title: RbohB, a Phaseolus vulgaris NADPH oxidase gene, enhances symbiosome number, bacteroid size, and nitrogen fixation in nodules and impairs mycorrhizal colonization.
abstract: The reactive oxygen species (ROS) generated by respiratory burst oxidative homologs (Rbohs) are involved in numerous plant cell signaling processes, and have critical roles in the symbiosis between legumes and nitrogen-fixing bacteria. Previously, down-regulation of RbohB in Phaseolus vulgaris was shown to suppress ROS production and abolish Rhizobium infection thread (IT) progression, but also to enhance arbuscular mycorrhizal fungal (AMF) colonization. Thus, Rbohs function both as positive and negative regulators. Here, we assessed the effect of enhancing ROS concentrations, by overexpressing PvRbohB, on the P. vulgaris--rhizobia and P. vulgaris--AMF symbioses. We estimated superoxide concentrations in hairy roots overexpressing PvRbohB, determined the status of early and late events of both Rhizobium and AMF interactions in symbiont-inoculated roots, and analyzed the nodule ultrastructure of transgenic plants overexpressing PvRbohB. Overexpression of PvRbohB significantly enhanced ROS production, the formation of ITs, nodule biomass, and nitrogen-fixing activity, and increased the density of symbiosomes in nodules, and the density and size of bacteroides in symbiosomes. Furthermore, PvCAT, early nodulin, PvSS1, and PvGOGAT transcript abundances were elevated in these nodules. By contrast, mycorrhizal colonization was reduced in roots that overexpressed RbohB. Overexpression of PvRbohB augmented nodule efficiency by enhancing nitrogen fixation and delaying nodule senescence, but impaired AMF colonization.
authors.affiliation: Departamento de Biología Molecular de Plantas, Instituto de Biotecnología, Universidad Nacional Autónoma de México, UNAM, Apartado Postal 510-3, Cuernavaca, Morelos, 62271, México.
authors.forename: Manoj-Kumar
authors.initials: MK
authors.lastname: Arthikala
authors.affiliation: Departamento de Biología Molecular de Plantas, Instituto de Biotecnología, Universidad Nacional Autónoma de México, UNAM, Apartado Postal 510-3, Cuernavaca, Morelos, 62271, México.
authors.forename: Rosana
authors.initials: R
authors.lastname: Sánchez-López
authors.affiliation: Departamento de Biología Molecular de Plantas, Instituto de Biotecnología, Universidad Nacional Autónoma de México, UNAM, Apartado Postal 510-3, Cuernavaca, Morelos, 62271, México.
authors.forename: Noreide
authors.initials: N
authors.lastname: Nava
authors.affiliation: Departamento de Biología Molecular de Plantas, Instituto de Biotecnología, Universidad Nacional Autónoma de México, UNAM, Apartado Postal 510-3, Cuernavaca, Morelos, 62271, México.
authors.forename: Olivia
authors.initials: O
authors.lastname: Santana
authors.affiliation: Departamento de Biología Molecular de Plantas, Instituto de Biotecnología, Universidad Nacional Autónoma de México, UNAM, Apartado Postal 510-3, Cuernavaca, Morelos, 62271, México.
authors.forename: Luis
authors.initials: L
authors.lastname: Cárdenas
authors.affiliation: Departamento de Biología Molecular de Plantas, Instituto de Biotecnología, Universidad Nacional Autónoma de México, UNAM, Apartado Postal 510-3, Cuernavaca, Morelos, 62271, México.
authors.forename: Carmen
authors.initials: C
authors.lastname: Quinto
mesh_terms: D018533:Biomass; D003001:Cloning, Molecular; D015169:Colony Count, Microbial; D015536:Down-Regulation / Q000235:genetics; D018506:Gene Expression Regulation, Plant; D017343:Genes, Plant; D008954:Models, Biological; D038821:Mycorrhizae / Q000254:growth & development*; D019255:NADPH Oxidases / Q000235:genetics* / Q000378:metabolism; D009586:Nitrogen Fixation / Q000235:genetics*; D027805:Phaseolus / Q000201:enzymology* / Q000235:genetics / Q000382:microbiology / Q000648:ultrastructure; D010940:Plant Proteins / Q000378:metabolism; D030821:Plants, Genetically Modified; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D017382:Reactive Oxygen Species / Q000378:metabolism; D012231:Rhizobium / Q000502:physiology*; D053204:Root Nodules, Plant / Q000254:growth & development / Q000382:microbiology* / Q000648:ultrastructure; D013559:Symbiosis / Q000235:genetics*
chemical_list: D010940:Plant Proteins; D012333:RNA, Messenger; D017382:Reactive Oxygen Species; D019255:NADPH Oxidases
keywords: NADPH oxidase homologs; Phaseolus vulgaris symbiosis; arbuscular mycorrhizal fungi (AMF); bacteroids; infection threads; nodule senescence; reactive oxygen species (ROS); symbiosomes