A GPS2-like protein interacts with HOS15 and HDA6 to form a repressor complex that regulates ABA signaling and drought adaptation in Arabidopsis

Plants rely on chromatin-mediated transcriptional control to fine-tune stress responses, yet the evolutionary conservation and functional adaptation of repressor complexes remain incompletely understood. Here, we identify GPS2-like protein (GPL) as the missing component of the plant equivalent of the animal NR-co-repressor complex. GPL interacts with HOS15, PWR, and HDA6/HDA9 to form a chromatin repressor module that suppresses abscisic acid (ABA)-responsive genes. Loss-of-function gpl-mutants exhibit ABA hypersensitivity and enhanced drought tolerance, while overexpression confers ABA insensitivity. Mechanistically, GPL promotes histone H3K9 deacetylation and dimethylation at stress-responsive loci and stabilizes HOS15 to ensure its nuclear retention. Global RNA-seq revealed widespread de-repression of ABA-responsive transcriptional networks in gpl-mutants. Under stress, ABA destabilizes the GPL-HOS15 complex, releasing repression and activating defense genes. These findings establish GPL as the plant homolog of GPS2 and reveal that the GPL-HOS15 repressor complex acts as a chromatin-mediated rheostat to dynamically balance growth and drought adaptation. Our work provides mechanistic insight into stress-responsive chromatin remodeling and identifies GPL as a potential target for engineering climate-resilient crops.