A Rho family GTPase controls actin dynamics and tip growth via two counteracting downstream pathways in pollen tubes.

Tip growth in neuronal cells, plant cells, and fungal hyphae is known to require tip-localized Rho GTPase, calcium, and filamentous actin (F-actin), but how they interact with each other is unclear. The pollen tube is an exciting model to study spatiotemporal regulation of tip growth and F-actin dynamics. An Arabidopsis thaliana Rho family GTPase, ROP1, controls pollen tube growth by regulating apical F-actin dynamics. This paper shows that ROP1 activates two counteracting pathways involving the direct targets of tip-localized ROP1: RIC3 and RIC4. RIC4 promotes F-actin assembly, whereas RIC3 activates Ca(2+) signaling that leads to F-actin disassembly. Overproduction or depletion of either RIC4 or RIC3 causes tip growth defects that are rescued by overproduction or depletion of RIC3 or RIC4, respectively. Thus, ROP1 controls actin dynamics and tip growth through a check and balance between the two pathways. The dual and antagonistic roles of this GTPase may provide a unifying mechanism by which Rho modulates various processes dependent on actin dynamics in eukaryotic cells

The role of the testa during development and in establishment of dormancy of the legume seed

Timing of seed germination is one of the key steps in plant life cycles. It determines the beginning of plant growth in natural or agricultural ecosystems. In the wild, many seeds exhibit dormancy and will only germinate after exposure to certain environmental conditions. In contrast, crop seeds germinate as soon as they are imbibed usually at planting time. These domestication-triggered changes represent adaptations to cultivation and human harvesting. Germination is one of the common sets of traits recorded in different crops and termed the “domestication syndrome.” Moreover, legume seed imbibition has a crucial role in cooking properties. Different seed dormancy classes exist among plant species. Physical dormancy (often called hardseededness), as found in legumes, involves the development of a water-impermeable seed coat, caused by the presence of phenolics- and suberin-impregnated layers of palisade cells. The dormancy release mechanism primarily involves seed responses to temperature changes in the habitat, resulting in testa permeability to water. The underlying genetic controls in legumes have not been identified yet. However, positive correlation was shown between phenolics content (e.g., pigmentation), the requirement for oxidation and the activity of catechol oxidase in relation to pea seed dormancy, while epicatechin levels showed a significant positive correlation with soybean hardseededness. myeloblastosis family of transcription factors, WD40 proteins and enzymes of the anthocyanin biosynthesis pathway were involved in seed testa color in soybean, pea and Medicago, but were not tested directly in relation to seed dormancy. These phenolic compounds play important roles in defense against pathogens, as well as affecting the nutritional quality of products, and because of their health benefits, they are of industrial and medicinal interest. In this review, we discuss the role of the testa in mediating legume seed germination, with a focus on structural and chemical aspects

Propriétés organoleptiques des graines de pois : la génétique peut-elle améliorer le goût ?

National audiencePrésentation de l'Atelier :Les protéines sont des macronutriments majeurs dans l’alimentation des hommes et des animaux. Or la production de protéines végétales est toujours déficitaire en France qui a recours à des importations pour couvrir ses besoins.Les légumineuses contiennent plus de protéines que les céréales. En outre, leur culture contribue à la mise en œuvre de systèmes moins demandeurs en intrants qui peuvent ainsi, seuls, en rotation ou en mélange, contribuer efficacement à la démarche one health, vers une meilleure santé globale des hommes, des animaux, des cultures et de l’environnement. Améliorer la qualité des protéines végétales, tout en maintenant voire en augmentant le rendement est un objectif à poursuivre.Dans ce contexte, l’atelier a pour but de rapprocher les communautés de recherche en alimentation, en biologie végétale et en amélioration des plantes, des secteurs public et privé, afin de dégager les priorités communes interdisciplinaires.Cet atelier se tiendra soit sous forme de webinaire, soit en présentiel, en fonction de l'évolution de la situation sanitaire

Rôle du métabolisme soufré dans la réponse à la sécheresse chez le pois

Le pois (Pisum sativum L.) produit des graines riches en protéines pour l'alimentation humaine et animale, même en l’absence de fertilisation azotée, et sa culture enrichit les sols en azote, réduisant la nécessité d'une fertilisation azotée pour les cultures suivantes. L'augmentation de la culture et de la productivité du pois est un défi agroécologique nécessitant d’améliorer la tolérance du pois aux stress divers. La sécheresse et le manque de soufre dans les sols sont deux stress abiotiques qui interagissent dans le contexte actuel de changement climatique et de réduction des émissions de dioxyde de soufre. Des produits du métabolisme soufré, comme le glutathion, sont connus pour jouer un rôle protecteur contre de nombreux stress mais leur interaction avec la réponse des plantes à la sécheresse reste à étudier. Une approche de biologie des systèmes est utilisée pour étudier l'influence de la nutrition soufrée sur la dynamique des réseaux de gènes et de protéines associés à la sécheresse dans les feuilles de pois au cours de la phase reproductive. Cette approche fournira des modèles de régulation métabolique reliant la nutrition soufrée à la réponse du pois à la sécheresse. L'intégration d'autres données (physiologiques, rendement) révélera des facteurs de régulation potentiellement responsables des variations physiologiques observées et / ou des modifications des caractéristiques agronomiques sous ces contraintes abiotiques. En plus de fournir une meilleure compréhension du rôle du soufre dans la réponse du pois à la sécheresse, le projet permettra d'identifier des gènes et protéines candidat(e)s pour stabiliser ou améliorer la productivité et la qualité des graines de pois

The role of sulfur metabolism in the pea response to drought

National audiencePea (Pisum sativum L.) produces seeds rich in proteins for human and animal nutrition and its cultivation enriches the soils in nitrogen, thus decreasing the need for nitrogen fertilization. Increasing pea cultivation and productivity is an agroecological challenge which requires to improve pea tolerance to environmental stresses. Drought and the lack of sulfur in soils are two abiotic stresses that interact in the current context of climate change and low-input practices. Products of sulfur metabolism, like glutathione, are known to play a protective role against many stresses but their interaction with the plant response to drought remains to be studied. A system biology approach will be used to study the influence of sulfur nutrition on the dynamics of gene and protein networks associated with the response of pea leaves to drought during the reproductive phase. This approach will provide metabolic regulation models connecting sulfur nutrition to the drought response. The integration of other data (e.g., physiological, yield components) will reveal regulatory factors potentially responsible for the physiological variations observed and/or for the modifications of agronomic traits under these environmental constraints. In addition to provide a better understanding of the role of sulfur in the plant’s response to drought, the project will lead to the identification of gene and protein candidates for stabilizing or improving the productivity and seed quality of pea

The role of sulfur nutrition in the pea response to drought

International audienc

How does pea (Pisum sativum) recover from water deficit?

International audienc

Epidermis: the formation and functions of a fundamental plant tissue

International audienceEpidermis differentiation and maintenance are essential for plant survival. Constant cross-talk between epidermal cells and their immediate environment is at the heart of epidermal cell fate, and regulates epidermis-specific transcription factors. These factors in turn direct epidermal differentiation involving a whole array of epidermis-specific pathways including specialized lipid metabolism necessary to build the protective cuticle layer. An intact epidermis is crucial for certain key processes in plant development, shoot growth and plant defence. Here, we discuss the control of epidermal cell fate and the function of the epidermal cell layer in the light of recent advances in the field