Genetic engineering of oxidative stress resistance in higher plants

Many environmental conditions induce an oxidative stress in plant cells by the generation of abnormal concentrations of reactive-oxygen intermediates (ROI) such as superoxide radicals, hydrogen peroxide and hydroxyl radicals. To protect themselves against these potentially damaging molecules, plants have evolved several enzymic mechanisms including superoxide dismutases (SODs), peroxidases and catalases. Recent molecular studies in Nicotiana species showed that the genes coding for the different ROI-scavenging enzymes are differentially regulated in response to environmental stress. Transgenic plants which overexpressed SOD genes in chloroplasts are more tolerant to treatment with the superoxide-generating herbicide paraquat and to ozone fumigation. Strategies to engineer plants with high resistance to oxidative stress are discussed.