Hydrogen sulfide mediates ion fluxes inducing stomatal closure in response to drought stress in Arabidopsis thaliana

In many plant species, hydrogen sulfide (H2S) triggers stomatal closure, which is produced mainly by two classes of enzymes, cysteine desulfhydrases (CDes) and O-acetyl-L-serine (thiol) lyases (OASTLs). Stomatal movement is accompanied by several ion fluxes across the plasma membranes of guard cells. In this paper, we detected the fluxes of H+, Ca2+, K+ and Cl- in guard cells of wild-type Arabidopsis thaliana and the mutants associated with H2S production (lcd, OE-LCD, des, OE-DES, oastl-a1, oastl-a2, oastl-b and oastl-c), using a non-invasive micro-test technique. The results showed that endogenous H2S induced a transmembrane K+ efflux, and Ca2+ and Cl- influxes, while not affecting the flow of H+. Furthermore, the K+ channel was the main osmolyte responder during the regulation of stomatal movement by H2S in response to drought stress. Finally, the two classes of enzymes produced H2S, CDes and OASTLs, played different roles in regulating stomatal movements. Thus, H2S mediates ion fluxes inducing stomatal closure in response to drought stress in Arabidopsis thaliana.