Fig. 6. YABBY and lamina expansion. (A) In kan1-2 kan2-1 syd-2 leaves, no abaxial outgrowths form, and the leaves are radialized. (B) PHB, normally confined to the adaxial regions of the developing leaves, is expressed throughout kan1 kan2 syd leaves. (C,D) Consistent with YABBY gene expression being responsible for the abaxial outgrowths on kan1-2 kan2-1 leaves, FIL expression is greatly reduced in kan1-2 kan2-1 syd-2 triple mutants as seen in both longitudinal (C) and transverse (D) sections of developing leaves. (E,F) In developing Solanum tuberosum leaves (E), YABBY1 expression is associated with abaxial regions in which cells are cytoplasmically dense (F). These regions include the entire abaxial domain in young leaf primordia (*), and in differentiating leaves, the marginal abaxial regions (arrows) and towards the center of the leaf, along the boundary between the abaxial and adaxial domains (arrowhead). lp, leaf primordium; m, meristem.