Hydrogen sulfide protects soybean seedlings against drought-induced oxidative stress

Increasing evidence indicates that hydrogen sulfide (H2S) is the third gas signal molecule'' after NO and CO in animal. In the present study, we found that soybean (Glycine max L.) seedlings sprayed with exogenous H2S donor NaHS prolonged the longer survival time of life, and enlarged higher biomass of both leaf and root than in non-sprayed controls under continuous drought stress. With the continuous drought stress, the content of chlorophyll in the leaves of both Xu-1 and Xu-6 cultivar of soybean decreased dramatically. The drought-induced decrease in chlorophyll could be alleviated by spraying H2S donor. It was also shown that spraying with H2S donor dramatically retained higher activities of superoxide dismutase (SOD, EC 1.1.5.1.1), catalase (CAT, EC1.11.1.6) and lower activity of lipoxygenases (LOX, EC 1.13.11.12), delayed excessive accumulation of malondialdehyde, hydrogen peroxide, and superoxide anion (O-2(center dot-)) compared with the control. These results suggest that H2S can increase drought tolerance in soybean seedlings by acting as an antioxidant signal molecule for the response.