Liens entre le nitrate et le monoxyde d'azote dans la réponse immunitaire de <em>Medicago truncatula</em>

Description

Plants are under the constant threat of microbial pathogens. To defend themselves, plants have evolved a sophisticated immune system involving complex signaling by reactive oxygen and nitrogen species (including nitric oxide, NO) and downstream the activation of the synthesis of defense compounds that can lead to resistance. However, these plant defense responses are costly and lead plants to continuously face a dilemma regarding the partitioning of their available resources. The aim of this project is to highlight the functional links between NO, nitrogen nutrition and plant defense responses. We analyzed the impact of nitrogen (N) nutrition and NO on the capacity of different M. truncatula genotypes to resist against A. euteiches, the causal agent of legume root rot disease. Both N deficiency and interaction with A. euteiches appear to enhance NO levels in M. truncatula roots as assessed by SNO measurements. Using transformed roots altered in NO homeostasis, we highlighted the role of NO production on resistance or sensitivity to A. euteiches. Furthermore, alteration of NO homeostasis was correlated with changes in intracellular nitrate concentrations. To further assess the importance of NO production in these conditions we have analyzed the tyrosine nitration profiles (a post-translational modification of proteins generated indirectly by NO) of protein extracts from roots of plants cultivated under N deficiency or interacting with the pathogen. These profiles were indeed different. Last, a targeted approach focusing on tyrosine nitration of glutamine synthetase, an important enzyme involved in N assimilation/remobilisation, highlighted the role of NO in modulating possibly this enzymatic activity. Altogether our results confirm the role of NO in plant immune response and in the modulation of plant N metabolism.

Abstract

IPM SPE Agrosup

Abstract

Master

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