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 (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 exosure 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.
All Science Journal Classification (ASJC) codes
- Molecular Biology