Over-expression of exotic superoxide dismutase gene MnSOD and increase in stress resistance in maize

To evaluate the effect of over-expressed Mn-superoxide dismutase (MnSOD) on stress resistance in maize, an over-expression vector with MnSOD gene of wheat was constructed and used to transform embryonic calli of elite maize inbred line by gene gun. After screening with a concentration gradient of hygromycin, 9 plants were regenerated from the positive calli and reproduced fertile seeds, 5 of which were shown to be positive by PCR and Southern blot analysis. This result indicated that the exotic gene had been integrated in maize genome. SOD enzyme extracts were separated by non-denatured polyacrylamide gel electrophoresis of gradient concentration. After inhibition with 5 mmol/L H(2)O(2) to FeSOD and Cu/ZnSOD, MnSOD enzyme activity was assayed with nitrotetrazolium chloride blue staining. All the 5 plants shown to be positive in Southern blot had higher MnSOD activity than untransformed control. Electric conductivity of leaf exudate was assayed after damage treatment with methyl viologen. The result suggested that the resistance of the transformed plants to oxidative damage was significantly higher than untransformed control.