Figure 4.

Model for Radiality Establishment at the Top End of a Growing Organ

Model showing how auxin-signaling accumulation (green) through polar auxin transport (PAT, arrows) presides over the bilateral-to-radial symmetry switch during gynoecium development. At stage 5, auxin signaling peaks at the lateral top part of the gynoecium, sustaining the apical-basal growth. At stages 8 and 9, SPT and IND repress PID expression, thus promoting apolar PIN localization leading to accumulation of auxin signaling at the medial top and subsequently formation of the radial auxin ring at stages 10 and 11.