Acts as a cell-specific local repressor of quiescent center (QC) self-renewal by cell divisions in the primary root. Counteracts brassinosteroid (BR)-mediated cell division in the QC cells (PubMed:24981610). Regulates maternally seed size, especially before the heart stage, promoting both endothelial cells expansion and cell number in the outer integument layer of the seed coat (PubMed:23911125). Modulates the expression of genes involved in cell wall metabolism such as cell division and expansion (PubMed:23911125, PubMed:24981610). Negative regulator of flowering via the repression of FT transcription (PubMed:25343985). Forms homodimer (PubMed:25343985). Interacts with the dephosphorylated active form of BES1 in the nucleus of quiescent center (QC) cells (PubMed:24981610). Interacts with BPM1, BPM2, BPM3, BPM4, BPM5 and BPM6 at the promoter of FLOWERING LOCUS T (FT) (PubMed:25343985). Mostly expressed in flowers (at protein level) and siliques, and, to a lower extent, in roots, stems and leaves (PubMed:25343985). Expressed in embryos (e.g. heart and torpedo stages) and cotyledons, and, at low levels, in roots and inflorescence (PubMed:23911125). Accumulates specifically in root apical meristem quiescent center (QC) and vascular initial cells (PubMed:16581911, PubMed:24981610). Expressed in developing seeds. Levels follow a circadian cycle with a progressive decrease during the day time (at protein level) (PubMed:25343985). Down-regulated by brassinosteroids (BRs) in a dose- and time-dependent manner. Repressed by BES1. Auto-activation of expression (PubMed:24981610). Targeted to 26S proteasomal degradation by the CULLIN3 (CUL3)-based E3 ligases CRL3(BPMs) (PubMed:25343985). Smaller seeds and embryos associated with smaller contracted endothelial cells and reduced cell number in the outer integument layer of the seed coat during the seed development (PubMed:23911125). Increased quiescent center (QC) cell divisions (PubMed:24981610). Early flowering under long-day (LD) associated with FT accumulation (PubMed:25343985). Truncated N-terminus.