The Regulation of Dorsiventral Symmetry in Plants

The higher plant shoots are generally radially symmetrical; leaves produced at the shoot apex are dorsiventral while axillary shoots again show radial symmetry. Recently analyzed mutants in different plants indicate that the proper definition of adaxial and abaxial identities is necessary to generate a leaf margin and dorsiventral symmetry, Two genes important in the regulation of transsectional leaf symmetry are PHANTASTICA (a MYB (Myeloblastosis oncogene)-domain transcription factor) and KNOTTED1-like genes (homeodomain transcription factors). We review these results in light of hypotheses about the evolutionary origin of leaves and discuss similarities of mutant phenotypes to unifacial l…