Genetic Engineering of More Antioxidants for Greater Abiotic Stress Tolerance

Environmental stresses such as drought, salt, heavy metals and the herbicides use accelerate the accumulation of the reactive oxygen species, ROS (free radicals) that are capable of unrestricted oxidation of many cellular components and can lead to oxidative destruction of the plant cells. Ascorbate (AsA) and glutathione (GSH) are powerful antioxidants and scavenger of free radicals, and maintaining their reduced pools are crucial for the continuous removal of free radicals. In this study we developed transgenic potato (Solanum tuberosum L.) plants overexpressing either the Arabidopsis thaliana DHAR gene (AtDHAR1) or glutathione reductase (AtGR1) which are functioning in reducing the oxidized forms of AsA and GSH, respectively. DHAR transgenic potato exhibited up to 4.5 folds higher DHAR activity and up to 2.8 folds of AsA, while GR transgenic potato maintained up to 6.5 folds higher GR activity and 5.8 folds GSH compared to non-transformed plants. Both types of transgenics maintained an enhanced tolerance to the herbicide methylviologen and drought stress. Moreover, DHAR transgenic potato showed enhanced tolerance to salt stress, while the GR transgenic maintained greater protection under cadmium stress. These results demonstrate that recycling the oxidized forms of either AsA or GSH provides reliable approach for the development of abiotic stress tolerant potato.