[Identification, expression and DNA variation analysis of high affinity nitrate transporter / gene family in ].

Nitrate is the main form of inorganic nitrogen that crop absorbs, and nitrate transporter 2 (NRT2) is a high affinity transporter using nitrate as a specific substrate. When the available nitrate is limited, the high affinity transport systems are activated and play an important role in the process of nitrate absorption and transport. Most NRT2 cannot transport nitrates alone and require the assistance of a helper protein belonging to nitrate assimilation related family (NAR2) to complete the absorption or transport of nitrates. Crop nitrogen utilization efficiency is affected by environmental conditions, and there are differences between varieties, so it is of great significance to develop varieties with high nitrogen utilization efficiency. has high stress tolerance and is more efficient in soil nitrogen uptake and utilization. The . genome database was scanned to systematically analyze the gene structure, chromosomal localization, physicochemical properties, secondary structure and transmembrane domain, signal peptide and subcellular localization, promoter region -acting elements, phylogenetic evolution, single nucleotide polymorphism (SNP) recognition and annotation, and selection pressure of the gene family members. Through bioinformatics analysis, 5 gene members (designated as -, -, - - and -) and 2 gene members (designated as - and -) were identified, the number of which was less than that of foxtail millet. / were distributed on 3 chromosomes, and could be divided into four subfamilies. The genetic structure of the same subfamilies was highly similar. The average value of SbNRT2/3 hydrophilicity was positive, indicating that they were all hydrophobic proteins, whereas α-helix and random coil accounted for more than 70% of the total secondary structure. Subcellular localization occurred on plasma membrane, where SbNRT2 proteins did not contain signal peptides, but SbNRT3 proteins contained signal peptides. Further analysis revealed that the number of transmembrane domains of the SbNRT2s family members was greater than 10, while that of the SbNRT3s were 2. There was a close collinearity between / of . and . Protein domains analysis showed the presence of MFS_1 and NAR2 protein domains, which supported executing high affinity nitrate transport. Phylogenetic tree analysis showed that / were more closely related to those of . and . Analysis of gene promoter -acting elements indicated that the promoter region of / had several plant hormones and stress response elements, which might respond to growth and environmental cues. Gene expression heat map showed that - and - were induced by nitrate in the root and stem, respectively, and - and - were induced by low nitrogen in the root and stem. Non-synonymous SNP variants were found in - and -. Selection pressure analysis showed that the / were subject to purification and selection during evolution. The expression of / gene and the effect of aphid infection were consistent with the expression analysis results of genes in different tissues, and - and - were significantly expressed in the roots of aphid lines 5-27sug, and the expression levels of -, - and - were significantly reduced in sorghum aphid infested leaves. Overall, genome-wide identification, expression and DNA variation analysis of NRT2/3 gene family of provided a basis for elucidating the high efficiency of sorghum in nitrogen utilization.