Overexpression of flavodoxin in bacteroids induces changes in antioxidant metabolism leading to delayed senescence and starch accumulation in alfalfa root nodules.
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.
Redondo
Francisco J
FJ
Department of Plant Physiology and Ecology, Instituto de Recursos Naturales, Centro de Ciencias Medioambientales, Consejo Superior de Investigaciones Científicas, E-28006 Madrid, Spain.
de la Peña
Teodoro Coba
TC
Morcillo
César N
CN
Lucas
M Mercedes
MM
Pueyo
José J
JJ
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
D005418:Flavodoxin; D010940:Plant Proteins; D009591:Nitrogenase