The histone acetyltransferase GCN5 regulates floral meristem activity and flower development in Arabidopsis

The histone acetyltransferase GENERAL CONTROL NON DEREPRESSIBLE5 (GCN5) participates in various developmental processes in Arabidopsis (Arabidopsis thaliana). Notably, GCN5 ensures proper flower development, but the underlying mechanism remains unknown. Here, we show that during early flower development, GCN5 catalyzes histone acetylation at WUSCHEL (WUS) and CLAVATA3 (CLV3) chromatin, activating their expression. WUS and CLV3 are required for floral meristem (FM) maintenance. Furthermore, we demonstrate that the GCN5–ALTERATION/DEFICIENCY IN ACTIVATION 2 (ADA2) histone acetyltransferase module interacts with the Switch/Sucrose non-fermentable ATPase SPLAYED (SYD) to form a GCN5–ADA2b–SYD ternary complex. The cytokinin responsive type-B Arabidopsis response regulators (ARRs) recruit this ternary complex for WUS activation. During floral organogenesis, PERIANTHIA recruits the GCN5–ADA2b module for AGAMOUS activation, which promotes FM determinacy. GCN5 also activates KNUCKLES, which ensures the timely termination of FM activity. Moreover, GCN5 modulates the expression pattern of the B-class gene APETALA3 and promotes the expression of SUPERMAN and CRABS CLAW, which are required for FM determinacy, thereby safeguarding meristem determinacy and correct floral organ formation. Thus, our study demonstrates the indispensable role of GCN5 in establishing a permissive chromatin environment to regulate the key genes required for precise flower development.