Hydrogen sulfide acts downstream of methane to induce cucumber adventitious root development

Previous results have shown that hydrogen sulfide (H₂S), mainly catalyzed by l-cysteine desulfhydrase (DES) in plants, triggers adventitious rooting. The objective of this study was to test whether H₂S is involved in methane (CH₄)-induced adventitious root development in cucumber explants. First, we observed that the activities of DES, endogenous H₂S production, and thereafter adventitious root development were induced by CH₄ and NaHS (an H₂S donor). Some responses were sensitive to hypotaurine (HT; a scavenger of H₂S), showing that endogenous H₂S production and adventitious rooting were obviously blocked. The development of adventitious root primordia was also impaired. Further molecular evidence revealed that CH₄-induced gene expression of CsDNAJ-1, CsCDPK1, CsCDPK5, CsCDC6 (a cell-division-related gene), CsAux22D-like, and CsAux22B-like (two auxin-signaling genes), several molecular markers responsible for adventitious rooting, were blocked by the co-treatment with HT. The occurrence of CH₄-elicited S-sulfhydration during the above responses was also sensitive to the removal of endogenous H₂S, suggesting the requirement of H₂S. Taken together, our results reveal a vital role of endogenous H₂S in CH₄-triggered cucumber adventitious root development, and thus provide a comprehensive window into the complex signaling transduction pathway in CH₄-mediated root organogenesis.