Evo-Devo of Leaf Shape Control with a Special Emphasis on Unifacial Leaves in Monocots

In angiosperms, leaves typically develop as three-dimensional structure with dorsoventral, longitudinal, and lateral axes. We have shown that the control of two axes of leaves, longitudinal and lateral axis, can be genetically separable, and four classes of genes are responsible for the polar cell expansion and polar cell proliferation in Arabidopsis. In monocots, unifacial leaf, in which leaf surface consists only of abaxial identity, has been evolved in a number of divergent species. The unifacial leaves provide very unique opportunities for the developmental studies of the leaf axes formation in monocots, because their leaf polarities are highly disorganized. In addition, the mechanism of the parallel evolution of such drastic changes in leaf polarities is of interest from an evolutionary viewpoint. In this article, we describe our recent approaches to reveal the mechanism of unifacial leaf development and evolution, including recent advances in the leaf polarity specification in angiosperms.