H2S acting as a downstream signaling molecule of SA regulates Cd tolerance in Arabidopsis

In plants, salicylic acid (SA) acting as one of the signaling molecules can regulate and respond to cadmium (Cd) stress. It is well known that hydrogen sulfide (H2S) could alleviate toxicity of Cd stress but the crosstalk between SA and H2S in regulating Cd stress still remains unclear. We studied on it through the physiological and biochemical method together with the microstructure synthesis. Our results indicated that the plants exhibited enhanced tolerance to Cd when pretreated with SA, which included weakening oxidative damage and intensifying photosynthesis as well as boosting L-cysteine desulfhydrase (LCD) activity and raising the content of endogenous H2S. In parallel, the plants pretreated with NaHS, a donor of H2S, showed a stronger ability to tolerate Cd stress, SA- pretreated plants presented normal growth and meanwhile the content of chlorophyll and the microstructure of roots were significantly different compared to those treated with Cd only. By contrast, with the same treatments, the positive function and effect of SA on the LCD-knockout mutants, lcd was not observed. Pharmacological experiments further testified these results. All of the results suggest that H2S may be a downstream signal molecule in SA-induced Cd tolerance of Arabidopsis.