Activation of plasma membrane H + -ATPases participates in dormancy alleviation in sunflower seeds

International audienceUsing various inhibitors and scavengers we took advantage of the size of sunflower (Helianthus annuus) seeds to investigate in vivo the effects of hormones, namely abscisic acid (ABA) and ethylene (ET), and reactive oxygen species (ROS) on the polarization of dormant (D) and non-dormant (ND) embryonic seed cells using microelectrodes. Our data show that D and ND seed cells present different polarization likely due to the regulation of plasma membrane (PM) H+-ATPase activity. The data obtained after addition of hormones or ROS scavengers further suggest that ABA dependent inhibition of PM H+-ATPases could participate in dormancy maintenance and that ET-and ROS-dependent PM H+-ATPase stimulation could participate in dormancy release in sunflower seeds

Early events induced by the toxin deoxynivalenol lead to programmed cell death in Nicotiana tabacum cells

Deoxynivalenol (DON) is a mycotoxin affecting animals and plants. This toxin synthesized by Fusarium culmorum and Fusarium graminearum is currently believed to play a decisive role in the fungal phytopathogenesis as a virulence factor. Using cultured cells of Nicotiana tabacum BY2, we showed that DON-induced programmed cell death (PCD) could require transcription and translation processes, in contrast to what was observed in animal cells. DON could induce different cross-linked pathways involving (i) reactive oxygen species (ROS) generation linked, at least partly, to a mitochondrial dysfunction and a transcriptional down-regulation of the alternative oxidase (Aox1) gene and (ii) regulation of ion channel activities participating in cell shrinkage, to achieve PCD

L’anesthésie, un processus commun à tout le vivant

International audienceDu fait de leur intérêt en médecine, la majeure partie des études actuelles sur les anesthésiques se concentrent sur le système nerveux des animaux et négligent le fait que toute forme de vie peut être anesthésiée. En effet, l’anesthésie cible des canaux dépendants du voltage, canaux qui existent dans un grand nombre d’espèces diverses et qui proviennent de canaux ancestraux antérieurs à l’apparition même des eucaryotes. La question demeure : le maintien au cours de l’évolution de la capacité à être anesthésié est-il dû à un avantage adaptatif ou à un simple défaut intrinsèque des canaux ioniques ? Le regain d’intérêt actuel pour les modèles non animaux ouvre l’espoir non seulement de découvrir de nouvelles molécules anesthésiantes, mais aussi de progresser dans notre connaissance fondamentale de ce phénomène encore mal compris

Disruption of the Bcchs3a chitin synthase gene in Botrytis cinerea is responsible for altered adhesion and overstimulation of host plant immunity.

International audienceThe fungal cell wall is a dynamic structure that protects the cell from different environmental stresses suggesting that wall synthesizing enzymes are of great importance for fungal virulence. Previously, we reported the isolation and characterization of a mutant in class III chitin synthase, Bcchs3a, in the phytopathogenic fungus Botrytis cinerea. We demonstrated that virulence of this mutant is severely impaired. Here, we describe the virulence phenotype of the cell-wall mutant Bcchs3a on the model plant Arabidopsis thaliana and analyze its virulence properties, using a variety of A. thaliana mutants. We found that mutant Bcchs3a is virulent on pad2 and pad3 mutant leaves defective in camalexin. Mutant Bcchs3a was not more susceptible towards camalexin than the wild-type strain but induced phytoalexin accumulation at the infection site on Col-0 plants. Moreover, this increase in camalexin was correlated with overexpression of the PAD3 gene observed as early as 18 h postinoculation. The infection process of the mutant mycelium was always delayed by 48 h, even on pad3 plants, probably because of lack of mycelium adhesion. No loss in virulence was found when Bcchs3a conidia were used as the inoculum source. Collectively, these data led us to assign a critical role to the BcCHS3a chitin synthase isoform, both in fungal virulence and plant defense response

Our sisters the plants? Notes from phylogenetics and botany on plant kinship blindness

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Au delà de la frontière académique : la recherche participative dans nos jardins: Podcast « Restez pas planté là ! », Épisode 12

Depuis 2013, un groupe d’habitants de la commune de Marigny (département des Deux-Sèvres) s’est mobilisé pour interroger les liens entre la façon dont les jardins privés sont perçus et vécus, et la façon dont leurs habitants se positionnent par rapport aux enjeux de biodiversité . Ce questionnement a été développé dans le cadre du programme de recherche participative Nouveaux Commanditaires – Sciences , un programme mis en œuvre par l’Atelier des Jours à venir qui permet à des collectifs de citoyens de commanditer une recherche auprès de chercheurs professionnels, en travaillant avec un médiateur ou une médiatrice. Dans le prolongement d’un travail mené avec O. Bories et F. Kaposztas (2015-2018), suite auquel les habitants se sont notamment positionnés en “habitants-chercheurs” , une nouvelle collaboration s’est mise en place en 2019 avec Mathilde Riboulot-Chetrit (Université Paris 1 Panthéon Sorbonne) et Etienne Grésillon (Université Paris Cité), enseignants-chercheurs en géographie au Laboratoire Dynamiques Sociales et Recomposition des Espaces (UMR 7533 - LADYSS). Les questions sur lesquelles ces deux chercheurs ont été sollicités sont les suivantes : comment les enjeux de biodiversité sont-ils saisis par les habitants de ce territoire ? Qu’est-ce qui façonne leur rapport à la « nature » et leur prise en compte des enjeux environnementaux ? Comment ce rapport à la nature se construit à travers l'expérience dans leur jardin privé, individuellement et collectivement

