LEUNIG and SEUSS co-repressors regulate miR172 expression in Arabidopsis flowers.

Central to the ABCE model of flower development is the antagonistic interaction between class A and class C genes. The molecular mechanisms underlying the A-C antagonism are not completely understood. In Arabidopsis thaliana, miR172 is expressed in the inner floral whorls where it downregulates the class A gene APETALA 2 (AP2). However, what controls this predominantly inner whorl-specific expression of miR172 is not known. We show that the LEUNIG (LUG) and SEUSS (SEU) co-repressors repress miR172 expression in the outer whorls of A. thaliana flowers. The recruitment of LUG/SEU to the miR172 promoters is dependent on AP2, suggesting that AP2 represses the expression of its cognate microRNA. Our study provides new insights into the molecular mechanisms underlying the A-C antagonism and shed light on the transcriptional regulation of miR172 during flower development.