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Expression and Localization of a Rhizobium-Derived Cambialistic Superoxide Dismutase in Pea (Pisum sativum) Nodules Subjected to Oxidative Stress

October 2011 , Volume 24 , Number  10
Pages  1,247 - 1,257

Aaron C. Asensio,1 Daniel Marino,2 Euan K. James,3 Idoia Ariz,1 Cesar Arrese-Igor,2 Pedro M. Aparicio-Tejo,1 Raúl Arredondo-Peter,4 and Jose F. Moran1

1Institute of Agro-Biotechnology, IdAB-CSIC-UPNa-GN, Public University of Navarre, Spain; 2Department of Environmental Sciences, Public University of Navarre, Spain; 3Scottish Crop Research Institute, Invergowrie, Dundee DD2 5DA, U.K.; 4Laboratorio de Biofísica y Biología Molecular, Facultad de Ciencias, Universidad Autónoma del Estado de Morelos, Cuernavaca, Morelos, México

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Accepted 23 June 2011.

Two phylogenetically unrelated superoxide dismutase (SOD) families, i.e., CuZnSOD (copper and zinc SOD) and FeMn-CamSOD (iron, manganese, or cambialistic SOD), eliminate superoxide radicals in different locations within the plant cell. CuZnSOD are located within the cytosol and plastids, while the second family of SOD, which are considered to be of bacterial origin, are usually located within organelles, such as mitochondria. We have used the reactive oxygen species–producer methylviologen (MV) to study SOD isozymes in the indeterminate nodules on pea (Pisum sativum). MV caused severe effects on nodule physiology and structure and also resulted in an increase in SOD activity. Purification and N-terminal analysis identified CamSOD from the Rhizobium leguminosarum endosymbiont as one of the most active SOD in response to the oxidative stress. Fractionation of cell extracts and immunogold labeling confirmed that the CamSOD was present in both the bacteroids and the cytosol (including the nuclei, plastids, and mitochondria) of the N-fixing cells, and also within the uninfected cortical and interstitial cells. These findings, together with previous reports of the occurrence of FeSOD in determinate nodules, indicate that FeMnCamSOD have specific functions in legumes, some of which may be related to signaling between plant and bacterial symbionts, but the occurrence of one or more particular isozymes depends upon the nodule type.

© 2011 The American Phytopathological Society