H2S-modulated alternative splicing of the protein phosphatase gene <i>HAB2</i> drives divergent stomatal dynamics in Arabidopsis

Abscisic acid (ABA) serves as a critical regulator of plant adaptive responses to environmental stresses. However, the function of AtHAB2, a member of the ABA signaling component AtPP2C family, remains uncharacterized. As a gasotransmitter, hydrogen sulfide (H2S) plays a vital role throughout the plant life cycle. Our results indicated that exogenous H2S induced stomatal closure in athab2 mutants. Then we characterized that AtHAB2 underwent alternative splicing (AS), generating three transcripts designated AtHAB2.1/2.2/2.3, with AtHAB2.2 targeted for degradation. H2S affected the AS of AtHAB2 through AtRBM25, with AtHAB2.1 and AtHAB2.3 playing distinct roles in H2S-regulated stomatal movement. AtHAB2.1 interacted with AtPYL3/5/6/7/8/9/10/11/12/13, whereas AtHAB2.3 lost this interaction. Additionally, both AtHAB2.1 and AtHAB2.3 physically interacted with AtSnRK2s, but their effects on inhibiting AtOST1 phosphorylation differed significantly. Ultimately, we found that AtHAB2.1 and AtHAB2.3 had opposite functions in ABA sensitivity, stomatal movement, and drought tolerance. Overall, H2S regulates the AS pattern of AtHAB2 through AtRBM25, thereby promoting stomatal closure. In this regard, AtHAB2.1 and AtHAB2.3 play significantly different roles. These results not only provide the possibility of a new mechanism by which H2S regulates stomatal movement by altering the AS pattern but also elucidate the functional differences between AtHAB2.1 and AtHAB2.3.