Jasmonate regulatory circuits in rice adaptation to environmental stress

Les jasmonates, initialement caractérisés comme régulateurs de la croissance et de réponses de défense contre les pathogènes, ont plus récemment été associés à la réponse à divers stress abiotiques. L'élucidation de mécanismes d'activation de cette voie hormonale pour l'établissement des réponses à ces processus biologiques est documentée principalement chez Arabidopsis thaliana. Ici nous avons mené une telle recherche chez le Riz (Oryza sativa), pour comprendre le métabolisme et la signalisation spécifique des JAs chez une céréale. Les résultats de ma thèse avancent la connaissance des fonctions des JAs chez le Riz. D'une part, ils démontrent la conservation de la voie catabolique JAO dans le contrôle du niveau basal de signalisation JAs, illustrent sa régulation des processus JAs-dépendants tels que la réponse à des stress abiotiques, et dévoilent une possible origine évolutive de l’activité JAO. D’autre part, les données transcriptomiques et métaboliques générées révèlent différentes cibles des JAs dans la réponse au sel, permettant d'expliquer les rôles très opposés des JAs dans la tolérance aux composantes osmotique et ionique du stress salin.Jasmonates, initially characterized as regulators of growth and pathogen defense responses, have more recently been associated with the response to various abiotic stresses. Elucidation of the activation mechanisms of JAs signaling for the establishment of responses to these processes has been mainly performed in Arabidopsis thaliana. Here we undertook to investigate new aspects of JAs metabolism and signaling in the cereal rice (Oryza sativa). The results generated during my thesis advance our understanding of JA functions in rice. On the one hand, they demonstrate the conservation of the JA Oxidase catabolic pathway in rice in the control of the basal levels of JAs signaling, they illustrate its regulation of JAs-dependent processes as abiotic stress tolerance, and uncover a possible evolutionary origin of JAO activity. On the other hand, the transcriptomic and metabolic data we generated reveal different targets of JAs in the plant response to salt, making it possible to explain the very opposite roles of JAs in the tolerance of osmotic and ionic components of salt stress

Jasmonate signaling controls negative and positive effectors of salt stress tolerance in rice

International audiencePlant responses to salt exposure involve large reconfiguration of hormonal pathways that orchestrate physiological changes towards tolerance. Jasmonate (JA) hormones are essential to withstand biotic and abiotic assaults, but their roles in salt tolerance remain unclear. Here we describe the dynamics of JA metabolism and signaling in root and leaf of rice, a plant species that is highly exposed and sensitive to salt. Roots activate the JA pathway in an early pulse, while 2nd leaf displays a biphasic JA response with peaks at 1 hour and 3 days post-exposure. Based on higher salt tolerance of a rice JA-deficient mutant (aoc), we examined through kinetic transcriptome and physiological analysis the salt-triggered processes that are under JA control. Profound genotype-differential features emerged that could underlie observed phenotypes. ABA content and ABA-dependent water deprivation responses were impaired in aoc shoots. Moreover, aoc accumulated more Na+ in roots, and less in leaf, with reduced ion translocation correlating with root derepression of the HAK4 Na+ transporter. Distinct reactive oxygen species scavengers were also stronger in aoc leaf, along with reduced senescence and chlorophyll catabolism markers. Collectively, the data identify contrasted contributions of JA signaling to different sectors of the salt stress response in rice

ARTICLE RST1 and RIPR connect the cytosolic RNA exosome to the Ski complex in Arabidopsis

International audienceThe RNA exosome is a key 3'−5' exoribonuclease with an evolutionarily conserved structure and function. Its cytosolic functions require the co-factors SKI7 and the Ski complex. Here we demonstrate by co-purification experiments that the ARM-repeat protein RESURRECTION1 (RST1) and RST1 INTERACTING PROTEIN (RIPR) connect the cytosolic Arabidopsis RNA exosome to the Ski complex. rst1 and ripr mutants accumulate RNA quality control siRNAs (rqc-siRNAs) produced by the post-transcriptional gene silencing (PTGS) machinery when mRNA degradation is compromised. The small RNA populations observed in rst1 and ripr mutants are also detected in mutants lacking the RRP45B/CER7 core exosome subunit. Thus, molecular and genetic evidence supports a physical and functional link between RST1, RIPR and the RNA exosome. Our data reveal the existence of additional cytosolic exosome co-factors besides the known Ski subunits. RST1 is not restricted to plants, as homologues with a similar domain architecture but unknown function exist in animals, including humans