton disrupting drugs confirmed that
FH1FH2-RFP bound to microtubules. Moreover, the
binding of FH1FH2-RFP to microtubules were revealed
to be dynamic by fluorescence recovery after
photobleaching experiment. Time-lapse confocal
microscopy showed that FH1FH2-RFP could display a
dynamics similar to the microtubule dynamic instability.
These results suggest that AtFH14 is a unique plant
formin that tracks microtubule dynamics and is involved
in cell division.
ACTIN7 is specifically required for chloroplast
repositioning in dedifferentiating plant cells
Sheahan, M1, Kandasamy, M2, Meagher, R2, Rose, R1,
McCurdy, D1
1
eukaryotes actins are encoded by multi-gene families. In
Arabidopsis, eight expressed actin isoforms exist. Based
on their phylogenetic relationship and expression pattern,
Arabidopsis actins are classified as either vegetative or
reproductive, with each class being expressed
predominantly in vegetative and reproductive tissues,
respectively. The vegetative class of actins comprises
ACT2, ACT7 and ACT8. Interestingly, the sequence
divergence between individual actin isoforms in plants is
greater than the divergence between actin isoforms in
animals, suggesting there is a potential for plant actin
isoforms to perform discrete functions within the cell.
Alternately, such divergence may simply reflect
developmental rather than intracellular specialisation. In
this regard, we have been investigating chloroplast
partitioning before the first cell division of Arabidopsis
mesophyll protoplasts. In protoplasts of a number of
plant species we have examined, chloroplasts cluster
around the nucleus in an actin-dependent manner before
the cell divides. This repositioning acts as a mechanism
to ensure unbiased chloroplast inheritance. We have
shown that chloroplast repositioning occurring before the
re-initiation of cell division in cultured plant cells is
defective in Arabidopsis plants carrying mutations in
ACT7 but not ACT2 or ACT8. Here, we investigated
whether this apparent differential requirement for actin
isoforms reflects differential expression or a specific
functional requirement for ACT7 in chloroplast
repositioning. Quantitative real-time PCR confirmed that
ACT7 was upregulated, while the two other vegetative
actins, ACT2 and ACT8 were down-regulated slightly
during protoplast culture. Among the reproductive actins,
expression of ACT4 and ACT12 was not detected;
ACT11 expression remained relatively stable, whereas
expression of ACT1 and ACT3 was upregulated.
Quantitative immunoblotting using cultured protoplasts
derived from wild-type and act2-1 or act7-1 mutant
backgrounds revealed an increase in total actin as
protoplasts culture proceeded. Expectedly, there were
reduced levels of total actin in the act7-1 mutant, yet total
actin did increase during culture, indicating that other
actin isoforms are present in these cells. Currently, we
are examining chloroplast repositioning in act7-4 mutants
expressing either ACT2 or ACT8 under control of the
ACT7 promoter to determine if the requirement for
ACT7 represents a developmental specialisation for this
isoform or whether is simply represents the most
abundantly expressed actin. Further, we report on the
structural features of the actin cytoskeleton in wild-type,
act2-1, act7-4 and act8-1 mutant backgrounds.
Sym062: Pollen biology and pollen–pistil
interaction – 26 July
Novel and ancient aspects of flowering plant pollen
tubes and their pathways
Williams, J1
2
Newcastle University, Australia; University of Georgia,
USA
The actin cytoskeleton facilitates numerous cellular
processes required for the correct functioning and
development of multicellular eukaryotes. Unlike yeast,
where actin is encoded by a single gene, in multicellular
1
Dept of Ecology and Evolutionary Biology, University
of Tennessee, USA
Early angiosperm history was strongly marked by a shift
from a long to an exceptionally brief fertilization process.
Ovules and their associated female gametophytes became
163
greatly reduced in size, causing precocious production of
an egg, and consequently a much abbreviated pollination
to fertilization period (progamic phase). The shift to
small ovules was accompanied by the origin of an
enclosing carpel as well as the flower, which was itself
small and ephemeral. Early angiosperm pollen tube
evolution occurred within the context of many
developmental modifications that affected the size and
longevity of pollen tube pathways. A central innovation
underlying the integration of interdependent floral and
ovular tissues was the evolution of faster pollen tube
growth rates. I studied pollen tube development and
growth in a number of ancient lineages of angiosperms,
including Amborella, Nymphaeales and Austrobaileyales.
