Figure 5: VEG1 is expressed in I₂ meristems of wild type and in ectopic I₂ meristems of pea inflorescence mutants.

(a) Inflorescence of a pea wild-type plant. The inflorescence apex (arrowhead) exhibits indeterminate growth. (b) SEM image showing the different meristem types in a wild-type inflorescence. The SAM is a primary inflorescence (I₁) meristem that has produced secondary inflorescence (I₂) meristems, one of which has produced a floral meristem (F). (c) In situ hybridization of VEG1 mRNA in the inflorescence apex of the wild type. VEG1 is expressed in the lateral I₂ meristems, not in the I₁ neither in the floral meristem (F). (d) In situ hybridization of PIM mRNA in the wild-type inflorescence, in a contiguous section to that in (c). The PIM signal is observed only in the floral meristem, which does not express VEG1. (e) Inflorescence of a det mutant, where the apex has converted into an I₂ (arrowhead). The terminal I₂ stem subtends a flower and ends into a stub (arrowhead in inset). (f) SEM image of a det inflorescence apex. The SAM has the characteristic shape of an I₂ meristem (I₂*). (g) Schematic representation of meristem identity in the det inflorescence. V, vegetative meristem; orange triangles, stubs. (h) Inflorescence of a pim mutant, showing proliferative I₂ s (arrowhead) with abnormal flowers. (i) SEM image of a pim inflorescence apex, showing I₂s that, rather than flowers, produce new I₂s (I₂*). One of the proliferative I₂s is producing a floral primordium (F*). (j) Schematic representation of meristem identity in the pim inflorescence. (k) In situ hybridization of VEG1 mRNA in the inflorescence apex of det. In the det mutant VEG1 is also expressed in the SAM (I₂*), which is converted into an I₂. (l) In situ hybridization of VEG1 mRNA in the inflorescence apex of pim. Expression of VEG1 is observed not only in the lateral I₂s but also in the meristem being formed by the I₂ at the right (I₂*), which is converted from a floral meristem to an I₂ meristem. Scale bars, 100 μm.