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News
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Plant growth and human diseases: deciphering common regulators

From plant adaptation to the environment to human disease control, the team of Christian Meyer "Nitrogen 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 diseases.

Found in animals, plants, fungi and yeasts, the protein « Target Of Rapamycin » (TOR) control many key biological processes as cell proliferation and metabolic activities. TOR is an enzyme of kinase type; it means that this enzyme adds a phosphate on aminoacids of target proteins to regulate its activity or stabilize it.

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.

TOR's hammer

Scientists of the IJPB team of Christian Meyer "Nitrogen Use, Transport and signaling" in collaboration with Belgium teams, used the model plant Arabidopsis thaliana to identify new mutations suppressing the growth and allowing to compensate TOR defects. Thanks to this strategy another kinase, YAK1 (Yet Another Kinase 1) also existing in yeast, was identified. The mutated YAK1 allow to plants already affected in TOR activity to recover a bigger size and a better growth. The metabolic disturbances linked to the inactivation of TOR are also decreased. Then, YAK1 inactivation by TOR seams to be necessary to activate the plant growth.

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.

 

Wild type Arabidopsis plants (top left) show a very reduced growth when the LST8 protein, a component of the TOR complex, is mutated (top right). Extra mutations of the kiinase YAK1 supress partially defects of the plant growth and development (bottom left and right). The YAK1 kinase is located in the nucleus and cytoplasm of vegetal cells (in the center, detection of a protein fusion between YAK1 and a fluorescent marker). Photos IINRA, Céline Forzani

  A model of the relationship between TOR, YAK1 and growth in plants. RAPTOR, LST8 and TOR proteins are components of the TORC1 complex in Eucaryotes. the reversed T corresponds to an inhibition. copyright INRA

Communiqué de presse INRA 06/06/19

Contact:
Christian Meyer (01 30 83 30 67)
Institut Jean-Pierre Bourgin (INRA, AgroParisTech ; ERL CNRS)
Associated Department:
Plant Biology and Breeding
Associated Centre:
Ile-de-France-Versailles-Grignon

Contact(s) press:
Inra Press Room (01 42 75 91 86)

Référence:
Mutations of the AtYAK1 kinase suppress TOR deficiency in Arabidopsis. Céline Forzanni, Gustavo T. Duarte, Jelle Van Leene, Gilles Clément, Stéphanie Huguet, Christine Paysant-Le Roux, Raphaël Mercier, Geert De Jaeger, Anne-Sophie Leprince, Christian Meyer. Cell Reports. 18 juin 2019. doi: 10.1016/j.celrep.2019.05.074

24th June 2019


How To turn his loss into a win during complex genome species evolution?

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 méiotique.

Always alone !
Les chercheurs de l'équipe "Recombinaison méiotique chez les polyploïdes" se sont intéressés à l’évolution des gènes codant une protéine impliquée dans les échanges génétiques entre chromosomes appelée MSH4. Ils ont montré que les gènes codant pour la protéine MSH4 sont revenus sous forme de copie unique suite aux évènements de polyploïdie qui ont jalonné l’histoire des plantes à fleurs. Seuls les polyploïde plus récents comme le au blé, le coton ou le colza présentent plusieurs copies. Étonnés par le caractère systématique de cette perte de gènes dupliqués sur un pas de temps court, les chercheurs ont étudié les conséquences de la perte d’une des copies de MSH4 chez le colza qui en possède deux.


Waste without consequence
L’inactivation simultanée des deux copies de MSH4 chez le colza conduit à une diminution drastique du nombre d’échanges génétiques entre chromosomes, confirmant le rôle essentiel que joue cette protéine dans la recombinaison méiotique chez cette espèce. En revanche, la perte de l’une ou de l’autre des deux copies est sans conséquence sur le bon déroulement de la méiose chez cette espèce. Il suffit d’un seul exemplaire (allèle) fonctionnel assurer une ségrégation équilibrée des chromosomes au cours de la méiose.


