Figure 4.

Influence of the ad-ab boundary on leaf growth. (A) Illustration showing how the shape of the auxin-responsive ad-ab boundary (blue) together with auxin (yellow) influences the configuration of organ founder cells (domain outlined by dashed line). As the boundary represents where response to auxin is maximized, cells farther away from the boundary are not recruited. As a consequence, while a broader auxin distribution promotes widening of the leaf primordium along the ad-ab boundary, its thickness across the ad-ab boundary remains unchanged. (B) Changes to the configuration of adaxial (red) and abaxial (green) cell types in the SAM mean that the spatial configuration of the auxin responsive boundary (blue) in relation to organ founder cells (dashed outline) changes. In turn, this can result in dramatic alterations to leaf morphology and cell type patterning. The top configuration shows wild-type development while the other configurations show alterations caused by ectopic expression of KAN1 in the SAM central zone.