Npgrj_ng_2056 901..905

It is commonly thought that deep phylogenetic conservation of plant microRNAs (miRNAs) and their targets1,2 indicates conserved regulatory functions. We show that the blind (bl) mutant of Petunia hybrida3 and the fistulata (fis) mutant of Antirrhinum majus4,5, which have similar homeotic phenotypes, are recessive alleles of two homologous miRNA-encoding genes. The BL and FIS genes control the spatial restriction of homeotic class C genes6,7 to the inner floral whorls, but their ubiquitous early floral expression patterns are in contradiction with a potential role in patterning C gene expression. We provide genetic evidence for the unexpected function of the MIRFIS and MIRBL genes in the center of the flower and propose a dynamic mechanism underlying their regulatory role. Notably, Arabidopsis thaliana, a more distantly related species, also contains this miRNA module but does not seem to use it to confine early C gene expression to the center of the flower.