I used ancestral reconstruction methods on these and
other published studies to infer ancestral features of early
angiosperm
progamic
phase
biology.
These
reconstructions have revealed a surprising connection
between the evolution of the microscopic fertilization
process and ecological traits such as the duration of
reproductive cycles and floral form and size. A survey of
275 angiosperm species shows that in vivo pollen tube
growth rates range from 0.044 – 24 mm/h (median =
0.840 mm/h). Among ancient angiosperms, woody
perennials have among the slowest pollen tube growth
rates known, whereas a number of ancient aquatic
lineages are characterized as having growth rates near or
higher than the angiosperm median. Ancient angiosperm
pollen tubes develop in a great diversity of environments:
they germinate in water or on dry or wet stigmas, and
tubes grow in water, free secretions, secretions between
appressed tissues, zones of secondary fusion, and within
middle lamellae between cells. Pollen tube structure is
less variable. Ancient angiosperm pollen tubes are
narrower in diameter and have thinner walls than those of
other seed plants. Their thin walls are composed
primarily of callose, whereas those of gymnosperms and
most other plant cells are generally pecto-cellulosic and
have a different pattern of callose expression, if present.
Callose is known to be deposited more rapidly than
cellulose and has mechanical properties that support
long-distance growth. It is synthesized in pollen tube
walls and callose plugs via the same gene copy (CalS-5)
in Arabidopsis as in ancient angiosperms such as
Amborella. CalS-5 is itself an ancient gene and is
expressed in the intine of pollen of Ginkgo and Zamia. It
was likely co-opted from a role within the pollen grain to
its novel structural function in the pollen tube wall. Early
increases in pollen tube growth rates evolved by
streamlining of ancestral features (size changes) and by
the origin of novelties (the permanent callose wall).
Subsequent changes must also have involved increases in
rates of synthesis of callose and other wall materials.
Ultimately, rapid pollen tube growth rates enabled a
dissociation of the pollen reception apparatus (the
stigma) from the egg-bearing structure (the ovule),
making possible a tremendous diversification in sizes and
lifespans of floral and fruit organs.
Ions, energy, actin and pectin in the control of pollen
tube growth
Hepler, P1, Rounds, C1, Kunkel, J1, Shipley, A1,
Winship, L2
1
2
University of Massachusetts, Amherst, MA, USA;
Hampshire College, Amherst, MA, USA
164
Multiple coordinated processes are essential for the
deposition of new membrane and wall material at the
apex of the pollen tube, allowing rapid growth of the cell
through the style and delivery of the two sperm cells to
the embryo sac. Here we focus on four processes in lily
pollen tubes; ion flux (calcium and protons), energy
transduction, the structure and role of actin filaments, and
the delivery, incorporation, and covalent modification of
pectins. Our primary method is time lapse imaging with
high resolution microscope optics coupled with specific
endogenous or introduced fluorescent probes. We further
exploit the oscillatory character of pollen tube growth,
which is accompanied by a corresponding oscillation in
the structure and/or activity of these underlying factors.
Calcium and protons show specific profiles in the tube
apex. Calcium forms a steep tip-focused gradient, in
which the concentration is high at the apical plasma
membrane and declines to basal levels of 150 nM, within
20 µm. During oscillatory growth the concentration
changes from 750 nM to above 3,000 nM with a period
of 15–50 sec. Phase analysis reveals, however, that the
increase in calcium follows the increase in growth rate,
suggesting that its changes do not stimulate growth.
Proton imaging yields a more complex pattern wherein
the extreme apex is slightly acidic, and the base of the
clear zone possesses an alkaline band. Analysis of the
oscillatory activity indicates that the increase in pH of the
alkaline band, presumably driven by the plasma
membrane localized proton ATPase, anticipates the
increase in growth rate and may control other transport
processes that are essential for growth. Cellular energy
status, monitored as the endogenous fluorescence of
reduced mitochondrial NAD(P)H, reveals that maximal
NAD(P)+ precedes the increase in growth rate. These
observations fueled the idea that a corresponding
increase in ATP might be pivotal in driving oscillatory
growth. However, inhibition of the mitochondrial
electron transport chain only momentarily blocks growth;
cell elongation soon resumes and exhibits oscillations,
which are not accompanied by oscillations in NAD(P)H.
Further studies reveal that the challenged pollen tubes
produce ethanol, indicating that their metabolism shifts
from oxidative phosphorylation to aerobic fermentation.
