Endogenous hydrogen sulfide regulated by calcium is involved in thermotolerance in tobacco Nicotiana tabacum L. suspension cell cultures

Abstract

Calcium (Ca2+)/calmodulin (CaM), a core component of calcium messenger system, is a multiple second messenger that is involved in multiple stress tolerance including heat tolerance in plants, hydrogen sulfide (H2S) is fast emerging similar functions, but Ca2+ and H2S crosstalk in the acquisition of thermotolerance is not completely understood. In this article, Ca2+ and CaM activated the activity of cysteine desulfhydrase (L-DES), followed by inducing endogenous H2S accumulation in tobacco suspension cultured cells, while treatment with Ca2+ chelator ethylene glycol-bis(b-aminoethylether)-N,N,N′,N′-tetraacetic acid and CaM antagonists chlorpromazine lowered L-DES activity and H2S accumulation. Interestingly, Ca2+- and CaM-activated L-DES activity and endogenous H2S accumulation were eliminated by H2S synthesis inhibitors DL-propargylglycine (PAG), aminooxy acetic acid (AOA), potassium pyruvate (PP) and hydroxylamine (HA), and the H2S scavenger hypotaurine (HT), indicating that Ca2+ and CaM regulated endogenous H2S generation via activating L-DES activity in tobacco cells. Furthermore, H2S donor NaHS, Ca2+ and CaM treatment alone significantly improved the thermotolerance of tobacco cells, and heat tolerance induced by Ca2+ and CaM was enhanced by exogenous NaHS, while weakened by PAG, AOA, PP, HA or HT. All above-mentioned results suggest that endogenous H2S generated by L-DES was involved, at least partly, in the thermotolerance induced by Ca2+ and CaM in tobacco suspension cell cultures.