|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|
From plant adaptation to the
environment to human disease control, the
team of Christian Meyer
Use, Transport and signaling" in collaboration with Belgium teams
of the Vlaams Instituut voor Biotechnologie (VIB), found common regulators
to plants and animals. They show that a mutated protein (YAK1) allow to
counteract the effects of another protein (TOR) consequently reducing
growth and metabolism. published in Cell Reports, their results open up
new perspectives to improve plant growth, human cancer therapy or neurological
TOR activity is increased in numerous human cancers and its inhibitors can reduce the proliferation of cancers. Among them, the most famous is rapamycin, an antibiotic discovered in the 70s and produced by a bacterium found in the Easter Islands (Rapa Nui).
In plants TOR regulates growth and yield of defense against pathogens. Scientists shown that genetic mutations of TOR affecting the activity of the protein reduce drastically growth and slow down the development.
Homologues of the YAK1 kinase do exit in animals. In human notably, those homologues (including DYRK1A) are involved among others in symptoms of trisomy 21 or autism.
A better understanding of links between TOR and YAK1 could improve cultivated plants adaptation performances to the environment, but also therapies of human diseases linked to cell proliferation (as cancers) or to neurological development. Indeed, a hight proportion of genes involved in human cancers do also exist in Arabidopsis and cell processes associated to cell proliferation are very similars, for example, in response to some pathogens.
de presse INRA 06/06/19
24th June 2019
Could duplicated genes loss be an evolutionary driving force as genes duplication do? Studiing rapeseed reproduction, the team of Eric Jenczewski "Meiotic recombination in polyploids" show that, far from beeing deleterious, loss of a duplicated copy of a main gene involved in chromosomes exchanges during meiosis could give an adaptative advantage. Published in Nature Communications, these results open up new perspectives in plant breeding, in particular to select new grown species harboring several genomes as for example triticale, hybrid between wheat and rye.
Toutes les plantes à fleurs ont
connu au moins un, et souvent plusieurs évènements de polyploïdie
(duplication complète de génome) au cours de leur évolution.
Ce succès évolutif ne va pourtant pas de soi car la présence
de plus de deux lots complets de chromosomes, souvent issus d’espèces
différentes, conduit à des défauts au cours de la
méiose. Depuis plusieurs dizaines d'années, les scientifiques
cherchent à comprendre comment les espèces polyploïdes
réussissent malgré tout à assurer une bonne transmission
de leurs chromosomes à leur descendance au cours de cette étape
essentielle à leur reproduction. Les travaux menés à
l’Inra conduisent à envisager une réponse étonnamment
simple à cette question : l’élimination d’une
des copies dupliquées de gènes essentiels pour la recombinaison
Financial support (PhD) by the european training network COMREC.
de presse INRA 06/06/19
Plus d'info :
6th june 2019
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 traits.
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
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
2 mai 2019
Trehalose 6-phosphate (Tre6P), the
intermediate of trehalose biosynthesis, is an essential signal metabolite
in plants that links developmental processes, such as flowering, shoot
branching and embryogenesis, to the metabolic status of the plant. The
sucrose-Tre6P nexus model postulates that Tre6P is both a signal and
negative feedback regulator of sucrose levels in plant cells. The model
envisages a role for Tre6P in sucrose homeostasis in plants that is
analogous to the regulation of blood glucose levels by insulin in animals.
In source leaves, Tre6P controls sucrose levels by regulating the partitioning
of photoassimilates during the day and the turnover of transitory starch
reserves at night. It also has a particularly important function in
guard cells, affecting the sensitivity of stomata to abscisic acid.
In sink organs, Tre6P regulates the import and utilization of sucrose
for growth and the accumulation of storage reserves. We are using forward
and reverse genetics approaches to dissect the functions of Tre6P in
specific source and sink tissues, to understand the molecular mechanisms
that underlie the sucrose-Tre6P nexus and how Tre6P links plant growth
and development to the availability of sucrose.
Invited by Catherine Rameau
Invited by Martine Pastuglia
Nos recherches portent sur la compréhension des mécanismes moléculaires qui contrôlent l’initiation, le développement et la fonction de la fleur en utilisant deux plantes modèles, la Rose et Arabidopsis. Nous avons caractérisé deux voies de régulation génique qui coordonnent la croissance mitotique et post-mitotique du pétale chez Arabidopsis. La première voie, impliquant la protéine TCTP, contrôle positivement la croissance mitotique, et plus spécifiquement la progression du cycle cellulaire via les complexes CSN et CRL. La deuxième voie, impliquant un crosstalk entre deux phytohormones (jasmonate et auxine) et un facteur de transcription bHLH (BPEp), régule la croissance des pétales en contrôlant l'expansion cellulaire. Chez Rosa sp, nous avons développé plusieurs ressources génomiques, transcriptomiques et biotechnologiques, notamment un assemblage de très haute qualité du génome de la rose et le séquençage des principaux cultivars et espèces ayant participé à la domestication de la rose. Ce travail, réalisé dans le cadre d’un consortium international, a permis de décrypter les voies de régulation génétiques associées aux caractères importants (parfum, couleur, fleur double) ainsi que la reconstruction de la paléohistoire de la famille des rosacées.
