title: Overexpression of flavodoxin in bacteroids induces changes in antioxidant metabolism leading to delayed senescence and starch accumulation in alfalfa root nodules.
abstract: Sinorhizobium meliloti cells were engineered to overexpress Anabaena variabilis flavodoxin, a protein that is involved in the response to oxidative stress. Nodule natural senescence was characterized in alfalfa (Medicago sativa) plants nodulated by the flavodoxin-overexpressing rhizobia or the corresponding control bacteria. The decline of nitrogenase activity and the nodule structural and ultrastructural alterations that are associated with nodule senescence were significantly delayed in flavodoxin-expressing nodules. Substantial changes in nodule antioxidant metabolism, involving antioxidant enzymes and ascorbate-glutathione cycle enzymes and metabolites, were detected in flavodoxin-containing nodules. Lipid peroxidation was also significantly lower in flavodoxin-expressing nodules than in control nodules. The observed amelioration of the oxidative balance suggests that the delay in nodule senescence was most likely due to a role of the protein in reactive oxygen species detoxification. Flavodoxin overexpression also led to high starch accumulation in nodules, without reduction of the nitrogen-fixing activity.
authors.affiliation: Department of Plant Physiology and Ecology, Instituto de Recursos Naturales, Centro de Ciencias Medioambientales, Consejo Superior de Investigaciones Científicas, E-28006 Madrid, Spain.
authors.forename: Francisco J
authors.initials: FJ
authors.lastname: Redondo
authors.forename: Teodoro Coba
authors.initials: TC
authors.lastname: de la Peña
authors.forename: César N
authors.initials: CN
authors.lastname: Morcillo
authors.forename: M Mercedes
authors.initials: MM
authors.lastname: Lucas
authors.forename: José J
authors.initials: JJ
authors.lastname: Pueyo
mesh_terms: D001439:Bacteroides / Q000235:genetics*; D016922:Cellular Senescence / Q000235:genetics / Q000502:physiology; D005418:Flavodoxin / Q000235:genetics*; D005784:Gene Amplification; D015964:Gene Expression Regulation, Bacterial; D000455:Medicago sativa / Q000254:growth & development / Q000502:physiology*; D009586:Nitrogen Fixation; D009591:Nitrogenase / Q000378:metabolism; D018384:Oxidative Stress; D010940:Plant Proteins / Q000378:metabolism; D018517:Plant Roots / Q000254:growth & development / Q000502:physiology*; D016133:Polymerase Chain Reaction; D013559:Symbiosis
chemical_list: D005418:Flavodoxin; D010940:Plant Proteins; D009591:Nitrogenase