Hydrogen sulfide enhances salt tolerance in tomato by regulating cell wall degradation in a SlSR3-dependent manner

Abstract

Soil salinization is an important abiotic stress that limits the productivity and quality of horticultural crops. As critical signaling molecules, hydrogen sulfide (H₂S) and calcium ions (Ca^2 +) are crucial in plant stress reponse. However, the molecular basis of their synergistic action in improving salt tolerance in plants is unclear. In this study, tomato (Solanum lycopersicum L.) seedlings were utilized as a material to explore the synergistic effect of H₂S and Ca²⁺ on salt stress tolerance. The results show that exogenous sodium hydrosulfide (NaHS, a H₂S donor) and CaCl₂ independently ameliorated the inhibitory effects of salt stress on tomato seedling growth, with their co-application demonstrating a synergistic alleviation of stress-induced growth impairment. Further studies reveal that H₂S promoted Ca²⁺ level and up-regulated signal-responsive 3 (SR3) expression. SlSR3 knockout mutants were more sensitive to salt stress, whereas overexpression of SlSR3 displayed enhanced salt tolerance. Moreover, SlSR3 conferred protection against salt stress-induced cell wall degradation and sustained its stability by repressing the expression of genes implicated in cell wall degradation. Further results demonstrate that NaHS treatment did not enhance cell wall integrity or salt tolerance in SlSR3 knockout mutants. Conversely, NaHS treatment effectively inhibited cell wall degradation and improved salt tolerance in SlSR3-overexpressing plants. Therefore, SlSR3 is likely implicated in the H₂S-mediated inhibition of cell wall degradation in tomato seedlings under salt stress, ultimately enhancing salt tolerance. This study delineates the mechanistic interplay between H₂S and Ca²⁺ in plant salt tolerance, thereby enhancing the potential for breeding horticultural crops with improved stress resilience.