Growth stage and nitrate limiting response of NRT2 and NAR2 gene families of bread wheat, and complementation and retrieval of nitrate uptake of atnrt2.1 mutant by a wheat NRT2 gene

The Nitrate Transporter 2 (NRT2), together with accessory protein (NAR), form high-affinity nitrate transport systems (HATS) responsible for nitrate uptake and translocation under its limited availability in plants. In the present study, we aimed to identify members of these two families’ genes in the bread wheat genome on a genome-wide scale, the evolutionary relationship of these families to major cereals, and their expression dynamics. A total of 46 and 8 NRT2 and NAR2 family genes, respectively, have been identified, which showed tissue and growth-stage specific nitrate limiting responses in all major tissues with a tendency of homeolog expression bias in two wheat genotypes. The high-affinity transport capacity of four wheat genotypes using 15 N influx at three major physiological stages also showed significant roles of HATS at tissue and growth stage levels. The complementation of atnrt2.1 mutant with one of the high-affinity nitrate transporter genes, i.e., TaNRT2.1 -B6, caused recovery of about 1.5 times 15 N influx in N + and N- conditions in Arabidopsis mutant than wild type. The present study contributes to the genomic and functional understanding of NRT2 and NAR2 genes of bread wheat, providing a platform for further learning the underlying mechanism of nitrate uptake in bread wheat.