Involved in nitrate transport, but does not seem to be able to mediate transport by its own. Acts as a dual component transporter with NAR2.1. Imports nitrate with high affinity when expressed with NAR2.1 in a heterologous system (Xenopus oocytes). Heterotetramer composed of two NRT2.2 and two NAR2.1 (By similarity). Interacts with NAR2.1. Expressed in primary and lateral roots, root-shoot junction zone, vascular tissues of adventitious root primordia, leaves, embryo and coleoptiles of germinating seeds, husks and anthers. Circadian-regulation with a peak in the middle of the morning and at the end of the light period. Induced by nitrate and sucrose in roots. Down-regulated by ammonium, glutamine, asparagine and aspartate in roots. Plants over-expressing NRT2.2 have accelerated growth under low nitrate conditions (Ref.6). Belongs to the major facilitator superfamily. Nitrate/nitrite porter (TC 2.A.1.8) family.