ON THE COVER

Flower development requires accurate patterning of the floral organ identity genes since their misexpression leads to homeotic conversion of one floral organ type into another. The cover image illustrates a subtle defect in the patterning of the homeotic B-class genes in the petunia ben mutant, leading to a partial homeotic conversion of sepals into petals. Morel et al. (pages 1605–1621) analyzed the mechanisms that pattern the floral homeotic B- and C-functions during petunia flower development and discovered that BEN, a TOE-type AP2, confines the C-function to the inner petunia floral whorls, in parallel with the microRNA BLIND. In turn, they show that the petunia AP2-type ROB genes repress the B-function (but not the C-function) in the first floral whorl, together with BEN. These findings suggest that the molecular mechanisms controlling the spatial restriction of the floral organ identity genes are more diverse than the well-conserved B and C floral organ identity functions. Photo by Michiel Vandenbussche.