The plant-specific LEAFY (LFY) protein is necessary and sufficient for the vital switch from vegetative to reproductive development in dicotyledonous plant species. LFY controls the production of the flowers, which are formed in lieu of secondary inflorescences from the flanks of the shoot apical meristem. Because LFY is required for all of the major features that differentiate flowers from inflorescence branches, it is referred to as a meristem identity gene.
After initiating the meristem identity switch, LFY has a second role in the activation of the floral homeotic genes that specify the identity of organs in the flower. The two roles of LFY are separable genetically and molecularly. LFY exerts its developmental effects by means of transcriptional regulation; LFY has been shown to be a transcription factor in vivo.
Despite the critical importance of this regulator, only three direct targets of LFY have been identified. Two of the targets, AGAMOUS and APETALA3, are floral homeotic genes that act directly downstream of LFY in flower morphogenesis. Only one known direct LFY target gene product, APETALA1 (AP1), acts in the meristem identity pathway.