Methanol induces cytosolic calcium variations, membrane depolarization and ethylene production in arabidopsis and tobacco

International audienceMethanol is a volatile organic compound released from plants through the action of pectin methylesterases (PMEs), which demethylesterify cell wall pectins. Plant PMEs play a role in developmental processes but also in responses to herbivory and infection by fungal or bacterial pathogens. However, molecular mechanisms that explain how methanol could affect plant defences remain poorly understood

Deciphering the dual effect of lipopolysaccharides from plant pathogenic Pectobacterium

International audienceLipopolysaccharides (LPS) are a component of the outer cell surface of almost all Gram-negative bacteria and play an essential role for bacterial growth and survival. Lipopolysaccharides represent typical microbe-associated molecular pattern (MAMP) molecules and have been reported to induce defense-related responses, including the expression of defense genes and the suppression of the hypersensitive response in plants. However, depending on their origin and the challenged plant, LPS were shown to have complex and different roles. In this study we showed that LPS from plant pathogens Pectobacterium atrosepticum and Pectobacterium carotovorum subsp. carotovorum induce common and different responses in A. thaliana cells when compared to those induced by LPS from non-phytopathogens Escherichia coli and Pseudomonas aeruginosa. Among common responses to both types of LPS are the transcription of defense genes and their ability to limit of cell death induced by Pectobacterium carotovorum subsp carotovorum. However, the differential kinetics and amplitude in reactive oxygen species (ROS) generation seemed to regulate defense gene transcription and be determinant to induce programmed cell death in response to LPS from the plant pathogenic Pectobacterium. These data suggest that different signaling pathways could be activated by LPS in A. thaliana cells

Metabolism regulation during salt exposure in the halophyte Cakile maritima

International audienceThe halophyte Cakile maritima is a Brassicacea that has developed numerous mechanisms for managing salt. In the present study, we analyze the metabolic responses of C. maritima to increasing salt exposure in parallel with growth and photosynthetic parameters. At 10 days, 100 mM NaCl treatment has no effect, whereas 400 mM treatment decreases both growth and photosynthetic capacity. Accordingly, the metabolism was weakly impacted at 100 mM NaCl with an increase in only a few amino acids and sugars, whereas 400 mM treated plants shows noticeable changes: an increase in amino acid abundance, sugars decrease and an organic acid depletion. At 20 days, 400 mM treatment leads to more severe effects on growth and photosynthesis, whereas plant growth remains unaffected by the 100 mM NaCl treatment, despite a reduction in photosynthetic capacity. Plants treated with 400 mM NaCl present an amplified metabolic response with additional metabolites reflecting salt stress as GABA, proline and glycine. One noticeable feature of halophily in C. maritima is the increase in sugar content at low stress whereas longer or higher stress lead to a decrease in sugar content. In high salt conditions the stimulation of amino acid biosynthesis is the main strategy for osmoprotection to cope for salt stress

Deciphering the dual effect of lipopolysaccharides from plant pathogenic <i>Pectobacterium</i>

<div><p>Lipopolysaccharides (LPS) are a component of the outer cell surface of almost all Gram-negative bacteria and play an essential role for bacterial growth and survival. Lipopolysaccharides represent typical microbe-associated molecular pattern (MAMP) molecules and have been reported to induce defense-related responses, including the expression of defense genes and the suppression of the hypersensitive response in plants. However, depending on their origin and the challenged plant, LPS were shown to have complex and different roles. In this study we showed that LPS from plant pathogens <i>Pectobacterium atrosepticum</i> and <i>Pectobacterium carotovorum subsp. carotovorum</i> induce common and different responses in <i>A. thaliana</i> cells when compared to those induced by LPS from non-phytopathogens <i>Escherichia coli</i> and <i>Pseudomonas aeruginosa</i>. Among common responses to both types of LPS are the transcription of defense genes and their ability to limit of cell death induced by <i>Pectobacterium carotovorum subsp carotovorum</i>. However, the differential kinetics and amplitude in reactive oxygen species (ROS) generation seemed to regulate defense gene transcription and be determinant to induce programmed cell death in response to LPS from the plant pathogenic <i>Pectobacterium</i>. These data suggest that different signaling pathways could be activated by LPS in <i>A. thaliana</i> cells.</p></div