OVEREXPRESSION OF EsDHAR1 IMPROVED TOLERANCE IN TRANSGENIC TOBACCO WITH INCREASED ASCORBIC ACID LEVELS

Vitamin C (ascorbic acid, AsA) is a pivotal antioxidant that alleviates oxidative damage imposed by various environmental stresses such as drought, cold and salinity. The dehydroascorbate reductase (DHAR) has recently been shown to play an essential role in the regeneration of AsA. In this work, a novel cDNA encoding DHAR, designated as EsDHAR1, was isolated from Eutrema salsugineum. To investigate the protective role of EsDHAR1 against oxidative stress, a constructed plasmid carrying its coding region was introduced into tobacco plants. Our results revealed that the EsDHAR1-overexpressing lines had higher content of AsA and glutathione (GSH) relative to wild type (WT) plants under well-watered and drought stress conditions. When plants were subjected to drought stress or in vitro leaf discs were treated with NaCl or mannitol, the transgenic lines exhibited a greater tolerance to these stresses compared with WT plants. Furthermore, these transgenic lines accumulated lower reactive oxygen species (ROS) including H2O2 and O-2(-) than WT plants under drought stress. Collectively, our study demonstrated that overexpression of EsDHAR1 enhanced the AsA biosynthesis in transgenic tobacco plants and provided important evidence that this gene could be used to improve plant adaptation to adverse environments.