|comité de direction|
|morphogenèse, signalisation, modélisation|
|dynamique et expression des génomes|
|adaptation des plantes à leur environnement|
|reproduction et graines|
|paroi végétale, fonction et usage|
Fine-tuning plant growth throughout development and in response to environmental limitations is a decisive process to optimize fitness and population survival in the wild, especially for plants being sessile organisms. The team of Olivier Loudet “Variation and Abiotic Stress Tolerance” reveled the high genetic complexity allowing shoot growth variations in response to water limitation. Published in PLoS Genetics on the 22th of April 2019, theses results open new perspectives in the discovering of genetics variations controlling stress response for interesting adaptative and agronomic traits.
As a sessiles organisms, plants have to cope with environmental fluctuations and evolved a wide range of responses well illustrated by their great phenotypic plasticity and their ability to colonize very diverse habitats, through intraspecific genetic diversity.
Thanks to the Phenoscope, a robotised platform designed to cultivate plant and perform high throughput under strictly-controlled and reproducible conditions (see below), The team of Olivier Loudet managed to decifer the basal genetics of this vegetal diversity. On the Phenoscope, more than 700 cultivated Arabidopsis thaliana plants are moving continuously and consequently in an equivalent environment. They are weighed and watered and photographed very regularly. As a sessile organism, plants have to cope with environmental fluctuations and evolved a wide range of responses well illustrated by their great phenotypic plasticity and their ability to colonize very diverse habitats, through intraspecific genetic diversity.
Quantitative genetics approaches exploiting different crosses allowed to map the individual genetic loci (QTLs’: 'Quantitative Trait Loci') controlling different parameters linked to leaf growth with a precision never reach so far. Shoot growth and morphology have been analyzed in response to moderate water limitation. The team of Olivier Loudet studied Integrative traits such as those related to vegetative growth (highlighting either cumulative growth, growth rate) for 4 crosses between Arabidopsis variants (recombinant populations, RILs: Recombinant Inbred Lines). Subsequently, by focusing all of the mapping power on a small region representing 2.5% (3 Mégabases) of the genome of the model plant Arabidopsis in an unprecedentedly phenotyping effort, the unique cross analyzed revealed an underlying very complex so-called 'genetic architecture'. For example, several independent genes had remained hidden in this region beyond a major-effect gene controlling growth variation. Taking into account this hidden effects in cartography of QTLs is important to understand the variation of quantitative characters.
To study growth natural variability in a wild type species as Arabidopsis open doors to the discovery of new variants responding to stress and controlling adaptative characters of agronomic interest. A new order of magniture in predictive or digital biology could be announced: results of this study suggest that the genetics complexity being the base of phenotypic diversity is probably very underestimated.
Focus on the ‘Phenoscope’
The future XL Phenoscope is now being deviced: this prototype will receive plants including ones behond the flowering stage, up to the seed.
More information: https://phenoscope.versailles.inra.fr/
de presse INRA 22/04/19
23th April 2019
Grown throughout the world, F1 hybrid crop varieties have highly desirable traits. However, they remain expensive to produce. This situation may be about to change. By modifying the expression of certain genes, Raphaël Mercier, the group leader of "Mécanisms of meiose" from l'IJPB, INRA, Versailles, in collaboration with the University of Californie Davis and the China National Rice Research Institute, have created hybrid. This breakthrough research has been published in Nature and Nature Biotechnology.
Methods for breeding better crops focus
on two key tasks: 1) producing high performing hybrids by crossing different
plant lineages and 2) attempting to preserve and perpetuate the resulting
genetic combinations such that the resulting seeds carry the target
From meiosis to mitosis
A spitting genetic image
In the longer term, this discovery will revolutionise strategies for improving crops, notably by making it possible to generate clones of F1 hybrids for most species of agricultural interest. The simplicity of the process means that it should be straightforward to test a greater number of genetic combinations and thus generate new types of hybrids, which could lead to a broader diversity of crop varieties. Furthermore, farmers would be able to replant seeds from crops that they had grown themselves, knowing that the resulting plants would reliably display hybrid vigour across generations. This would be a major boon for farmers, and especially for farmers in developing countries, as the annual cost of purchasing seeds represents a significant expense. For everyone to be able to take advantage of these technological advances, the plant breeding and seed production industries will need to change their current economic models.
Seed crops are produced via sexual reproduction: the male gamete, which contains half the chromosomes of its parent cell, fertilises the female gamete, which also contains half the chromosomes of its parent cell. This resulting embryo (and the plant into which it will develop) thus contains chromosomes from both parents. During meiosis in this offspring plant, the chromosomes that it obtained from its parents will recombine. As a result, the male and female gametes produced will contain a mixture of the parental genetic information. This process is repeated each generation. In crops that self-fertilise, such as wheat, male and female gametes display homogeneity after a certain number of generations, leading to pure lineages that remain stable over time. In crops that cross-fertilise, such as maize, offspring always differ from their mother plants
In contrast, certain seed crops reproduce using apomixis—embryos develop without the need for either meiosis or fertilisation. Offspring resulting from apomixis only contain and pass along genetic information from the mother plant. Certain wild plants such as dandelions and hawthorns clonally reproduce in this way through seeds.
release INRA 10/01/19
Chun Wang, Qing Liu, Yi Shen, Yufeng Hua, Junjie Wang, Jianrong Lin, Mingguo Wu, Tingting Sun, Zhukuan Cheng, Raphael Mercier & Kejian Wang. Clonal seeds from hybrid rice by simultaneous genome engineering of meiosis and fertilization genes.Nature Biotechnology (2019). https://doi.org/10.1038/s41587-018-0003-0 Abstract
10th January 2019
Ribosomes are the molecular machines that translate messenger RNAs into proteins. They consist of two subunits. The small one decodes messenger RNA and the large one carries out the polymerization of amino acids to form the corresponding protein. Hakim Mireau, INRA senior scientistand collaborators of the group "Organelles and reproduction" from IJPB, INRA, Versailles in collaboration with the teams of Philippe Giegé (IBMP, Strasbourg university) and Yaser Hashem (IECB, INSERM, Bordeaux) has determined the specific composition and architecture of Arabidopsis mitochondrial ribosomes. This study is published in the journal Nature Plants january the 9th 2019.
