GENETIC-ENGINEERING OF OXIDATIVE STRESS RESISTANCE IN HIGHER-PLANTS

Many environmental conditions induce an oxidative stress in plant cell s by the generation of abnormal concentrations of reactive-oxygen inte rmediates (ROI) such as superoxide radicals, hydrogen peroxide and hyd roxyl radicals. To protect themselves against these potentially damagi ng molecules, plants have evolved several enzymic mechanisms including superoxide dismutases (SODs), peroxidases and catalases. Recent molec ular studies in Nicotiana species showed that the genes coding for the different ROI-scavenging enzymes are differentially regulated in resp onse to environmental stress. Transgenic plants which overexpressed SO D genes in chloroplasts are more tolerant to treatment with the supero xide-generating herbicide paraquat and to ozone fumigation. Strategies to engineer plants with high resistance to oxidative stress are discu ssed.