TGase regulates salt stress tolerance through enhancing bound polyamines- mediated antioxidant enzymes activity in tomato

摘要

The accumulation of free polyamines (PAs) plays critical role in plants under abiotic stress conditions, while protective traits of bound PAs receiving much less attention, our understanding of the regulation of free PAs converted to bound PAs is limited. In this study, we demonstrated that the PA mediator transglutaminase (TGase) play an important role in improving tomato tolerance to salinity stress, in part because its critical role in inducing accumulation of bound PAs under salt stress. TGase expression was induced upon salt stress. Exogenous phenanthroline (O-phen, a TGase and bound PAs synthesis inhibitor) abolished the TGase-mediated salt tolerance with terminating bound PAs accumulation in TGaseOE plants. O-phen also had a negatively altered on Na+/K+ uptake or homeostasis under salt stress in leaves of TGaseOE plants. Instead, the overexpression of TGase effectively alleviated salt-induced oxidative damage and reduced reactive oxygen species (ROS) overproduction, but it was significantly aggravated by O-phen in the TGaseOE plants. Although the ROS generating enzymes (PA oxidase, diamine oxidase and NADPH oxidase) was not affected by application of O-phen, the antioxidant enzyme (superoxide dismutase, catalase, ascorbate peroxidase and monodehydroascorbate reductase) activity was significantly decreased by exogenous O-phen in plants. Furthermore, further analysis showed that the antioxidant enzyme activity positively and closely correlated with the level of bound PAs in TGaseOE plant. Together, these results uncovered a probably function mechanism of TGase-mediated antioxidant enzyme activity to reduced salt-induced oxidative damage, which is partially depended on bound PAs accumulation.