The secret to leaf forever: Mechanisms controlling simple leaf development (Nature Plants)

The final shape of a leaf is a consequence of differential growth at its margins. Simple (or lightly serrated) leaves result from limited growth in the margins, while compound leaves result from a constant initiation of leaflets. A recent work by Challa, Rath, and colleagues dissected the regulatory network controlling leaf shape. Two modules control the growth at the leaf margin, one involving CINCINNATA-like TCP (CIN-TCP) and the other that includes some class-II KNOTTED1-LIKE (KNOX-II) transcription factors. Mutants affected in any of these modules display deep serrations in the leaves. The combined suppression of the CIN-TPC and KNOX-II modules causes the continued emergence of leaflets, resembling a compound leaf. In this background, the inactivation of both CIN-TCP and the KNOX-II modules allows the enhanced activity of KNOX-I genes (KNAT2, KNAT6) and CUC2. This circuit restores meristematic features in the leaf margins and causes the emergence of leaflets. The absence of the suppression modules confers indeterminate growth features to the leaves. (Summary by Humberto Herrera-Ubaldo @herrera_h) Nature Plants 10.1038/s41477-021-00965-3