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Pacoud, M.

Publications and source records attributed to Pacoud, M..

2 recordsLinked to original sources
bioRxiv2024

Differential induction of Medicago truncatula defence metabolites in response to rhizobial symbiosis and pea aphid infestation

O_LILegumes symbiosis with rhizobial nitrogen-fixing bacteria enable them to grow in nitrate-depleted soils. Rhizobial symbioses also induces systemic plant defence against bioagressors. C_LIO_LIWe investigate how nitrogen-fixing symbiosis (NFS) in the legume Medicago truncatula can prime plant defence against the pea aphid Acyrthosiphon pisum. We analysed metabolite modification both by LC-MS and GC-MS and defence pathway gene expression by qPCR in leaves of both NFS and nitrate-fed (non-inoculated; NI) plants after aphid infestation (Amp). C_LIO_LIThe accumulation of primary and secondary metabolites was modulated by both NFS and aphid infestation. 62 defense-related metabolites such as salicylate, pipecolate, gentisic acid and several soluble sugars were differentially regulated by aphid infestation in both NFS and NI conditions. 19 metabolites, including triterpenoid saponins, accumulated specifically in NFS_Amp conditions. Gene expression analysis showed that aphid-infested plants exhibited significantly higher expression of Chalcone isomerase, flavonol synthase, hydroxyisoflavone-O-methyl transferase and Pterocarpan synthase, while D-pinitol dehydrogenase was only significantly induced in NI infested leaves. C_LIO_LIOur data suggest that NFS, in addition to being a plant nitrogen provider, stimulates specific legume defenses upon pest attack and should also be considered as a potential tool in Integrated Pest Management strategy. C_LI

plant biology↗
bioRxiv2024

Nitrate reductase activity is required in Medicago truncatula-Sinorhizobium meliloti nitrogen-fixing symbiosis

Nitrate reductase (NR) is a key enzyme in higher land plants, catalyzing the rate-limiting reduction of nitrate to nitrite in the nitrate assimilation pathway. Phylogenetic analysis of NR protein sequences indicates that duplication events responsible for the existence of two NR branches, corresponding to NR1 and NR2 genes, occurred after the divergence of the different orders within the Rosids clade. A third NR sequence branch, named NR3-type, emerged in the inverted repeat-lacking clade of the Fabales order. An intriguing feature of the NR3-type sequences is the absence of conserved phosphorylation sites in the two hinge regions, in contrast to all other NRs. To investigate the respective roles of MtNR1, MtNR2 and MtNR3 in M. truncatula, three single Tnt1 retrotransposon-tagged nr mutants and one nr1/nr2 double mutant were analyzed on plants growing either on nitrate, or during the nodulation process. Overall, the absence of phenotypes observed in M. truncatula single mutants suggests a significant functional redundancy between the different NRs in M. truncatula. The most striking outcome of this work is the almost complete impairment of nodulation capacity observed in the nr1/nr2 double mutant, demonstrating that NR activity is required for the functioning of the N2-fixing symbiosis.

plant biology↗