Low-affinity nitrate transporter facilitating nitrate loading into root phloem. Not involved in dipeptides transport, but has a weak glucosinolate transport activity. Expressed in roots, stems and major veins of the leaves. Detected in the companion cells of the root phloem. Up-regulated by nitrate after long time exposure. Decreased nitrate content in root phloem exudates. Enhanced root-to shoot nitrate transport and plant growth under high nitrate conditions. Belongs to the major facilitator superfamily. Proton-dependent oligopeptide transporter (POT/PTR) (TC 2.A.17) family.