Effects of glutathione on waterlogging-induced damage in sesame crop

Sesame (Sesamum indicum) is an important oil crop, occupying the seventh position in the edible oil industry; however, it is relatively sensitive to waterlogging (WL) stress. Reduced glutathione (GSH) is known to have mitigating effects against various abiotic stresses in plants; however, its exploration to improve WL tolerance in sesame is still elusive. In this study, we investigated the multiple effects of exogenously applied GSH in sesame plants subjected to WL for 3 days. Our results showed improvement in growth and biomass production of GSH-sprayed waterlogged sesame when compared with WL-stressed counterpart alone. The improved performance of GSH-sprayed WL-stressed plants was supported by the increased leaf area, the levels of photosynthetic pigments and gas exchange attributes, and chlorophyll fluorescence parameters. Exogenous GSH treatment significantly increased the levels of total soluble sugars and total free amino acids in the leaves of sesame plants for the improvement of water balance under WL conditions. Accumulations of superoxide and hydrogen peroxide, enhancement of malondialdehyde level, and electrolyte leakage in sesame leaves indicated evident oxidative damage induced by WL. On the other hand, exogenous GSH application diminished oxidative stress by enhancing the activities of catalase, ascorbate peroxidase, peroxidase, glutathione peroxidase, and glutathione S-transferase, as well as total flavonoid and GSH levels in the leaf tissues. Furthermore, GSH supplementation to WL plants increased the transcript levels of numerous antioxidant defense-related genes, such as SiCAT1, SiCATX1, SiAPX3, SiPOD40, SiPOD44, SiGPX4, SiPHGPX1, SiGSTU23, and SiGSTU25 in shoots, corresponding to enhanced activities of respective antioxidant enzymes. Our results highlight the potential roles of GSH in modulating adaptive mechanisms of sesame plants for reduction of WL-induced damage, and this GSH-mediated effective strategy could be implemented at the field level to sustain sesame production under WL conditions.