Cell wall modification is one of the essential activities to sustain plant life cycles by building barriers for maintaining their homeostasis or adjusting physical properties for developmental processes and stress responses. Among various types of cell wall modifications, Casparian strip, which functions as a root apoplastic barrier, forms a longitudinal ring structure in the central position of endodermal surface. Although this structure was described by Robert Caspary in 1865, molecular mechanisms underlying how this barrier is formed had been completely uncovered. Recently, two groups independently reported a peptides (CIFs)/receptor (SGN3) pair for the functional root barrier formation. Interestingly, the CIF peptides are expressed in the steles and the SGN3 receptor is expressed in the endodermal cells, suggesting non-cell autonomous regulation is required for establishing functional Casparian strips in the endodermis (Doblas et al. 2017, Nakayama et al. 2017). However, how this signaling pathway coordinate the Casparian strip formation at molecular or tissue levels is still unclear. Here, I will present localized ROS production around Casparian strips and global transcriptional changes as downstream events of the peptide/receptor signaling pathway. Furthermore, possible spatial regulation of this signaling pathway at the tissue level will be discussed.
Invited by: Verónica
González Doblas & Herman Höften
Maize is blessed with relatively large reproductive cells, and an exceptional cytology. It is thus a powerful experimental model to analyze chromatin dynamics during reproduction at high resolution, in a stage-specific manner, using a combination of methylome analysis, and hyper-resolution microscopy. We have developed efficient protocols to study DNA methylation using bisulfite sequencing in isolated reproductive cells, in both wild type plants and mutants affected in DNA methyl-transferase activity. We have generated a temporal series of methylomes covering individual stages of male meiosis, including prophase I (leptotene, pachytene, dyakinesis), metaphase I, dyades, metaphase II, tetrads and young spores. The data shows that DNA methylation during meiosis is dynamic, and significantly different from the patterns observed in somatic cells. We further looked at the dynamic of methylation in developing embryos. We uncovered a rapid process of hyper-methylation specifically in the CHH context, which is strictly dependent on RNA-directed DNA methylation. DNA methyltranferase mutants in maize display a number of developmental deffects, including strict embryo lethality for CG methyltransferases, but also distinctive effects on meiosis, gametogenesis and embryogenesis for mutants affecting CHG and CHH methylation. We are currently analyzing the functional bases of these phenotypes using both classical cytology, bisulfite sequencing and hyper-resolution microscopy. The data shows that Zmet5, a maize homologue of Arabidopsis CMTs, is a key player of meiocyte methylation at non-CG sites. The mutant shows high degrees of sterility, linked to clear meiotic abnormalities. Altogether, the data indicates that maize represents a remarkable model to establish causal relationships between DNA methylation patterns and reproductive functions.
Yuan Lab webpage
Bennett Lab webpage
is an important product of the photosynthesis
that accumulate during the day in chloroplasts
and which is remobilized during the night.
It serves as an energy storage and impairment
in starch content and/or turnover affects
the growth of the plants. In order to
prevent any starvation, starch metabolism
is tightly regulated jointly to the circadian
clock. However, mechanisms that regulate
starch biosynthesis and degradation are
not fully understood.
In eukaryotes, small regulatory RNAs guide RNAi and epigenetic modification through repression of complementary RNA and DNA. Arabidopsis thaliana has proved to be an excellent model species for uncovering the pathways and potential mechanisms of RNAi and epigenetics in eukaryotes. In contrast to many other eukaryotic lineages including humans, gene duplication is a common feature of gene silencing pathways in flowering plants. For example, there is one DICER gene in humans compared to at least four DICER-LIKE (DCL) genes in flowering plants. This division of biological function between duplicated members of gene families involved in gene silencing has not only enabled the discovery of the function of individual genes, but also the composite biological function of the gene family as a whole. As examples, mechanisms of systemic RNA interference (RNAi) and RNA-directed epigenetic regulation of gene expression in Arabidopsis will be discussed.
oriented plant breeding must have access
to the widest possible source of heritable
variations just as it needs an effective
mechanism to deliver high quality seeds
to the growers. Hence, accelerating the
genetic gain through a combination of
next-generation tools and technologies
becomes critical in situations where it
is either impossible or impractical to
source heritable variations from existing
germplasm. Towards this, the Research
Theme on Cell, Molecular Biology and Genetic
Engineering at ICRISAT consolidates its
efforts on developing biotechnological
tools towards trait discovery and candidate
gene validations; transgenic breeding
by developing the foundational tools and
using these to generate innovative biological
applications for cutting-edge agricultural
research. Considering that the overwhelming
physical details of natural biology (gene
sequences, protein properties, biological
systems) must be organized, researchers
combine forward and reverse genetic and
biological-engineering approaches, to
design and build robust breeding pipelines.
Our pipelines encompass a broad range
of biotechnology solutions in grain legumes
and dry land cereals. In my talk, I’ll
be talking about our research to delivver
effective solutions to reflect our holistic
approach on each crop.
Invités par : Nicolas Bouché
Invité par : Helen North et Annie Marion-Poll
Invité par : Herman Höfte
Invité par : Françoise Budar
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