Genome-wide identification and expression analyses of nitrate transporter family genes in wild soybean (Glycine soja)

Nitrate transporters (NRTs) are important channel proteins facilitating cross-membrane movement of small molecules like NO(3)(-)which is a critical nutrient for all life. However, the classification and evolution of nitrate transporters in the legume plants are still elusive. In this study, we surveyed the wild soybean (G. soja) genomic databases and identified 120 GsNRT1 and 5 GsNRT2 encoding genes. Phylogenetic analyses show that GsNRT1 subfamily is consisted of eight clades (NPF1 to NPF8), while GsNRT2 subfamily has only one clade. Gene chromosomal location and evolutionary historic analyses indicate thatGsNRTgenes are unevenly distributed on 19 out of 20G. sojachromosomes and segmental duplications may take a major part in the expansion ofGsNRTfamily. Investigations of gene structure and protein motif compositions suggest that GsNRT family members are highly conserved in structures of both gene and protein levels. In addition, we analyzed the spatial expression patterns of representativeGsNRTgenes and their responses to exogenous nitrogen and carbon supplies and different abiotic stresses. The qRT-PCR data indicated that 16 selectedGsNRTgenes showed various expression levels in the roots, stems, leaves, and pods of youngG. sojaplants, and these genes were regulated by not only nitrogen and carbohydrate nutrients but also NaCl, NaHCO3, abscisic acid (ABA), and salicylic acid (SA). These results suggest thatGsNRTgenes may be involved in the regulation of plant growth, development, and adaptation to environmental stresses, and the study will shed light on functional dissection of plant nitrate transporter proteins in the future.