Abstract
Aluminum (Al) stress has been widely reported to induce oxidative stress through formation of reactive oxygen species (ROS) in plant cells. Ascorbic acid (AsA) is a major antioxidant and free radical scavenger in plant cells. Dehydroascorbate reductase (DHAR; EC 1.8.5.1) is an important enzyme for AsA regeneration. To examine the protective role of DHAR against Al stress, we developed transgenic tobacco plants overexpressing cytosolic DHAR gene from Arabidopsis thaliana. DHAR transgenic plants exhibited better root elongation, less lipid peroxidation and maintained greater plasma membrane integrity compared to wild-type plants under Al stress. Although no differences of Al accumulation was observed in root tips of transgenic and wild-type plants after 24 h Al treatment, DHAR transgenic plants showed higher AsA/DHA ratio and higher activities of DHAR and ascorbate peroxidase (APX) in both leaves and roots. These results demonstrate that overexpressed levels of DHAR properly confer enhanced tolerance to Al stress.
