title: A Medicago truncatula NADPH oxidase is involved in symbiotic nodule functioning.
abstract: The plant plasma membrane-localized NADPH oxidases, known as respiratory burst oxidase homologues (RBOHs), appear to play crucial roles in plant growth and development. They are involved in important processes, such as root hair growth, plant defence reactions and abscisic acid signalling. Using sequence similarity searches, we identified seven putative RBOH-encoding genes in the Medicago truncatula genome. A phylogenetic reconstruction showed that Rboh gene duplications occurred in legume species. We analysed the expression of these MtRboh genes in different M. truncatula tissues: one of them, MtRbohA, was significantly up-regulated in Sinorhizobium meliloti-induced symbiotic nodules. MtRbohA expression appeared to be restricted to the nitrogen-fixing zone of the functional nodule. Moreover, using S. meliloti bacA and nifH mutants unable to form efficient nodules, a strong link between nodule nitrogen fixation and MtRbohA up-regulation was shown. MtRbohA expression was largely enhanced under hypoxic conditions. Specific RNA interference for MtRbohA provoked a decrease in the nodule nitrogen fixation activity and the modulation of genes encoding the microsymbiont nitrogenase. These results suggest that hypoxia, prevailing in the nodule-fixing zone, may drive the stimulation of MtRbohA expression, which would, in turn, lead to the regulation of nodule functioning.
authors.affiliation: Interactions Biotiques et Santé Végétale, UMR Université de Nice-Sophia Antipolis - INRA 1301 - CNRS 6243, 400 Route des Chappes, BP 167, F-06903 Sophia Antipolis Cedex, France.
authors.forename: Daniel
authors.initials: D
authors.lastname: Marino
authors.forename: Emilie
authors.initials: E
authors.lastname: Andrio
authors.forename: Etienne G J
authors.initials: EG
authors.lastname: Danchin
authors.forename: Elodie
authors.initials: E
authors.lastname: Oger
authors.forename: Sébastien
authors.initials: S
authors.lastname: Gucciardo
authors.forename: Annie
authors.initials: A
authors.lastname: Lambert
authors.forename: Alain
authors.initials: A
authors.lastname: Puppo
authors.forename: Nicolas
authors.initials: N
authors.lastname: Pauly
mesh_terms: D020869:Gene Expression Profiling; D015971:Gene Expression Regulation, Enzymologic; D018506:Gene Expression Regulation, Plant; D017343:Genes, Plant / Q000235:genetics; D046913:Medicago truncatula / Q000166:cytology / Q000201:enzymology* / Q000235:genetics / Q000382:microbiology; D058977:Molecular Sequence Annotation; D019255:NADPH Oxidases / Q000235:genetics / Q000378:metabolism*; D009586:Nitrogen Fixation / Q000235:genetics; D010641:Phenotype; D010802:Phylogeny; D021381:Protein Transport; D034622:RNA Interference; D053204:Root Nodules, Plant / Q000201:enzymology* / Q000235:genetics / Q000254:growth & development / Q000382:microbiology; D016962:Sinorhizobium meliloti / Q000502:physiology; D013559:Symbiosis / Q000502:physiology*
chemical_list: D019255:NADPH Oxidases