Hydrogen sulfide induced by nitric oxide mediates ethylene-induced stomatal closure of Arabidopsis thaliana

Pharmacological, laser scanning confocal microscopic （LSCM）, real-time PCR and spectrophotographic approaches are used to study the roles of hydrogen sulfide （H2S） and nitric oxide （NO） in signaling transduction of stomatal movement response to ethylene in Arabidopsis thaliana. In the present study, inhibitors of H2S synthesis were found to block ethylene-induced stomatal closure of Arabidopsis. Treatment with ethylene induced H2S generation and increased L-/D-cysteine desulfhydrase （pyridoxal- phosphate-dependent enzyme） activity in leaves. Quantitative PCR analysis showed AtL-CDes and AtD-CDes transcripts were induced by ethylene. It is suggested that ethylene-induced H2S levels and L-/D-cysteine desulfhydrase activity decreased when NO was compromised. The data clearly show that ethylene was able to induce H2S generation and stomatal closure in Atnoal plants, but failed in the Atnial,nia2 mutant. Inhibitors of H2S synthesis had no effect on ethylene-induced NO accumulation and nitrate reductase （NR） activity in guard cells or leaves of Arabidopsis, whereas ethylene was able to induce NO synthesis. There- fore, we conclude that H2S and NO are involved in the signal transduction pathway of ethylene-induced stomatal closure. In Arabidopsis, H2S may represent a novel downstream indicator of NO during ethylene-induced stomatal movement.