Abstract
In angiosperms, leaves generally develop as a bifacial structure with distinct adaxial and abaxial identities. The juxtaposition between adaxial and abaxial identities promotes the lateral outgrowth of the leaf blade, leading to the dorsoventrally flattened structure. In monocots, however, unusual leaf type called unifacial leaf is found in a number of divergent taxa. In unifacial leaves, the leaf blade has only the abaxial identity. Unifacial leaves could be an unique material to study the leaf axes formation in monocots, because leaf polarities in unifacial leaves are distinct from those in bifacial leaves. In addition, the mechanism of repeated evolution of such drastic changes in leaf polarities is of interest from an evolutionary viewpoint. To reveal the mechanism of unifacial leaf development and evolution, I focused on genus Juncus (Juncaceae) as a model system. In this review, I summarize recent advances in leaf polarity specification in angiosperms, and present my recent approaches to reveal the mechanism of unifacial leaf development and evolution.
