Exogenous hydrogen sulfide regulates plant salt stress response through the Arabidopsis splicing factor AtU2AF65a

Hydrogen sulfide (H₂S) functions as a signaling molecule that modulates plant development and stress adaptation. Alternative splicing (AS) is a crucial co-transcriptional regulatory mechanism by which plants adapt to environmental stresses. Splicing factors regulate changes in the splicing patterns of target genes and play important roles in plant responses to abiotic stresses. Previous investigations had revealed that the splicing protein U2AF65a and H₂S both contributed to plant adaptation under abiotic stresses. In the current study, we found that atu2af65a-4 mutant plants exhibited increased sensitivity to salt stress, while the effect of H₂S in alleviating salt stress in the wild-type plant was significantly suppressed in this mutant. Overexpressing the three alternative AtU2AF65a transcripts partially restored salt stress tolerance in the atu2af65a-4 mutants, with AtU2AF65a.1 exhibiting the most pronounced response to H₂S. RNA immunoprecipitation assays demonstrated that H₂S enhanced the association of AtU2AF65a.1 with the pre-mRNAs of the salt-stress- responsive genes CRK42 and VOZ1. Additionally, the regulatory effect of H₂S on the AS of salt-stress-responsive genes (including ABA3, VOZ1, AtSFT12, YY1, RBGD4, and CRK42) was diminished in the atu2af65a-4 mutants. These results indicate that H₂S can enhance plant tolerance to salt stress through the action of AtU2AF65a, with AtU2AF65a.1 being a key transcript in H₂S-mediated salt stress tolerance.