Less to be, better it is !
Il en va différemment si on s’intéresse aux échanges génétiques qui peuvent survenir entre les chromosomes hérités des espèces parentales du colza. Leur nombre est proportionnel au nombre de copie fonctionnelle de MSH4 : il est maximal lorsque les deux copies sont fonctionnelles, décroit progressivement au fur et à mesure que la plante accumule des allèles délétères pour l’une ou pour l’autre des deux copies, et il est pratiquement nul lorsque les deux copies sont inactivées. Loin d’être délétère, cette perte de copie dupliquée pourrait donc s’avérer bénéfique, en limitant les risques que des échanges illégitimes perturbent la ségrégation des chromosomes de colza. Ces travaux ouvrent donc la voie à la sélection de nouvelles espèces cultivées combinant les génomes de plusieurs espèces, comme cela a été fait pour le triticale.

Financial support (PhD) by the european training network COMREC.

Communiqué de presse INRA 06/06/19

Contact:
Eric Jenczewski (01 30 83 33 08)
Institut Jean-Pierre Bourgin (INRA, AgroParisTech ; ERL CNRS)
Associated Department:
Plant Biology and Breeding
Associated Centre:
Ile-de-France-Versailles-Grignon

Contact(s) press:
Inra Press Room (01 42 75 91 86)

Référence:
Reducing MSH4 copy number prevents meiotic crossovers between non-homologous chromosomes in Brassica napus.Adrián Gonzalo, Marie-Odile Lucas, Catherine Charpentier, Greta Sandmann, Andrew Lloyd et Eric Jenczewski. Nature Communications. 29 mai 2019.
DOI : orcid.org/0000-0001-7821-5384

Plus d'info :
Adrian Gonzalo Sanchez, lauréat d’une bourse doctorale dans le cadre des actions Marie Curie, Internet Centre Ile-de-France-Versailles-Grignon

6th june 2019


Zoom on genetics complexity in plants

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’
Deviced at the Institut Jean-Pierre Bourgin (IJPB, INRA Versailles-Grignon -Ile-de-France) and thanks to genetic ressources of the Arabidopsis thaliana Stock Center, the Phenoscope gather 4 unique robots in two culture chambers of the Plant Observatory (INRA patent) to observe plants at the vegetative stage (shoot).
It allows :
> to study more than 700 cultivated plants per robot
> to analyse large populations in controlled and reproducible conditions, being not feasible by hand and represent a bottle neck in modern biology
> or to characterize in detail a small number of different plants (genotypes) in a wide range of conditions (watering for example)
> to homogenise conditions by a continuous movement of plants (ex: typical cycle of 4 hours)
> 3 time less of repetitions necessary within each experiment
> dynamic shooting of growth with automatic extraction of characters by image analysis

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/

Communiqué de presse INRA 22/04/19

Contact:
Olivier Loudet (01 30 83 32 17)
Institut Jean-Pierre Bourgin (INRA, AgroParisTech ; ERL CNRS)
Département scientifique Biologie et amélioration des plantes
Ile-de-France-Versailles-Grignon

Contact(s) press:
Inra service de presse (01 42 75 91 86)

Associated Department:
Plant Biology and Breeding
Associated Centre:
Ile-de-France-Versailles-Grignon

Référence:
The complex genetic architecture of shoot growth natural variation in Arabidopsis thaliana. Elodie Marchadier, Mathieu Hanemian, Sébastien Tisné, Liên Bach, Christos Bazakos, Elodie Gilbault, Parham Haddadi, Laetitia Virlouvet, Olivier Loudet. PLoS Genetics. 22th Avril 2019. https://doi.org/10.1371/journal.pgen.1007954

23th April 2019


 

Clonal reproduction by seed is now possible in crops

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.

