Characterization of the floral homeotic gene APETALA1 (AP1) and its role in gene repression in stem cells

For an organism to properly form, fate-specifying genes are intricately controlled to establish a precise pattern of what genes are turned on and turned off throughout development. In the angiosperm, Arabidopsis thaliana, the homeotic gene APETALA1 (AP1) plays a significant role in coordinating this pattern for proper specification of floral organs. Here, we show that mutation of the EAR motif in AP1 leads to misexpression of the petal genes in the sepals demonstrating the EAR motif of AP1 is necessary for repressing these petal genes in the outer whorl. We also show that AP1 may be recruiting the TOPLESS RELATED (TPR1-4) proteins as corepressors for repression of the petal genes. This is supported by the confirmation that AP1 acts as a repressor in the sepal tissues. These results present an addition to the known diverse role of AP1, further characterizing its function in specifying sepal identity.