Hydrogen sulphide may be a novel downstream signal molecule in nitric oxide-induced heat tolerance of maize (Zea mays L.) seedlings.

Nitric oxide (NO) is a second messenger with multifunction that is involved in plant growth, development and the acquisition of stress tolerance. In recent years, hydrogen sulphide (H(2)S) has been found to have similar functions, but crosstalk between NO and H(2)S in the acquisition of heat tolerance is not clear. In this study, pretreatment with the NO donor sodium nitroprusside (SNP) improved the survival percentage of maize seedlings and alleviated an increase in electrolyte leakage and a decrease in tissue vitality as well as accumulation of malondialdehyde, indicating that pretreatment with SNP improved the heat tolerance of maize seedlings. In addition, pretreatment with SNP enhanced the activity of L-cystine desulfhydrase, which, in turn, induced accumulation of endogenous H(2)S, while application of H(2)S donors, NaHS and GYY4137, increased endogenous H(2)S content, followed by mitigating increase in electrolyte leakage and enhanced survival percentage of seedlings under heat stress. Interestingly, SNP-induced heat tolerance was enhanced by application of NaHS and GYY4137, but was eliminated by inhibitors of H(2)S synthesis DL-propargylglycine, aminooxyacetic acid, potassium pyruvate and hydroxylamine, and the H(2)S scavenger hypotaurine. All of the above-mentioned results suggest that SNP pretreatment could improve heat tolerance, and H(2)S may be a downstream signal molecule in NO-induced heat tolerance of maize seedlings.