To this end, agriculture has been using F1 hybrids since the 1930s. Generated by crossing two pure crop lineages that contain genes of interest, F1 hybrids combine the desirable traits exhibited by each of their parents. They display "hybrid vigour”, benefits that are greater than the sum of the individual agricultural values of the two parental lineages. In crops where individual plants have both male and female organs (e.g., maize, tomato), F1 hybrids are produced by removing the male organs and then carrying out manual pollination. In crops where individual plants are unisexual (e.g., rapeseed, beet), controlled pollination of female plants is performed. The problem is that the offspring of F1 hybrids do not display the same traits as their parents because of the dynamics of meiosis, during which chromosome exchange occurs. Each year, it is therefore necessary to reuse F1 hybrid seeds from the original parental cross to obtain the desired trait combinations.

From meiosis to mitosis
For decades, scientists have searched for a way to preserve the desirable gene combinations represented in high-performing hybrids. In particular, attention has been focused on apomixis, a process used by certain plants (such as dandelions and hawthorns) to asexually reproduce though seeds, which allows them to forgo meiosis and fertilisation. The offspring produced are thus clones of their parents—they are identical to each other. Recently, in Arabidopsis (a model plant species) and in rice, INRA researchers were able to replace meiosis with a mitosis-like process (MiMe) by inactivating three genes involved in meiosis. The result: plants produced gametes (i.e., reproductive cells) containing the same exact chromosomes as their mother plants. However, to engineer apomixis, there is an important additional step. Female gametes must be able to give rise to embryos despite being unfertilised. INRA researchers were able to surmount this hurdle thanks to two separate collaborations: one with Venkatesan Sundaresan's team at University of California Davis and a second with Kejian Wang's team at the China National Rice Research Institute. These two groups independently discovered how to induce embryogenesis without the need for female gametes to be fertilised by male gametes.

A spitting genetic image
To accomplish this feat, they used CRISPR-Cas9 to inactivate the three MiMe-related genes identified by INRA scientists. Sundaresan's team then activated a gene called BABYBOOM 1 in the female gametes. Normally, this gene is only expressed following fertilisation. In contrast, Wang's team inactivated the MATRILINEAL gene (also known as the NOT LIKE DAD gene), which is involved in the fertilisation process. In this way, both teams managed to induce fertilisation-free embryogenesis, which produced rice seeds that gave rise to plants that were identical to the hybrid mother plant. Furthermore, Sundaresan's team showed that these clones also produced clonal offspring: three generations later, identical plants were still being generated. It is therefore possible to preserve hybrid vigour in the offspring of F1 hybrids in rice!

Tremendous possibilities
In both cases, the seed production rates are too low for the processes to be immediately used for commercial seed production. However, the researchers are exploring how these rates can be boosted.

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.

Press release INRA 10/01/19


Contact:
Raphaël Mercier (01 30 83 39 89)
Institut Jean-Pierre Bourgin (INRA, AgroParisTech, ERL CNRS)

Contact(s) press:
Inra service de presse (01 42 75 91 86)
Associated Department:
Biologie et amélioration des plantes
Associated Centre:
Ile-de-France-Versailles-Grignon

Références:
Imtiyaz Khanday, Debra Skinner, Bing Yang, Raphael Mercier & Venkatesan Sundaresan.A male-expressed rice embryogenic trigger redirected for asexual propagation through seeds. Nature (2019). https://doi.org/10.1038/s41586-018-0785-8 Abstract

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

See also:
Raphaël Mercier, INRA award "Scientific challenge" 2016

10th January 2019


Small is big in Arabidopsis mitochondrial ribosome:
machinery translating proteins

 

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.

Contact:
Hakim Mireau  
Institut Jean-Pierre Bourgin (INRA, AgroParisTech, ERL CNRS)

Référence :
Florent Waltz F, Tan-Trung Nguyen, Mathilde Arrivé, Anthony Bochle, Johana Chicher, Philippe Hammann, Lauriane Kuhn, Martine Quadrado, Hakim Mireau, Yaser Hashem, Philippe Giegé. Small is big in Arabidopsis mitochondrial ribosome. Nature Plants doi: https://doi.org/10.1038/s41477-018-0339-y Abstract

 

9th January 2019


Recombination increased in crops by the RECQ4 gene inactivation

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.

