AUX1 (Auxin transporter protein 1) is a carrier protein involved in proton-driven auxin influx. Synthesized in developing leaves and transpported to tips. Involved in lateral root formation, trichoblast polarization and root hair elongation. Required for gravitropism and thigmotropism, especially in roots, by modulating responses to auxin, ethylene and cytokinins. Needed for ammonium-mediated root-growth inhibition. Alternative names: AUX1, AUXIN RESISTANT 1, WAV5, WAVY ROOTS 5, PIR1, MAP1, MODIFIER OF ARF7/NPH4 PHENOTYPES 1, Auxin influx carrier protein 1, Polar auxin transport inhibitor-resistant protein 1.