Involved in cellular auxin homeostasis by regulating auxin metabolism. Regulates intracellular auxin accumulation at the endoplasmic reticulum and thus auxin availability for nuclear auxin signaling. Expressed in seedlings, cauline leaves and flowers. Up-regulated by auxin application. Increased root growth and lateral root initiation. Belongs to the auxin efflux carrier (TC 2.A.69.2) family.