title: Nitric oxide (NO): a key player in the senescence of Medicago truncatula root nodules.
abstract: Nitric oxide (NO) is a signalling and defence molecule involved in diverse plant developmental processes, as well as in the plant response to pathogens. NO has also been detected at different steps of the symbiosis between legumes and rhizobia. NO is required for an optimal establishment of the Medicago truncatula-Sinorhizobium meliloti symbiotic interaction, but little is known about the role of NO in mature nodules. Here, we investigate the role of NO in the late steps of symbiosis. Genetic and pharmacological approaches were conducted to modulate the NO level inside root nodules, and their effects on nitrogen fixation and root nodule senescence were monitored. An increase in endogenous NO levels led to a decrease in nitrogen fixation and early nodule senescence, characterized by cytological modifications of the nodule structure and the early expression of a specific senescence marker. By contrast, a decrease in NO levels led to a delay in nodule senescence. Together, our results strongly suggest that NO is a signal in developmental as well as stress-induced nodule senescence. In addition, this work demonstrates the pivotal role of the bacterial NO detoxification response in the prevention of early nodule senescence, and hence the maintenance of efficient symbiosis.
authors.affiliation: Laboratoire des Interactions Plantes-Microorganismes (LIPM), INRA, UMR441, 24 Chemin de Borde Rouge - Auzeville, CS 52627, F-31326, Castanet-Tolosan Cedex, France.|Laboratoire des Interactions Plantes-Microorganismes (LIPM), CNRS, UMR2594, 24 Chemin de Borde Rouge - Auzeville, CS 52627, F-31326, Castanet-Tolosan Cedex, France.
authors.forename: Yvan
authors.initials: Y
authors.lastname: Cam
authors.affiliation: 'Institut Sophia Agrobiotech', UMR ISA, INRA 1355-CNRS 7254-Université de Nice-Sophia Antipolis (UNS), 400 route des Chappes BP 167, F-06903, Sophia-Antipolis Cedex, France.
authors.forename: Olivier
authors.initials: O
authors.lastname: Pierre
authors.affiliation: 'Institut Sophia Agrobiotech', UMR ISA, INRA 1355-CNRS 7254-Université de Nice-Sophia Antipolis (UNS), 400 route des Chappes BP 167, F-06903, Sophia-Antipolis Cedex, France.
authors.forename: Eric
authors.initials: E
authors.lastname: Boncompagni
authors.affiliation: 'Institut Sophia Agrobiotech', UMR ISA, INRA 1355-CNRS 7254-Université de Nice-Sophia Antipolis (UNS), 400 route des Chappes BP 167, F-06903, Sophia-Antipolis Cedex, France.
authors.forename: Didier
authors.initials: D
authors.lastname: Hérouart
authors.affiliation: Laboratoire des Interactions Plantes-Microorganismes (LIPM), INRA, UMR441, 24 Chemin de Borde Rouge - Auzeville, CS 52627, F-31326, Castanet-Tolosan Cedex, France.|Laboratoire des Interactions Plantes-Microorganismes (LIPM), CNRS, UMR2594, 24 Chemin de Borde Rouge - Auzeville, CS 52627, F-31326, Castanet-Tolosan Cedex, France.
authors.forename: Eliane
authors.initials: E
authors.lastname: Meilhoc
authors.affiliation: Laboratoire des Interactions Plantes-Microorganismes (LIPM), INRA, UMR441, 24 Chemin de Borde Rouge - Auzeville, CS 52627, F-31326, Castanet-Tolosan Cedex, France.|Laboratoire des Interactions Plantes-Microorganismes (LIPM), CNRS, UMR2594, 24 Chemin de Borde Rouge - Auzeville, CS 52627, F-31326, Castanet-Tolosan Cedex, France.
authors.forename: Claude
authors.initials: C
authors.lastname: Bruand
mesh_terms: D001426:Bacterial Proteins / Q000378:metabolism; D018533:Biomass; D003624:Darkness; D006420:Hemeproteins / Q000378:metabolism; D006834:Hydrazines / Q000494:pharmacology; D046913:Medicago truncatula / Q000166:cytology / Q000254:growth & development* / Q000378:metabolism* / Q000382:microbiology; D018613:Microscopy, Confocal; D009569:Nitric Oxide / Q000378:metabolism* / Q000494:pharmacology; D009591:Nitrogenase / Q000378:metabolism; D018520:Plant Shoots / Q000033:anatomy & histology / Q000187:drug effects; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D053204:Root Nodules, Plant / Q000166:cytology / Q000187:drug effects / Q000201:enzymology / Q000254:growth & development*; D015398:Signal Transduction / Q000187:drug effects; D016962:Sinorhizobium meliloti / Q000166:cytology / Q000187:drug effects / Q000378:metabolism; D013312:Stress, Physiological / Q000187:drug effects; D013347:Subcellular Fractions / Q000187:drug effects / Q000378:metabolism; D013559:Symbiosis / Q000187:drug effects
chemical_list: D001426:Bacterial Proteins; D006420:Hemeproteins; D006834:Hydrazines; D011993:Recombinant Fusion Proteins; C086193:flavohemoprotein, Bacteria; D009569:Nitric Oxide; C084012:1,1-diethyl-2-hydroxy-2-nitrosohydrazine; D009591:Nitrogenase