Ectopic expression of a wheat superoxide dismutase gene TaSOD5 enhances salt and oxidative stress tolerance in Arabidopsis

Superoxide dismutase (SOD) is a crucial reactive oxygen species (ROS) scavenger, which converts superoxide radical to H2O2, so it is thought to enhance abiotic stress tolerance by reducing ROS and thus avoiding oxidative damage. In this study, we isolated a salt- and oxidative stress-responsive copper-zinc (Cu/Zn) SOD encoding gene TaSOD5 from wheat. The ectopic overexpression of TaSOD5 in Arabidopsis thaliana increased total SOD and Cu/Zn SOD activities and enhanced tolerance to salt stress. Arabidopsis ectopically expressing TaSOD5 possessed a superior resistance to oxidative stress stimulated by exogenous H2O2. Ectopic overexpression of TaSOD5 elevated the activities of both ROS scavengers and an O2.- producer - NADPH oxidase. These findings show that Cu/Zn SOD enhanced salt tolerance via regulating the machinery of redox homeostasis rather than improving SOD activity alone.