Hydrogen Sulfide Regulates Ethylene-induced Stomatal Closure in Arabidopsis thaliana

Hydrogen sulfide (H2S) is a newly-discovered signaling molecule in plants and has caused increasing attention in recent years, but its function in stomatal movement is unclear. In plants, H2S is synthesized via cysteine degradation catalyzed by D-/L-cysteine desulfhydrase (D-/L-CDes). AtD-/L-CDes::GUS transgenic Arabidopsis thaliana (L.) Heynh. plants were generated and used to investigate gene expression patterns, and results showed that AtD-/L-CDes can be expressed in guard cells. We also determined the subcellular localization of AtD-/L-CDes using transgenic plants of AtD-/L-CDes::GFP, and the results showed that AtD-CDes and AtL-CDes are located in the chloroplast and in the cytoplasm, respectively. The transcript levels of AtD-CDes and AtL-CDes were affected by the chemicals that cause stomatal closure. Among these factors, ACC, a precursor of ethylene, has the most significant effect, which indicates that the H2S generated from D-/L-CDes may play an important role in ethylene-induced stomatal closure. Meanwhile, H2S synthetic inhibitors significantly inhibited ethylene-induced stomatal closure in Arabidopsis. Ethylene treatment caused an increase of H2S production and of AtD-/L-CDes activity in Arabidopsis leaves. AtD-/L-CDes over-expressing plants exhibited enhanced induction of stomatal closure compared to the wild-type after ethylene treatment; however, the effect was not observed in the Atd-cdes and Atl-cdes mutants. In conclusion, our results suggest that the D-/L-CDes-generated H2S is involved in the regulation of ethylene-induced stomatal closure in Arabidopsis thaliana.