Hydrogen sulfide (H2S) and potassium (K+) synergistically induce drought stress tolerance through regulation of H+-ATPase activity, sugar metabolism, and antioxidative defense in tomato seedlings

Key message Exogenous potassium (K + ) and endogenous hydrogen sulfide (H 2 S) synergistically alleviate drought stress through regulating H + -ATPase activity, sugar metabolism and redox homoeostasis in tomato seedlings . Present work evaluates the role of K + in the regulation of endogenous H 2 S signaling in modulating the tolerance of tomato ( Solanum lycopersicum L. Mill.) seedlings to drought stress. The findings reveal that exposure of seedlings to 15% (w/v) polyethylene glycol 8000 (PEG) led to a substantial decrease in leaf K + content which was associated with reduced H + -ATPase activity. Treatment with sodium orthovanadate (SOV, PM H + -ATPase inhibitor) and tetraethylammonium chloride (TEA, K + channel blocker) suggests that exogenous K + stimulated H + -ATPase activity that further regulated endogenous K + content in tomato seedlings subjected to drought stress. Moreover, reduction in H + -ATPase activity by hypotaurine (HT; H 2 S scavenger) substantiates the role of endogenous H 2 S in the regulation of H + -ATPase activity. Elevation in endogenous K + content enhanced the biosynthesis of H 2 S through enhancing the synthesis of cysteine, the H 2 S precursor. Synergistic action of H 2 S and K + effectively neutralized drought stress by regulating sugar metabolism and redox homoeostasis that resulted in osmotic adjustment, as witnessed by reduced water loss, and improved hydration level of the stressed seedlings. The integrative role of endogenous H 2 S in K + homeostasis was validated using HT and TEA which weakened the protection against drought stress induced impairments. In conclusion, exogenous K + and endogenous H 2 S regulate H + -ATPase activity which plays a decisive role in the maintenance of endogenous K + homeostasis. Thus, present work reveals that K + and H 2 S crosstalk is essential for modulation of drought stress tolerance in tomato seedlings. Graphic abstract