The presence of a prominent actin fringe in the pollen
tube apex has led to speculation that these microfilaments
transport and direct vesicles to fusion sites on the plasma
membrane. However, inhibition and reinitiation studies
reveal that polarized growth precedes the appearance of
the actin fringe. Cell wall deposition emerges as a
possible polarizing factor, wherein the newly thickened
wall biases the direction of future growth. In addition, the
deposition of wall material at the tip anticipates the
increase in growth rate. Statistical analysis indicates that
the magnitude and extent of wall deposition predicts to a
high degree the subsequent growth profile. We suggest
that the intercalation of newly secreted pectins into the
existing wall relaxes the wall structure and allows for
turgor dependent expansion of the cell. The location and
rate of pectin exocytosis and intercalation may directly
control growth rate and direction.
Space and time coordination of cellular growth
processes in pollen tubes
Feijo, J1
1
Dep. Biologia Vegetal, Fac.Ciencias, Universidade
Lisboa, Portugal
Pollen tubes are favourable models for fundamental
understanding of cellular growth and morphogenesis in
apically growing cells. Transcriptomics reveals the
expression of about 7.000 genes, but theoretical
modeling suggests that the cooperation of all of these
into the processes of wall surface and cytoplasmic
volume production, is a minimal condition to explain
most of the morphogenic events that characterize these
cells. Spatial and temporal integration of extended
biochemical and biophysical processes is mandatory, and
in the past we have proposed and demonstrated that ion
dynamics can be a common regulator of fundamental
growth processes. In order to test this hypothesis we are
developing a number of genetic, imaging and
electrophysiological approaches to define the set of
membrane transporters that could underlie the
transduction necessary for spatial and temporal
coordination. We have uncovered original data in terms
of proton pumping, and will describe new mechanisms
for calcium and chloride (anion) transport. We will
provide data suggestive that the feed-back mechanisms
by which these ions could affect fundamental cell
biology mechanisms is centered on the membrane
recycling mechanisms. In fact advanced imaging
methods and Monte-Carlo simulations suggest that
sorting of exocytic vesicles might be achieved by direct
electric interaction with ion fluxes. Finally we developed
stringent 3-D theoretical modeling of ion fluxes and
cytosolic diffusion based on the current knowledge of the
system. These models are instrumental to define the
minimal needs for channels to explain all the available
evidence. Hopefully they will allow us to expand these
conclusions to a broader understanding of the
fundamental basis that govern cellular growth and
morphogenesis by directed exocytosis, and will give us
new insights on sexual plant reproduction, namely on the
evolutionary advantage that pollen tubes rapid growth
seemed to have given to angiosperm radiation and
overwhelming success, Darwin's 'abominable mystery'.
S-RNase-based self-incompatibility: a complex nonself recognition system between pollen and pistil
Kao, T-H1,2, Wang, N1, Sun, P1, Li, S1, Natale, CA2,
Fields, AM2, Hua, Z3
1
Intercollege Graduate Degree Program In Plant
Biology, Penn State University, USA; 2Dept of
Biochemistry and Molecular Biology, Penn State
University, USA; 3Dept of Genetics, University of
Wisconsin, Madison, USA
Self-incompatibility (SI) possessed by Petunia inflata is
controlled by a highly polymorphic locus, named the Slocus, which contains the genes that encode pollen and
pistil specificity determinants in SI interactions. Our lab
showed that the S-RNase gene controls pistil specificity
(Lee et al. 1994) and that the RNase activity of S-RNase
is essential for its function in SI, suggesting that
degradation of pollen tube RNAs is responsible for
growth inhibition of self-pollen tubes (Huang et al.
1994). Our lab identified the PiSLF (P. inflata S-locus Fbox) gene from sequencing a 328-kb region of the S2locus containing S-RNase (Wang et al. 2004), and
established its SI function in pollen by showing that
expression of PiSLF2, the S2-allele of PiSLF, in pollen
of S1S2 and S2S3 transgenic plants caused breakdown of
SI in S1 and S3 pollen (heteroallelic pollen), but not in
S2 pollen (homoallelic pollen), a finding as predicted by
competitive interaction (Sijacic et al. 2004). We
proposed a model predicted on the preferential non-self
interactions between PiSLF and S-RNase resulting in
specific degradation of non-self S-RNases inside a pollen
tube (Hua and Kao 2006). We further tested the function
of two additional PiSLF alleles, PiSLF1 and PiSLF3, in
transgenic plants of S2S3 genotype. The results, along
with those obtained by the lab of Professor Seiji
Takayama (Nara Institute of Science and Technology,
Japan), led to the discovery that the pollen specificity
determinant is encoded by multiple types of SLF genes,
with each type of SLF responsible for detoxifying a
different subset of non-self S-RNases (Kubo et al. 2010).
