Auxin response factors (ARFs) are transcriptional factors that bind specifically to the DNA sequence 5'-TGTCTC-3' found in the auxin-responsive promoter elements (AuxREs). Seems to act as transcriptional activator. Formation of heterodimers with Aux/IAA proteins may alter their ability to modulate early auxin response genes expression. Mediates embryo axis formation and vascular tissues differentiation. Functionally redundant with ARF7. May be necessary to counteract AMP1 activity. Homodimers and heterodimers. Interacts with BRX and the auxin-responsive proteins IAA1, IAA12 (BODENLOS), IAA17 and ARF7. Expressed in the whole plant with a lower expression in leaves. Detected in embryo axis, provascular tissues, procambium and some differentiated vascular regions of mature organs. In early embryo and during organ development. Interactions between auxin response factors (ARFs) and Aux/IAA proteins occur through their C-terminal dimerization domains III and IV. Absence of the protein probably causes early embryonic lethality. Premature stop codons are associated with vascular defects. Belongs to the ARF family.