The phytohormone abscisic acid (ABA) plays pivotal roles in triggering stomatal closure and facilitating adaptation of plants to drought stress. Hydrogen sulfide (H₂S), a small signaling gas molecule, is involved in ABA-dependent stomatal closure. However, how H₂S regulates ABA signaling remains largely unclear. Here, we show that ABA induces the production of H₂S catalyzed by L-CYSTEINE DESULFHYDRASE1 (DES1) in guard cells, and H₂S in turn positively regulates ABA signaling through persulfidation of Open Stomata 1 (OST1)/SNF1-RELATED PROTEIN KINASE2.6 (SnRK2.6). Two cysteine (Cys) sites, Cys131 and Cys137, which are exposed on the surface of SnRK2.6 and close to the activation loop, were identified to be persulfidated, which promotes the activity of SnRK2.6 and its interaction with ABA response element-binding factor 2 (ABF2), a transcription factor acting downstream of ABA signaling. When Cys131, Cys137, or both residues in SnRK2.6 were substituted with serine (S), H₂S-induced SnRK2.6 activity and SnRK2.6–ABF2 interaction were partially (SnRK2.6^C131S and SnRK2.6^C137S) or completely (SnRK2.6^C131SC137S) compromised. Introduction of SnRK2.6^C131S, SnRK2.6^C137S, or SnRK2.6^C131SC137S into the ost1-3 mutant could not rescue the mutant phenotype: less sensitivity to ABA- and H₂S-induced stomatal closure and Ca²⁺ influx as well as increased water loss and decreased drought tolerance. Taken together, our study reveals a novel post-translational regulatory mechanism of ABA signaling whereby H₂S persulfidates SnRK2.6 to promote ABA signaling and ABA-induced stomatal closure.

植物激素脱落酸（ABA）在触发气孔关闭和促进植物适应干旱胁迫方面起着关键作用。硫化氢（H ₂ S）是一种小的信号气体分子，与ABA依赖的气孔闭合有关。但是，H ₂ S如何调节ABA信号在很大程度上尚不清楚。在这里，我们表明，ABA诱导产生H的₂小号催化由L-半胱氨酸DESULFHYDRASE1（DES1）中保卫细胞和H ₂S通过开放气孔1（OST1）/ SNF1相关蛋白激酶2.6（SnRK2.6）的过硫化反过来正调控ABA信号传导。暴露在SnRK2.6表面并靠近激活环的两个半胱氨酸（Cys）位点Cys131和Cys137被鉴定为被过硫化，从而促进了SnRK2.6的活性及其与ABA反应元件的相互作用-结合因子2（ABF2），一种在ABA信号传导下游起作用的转录因子。当Cys131，Cys137，或在SnRK2.6两个残基被丝氨酸（S）取代的，H ₂ S-诱导SnRK2.6活性和SnRK2.6-ABF2相互作用是部分（SnRK2。6 ^C131S和SnRK2。6个^C137S）或完全（SnRK2。6 ^C131SC137S）已损坏。SnRK2的简介。6 ^C131S，SnRK2。6 ^C137S或SnRK2。6个^C131SC137S入ost1-3突变体不能挽救突变表型：不敏感性ABA-和H ₂ S-诱导的气孔关闭和Ca ²⁺内流，以及提高的水损失和降低的耐旱性。综上所述，我们的研究揭示了ABA信号转导后的新调节机制，其中H ₂ S过硫化SnRK2.6以促进ABA信号转导和ABA诱导的气孔关闭。