Immunolocalization of antioxidant enzymes in high-pressure frozen root and stem nodules of Sesbania rostrata.
The activities and localizations of superoxide dismutases (SODs) were compared in root and stem nodules of the semi-aquatic legume Sesbania rostrata using gel-activity assays and immunogold labelling, respectively. Nodules were fixed by high-pressure freezing and dehydrated by freeze substitution. Stem nodules showed more total and specific SOD activities than root nodules because of the presence of chloroplastic CuZnSOD. Most of the total SOD activity of stem and root nodules resulted from 'cytosolic' CuZnSOD, localized in the cytoplasm and chromatin, and from MnSOD in the bacteroids and in the mitochondria of vascular tissue. FeSOD was present in nodule plastids and in leaf chloroplasts, and was found to be associated with chromatin. Superoxide production was detected histochemically in the vascular bundles and in the infected tissue of stem and root nodules, whereas peroxide accumulation was observed in the cortical cell walls and intercellular spaces, as well as within the infection threads of both nodule types. These data suggest a role of CuZnSOD and FeSOD in protecting nuclear DNA from reactive oxygen species and/or in modulating gene activity. The enhanced levels of CuZnSOD, MnSOD and superoxide production in vascular bundle cells are consistent with a role of CuZnSOD and superoxide in the lignification of xylem vessels, but also suggest additional functions in coping with superoxide production by the high respiratory activity of parenchyma cells.
Rubio
Maria C
MC
Departamento de Nutrición Vegetal, Estación Experimental de Aula Dei, Consejo Superior de Investigaciones Científicas, ES-50080 Zaragoza, Spain.
Becana
Manuel
M
Departamento de Nutrición Vegetal, Estación Experimental de Aula Dei, Consejo Superior de Investigaciones Científicas, ES-50080 Zaragoza, Spain.
Kanematsu
Sumio
S
Department of Food Science, Minami-Kyushu University, Kirishima 5-1-2, Miyazaki 880-0032, Japan.
Ushimaru
Takashi
T
Department of Biology, Faculty of Science, Shizuoka University, 836 Ohya, Shizuoka 422-8529, Japan.
James
Euan K
EK
College of Life Sciences, University of Dundee, Dundee DD1 5EH, UK.|(present address) Scottish Crop Research Institute, Invergowrie, Dundee DD2 5DA, UK.
D000975:Antioxidants / Q000378:metabolism*; D005615:Freezing; D006861:Hydrogen Peroxide / Q000378:metabolism; D015151:Immunoblotting; D007150:Immunohistochemistry; D007527:Isoenzymes / Q000378:metabolism; D018515:Plant Leaves / Q000166:cytology / Q000201:enzymology; D018547:Plant Stems / Q000166:cytology / Q000201:enzymology* / Q000648:ultrastructure; D011312:Pressure; D053204:Root Nodules, Plant / Q000166:cytology / Q000201:enzymology* / Q000648:ultrastructure; D049931:Sesbania / Q000166:cytology / Q000201:enzymology* / Q000648:ultrastructure; D013482:Superoxide Dismutase / Q000378:metabolism; D013481:Superoxides / Q000378:metabolism
D000975:Antioxidants; D007527:Isoenzymes; D013481:Superoxides; D006861:Hydrogen Peroxide; D013482:Superoxide Dismutase