Involved in the abaxial cell fate determination during embryogenesis and organogenesis. Interacts with SPL/NZZ and SPEAR2 (PubMed:25527103). Expressed at low levels in abaxial regions of lateral aerial organ primordia leading to cotyledons, leaves, flower meristems, sepals, petals, stamen and carpels, but not in roots. Expressed in subepidermal cells of anlagen regions, then in abaxial part of primordia and finally in differentiating organs. Levels decrease in differentiated organs. In embryo, expressed from the heart stage in the abaxial domain of the cotyledon primordia and decrease as the embryo matures. In stamen, expression restricted to the abaxial region differentiating into the connective. In gynoecium, expressed in the abaxial cell layers differentiating into the valves. Belongs to the YABBY family.