Figure 6: Genetic model for specification of meristem identity in the compound inflorescence of pea.

(a) In the pea compound inflorescence, expression of DET (orthologue of TFL1) in the I₁, VEG1 in the I₂ and PIM (orthologue of AP1) in the floral meristems are required for those meristems to acquire their identity. Expression of these genes in their correct domains is maintained by a network of mutual repressive interactions. (b) The genetic model explains the phenotypes of the pea meristem identity mutants. The absence of DET in the det mutant allows expression of VEG1 in the SAM, which gets converted into an I₂. The absence of PIM allows the expression of VEG1 in the floral meristem, which gets converted into a proliferative I₂. In absence of VEG1, DET is expressed in all the meristems in the apex, and they get converted into I₁s. (c) Meristem identity in the simple inflorescence of Arabidopsis is maintained by a similar genetic network than in pea, but VEG1 function is absent and I₂ meristem is not formed.