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 roots, leaves and shoots. By nitrogen deficiency in roots. No visible phenotype under normal growth conditions, but when grown with urea as the sole source of nitrogen, plants show reduced growth and slight yellowing of shoots. Belongs to the sodium:solute symporter (SSF) (TC 2.A.21) family.