Histone Acetyltranserase GCN5 is required for floral meristem regulation and proper flower development in Arabidopsis

The histone acetyltransferase GENERAL CONTROL NON-REPRESSED PROTEIN5 (GCN5) participates in various developmental processes in Arabidopsis. It has been noted that GCN5 also regulates proper floral development, but the underlying mechanism remains unknown. Here we show that during innital flower development, GCN5 catalyzes histone acetylation at WUS and CLV3 chromatin for their active expression which are both required for floral meristem (FM) maintenance. Further, we demonstrate that the histone acetyltransferase module GCN5-ALTERATION/DEFICIENCY IN ACTIVATION 2b (ADA2b) can interact with the active SWI/SNF chromatin remodeling protein SPLAYED (SYD) to form the GCN5-ADA2b-SYD ternary protein complex, which can be recruited by cytokinin responsive type-B ARR transcription factors for WUS activation. During floral organongensis, the GCN5-ADA2b module is recruited by PERIANTHIA (PAN) for AGAMOUS (AG) activation, which promotes floral meristem determinacy. GCN5 also activates KNUCKLES (KNU) that timely terminates FM activity. Moreover, by modulating the expression pattern of B-class gene APETALA3 (AP3) and promoting expression of SUPERMAN (SUP) and CRABS CLAW (CRC) that are both required for FM determinacy, GCN5 safeguards correct reproductive floral organ formation. Thus, our study demonstrates an indispensable role of GCN5, which provides permissive chromatin environment for the above key genes required for the precise flower development.