But what limits the number of recombinations ?
To understand this the limitation of the number of recombination, scientists from INRA identified and studied, in the model plant Arabidopsis thaliana, genes involved in the control of recombination level. They discovered that REQ4, one of them, harbor a high anti-crossing-over activity. Recombination frequency is twice to four fold higher when RECQ4 is inactivated!

But what happens in cultivated plants?
It has been evaluated by the consortium associating INRA and CIRAD, studying the following important crops: pea, tomato and rice. The RECQ4 gene has been successfully switched of in these species, increasing by an average of three the number of crossing-over and consequently increasing chromosome shuffling and diversity for each generation. INRA, as an applied research Institute will focus now of integrating such a tool in plant breeding programs.

But why recombinations are so infrequent?
More recently, what explains the active mechanisms as RECQ4 which limits this process, and then the rhythm of diversity, within the majority of living organisms with sex reproduction? The question is still open. The most shared theory by scientists to explain this phenomenon is that the evolution of species happens in a quite globally stable environment. Consequently, combinations selected within the previous generations are well adapted to the environment where new individual develop themselves. Diversity being necessary to adapt to survive, to shuffle cards, as we could say jeopardize the equilibrium within each generation, is probably not the most optimum solution. In brief, diversity is needed but not too much.

Communiqué de presse INRA 26/11/18

Contact:
Raphaël Mercier (01 30 83 39 89) Institut Jean-Pierre Bourgin (INRA, AgroParisTech, ERL CNRS)

Contact(s) press:
Inra service de presse (01 42 75 91 86)
Scientific department associated:
Biologie et amélioration des plantes
Center associated:
Versailles-Grignon

Référence:
Delphine Mieulet, Gregoire Aubert, Cecile Bres, Anthony Klein, Gaëtan Droc, Emilie Vieille, Celine Rond-Coissieux, Myriam Sanchez, Marion Dalmais, Jean-Philippe Mauxion, Christophe Rothan, Emmanuel Guiderdoni and Raphael Mercier, Unleashing meiotic crossovers in crops, Nature Plants doi: https://doi.org/10.1101/343509 Abstract

See also:
Raphaël Mercier, INRA award "Scientific challenge" 2016

26th november 2018



Events
___

EMBO Workshop on Meiosis

25th-29th August 2019, La Rochelle, France

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.

Programme and Poster

Scientific Committee:
Christine Mézard, Institut Jean-Pierre Bourgin, INRA, Versailles, France
Harmit Malik, Fred Hutchinson Cancer Research, Seattle, USA
Matt Neale, University of Sussex, Brighton, United Kingdom
Melina Schuh, Max Planck Institute for Biophysical Chemistry, Berlin, Germany
Kikue Tachibana-Konwalski, Institute of Molecular Biotechnology, Vienna, Austria

Local Committee: Christine Mézard, Mathilde Grelon, Corine Enard, Hervé Frémineur, Stéphane Raude, Stéphanie Zimmerman
Institut Jean-Pierre Bourgin, INRA, Versailles, France


Contact and more information: Embo Workshop on Meiosis website

2 mai 2019


Séminars
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___________________________________________________

Monday 7th January 2019
_______________________________________________
_____

2:00 PM

Focus IJPB
Dr. Annie MARION-POLL
Group "Germination physiology" PHYGERM

Abscisic acid in the hormonal control of seed germination

Contact


___________________________________________________

Monday 14th January 2019
_______________________________________________
_____

2:00 PM

Invited Speaker IJPB/SPS

Dr. John LUNN
System Regulation, Max Planck Institute of Molecular Plant Physiology,
MPIMPP, Potsdam, Allemagne

