BIOLOGY 3404F
EVOLUTION OF PLANTS
Fall 2008
Lecture 5
Thursday October 2
Chapter 14, Fungi (part I)
Outline
• Life cycles: three types cover almost all e.g.s
• Groups of fungi and fungus-like organisms
and what they do
• Fungus-like Protists: Myxomycota,
Dictyosteliomycota, Oomycota, etc.
• Five Phyla of Kingdom Fungi:
Chytridiomycota, Zygomycota,
Glomeromycota, Ascomycota, Basidiomycota
• Unnatural groups: Deuteromycetes,
Lichenomycota
Zygotic Meiosis, Raven et al. Fig. 12-15a
Gametic Meiosis, Raven et al. Fig. 12-15b
Sporic Meiosis, Raven et al. Fig. 12-15c
Which is it? (Which are we?)
• Knowing Fig. 12-15 inside-out will make life-cycles in this
course much easier to manage
• We will see a lot of life cycles, but in essence there are
only three kinds: recognized by ploidy of the organism
– Haploid: zygotic (meiosis immediately follows formation of the
diploid zygote)
– Diploid: gametic (meiosis occurs in single cells of diploid
individual, long after zygote formation; meiosis produces gametes,
which unite to form zygote) [= delayed meiosis]
– Both haploid and diploid individuals: sporic (meiosis occurs in
single cells of diploid individual, long after zygote formation;
meiosis produces spores, which form haploid individuals) [=
delayed production of gametes]
But remember …
• Many organisms reproduce asexually, so their life
cycles do not fit in any of the three types described
above.
• Most asexually-reproducing organisms are derived
from sexually-reproducing ones, so you can infer
what type of life cycle their ancestors had
• Some asexually-reproducing organisms may be
“primitively asexual” - i.e., they have been around
since before sex was invented
[Fungus-like Protists I: the slime
moulds, Myxomycota and
Dictyosteliomycota] – FYI only
• Closely related to amoebae; spores germinate to form
amoeboid stage in life cycle
• Engulf food (phagocytosis) but may also have external
digestion via secreted enzymes, followed by absorptive
nutrition (as in Fungi)
• Amoebae aggregate (cAMP) and form acellular
plasmodium (Myxos) or cellular pseudoplasmodium
(Dictyos): “feeding slime”
Slime Moulds II
• Following nutritional or other environmental
trigger(s), feeding slime transforms into fruiting
(spore-producing) structures – very fungus-like, and
very beautiful
• See George Barron’s Myxo web site,
http://www.uoguelph.ca/~gbarron/myxoinde.htm
• Very important as nature’s vacuum-cleaners – eating
particulate organic matter, bacteria and spores, and
contributing to nutrient cycling
• Very common in soil and litter
Arcyria cinerea
(Photos: GL Barron)
Badhamia utricularis
Dictydium cancellatum
Myxomycete life cycle, Raven et al. Fig. 15-58
Is this zygotic, gametic, or sporic meiosis?
Dictyostelid life cycle, Fig. 15-60
Fungus-like Protists II: the water
moulds, Oomycota
• These are closely related to Chrysophyta and others in
the group sometimes called Kingdom Stramenopila (or
Heterokonta)
• Have motile cells (zoospores) with two flagella, one
tinsel and one whiplash
• Oomycota include some saprotrophs but also some
important plant pathogens, such as Late Blight of
Potato (Phytophthora infestans), Blue Mould of
Tobacco (Peronospora destructans), and Downy
Mildew of Grapes (Plasmopara viticola)
Late Blight of Potato, Raven et al. Fig. 15-19
Tinsel and whiplash flagella;
Kendrick 5th Kingdom
Oomycota life cycle, Raven et al. Fig. 15-17
(true) Kingdom Fungi Defined
• Heterotrophic, eukaryotic organisms generally
with extracellular digestion and absorptive
nutrition; cell walls contain chitin and
glucan/mannan, not cellulose
• Most are filamentous but some are unicellular
(yeasts); a few are motile
• Must either live as saprotrophs (decaying dead
organic matter) or symbionts (parasites or
mutualists, etc., with other living organisms
Chytridiomycota
•Approximately 1000 described species
•Depend on free water - flagellate
•Most groups have just one flagellum, and can be
recognized as chytrids by this
•Some (the rumen fungi) have multiple flagella, and
were considered protozoa
•Synchytrium endobioticum causes potato wart disease,
closed US to PEI potatoes.
