Auxin receptor that controls cell elongation and cell division (PubMed:9804548, PubMed:11297513). Involved in embryonic morphogenesis (PubMed:11297513). Acts on the cell cycle, endocycle, cell plate formation, and cell expansion and contributes to the control of auxin-related gene expression (PubMed:18952781). Controls root meristem size and mediates auxin responsiveness (PubMed:19777056). Involved in activation of ROP GTPases in response to auxin and regulation of clathrin-mediated endocytosis in roots (PubMed:20887895, PubMed:22683261). Acts as a positive factor in clathrin recruitment to the plasma membrane, thereby promoting endocytosis (PubMed:20887896, PubMed:25922490). Upon auxin binding, restricts the internalization of PIN proteins by inhibiting clathrin-mediated endocytosis (PubMed:20887896, PubMed:25922490). Involved in the regulation of polar auxin transport (PubMed:21223392). Behaves as a negative regulator of the SCF(TIR1/AFB) signaling pathway, protecting AUX/IAA repressors from degradation (PubMed:24051655). Regulates the expression of cell wall remodeling genes via an SCF(TIR1/AFB)-dependent pathway (PubMed:24424095). Involved in the modulation of hemicellulose xyloglucan structure (PubMed:24424095). Required for rapid auxin-mediated re-orientation of microtubules to regulate cell elongation in roots and dark-grown hypocotyls as well as asymmetric growth during gravitropic responses (PubMed:25409144). Involved in the shade avoidance response (PubMed:24052532). Forms with TMK1 a cell surface auxin perception complex that activates ROP signaling pathways (PubMed:24578577). ABP1 sensing of auxin is important for the ABP1-TMK1 complex formation (PubMed:24578577). Interacts functionally with phytochrome to regulate growth (PubMed:25392478). Homodimer (By similarity). May interact with the GPI-anchored plasma membrane protein SKU5 and its family members (PubMed:16649105). Interacts with TMK1 (via extracellular domain) (PubMed:24578577). In plasmolyzed cells, observed in strands connecting the apoplast and the plasma membrane. Up-regulated by auxin. Glycosylated. Ubiquitinated by RMA2, leading to proteasomal degradation. Embryo lethality, when homozygous (PubMed:11297513). No visible phenotype was found for other null mutants (PubMed:25646447). Analysis of new null mutants leads to the conclusion that plants do not need ABP1 for auxin signaling and for their growth and development under normal growth conditions.