Induction of new isoforms of superoxide dismutase and catalase enzymes in the flag leaf of wheat during monocarpic senescence.
Leaf senescence is a programmed cell death phenomenon and involves oxidative stress. Superoxide dismutase (SOD, EC 1.15.1.1) and catalase (CAT EC 1.11.1.6) activities were studied in the flag leaf of Triticum aestivum cv. Kundan at different stages of grain development. Both SOD and CAT activities showed a decline during monocarpic senescence. Three SOD isozymes were observed in the cytosol, of which one isozyme was observed in the chloroplasts as well. Mitochondria showed the presence of three low abundant SOD isoforms. Inhibitor studies revealed the cytosolic and chloroplastic isoforms to be Cu/Zn SODs. In mitochondria however, two isozymes were MnSOD and one of them appeared to be FeSOD. These isoforms present in the mitochondria increased in activity as senescence progressed. Three isoforms of CAT were observed in peroxisomes which responded differentially during monocarpic senescence. The changes in the kind and pattern of the antioxidant enzymes supported the ordered sequence of events during leaf senescence. This is the first report showing an increase in mitochondrial FeSOD activity during leaf senescence.
Srivalli
B
B
Stress Physiology Laboratory, Water Technology Centre, Indian Agricultural Research Institute, New Delhi-, 110012, India.
Khanna-Chopra
R
R
D000375:Aging / Q000502:physiology*; D000975:Antioxidants / Q000378:metabolism; D017209:Apoptosis; D002374:Catalase / Q000096:biosynthesis* / Q000235:genetics; D002736:Chloroplasts / Q000201:enzymology; D003600:Cytosol / Q000201:enzymology; D004790:Enzyme Induction; D006861:Hydrogen Peroxide / Q000378:metabolism; D007527:Isoenzymes / Q000037:antagonists & inhibitors / Q000096:biosynthesis / Q000235:genetics / Q000378:metabolism; D008928:Mitochondria / Q000201:enzymology; D018384:Oxidative Stress; D020675:Peroxisomes / Q000201:enzymology; D018515:Plant Leaves / Q000166:cytology / Q000201:enzymology* / Q000254:growth & development; D013482:Superoxide Dismutase / Q000037:antagonists & inhibitors / Q000096:biosynthesis* / Q000235:genetics / Q000378:metabolism; D014908:Triticum / Q000166:cytology / Q000201:enzymology* / Q000254:growth & development
D000975:Antioxidants; D007527:Isoenzymes; D006861:Hydrogen Peroxide; D002374:Catalase; D013482:Superoxide Dismutase