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

Previous results have shown that hydrogen sulfide (HS), mainly catalyzed by l-cysteine desulfhydrase (DES) in plants, triggers adventitious rooting. The objective of this study was to test whether HS is involved in methane (CH)-induced adventitious root development in cucumber explants. First, we observed that the activities of DES, endogenous HS production, and thereafter adventitious root development were induced by CH and NaHS (an HS donor). Some responses were sensitive to hypotaurine (HT; a scavenger of HS), showing that endogenous HS production and adventitious rooting were obviously blocked. The development of adventitious root primordia was also impaired. Further molecular evidence revealed that CH-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 CH-elicited S-sulfhydration during the above responses was also sensitive to the removal of endogenous HS, suggesting the requirement of HS. Taken together, our results reveal a vital role of endogenous HS in CH-triggered cucumber adventitious root development, and thus provide a comprehensive window into the complex signaling transduction pathway in CH-mediated root organogenesis.