title: Mitochondria are an early target of oxidative modifications in senescing legume nodules.
abstract: Legume nodule senescence is a poorly understood process involving a decrease in N(2)  fixation and an increase in proteolytic activity. Some physiological changes during nodule aging have been reported, but scarce information is available at the subcellular level. Biochemical, immunological and proteomic approaches were used to provide insight into the effects of aging on the mitochondria and cytosol of nodule host cells. In the mitochondria, the oxidative modification of lipids and proteins was associated with a marked decline in glutathione, a reduced capacity to regenerate ascorbate, and upregulation of alternative oxidase and manganese superoxide dismutase. In the cytosol, there were consistent reductions in the protein concentrations of carbon metabolism enzymes, inhibition of protein synthesis and increase in serine proteinase activity, disorganization of cytoskeleton, and a sharp reduction of cytosolic proteins, but no detectable accumulation of oxidized molecules. We conclude that nodule mitochondria are an early target of oxidative modifications and a likely source of redox signals. Alternative oxidase and manganese superoxide dismutase may play important roles in controlling ROS concentrations and the redox state of mitochondria. The finding that specific methionine residues of a cytosolic glutamine synthetase isoform are sulfoxidized suggests a regulatory role of this enzyme in senescing nodules.
authors.affiliation: Departamento de Nutrición Vegetal, Estación Experimental de Aula Dei, Consejo Superior de Investigaciones Científicas (CSIC), Apartado 13034, 50080, Zaragoza, Spain.
authors.forename: Manuel A
authors.initials: MA
authors.lastname: Matamoros
authors.affiliation: Departamento de Biología del Estrés y Patología Vegetal, Centro de Edafología y Biología Aplicada del Segura, CSIC, Campus de Espinardo, Apartado 164, 30100, Espinardo-Murcia, Spain.
authors.forename: Nieves
authors.initials: N
authors.lastname: Fernández-García
authors.affiliation: Department of Molecular Systems Biology, University of Vienna, 1090 Vienna, Austria.
authors.forename: Stefanie
authors.initials: S
authors.lastname: Wienkoop
authors.affiliation: Departamento de Nutrición Vegetal, Estación Experimental de Aula Dei, Consejo Superior de Investigaciones Científicas (CSIC), Apartado 13034, 50080, Zaragoza, Spain.
authors.forename: Jorge
authors.initials: J
authors.lastname: Loscos
authors.affiliation: Departamento de Nutrición Vegetal, Estación Experimental de Aula Dei, Consejo Superior de Investigaciones Científicas (CSIC), Apartado 13034, 50080, Zaragoza, Spain.
authors.forename: Ana
authors.initials: A
authors.lastname: Saiz
authors.affiliation: Departamento de Nutrición Vegetal, Estación Experimental de Aula Dei, Consejo Superior de Investigaciones Científicas (CSIC), Apartado 13034, 50080, Zaragoza, Spain.
authors.forename: Manuel
authors.initials: M
authors.lastname: Becana
mesh_terms: D018506:Gene Expression Regulation, Plant; D005974:Glutamate-Ammonia Ligase / Q000378:metabolism; D005978:Glutathione / Q000032:analysis / Q000378:metabolism; D050356:Lipid Metabolism; D008928:Mitochondria / Q000378:metabolism*; D024101:Mitochondrial Proteins / Q000378:metabolism / Q000502:physiology; D009586:Nitrogen Fixation; D010084:Oxidation-Reduction; D010088:Oxidoreductases / Q000378:metabolism / Q000502:physiology; D027805:Phaseolus / Q000201:enzymology / Q000378:metabolism*; D010940:Plant Proteins / Q000378:metabolism / Q000502:physiology; D020033:Protein Isoforms / Q000378:metabolism; D011499:Protein Processing, Post-Translational; D020543:Proteome; D017382:Reactive Oxygen Species / Q000378:metabolism; D013482:Superoxide Dismutase / Q000378:metabolism / Q000502:physiology; D000099188:Alternative Oxidase
chemical_list: D005974:Glutamate-Ammonia Ligase; D005978:Glutathione; D024101:Mitochondrial Proteins; D010088:Oxidoreductases; D010940:Plant Proteins; D020033:Protein Isoforms; D020543:Proteome; D017382:Reactive Oxygen Species; D013482:Superoxide Dismutase; D000099188:Alternative Oxidase