Sucrose signalling and regulation of sucrose metabolism by trehalose 6-phosphate

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

___________________________________________________

Monday 21th January 2019
_______________________________________________
_____

2:00 PM

Invited Speaker IJPB/SPS

Dr. Marie-Cécile CAILLAUD
Laboratoire Reproduction et Développement des Plantes, ENS, Lyon

INTERPLAY between phosphoinositide and cytoskeleton during cell division in Arabidopsis

Invited by Martine Pastuglia

___________________________________________________

Tuesday 29th January 2019
_______________________________________________
_____

2:00 PM

Invited Speaker

Dr. Mohammed BENDAHMANE
Morphogenèse florale, Laboratoire Reproduction et Développement des Plantes, ENS-Lyon

Molecular and genetic control of flower initiation and development in Arabidopsis and Rose plants

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.

Webpage Mohammmed Bendahmane Group

Invited by:  
Poster/résumé

___________________________________________________

Monday 4th February 2019
_______________________________________________
_____

2:00 PM

Visitor

Dr. Satoshi FUJITA
The Geldner Lab, University of Lausanne, Switzerland

Localized ROS production by polarized signaling module during Casparian strip formation

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

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Thursday 14th February 2019
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10 :00 AM

Grande salle Bât.7
Seminar

Dr. Kian HEMATY
The Geldner Lab, Université de Lausanne, Suisse
(équipe DIPOL, IJPB)

Polar trafficking: knowing where to go and how to come back

Invited by: Jean-Denis Faure

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Monday 18th February 2019
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2:00 PM

Invited Speaker IJPB/SPS

Dr. Daniel GRIMANELLI
Diversity - Adaptation - Development of plants, IRD, Montpellier

Dynamics of DNA methylation during maize reproductive development

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.


Invited by: Christine Mézard

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Thursday 28th March 2019
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10 :00 AM

Grande salle Bât.7
Invited Speaker IJPB/SPS

Pr. Ling YUAN
Prof. in Plant Biochemistry
Executive Director, KTRDC
Department of Plant and Soil Sciences
University of Kentucky, USA

A transcriptional mechanism mediates the switch between pathogen defense and cold tolerance

Ling Yuan Lab webpage

Invited by: Loïc Lepiniec

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Friday 29th March 2019
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2:00 PM

Grande salle Bât.7
Visitor

Dr. Renaud BASTIEN
Max Planck Institute for Ornithology, Constance, Allemagne

Collective Behaviour of Plants

Invited by: Herman Höfte
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Vendredi 19 Avril 2019
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2:00 PM

Grande salle Bât.7
Visitor

Prof. Richard BENNETT
Brown University, Rhode Island, USA
Genome Dynamics and Parasex in the Diploid Fungal Pathogen Candida albicans

The Bennett Lab webpage

Invited by : Christine Mézard

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Thursday 25th April 2019
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11:00 AM

Invited Speaker IJPB/SPS

Prof. Stephanie ROBERT
Dpt of Forest Genetics and Plant Physiology,
Swedish University of Agricultural Sciences, Umeå, Sweden

Towards a better understanding of cell shape acquisition with the example of pavement cells

Invited by: Leo Serra et Catherine Perrot-Rechenmann

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Jeudi 25 Avril 2019
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11h00

Séminaire invité IJPB/SPS

Pr. Stéphanie ROBERT
Dpt of Forest Genetics and Plant Physiology,
Swedish University of Agricultural Sciences, Umeå, Suède

Towards a better understanding of cell shape acquisition with the example of pavement cells

Invitée par : Leo Serra et Catherine Perrot-Rechenmann

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Jeudi 23 mai 2019
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11h00
Grande salle Bât. 7

Séminaire visiteur

Dr. Sandra DUHARCOURT
Régulation épigénétique de l'organisation du génome, Institut Jacques Monod, Paris

