Involvement of sulfhydryl compounds and antioxidant enzymes in H2S-induced heat tolerance in tobacco (Nicotiana tabacum L.) suspension-cultured cells

Abstract

Hydrogen sulfide (H2S) is a multifunctional second messenger involved in plant growth, development, and acquisition of stress tolerance, including heat tolerance, but the mechanism of H2S-induced heat tolerance in tobacco suspension-cultured cells is not completely clear. This study investigated the effects of pretreatment with the H2S donor sodium hydrosulfide (NaHS) and its precursors cysteine and potassium bisulfite (KHSO3) on the heat tolerance of tobacco suspension-cultured cells and the involvement of sulfhydryl compounds and antioxidant enzymes in conferring heat tolerance. Pretreatment with NaHS, cysteine, and KHSO3 significantly increased the survival percentage of tobacco suspension-cultured cells under heat stress, while treatment with the H2S scavenger hypotaurine in combination with NaHS eliminated heat tolerance induced by treatment with NaHS alone. In addition, NaHS treatment increased the levels of water-soluble sulfhydryl compounds such as H2S, total sulfhydryl compounds, total sulfhydryl proteins, cysteine, and glutathione (GSH) as well as the activities of antioxidant enzymes superoxide dismutase (SOD), catalase (CAT), guaiacol peroxidase (GPX), and glutathione reductase (GR) under normal culture conditions (26°C). Under heat stress at 43°C, the levels of water-soluble sulfhydryl compounds and the activities of antioxidant enzymes all dropped, but the cells treated with NaHS sustained significantly higher levels of water-soluble sulfhydryl compounds and activities of antioxidant enzymes than the control. These results suggest that the pretreatment with NaHS could improve the heat tolerance of tobacco suspension-cultured cells and that the acquisition of this heat tolerance is caused by the elevated levels of water-soluble sulfhydryl compounds and elevated activities of antioxidant enzymes induced by NaHS.