Chytrids II
• Closest to ancestral
choanoflagellate, the
common ancestor of both
fungi and multicellular [=
true] animals – Fig. 15-7
• At least some have sexual
and asexual phases, and
also haploid and diploid
phases in their life-cycle
(Allomyces) – Fig. 14-10
Allomyces life cycle, Raven et al. Fig. 14-10
Is this zygotic, gametic, or sporic meiosis?
Chytridiomycota
Catenaria, a chytrid that attacks and consumes living
nematodes (drawing by George Barron)
Glomeromycota
• Approx. 150 described species
• Thought to be 300-500M years old!
• These were formerly [i.e., in your textbook]
treated in Zygomycota as the Glomales
• The entire group (or what we know of them)
form symbioses with photoautotrophs
• Entirely asexual (?) – for millions of years, but
coenocytic, with different nuclei
Glomeromycota II
• One species (Geosiphon) has an endosymbiotic
cyanobacterium
• The rest form mycorrhizal relations with >80% of green
plants, called “endomycorrhizae” or Arbuscular
Mycorrhizae (AM) – Figs. 14-40, 14-44
• These relations are particularly important in delivering
phosphorus to herbaceous and tropical woody species in
nutrient-poor soils
Glomeromycota III
Hyphae and
a spore of a
Glomales
washed from
soil. The
spore is 1/10
mm in
diameter!
Zygomycota
• Approximately 1,000 described species
• Best known are the “bread moulds” Rhizopus and
relatives (Mucorales), with tall, broad, glassy
hyphae, growing on bread, fruit, and pumpkins
• Broad, coenocytic hyphae, thin-walled
(occasionally wall-less when growing within
insects)
• May have both asexual and sexual reproduction
(sporangiospores and zygospores borne in
zygosporangia)
• May be homo- or heterothallic.
Zygomycota
Rhizopus
Zygomycota
Rhizopus hyphae
and asexual spores
Rhizopus
zygospores
Zygomycota
Asexual spores
(sporangiospores) of
Cunninghamella (photo
by George Barron)
Rhizopus life cycle, Raven et al. Fig. 14-11
Is this zygotic, gametic, or sporic meiosis?
Ascomycota
• Approximately 48,000 described species
• Include most yeasts, most “deuteromycota” and most
“mycophycophyta” or “lichenomycota” – we will return
to these fungi in lectures on “lichens”
• Ascomycota include many important plant diseases, as
well as diseases of humans
• Saprotrophs (some may be pests) degrade incredible
diversity of substrates
Ascomycota
Asci of a cup
fungus from dung,
each with eight
ascospores (dark
purplish brown
when mature).
Photo: George Barron
Ascomycete life cycle, Raven et al. Fig. 14-14
Is this zygotic, gametic, or sporic meiosis?
Ascomycota
Morels, Morchella esculenta, on a lawn in London
Ascomycota
“Tar spot” of maple caused by Rhytisma acerinum
Ascomycota
Ascomata
Asci
Powdery mildew of maple caused by Uncinula bicornis
Basidiomycota
• Approximately 30,000 described species
• Include most mushrooms, most major wood
decayers, and most mycorrhizae of boreal trees
(ectomycorrhizae – more next week)
• Basidiomycota include many important plant
diseases, including rusts and smuts
• Attine ants and termites cultivate saprotrophic
mushrooms
Basidiomycota
The “sexual cell” in
Basidiomycota is the
basidium (pl. basidia).
Two different haploid
nuclei are present in
every cell – the
dikaryon, and then
fuse to form a short-lived
diploid nucleus in the basidium.
Mushroom life cycle, Raven et al. Fig. 14-18
Is this zygotic, gametic, or sporic meiosis?
Clamps and dolipores
“Deuteromycota” – a fictitious group*
Penicillium, an asexual Ascomycete
*Your text now calls them “conidial fungi”
Penicillium (above) and
Aspergillus (right)
“Lichenomycota”
• Also called the Mycophycomycota, but are
a completely fictitious group
• Lichens (more next week) have evolved
many times in many groups of Ascomycota
(most) and some groups of Basidiomycota
(few)