Mitochondria represent the energy center of eukaryotic cells. For their metabolism as well as for their gene expression, mitochondria combine bacterial-like traits with traits that have evolved in eukaryotes. Translation is the least well-known step of mitochondrial gene expression. In plants, pentatricopeptide repeat (PPR) proteins are involved in all steps of gene expression but their function in mitochondrial translation remains unclear.
Using a biochemical approach, researchers have characterized the mitochondrial ribosome (mitoribosome) of the model plant Arabidopsis and identified its protein composition. 19 plant-specific mitoribosome proteins have been found, among which 10 are PPR proteins. Mutant analysis of genes encoding these PPR proteins, in particular using ribosome profiling, revealed their role in translation. Finally, a cryo-electron microscopy analysis revealed the unique three-dimensional architecture of these mitoribosomes. They are characterized by a very large small subunit, in particular with a new elongated domain never observed to date in other ribosomes.
This work contributes to understand the evolutionary diversity of translation systems. It illustrates remarkably how evolution has played with mitoribosomes to optimize protein synthesis in mitochondria.
Figure legend : Structural comparison between Arabidopsis mitoribosome and animal mitoribosome as well as with Arabidopsis cytosolic ribosome, which highlights the originality of this mitoribosome architecture. In particular, it is characterized by the presence of additional domains (circled in red). “SSU” represents small subunits and “LSU” large ribosomal subunits.
9th January 2019
During the process of sexual reproduction, chromosomes exchange genetic material by recombination (crossing-over) so participating in diversity. But shuffling is limited, exchanges being scarce, genes inhibiting this mechanism. Raphaël Mercier leader of the group "Mecanism of Meiosis", IJPB, INRA, Versailles, and other scientist of INRA and CIRAD have shown that when one of these genes: RECQ4, is desactivated, the number of recombinations is 3 fold higher in crops as rice, pea and tomatoe. That breakthrough published in Nature Plants, the 26th november 2018, could allow to speed up the selection process in plant breeding and the production of plants better adapted to environment conditions (pests resistance, climate change adaptation).
Recombination is a natural mechanism common to all organisms practicing sexual reproduction, as plants, fungi or animals. Genetic diversity within species takes its origin in chromosomes shuffling. Plant breeding, as practiced since ten thousand years, consisting in crossing two plants chosen for interesting and complementary characters is based on this mechanism. Then, to obtain a new tasty tomato variety resistant to a biopest, successive crosses are performed to select the suitable combination of characters (genes involved in taste and resistance). But this process takes a very long time, consequence of the low number of crossing-over i.e. - exchange points of genetic material (CO), during reproduction. In average, between 1 to 3 CO occur for each cross. Consequently, it is impossible for example to associate 6 interesting genes in a single generation, constituting an important curb to plant breeding.
limits the number of recombinations ?
happens in cultivated plants?
But why recombinations are
de presse INRA 26/11/18
26th november 2018
This workshop in organised as part of the EIG-Concert Japan Project “Improving crop yield by enhanced plant performance under stress conditions” (IPSC). IPSC takes a comprehensive systems biology approach, combining phenotypic, transcriptomic, and metabolomic datasets to investigate plant responses to environmental factors including biotic and abiotic stresses.
This second workshop organised by the
IPSC project takes place at the Institut Jean-Pierre Bourgin (IJPB),
a multidisciplinary research institute associated to INRA, AgroParisTech
and CNRS, and located on the INRA Versailles campus, next to the palace
park. IJPB is one of the largest plant biology research centres in Europe
and part of the Laboratory of Excellence Saclay
Plant Sciences (SPS).
9 mai 2019
The reduction-division process
in Meiosis is essential for sexual life. Starting out with a diploid
chromosome content, meiosis ends up with haploid products, ready to
fuel the cycle of sexual reproduction. This halving of the genetic content
is obtained by a remarkable series of specific mechanisms that have
evolved from the mitotic divisions. The meiosis field unravels the processes
behind this particular cell division in a variety of organisms from
fungi, to plants, various animals and human. Studies of these specific
mechanisms will be at the heart of the EMBO Workshop on Meiosis including
initiation of recombination, formation of crossovers between homologous
chromosomes, chromosome dynamics, cell cycle, kinetochore attachment,
chromosome segregation and consequences on fertility and diseases. We
choose conservation and diversities of the mechanisms as a focus for
the 2019 meeting to learn from a point of view of evolution and population
genetics on less well studied organisms.
Local Committee: Christine
2nd May 2019
The International Plant Growth
Substances Association (IPGSA) Conference welcomes researchers, academics
and students from university and industry interested in the hormones,
growth substances and signaling processes of plants. Held once every
three years, the IPGSA conference has long provided a stimulating platform
for scientists to share and discuss their latest research. The scientific
advisory committee is formed of leading scientists appointed by IPGSA
Council members elected from diverse countries and therefore promises
to deliver an exciting program. We welcome you to the heart of Paris,
and to a University venue which will ensure a rewarding experience to
2dn May 2019
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