Effect of the free radical-generating herbicide paraquat on the expression of the superoxide dismutase (Sod) genes in maize.
10-day-old maize leaves were treated with the oxygen free radical-generating herbicide paraquat for 12 h. Paraquat treatments (10(-5) M) resulted in a 40% increase in superoxide dismutase activity and a smaller increase in catalase activity. The increase in total superoxide dismutase (SOD) activity correlates with higher levels of specific isozymes. The chloroplast (SOD-1) and cytosolic (SOD-2 and SOD-4) forms were increased significantly; however, the mitochondrial form (SOD-3) was increased only slightly. Higher levels of SOD-4 and SOD-3 after paraquat exposure were the result of increased synthesis of these proteins, as determined by labeling in vivo with [35S]methionine. Isolation and in vitro translation of polysomes from 10(-5) M paraquat-treated leaves indicated that paraquat increased the amount of polysomal mRNA which codes for SOD-4 and SOD-3. Superoxide dismutase induction does not appear to be a response that is specific to paraquat, since another superoxide-generating compound, juglone, caused a similar increase in total superoxide dismutase activity. Therefore, the effect of these compounds on the expression of the maize Sod genes is exerted via their ability to generate superoxide.
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D002374:Catalase / Q000378:metabolism; D002736:Chloroplasts / Q000201:enzymology; D003600:Cytosol / Q000201:enzymology; D005786:Gene Expression Regulation / Q000187:drug effects* / Q000528:radiation effects; D007527:Isoenzymes / Q000096:biosynthesis* / Q000235:genetics; D008027:Light; D008928:Mitochondria / Q000201:enzymology; D010084:Oxidation-Reduction; D010269:Paraquat / Q000494:pharmacology*; D010940:Plant Proteins / Q000096:biosynthesis* / Q000235:genetics; D012333:RNA, Messenger / Q000378:metabolism; D013482:Superoxide Dismutase / Q000096:biosynthesis* / Q000235:genetics; D003313:Zea mays / Q000201:enzymology / Q000235:genetics
D007527:Isoenzymes; D010940:Plant Proteins; D012333:RNA, Messenger; D002374:Catalase; D013482:Superoxide Dismutase; D010269:Paraquat