FLORICAULA - A HOMEOTIC GENE REQUIRED FOR FLOWER DEVELOPMENT IN ANTIRRHINUM-MAJUS

Plants carrying the floricaula (flo) mutation cannot make the transition from inflorescence to floral meristems and have indeterminate shoots in place of flowers. The flo-613 allele carries a Tam3 transposon insertion, which allowed the isolation of the flo locus. The flow gene encodes a putative protein (FLO) containing a proline-rich N-terminus and a highly acidic region. In situ hybridization shows that the flo gene is transiently expressed in the very early stages of flower development. The earliest expression seen is in bract primordia, followed by sepal, petal, and carpal primordia, but no expression is detected in stamen primordia. This pattern of expression has implications for how flo affects phyllotaxis, organ identify, and determinancy. We propose that flo interacts in a sequential manner with other homeotic genes affecting floral organ identity.