Genome-Wide Identification and Characterization of NITRATE REGULATORY GENE 2 (NRG2) Family Genes in Brassica napus

Nitrate Regulatory Gene 2 (NRG2) serves as a pivotal positive regulator in the intricate nitrate signaling pathway. Despite its paramount importance, there been little known about its gene family and characteristics in Brassica napus, especially its rule under stress conditions. Using bioinformatics methods, this study unearthed 38 BnaNRG2 family members in Brassica napus, with Brassica rapa and Brassica oleracea harboring 19 and 21 members, respectively. Employing phylogenetic analysis, these members were classified into 3 subfamilies, unveiling conservation in family structure among gene members within subfamilies. Significantly, BnaNRG2s exhibited a remarkable conservation in gene structure, prominently characterized by conserved domains DUF630 and DUF632, and the subcellular localization is predicted to be the nucleus. Insights from collinearity and Ka/Ks analysis underscored the prominent role of genome duplication events in propelling the expansion of NRG2 members in Brassica napus, coupled with robust purifying selection during evolution, favoring the retention of variations conducive to gene functionality. The expression profiling unveiled the ubiquitous expression of BnaNRG2s across diverse tissues, with nuanced preferential expression in vegetative versus reproductive tissues among certain members. Intriguingly, comparison with the expression patterns of Arabidopsis NRG2 revealed conservation in the expression pattern of select BnaNRG2 members. Additionally, analysis of cis-acting elements revealed the presence of numerous regulatory elements, indicating their involvement in diverse physiological processes, including responses to light and hormones. Furthermore, qRT-PCR analysis suggested the potential role of BnaNRG2s in the response to low-temperature stress, consolidated the reliability of the bioinformatic analysis. This study offers a reference for elucidating the function of the NRG2 transcription factor in B. napus and a possibility for the improvement of cold-tolerant rapeseed varieties.