Activation of a floral homeotic gene in Arabidopsis

The patterned expression of floral homeotic genes in Arabidopsis depends on the earlier action of meristem-identity genes such as LEAFY, which encodes a transcription factor that determines whether a meristem will generate fl owers instead of Leaves and shoots. The LEAFY protein, which is expressed t hroughout the flower, participates in the activation of homeotic genes, whi ch are expressed in specific regions of the flower. Analysis of a LEAFY-res ponsive enhancer in the homeotic gene AGAMOUS indicates that direct interac tion of LEAFY with this enhancer is required for its activity in plants. Th us, LEAFY is a direct upstream regulator of floral homeotic genes.