Auxin efflux transporter that acts as a negative regulator of light signaling to promote hypocotyl elongation. Mediates the accumulation of chlorophyll and anthocyanin, as well as the expression of genes in response to light. Participates directly in auxin efflux and thus regulates the polar (presumably basipetal) auxin transport (from root tips to root elongating zone). Transports also some auxin metabolites such as oxindoleacetic acid and indoleacetaldehyde. Involved in diverse auxin-mediated responses including gravitropism, phototropism and lateral root formation. Confers resistance to herbicides such as dicamba, pendimethalin, oryzalin, and monosodium acid methanearsonate (MSMA), but not to herbicides such as glyphosate, atrazine, bentazon and fluazifop-p-butyl. Mediates also resistance to xenobiotics such as cycloheximide and the cytokinin N6-(2-isopentenyl)adenine (2IP). Transport activity inhibited by 1-N-naphthylphthalamic acid (NPA), cyclopropyl propane dione (CPD), cyclosporin A, verapamil and quercetin. Interacts with 1-naphthylphthalamic acid (NPA) and FKBP42/TWD1. Non-polar distribution in apical cells. Predominant basal (top) localization in root tissues above the elongation zone, especially in mature cortical and endodermal cells. Basal and apical localization in the root elongation zone. Ubiquitous, with high levels in peduncles. Mostly localized in young developing tissues, including meristems, as well as root and shoot apices. By auxin. Belongs to the ABC transporter superfamily. ABCB family. Multidrug resistance exporter (TC 3.A.1.201) subfamily.