Promotes adaxial cell identity. Regulates the initiation of embryonic shoot apical meristem (SAM) development. Binds to LUG and LUH; these complexes promote adaxial cell identity in leaves as well as embryonic shoot apical meristem (SAM) initiation and postembryonic SAM maintenance. Interacts with SPL/NZZ and SPEAR2 (PubMed:25527103). Leaves polarity and growth defects. Belongs to the YABBY family.