Cloning, in silico analysis of upstream sequences and tissue and different external conditions mediated expression studies of three homeologs of TaNPF7.2 of wheat (Triticum aestivum)

The present study was carried out during 2020–2021 at ICAR-National Institute for Plant Biotechnology, New Delhi during 2020–2021 to investigate the cis-regulatory elements, transcription factor (TF) binding sites and stress- and development-responsive expression dynamics of TaNPF7.2, a wheat (Triticum aestivum L.) homolog of the AtNRT1.5/ NPF7.3 responsible for root-to-shoot nitrate transport. Promoter regions (~2 kb) of TaNPF7.2-A, -B, and –D were analyzed to identify cis-regulatory elements and TF-binding sites. A homeolog-specific expression study was conducted at early and later developmental stages (GS19, GS39, GS65) under different treatments in the nitrogen-uptake-efficient genotype, i.e., K9107. Promoter analysis revealed strong homeolog divergenc with TaNPF7.2-A enriched in general stress-responsive STRE motifs, TaNPF7.2-B harbouring higher MYB and DRE content and TaNPF7.2-D uniquely lacking ABREs but exhibiting dense WRKY-, HD-ZIP– and ZF-HD–binding sites. Expression profiling showed that under optimal nitrate, TaNPF7.2-A was the most strongly induced in seminal roots. Salt stress caused widespread transcriptional suppression whereas drought triggered a delayed but strong induction of TaNPF7.2-B. Cadmium stress induced rapid activation of TaNPF7.2-D, consistent with its WRKY-rich promoter element. During later developmental stages, expression remained predominantly root-centric, with shifting homeolog dominance from 7.2-D (GS19) to 7.2- A (GS65). These findings provide insights into understanding of nitrate translocation in wheat and identify promising regulatory nodes for enhancing NUE under both favourable and stress conditions.