High-affinity urea-proton symporter involved in the active transport of urea across the plasma membrane into root cells. May play an important role in urea uptake by plant cells at low external urea concentrations. Expressed in root rhizodermis, including root hairs and cortex in more basal root zones. Expressed in shoots. By nitrogen deficiency in roots. No visible phenotype under normal growth conditions, but when grown with urea as a sole source of nitrogen, plants are chlorotic and accumulate increased levels of anthocyanin. The urease inhibitor phenylphosphorodiamidate (PPD) has no effect on urea uptake and translocation or DUR3 gene expression. Belongs to the sodium:solute symporter (SSF) (TC 2.A.21) family.