C-terminal domain of APETALA1 is essential for its functional divergence from CAULIFLOWER in Arabidopsis

APETALA1 (AP1) and CAULIFLOWER (CAL) are involved in floral meristem identity and suppress the inflorescence meristem program in flower meristem in Arabidopsis thaliana. Based on the ap1 mutant phenotype genetic studies demonstrated that it is involved in sepal and petal identity specification as well as bract suppression in flower. Despite having high sequence similarity with AP1, its closest paralog CAL does not show a defect in flower development. In ap1 cal1 double mutant, floral meristem turns into inflorescence meristem resulting in a cauliflower like phenotype. cal mutants appear like wild type, suggesting that AP1 compensates its function. Here, we report that AP1 can replace CAL by interacting its potential interactors. Functional studies using the truncated version of AP1 confirmed that the C-terminal domain of AP1 is exclusively involved in floral organ identity specification.