Actualité scientifique
Scientific news
Some wild plants show the
particular characteristic of
apomixis. This is a process
adopted for producing
seeds without fertilization or
genetic recombination,
giving rise to exact copies
of the mother plant. This is
an unusual method of
reproduction and IRD
researchers and their
partners1 are seeking to
apply it to agriculturally
useful plant species –in the
main sexually reproducing–
such as wheat or maize.
Such a revolution would
spare farmers of the need
to buy seed every year,
particularly in the countries
of the South.
However, several challenges
arise from the development
of these kinds of varieties.
Can a normally sexually
reproducing plant do
without paternal input?
Results reported in an
article in the journal Cell
shed light on this
fundamental question. A
research team recently
demonstrated that the
embryo could develop
without contribution from the
paternal genome. During
the first growth stages, the
genes expressed are
predominantly inherited
from the maternal genome.
The respective contributions
then become more
balanced, but the maternal
genome is still in control of
the relative parts played by
the two parents.
The research team hopes
that these results will
eventually pave the way to
developing crop plants that
will persistently keep their
selected qualities, harvest
after harvest, especially
beneficial for farmers in
countries of the South.
© IRD / Y. Savidan
May 2011
How can high-quality seed
be reproduced ?
© IRD / D. Grimanelli
N° 375
Actualidad cientifica
Scientists, as here in Mexico, are seeking to induce apomixis, a form of asexual reproduction, in crop plants such as maize, like in their wild cousin species
(upper right).
Sexual reproduction effectively redistributes the
genes of the two parents. However, in crop plants
the process tends to cause erosion from generation to generation of their selected beneficial
properties –such as productivity, plant vigour,
resistance to drought- or pathogens. This makes
it difficult for farmers to keep up the yields of a
field of maize or wheat year in year out. They are
obliged to renew the seed for each new growing
cycle. Worldwide 25 billion Euros per year are
given over to seed buying. But such expenditure
is difficult to support for many producers in the
developing countries.
An end to gene mixing
To enable farmers to produce their own seeds,
IRD biologists and their research partners1 have
been working for more than ten years on ways of
applying a relatively unusual reproductive strategy found in some wild plants to agronomically
important species. This is apomixis, meaning
simply “without mixing”. A form of asexual reproduction, it is a way of avoiding the usual genetic
intermingling. The process involves neither fertilization nor meiosis, in other words no genetic
recombination between the two parent plants; the
seeds give rise to exact copies of the mother
plant. In the wild, about 400 species, as diverse
as dandelion, mango or hawthorn adopt apomixis.
For further information
Can a sexually reproducing plant
do without paternal genes?
For each of 3000 genes observed, the method
How then can sexually reproducing plants, as
by maternally inherited chromosomes or from
most crops are, be made apomictic? Plant hybri-
paternally inherited ones. In this way the respec-
dization has not enabled scientists to arrive at
tive contributions from the two parents was quan-
satisfactory results*, so they have changed tack
tified.
deciding to prompt 100% maternal development
After the 2-4 cell stage, as the embryo’s develop-
in the embryo of a sexually reproducing plant
ment proceeds, the parental contributions
whose genome is normally made up half-and-
progressively become more balanced. However,
half by paternal and maternal DNA.
there again it is the maternal influence which
This innovatory approach presents a number of
controls the situation. In the same investigations,
tec hnical and theoretical c hallenges. For
the research team identified the two mecha-
instance, can the plant function completely inde-
nisms, set in train by the maternal genome,
pendently of the “father’s” input, without harm to
which hold back and keep silent the paternal
its development? This is indeed the case, as the
genes in early development, then activate them
research team reports in an article in the journal
by producing specific proteins.
detects whether the RNAs have been produced
Contacts
Daniel GRIMANELLI,
researcher at the IRD
Tél. : + 33 (0)4 67 41 63 76
daniel.grimanelli@ird.fr
Daphné AUTRAN,
researcher at the IRD
Tél. : + 33 (0)4 67 41 63 76
daphne.autran@ird.fr
UMR 232, Diversité, Adaptation, Développement des plantes (IRD/Université
Montpellier 2).
Address
IRD
911 avenue Agropolis
BP 64 501
34 394 Montpellier Cedex 5
Cell. Early in its development, the embryo grows
essentially under the activity of the maternal
These new results suggest that it would be
chromosomes it inherits, while the paternal ones
possible to prompt a sort of clonal multiplication
remain inactive. In total, more than 90% of the
in sexually reproducing species. Yet, with no
RNAs , the molecules that induce differentiation
fertilization involved, what is the signal that trig-
of the embryonic tissues and organs, prove to be
gers seed growth? The hope for the long term is
of maternal origin.
that, once that bar rier has been removed,
Dominant mother
farmers, especially in the countries of the South,
To shed light on this fundamental question, the
can be provided with apomictic food plants in
team’s geneticists chose the plant model mouse-
which selected agronomic properties would be
ear cress, Arabidopsis thaliana. Under the
fixed for successive generations.
2
References
Autran Daphné, Baroux C., Raissig M.
T., Lenormand T., Wittig M., Grob S.,
Steimer A., Barann M., Klostermeier U.
C., Leblanc Olivier, Vielle-Calzada
J-P., Rosenstiel P., Grimanelli Daniel,
Grossniklaus U. Maternal epigenetic
pathways control parental contributions
Arabidopsis early embryogenesis. Cell,
2011. doi:10.1016/j.cell.2011.04.014
to
microscope, they crossed two distinct varieties,
Key words
Crop plants, apomixis, genes
then extracted the young embryos 15 hours after
fertilization. These were composed of only two to
* see scientific news bulletin n°11 - Transfert de l’apomixie
four cells at this stage. Analysis of these cells’
au maïs par hybridation : les chercheurs approchent du but
RNA using very high throughput methods and
Copy editor – Gaëlle Courcoux - DIC, IRD
sequences between the two parental genomes.
Translation – Nicholas FLAY
Coordination
Gaëlle Courcoux
Information and Culture
Department
Tel. : +33 (0)4 91 99 94 90
Fax : +33 (0)4 91 99 92 28
fichesactu@ird.fr
1. These investigations were conducted in partnership with the University of Zurich in Switzerland, the LANGEBIO (Laboratorio
Nacional de Genomica para la Biodiversidad) in Irapuato in Mexico, the University of Kiel in Germany and the CNRS Centre d’Ecologie
Fonctionnelle at Montpellier.
Genome sequencing of an embryo of an asexually reproducing plant (left), enabled researchers determine how this develops. Will they eventually succeed
in totally inhibiting the paternal DNA to make a crop plant like wheat (here in the Moroccan High Atlas) apomictic?
Press office
Cristelle DUOS
+33 (0)4 91 99 94 87
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© IRD / O. Barrière
© IRD / O. Barrière
© IRD / D. Grimanelli
2. RNA is a substance present in cells which transports genetic information carried by DNA or which uses it to make proteins.
Indigo,
IRD photo library
Daina Rechner
+33 (0)4 91 99 94 81
indigo@ird.fr
View the IRD photos concerning this article,
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