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The antioxidants of legume nodule mitochondria

AuthorsIturbe-Ormaetxe, Iñaki ; Matamoros Galindo, Manuel Ángel ; Rubio Luna, María Carmen ; Dalton, David A.; Becana Ausejo, Manuel
KeywordsNodule organelles
Oxidative stress
Free radicals
Issue DateOct-2001
PublisherAmerican Phytopathological Society
CitationMolecular Plant-Microbe Interactions 14 (10): 1189-1196 (2001)
AbstractThe mitochondria of legume root nodules are critical to sustain the energy-intensive process of nitrogen fixation. They also generate reactive oxygen species at high rates and thus require the protection of antioxidant enzymes and metabolites. We show here that highly purified mitochondria from bean nodules (Phaseolus vulgaris L. cv. Contender x Rhizobium leguminosarum bv. phaseoli strain 3622) contain ascorbate peroxidase primarily in the inner membrane (with lesser amounts detected occasionally in the matrix), guaiacol peroxidases in the outer membrane and matrix, and manganese superoxide dismutase (MnSOD) and an ascorbate-regenerating system in the matrix. This regenerating system relies on homoglutathione (instead of glutathione) and pyridine nucleotides as electron donors and involves the enzymes monodehydroascorbate reductase, dehydroascorbate reductase, and homoglutathione reductase. Homoglutathione is synthesized in the cytosol and taken up by the mitochondria and bacteroids. Although bacteroids synthesize glutathione, it is not exported to the plant in significant amounts. We propose a model for the detoxification of peroxides in nodule mitochondria in which membrane-bound ascorbate peroxidase scavenges the peroxide formed by the electron transport chain using ascorbate provided by L-galactono-1,4-lactone dehydrogenase in the inner membrane. The resulting monodehydroascorbate and dehydroascorbate can be recycled in the matrix or cytosol. In the matrix, the peroxides formed by oxidative reactions and by MnSOD may be scavenged by specific isozymes of guaiacol peroxidase, ascorbate peroxidase, and catalase.
Description22 Pags. The definitive version, with Figs. and Tabls., is available at: http://apsjournals.apsnet.org/loi/mpmi All content of MPMI is open access without restriction 12 months after publication.
Publisher version (URL)http://dx.doi.org/10.1094/MPMI.2001.14.10.1189
Identifiersdoi: 10.1094/MPMI.2001.14.10.1189
issn: 0894-0282
Appears in Collections:(EEAD) Artículos
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