SPATULA regulates CLAVATA1 and GCN5 genetic interaction during gynoecium development in Arabidopsis thaliana

GENERAL CONTROL NONDEREPRESSIBLE 5 (GCN5) is a histone acetyltransferase in Arabidopsis thaliana that plays a key role in various biological processes, including the development of flowers and inflorescences. We have shown that GCN5 genetically interacts with the CLAVATA (CLV) signalling pathway, potentially affecting gynoecium and inflorescence development by modulating auxin and cytokinin dynamics and regulating WUSCHEL (WUS) expression. The bHLH transcription factor SPATULA (SPT) is also a crucial regulator of gynoecium formation. In clv1gcn5 double mutants, notable phenotypic changes include abnormal gynoecia characterised by reduced or missing valves, enlarged stigmas, elongated gynophores, and a fasciated inflorescence meristem that resembles a callus during later developmental stages. Interestingly, mutations in SPT partially rescue the gynoecial defects of clv1gcn5 mutants by restoring ovary formation. Gene expression analyses indicate that in clv1gcn5 gynoecia, genes involved in auxin and cytokinin homeostasis, as well as those governing apical-basal, mediolateral, and abaxial-adaxial axis formation, are misregulated. This misexpression is partially corrected in the sptclv1gcn5 triple mutant. These findings suggest that SPT, CLV1, and GCN5 collectively function as essential regulators of gynoecium development where the genetic interaction between CLV1 and GCN5 is mediated through SPT.