Plays a major role in ovule patterning and in determination of integument identity via its interaction with MADS-box factors. Formation of complex with AG-SEP dimers negatively regulates the carpel identity process and favors the maintenance of ovule identity. BEL1-STM complex maintains the indeterminacy of the inflorescence meristem. Required, with SPL, for cytokinin-induced PIN1 expression in ovules (PubMed:22786869). May form heterodimeric complexes with TALE/KNOX proteins STM, KNAT1/BP, KNAT2 and KNAT5 (PubMed:17873098). Interacts with AG-SEP1 and AG-SEP3 dimers (PubMed:17693535). Interacts with KNATM, isoform KNATM-B (PubMed:18398054). Interacts with BZIP30 (PubMed:27402171). Expressed in both floral and vegetative tissues. Early expression is detected in the inflorescence apex of developing flowers and also in the ovule primordium and the integuments. 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.