Alternative splicing of WRKY55 orchestrates ABA signaling to enhance plant stress resistance

Plant abiotic stress critically threatens plant survival and agricultural productivity. The phytohormone abscisic acid (ABA) plays a key role in regulating plant acclimation to abiotic stress. Although the perception and activation of ABA signaling have been extensively studied, the molecular regulatory mechanisms that terminate ABA signaling remain largely unknown. Here, we identified WRKY55 as a key regulator of ABA signaling. Disrupting WRKY55 function significantly reduced ABA sensitivity, leading to increased seed germination rates, cotyledon greening rates, and primary root length. Notably, WRKY55 undergoes alternative splicing (AS) to generate two protein isoforms, WRKY55.1 and WRKY55.2, which play opposite roles in ABA-mediated plant development. WRKY55.1 transcript levels gradually increased in response to short-term ABA treatment, followed by a rapid decrease during prolonged ABA treatment. WRKY55.2 transcript levels gradually increased under prolonged ABA treatment. We demonstrated that WRKY55.1 directly promotes the expression of ABSCISIC ACID INSENSITIVE5 (ABI5) to activate ABA responses. Notably, WRKY55.2 interacts with WRKY55.1 to suppress the direct activation of ABI5 expression. Moreover, WRKY46 interacts with WRKY55.1 to antagonistically regulate ABI5 expression. Collectively, our study reveals that WRKY55 acts as a master regulator that orchestrates both the activation and desensitization of ABA signaling, thereby enhancing plant resistance and acclimation under stress conditions.