Transcription factor that establishes leaf shape by repressing growth in specific subdomains of the leaf. Negatively regulates knox homeobox gene KNAT1/BP expression. May form heterodimeric complexes with TALE/KNOX proteins STM, KNAT1/BP, KNAT2 and KNAT5 (PubMed:17873098). Interacts OFP1, OFP2, OFP4 and OFP5 (PubMed:15781858). Interacts with KNATM, isoform KNATM-B (PubMed:18398054). Expressed in lateral organs. The SR/KY and BELL domains are responsive for the interaction between the TALE/BELL proteins and the TALE/KNOX proteins. Belongs to the TALE/BELL homeobox family.