Promoter of Nitrate Reductase Gene Behaves Differently Under Salinity Stress in Contrasting Rice Genotype

Soil salinity is a global agricultural issue that decreases both plant production and survival. Plants synthesize secondary nitrogen metabolites, which use nitrogen fixed by plants, to withstand salinity stress. Soil salinity is a global agricultural problem that reduces the yield as well as survivability of plants. Plants fix nitrogen by nitrate reductase (NR) which converts nitrate (NO3−) to nitrite (NO2−). Salinity affects NR control differentially and shows both increased and decreased activity. This increase or decrease in activity was due to its control of transcriptional and post-translation (activation). We characterized the NR gene promoter from salt-sensitive and resistant CVS with an in vivo reporter gene (gusA) by raising transgenic rice plants. The major difference in their actions at different salt levels (100 mM, 200 mM, and 300 mM) is verified by qPCR and quantitative expression of gusA. We found a collinear association with previously reported NR activity outcomes between relative transcript number or reporter gene. In addition, sequence analysis of NR promoters reveals that the tolerant CVS promoter (pCNR3) contains a higher number of elements of GATA (cis-regulatory elements, CREs) that are directly responsible for the response to salinity stress. The hypothesis that the promoter of the NR gene has a significant function in the regulation of NR activity under salinity stress is confirmed by the existence of a higher number of salt-sensitive CREs. This study was designed by considering the contrasting salt-sensitive (Jaya and CSR36) cultivars to understand the function of the promoter (transcriptional regulation) (CVS). In addition, this information leads to a stress-responsive promoter of endogenous salinity that can be further used in programs for research and crop improvement.