Lessons from Paramecium genome gymnastics: A dual histone H3 K9/K27 Polycomb protein ensures transposable element repression

Invitée par : Christine Mézard

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Mardi 18 juin 2019
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14h00

grande salle Bât.7
Séminaire visiteur

Dr. Laure DAVID
ETH Zurich, Suisse

Tetratricopeptide Repeat (TPR)-proteins are critical regulators of starch degradation

Starch 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.
We have identified several candidates that are involved in these processes, belonging to the Tetratricopeptide repeat (TPR)-like superfamily. TPR proteins are involved in regulation of different cellular functions through their protein-protein interaction motif. The sub-family we identified are the first related to the regulation of starch metabolism in Arabidopsis. Knocking-out several homologs lead to extreme phenotype, with plants exhausting their starch up to 4-5 hours before dawn. Data to be presented show that TPRS proteins play a critical role in regulating starch degradation at night, but also during the day.


Invitée par : Sylve Ferrario-Méry

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Vendredi 21 juin 2019
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10h00

grande salle Bât.7
Séminaire visiteur

Dr. Naoto KAWAKAMI
Meiji University, Tokyo, Japon

Genetic and environmental regulation of seed dormancy and germination in Arabidopsis

Invité par: Annie Marion-Poll

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Mardi 25 juin 2019
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11h00

Invited Speaker IJPB/SPS

Prof. Bernard CARROLL
The University of Queensland,
Brisbane, Autralie

Arabidopsis as a model organism for uncovering the mechanisms RNAi and epigenetics

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.

Bernard Carroll webpage

Invitée par : Hervé Vaucheret

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Mercredi 26 juin 2019
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11h00
grande salle Bât. 7
Séminaire invité IJPB/SPS

Dr. Pooja BHATNAGAR-MATHUR
ICRISAT, Hyderabad, Indes
Unlocking the power of genes and enabling technologies for game-changing innovations in legumes and nutri-cereals
– Discovery to Translation

A result 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.

Pooja Bhatnagar-Mathur webpage

Invitée par : Rajeev Kumar

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Jeudi 27 juin 2019
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14h00
grande salle Bât. 7
Séminaire

Dr. Vikas SHARMA
Génomique Info (URGI), INRA Versailles
Hidden diversity of endogeneous Geminiviridae across plant genomes and transcriptomes
&
Dr. Florian MAUMUS
Génomique Info (URGI), INRA Versailles
Towards adressing the macroevolution of LTR retrotransposons

Invités par : Nicolas Bouché

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Mardi 2 juillet 2019
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13h00
grande salle Bât. 7
Séminaire visiteur
Pr. Hiroyuki KASAHARA
Institute of Global Innovation Research, Tokyo University of Agriculture and Technology, Japon
Distinct characteristics of indole-3-acetic acid and phenylacetic acid, two natural auxins in plants

Invité par : Helen North et Annie Marion-Poll

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Lundi 8 juillet 2019
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14h00
grande salle Bât. 7
Séminaire visiteur
Pr. Zhenbiao YANG
University of California, Riverside, USA
& Fuzhou University, China
ROP signaling integrates chemical and mechanical signals

Invité par : Herman Höfte

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Jeudi 11 juillet 2019
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14h00
grande salle Bât. 7
Séminaire visiteur
Pr. Shin-Ichi ARIMURA
Tokyo University, Japon
Plant mitochondria, their dynamics and genome-editing

Invité par : Françoise Budar

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Monday 14th october 2019
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2:00 PM

Focus IJPB
Dr. Mathilde GRELON
Group "Mechanisms of meiosis" MeioMe
To be annonced

Registration compulsory except for INRA Versailles member up to 10/10/19

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Seminars location except other indications
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Amphitheatre, Building 10
INRA Centre de Versailles-Grignon
Route de St Cyr (RD10)
F-78026 Versailles Cedex
France

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