Hydrogen sulfide donor sodium hydrosulfide-induced accumulation of betaine is involved in the acquisition of heat tolerance in maize seedlings

Hydrogen sulfide (H 2 S) which is involved in plant growth, development, and the acquisition of stress tolerance including heat tolerance, is considered as the third signal molecule after nitric oxide and reactive oxygen species, while betaine is an important osmolyte with multiple physiological functions, but interaction between H 2 S and betaine in the acquisition of heat tolerance in plants is not clear. In this study, pretreatment with H 2 S donor sodium hydrosulfide (NaHS), as comparison to the control seedlings without NaHS treatment, significantly improved the activity of betaine aldehyde dehydrogenase (BADH), a key enzyme in the biosynthesis of betaine, which in turn induced the accumulation of endogenous betaine, eventually enhanced the survival percentage of maize seedlings under heat stress. In contrast, these effects induced by NaHS were eliminated by application of H 2 S scavenger hypotaurine and inhibitor of BADH disulfiram, respectively, indicating that H 2 S-improved heat tolerance of maize seedlings may be closely associated with the accumulation of endogenous betaine by activating the activity of BADH. In addition, exogenous betaine treatment enhanced the content of endogenous betaine, followed by improved the survival percentage of maize seedlings compared with the control without betaine treatment. All of the above-mentioned results showed that NaHS pretreatment could induce the accumulation of endogenous betaine by increasing BADH activity, and this accumulation may be involved in the acquisition of heat tolerance of maize seedlings, bridging a gap between H 2 S and betaine in the acquisition of heat tolerance in plants.