For example, for S2-haplotype, Type-1 SLF (old name
PiSLF) interacts with S1-RNase and S3-RNase, but not
with S6-RNase, which interacts with Type-8 SLF (old
name PiSLFLb), and no type of SLF interacts with selfS-RNase, S2-RNase. We have set out to determine the
biochemical basis that allows a particular type of SLF to
interact with certain non-self S-RNases, but not with
other non-self S-RNases or self S-RNase. The approach
is to express chimeric SLFs between different types of
SLFs, and between different alleles of the same type of
SLF, in appropriate S-genotypes of transgenic plants, and
to analyze the SI behavior of the transgenic plants. We
are also testing the effect of suppressing the expression
of a particular type of SLF on the SI behavior of the
transgenic plants.
FERONIA receptor kinase controls RAC/ROP
GTPase-mediated and ROS-regulated root hair
growth and pollen tube–ovule interaction
Cheung, AY1, Duan, Q1, Kita, D1, Johnson, E1, Wu, HM1
1
University of Massachusetts, USA
RAC/ROP (plant RHO) GTPases are activated by
guanine nucleotide exchange factors (ROPGEFs) and
regulate diverse cellular, growth and developmental
processes. We showed in 2002 and 2005 (1, 2) that auxin
rapidly activates Rac/Rops which in turn mediate auxinresponsive gene expression. Using ROPGEF1 from
Arabidopsis as bait, we identified the FERONIA (FER)
receptor kinase and a few other related kinases as
ROPGEF1 interacting proteins. Using feronia (fer)
mutants, we showed that (3) FERONIA regulates
RAC/ROP-mediated, reactive oxygen species (ROS)dependent and auxin-responsive root hair development,
defining a cell surface receptor to a well established
RAC/ROP signaling pathway (4). FER was previously
identified as an important regulator for female
gametophytic function (see 5). Loss of function fer
mutants fail to support pollen tube rupture upon entrance
into the female gametophyte, resulting female sterility
and a dramatic pollen tube overgrowth phenotype.
165
Furthermore, fer mutants fail to deter later arriving pollen
tubes, resulting in supernumerary pollen tube penetration
of the female gametophyte. We will discuss recent results
that show FER functions in the female gametophyte via
controlling ROS production in the synergid cells and that
ROS are crucial for pollen tube rupture. FER also
regulates pectin deposition at the filiform apparatus
gating the female gametophyte, providing a possible
gating mechanism to regulate pollen tube penetration.
References (1) Tao et al. 2002. (2) Tao et al. 2005. (3)
Duan et al. 2010. (4) Carol et al. 2005. (5) EscobarRestrepo et al. 2007. This work was supported by grants
from NSF (IOB0544222) and USDA (CSREES 200435304-14837).
Molecular controls of karyogamy in Arabidopsis
Berger, F1, Kawashima, T1, Jet Aw, S1
1
Temasek LifeScience Laboratory, NUS, Singapore
Fertilization in flowering plants involves two sperm cells
and two female gametes, the egg cell and the central cell,
progenitors of the embryo and the endosperm,
respectively. The mechanisms triggering zygotic
development are unknown and whether both parental
genomes are required for zygotic development is unclear.
Using the mutant in the CYCLIN DEPENDENT
KINASE A1 (CDKA;1) that impedes cell cycle
progression and other mutants we present evidence for
the control of karyogamy and activation of the zygote.
We monitor in vivo the fusion of the male and female
nuclei using fluorescent markers to study the expression
of the genome of each parent after fertilization. Our
results support that both parental genomes are expressed
in the zygote and that the paternal genome plays an
essential role during early seed development. We also
study the inheritance of parental chromatin in connection
with transcriptional reactivation and report the essential
role played by H3.3 variants in this step.
Sym063: Retrograde signaling in plants –
30 July
Identification of primary regulated genes – a genomewide approach defining specific nuclear target genes
responsive to retrograde photosynthetic redox signals
in Arabidopsis
Pfannschmidt, T1, Dietzel, L1
1
Plant Physiology, Friedrich-Schiller-University Jena,
Germany
In plant populati