Involved in the abaxial cell fate determination during embryogenesis and organogenesis. Regulates the initiation of embryonic shoot apical meristem (SAM) development (PubMed:10323860, PubMed:10331982, PubMed:10457020, PubMed:11812777, PubMed:12417699, PubMed:9878633, Ref.3, Ref.6, PubMed:19837869). Required during flower formation and development, particularly for the patterning of floral organs. Positive regulator of class B (AP3 and PI) activity in whorls 2 and 3. Negative regulator of class B activity in whorl 1 and of SUP activity in whorl 3. Interacts with class A proteins (AP1, AP2 and LUG) to repress class C (AG) activity in whorls 1 and 2. Contributes to the repression of KNOX genes (STM, KNAT1/BP and KNAT2) to avoid ectopic meristems. Binds DNA without sequence specificity. In vitro, can compete and displace the AP1 protein binding to DNA containing CArG box (PubMed:10323860, PubMed:10331982, PubMed:10457020, PubMed:11812777, PubMed:12417699, PubMed:9878633, Ref.3, Ref.6). Binds 2 Zn(2+) ions per subunit. Monomer and homomultimers (more than 20 subunits in vitro). Interacts with DNA as monomer. The release of 1 zinc ion from a monomer disrupts the binding to DNA and leads to multimerization. Interacts with SPL/NZZ (PubMed:15299139, PubMed:25527103). Interacts with SPEAR2 (PubMed:25527103). 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 (PubMed:19837869). Expressed in abaxial regions of young lateral aerial organs, and in 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 the expression starts during the transition between globular and heart stages in the cotyledon anlagen. From the heart stage, expression expands to 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. The non-canonical Cys-56 facilitates the zinc ion release from the zinc finger domain. Leaves polarity and growth defects. Belongs to the YABBY family.