Influence de la nutrition azotée sur la sensibilité d'Arabidopsis thaliana à Alternaria brassicicola aux stades plantule et rosette

The role of nitrogen nutrition was studied on the A. thaliana / A. brassicicola pathosystem. A. brassicicola is a necrotrophic fungus transmitted to and by the seed, causing damping-off but also leaf necrosis. To this end, the influence of different forms of nitrogen supply, nitrate vs ammonium, on plant susceptibility to the pathogen was studied, at two stages of development: rosette (adult plant) and seedling (early stage). At the rosette stage, plants grown under ammonium conditions are less susceptible to the fungus than under nitrate conditions. Metabolite analyzes and selected gene expression revealed that nitrogen nutrition appeared to control fungal infection via a complex set of signaling and nutritional events. A new experimental device has been developed for the study at the seedling stage to assess the fungus impact on the development of seedlings, by image analysis. The study of the effect of nitrogen nutrition, carried out on three genotypes, revealed that the seedlings are more susceptible to the fungus under ammonium conditions than under nitrate conditions. This study has therefore demonstrated for the first time that nitrogen nutrition has a different influence on A. thaliana susceptibility to A. brassicicola depending on the plant stage of development. The study, in seeds and seedlings, of metabolite abundances and expression of a selection of genes made it possible to link a reduced susceptibility to the fungus, notably to the indole glucosinolate pathway and to lower levels of polyamines.Le rôle de la nutrition azotée a été étudié sur le pathosystème A. thaliana / A. brassicicola. A. brassicicola est un champignon nécrotrophe transmis à et par la semence, provoquant des fontes de semis mais aussi des nécroses sur feuilles. Dans ce but, l’influence de l’apport de différentes formes d’azote dans le milieu nutritif de la plante, nitrate vs ammonium, sur leur sensibilité au pathogène a été étudiée, à deux stades de développement : rosette (plante adulte) et plantule (précoce). Au stade rosette, les plantes cultivées en condition ammonium sont moins sensibles au champignon qu’en condition nitrate. Des analyses métaboliques et d’expression d’une sélection de gènes ont révélé que la nutrition azotée semblait contrôler l’infection fongique via un ensemble complexe d’événements de signalisation et nutritionnels. Un nouveau dispositif expérimental a été développé pour l’étude au stade plantule permettant d’évaluer l’impact du champignon sur le développement des plantules par analyse d’images. L’étude de l’effet de la nutrition azotée, menée sur trois génotypes, a révélé que les plantules sont plus sensibles au champignon en condition ammonium qu’en condition nitrate. Cette étude a donc mis en évidence pour la première fois que la nutrition azotée influence différemment la sensibilité d'A. thaliana à A. brassicicola en fonction du stade de développement de la plante. L’étude, dans les graines et les plantules, des abondances métaboliques et de l’expression d’une sélection de gènes a permis de relier notamment une sensibilité réduite au champignon à la voie des glucosinolates indoliques et à des teneurs plus faibles en polyamines

Nitrogen Nutrition Modulates the Response to <i>Alternaria brassicicola</i> Infection via Metabolic Modifications in <i>Arabidopsis</i> Seedlings

Little is known about the effect of nitrogen nutrition on seedling susceptibility to seed-borne pathogens. We have previously shown that seedlings grown under high nitrate (5 mM) conditions are less susceptible than those grown under low nitrate (0.1 mM) and ammonium (5 mM) in the Arabidopsis-Alternaria brassicicola pathosystem. However, it is not known how seedling metabolism is modulated by nitrogen nutrition, nor what is its response to pathogen infection. Here, we addressed this question using the same pathosystem and nutritive conditions, examining germination kinetics, seedling development, but also shoot ion contents, metabolome, and selected gene expression. Nitrogen nutrition clearly altered the seedling metabolome. A similar metabolomic profile was observed in inoculated seedlings grown at high nitrate levels and in not inoculated-seedlings. High nitrate levels also led to specific gene expression patterns (e.g., polyamine metabolism), while other genes responded to inoculation regardless of nitrogen supply conditions. Furthermore, the metabolites best correlated with high disease symptoms were coumarate, tyrosine, hemicellulose sugars, and polyamines, and those associated with low symptoms were organic acids (tricarboxylic acid pathway, glycerate, shikimate), sugars derivatives and β-alanine. Overall, our results suggest that the beneficial effect of high nitrate nutrition on seedling susceptibility is likely due to nutritive and signaling mechanisms affecting developmental plant processes detrimental to the pathogen. In particular, it may be due to a constitutively high tryptophan metabolism, as well as down regulation of oxidative stress caused by polyamine catabolism

Neura: a specialized large language model solution in neurology

Large language models’ (LLM) ability in natural language processing holds promise for diverse applications, yet their deployment in fields such as neurology faces domain-specific challenges. Hence, we introduce Neura: a scalable, explainable solution to specialize LLM. Blindly evaluated on a select set of five complex clinical cases compared to a cohort of 13 neurologists, Neura achieved normalized scores of 86.17% overall, 85% for differential diagnoses, and 88.24% for final diagnoses (55.11%, 46.15%, and 70.93% for neurologists) with rapid response times of 28.8 and 19 seconds (9 minutes and 37.2 seconds and 8 minutes and 51 seconds for neurologists) while consistently providing relevant, accurately cited information. These findings support the emerging role of LLM-driven applications to articulate human-acquired and integrated data with a vast corpus of knowledge, augmenting human experiential reasoning for clinical and research purposes