Transcriptional Regulation of Salt Stress Tolerance in Triticum aestivum (Wheat): NAC Transcription Factors and Their Target Genes

Salinity is one of the key threats to food security and sustainability. To make saline soils productive again, we need to develop salt-tolerant crop varieties. Developing salt-tolerant wheat requires a detailed understanding of the molecular mechanisms underlying salt stress responses. In this study, we analyzed the Chinese Spring genome and identified 559 putative NAC transcription factors (TFs), which are recognized as key regulators of both abiotic and biotic stress. Protein family analysis revealed four distinct domain architectures, with more than 95% of the proteins containing a single NAC domain, consistent with their conserved regulatory role. Through in silico analyses, four salt stress-responsive TFs, NAC_1D, NAC_2D, NAC_4A, and NAC_5A, were highlighted, sharing nine of 13 DNA-binding residues. Promoter analysis of their putative target genes identified seven candidates, which, together with the NAC TFs, were subjected to RT-qPCR expression analysis in BARI Gom-25 plants exposed to 100 mM NaCl. The expression data revealed contrasting regulatory patterns between NAC TFs and their target genes. For example, Hsp70 was strongly upregulated in both shoots and roots, despite opposite patterns of NAC_1D expression between tissues. Similarly, bZIP expression mirrored the downregulation of NAC_2D, whereas HKT8 expression remained stable under salt stress. NAC_4A showed a root-specific pattern suggestive of positive regulation of a Non-specific serine/threonine protein kinase, while NAC_5A upregulation corresponded with downregulation of Plant cadmium resistance 2. Collectively, these results provide functional insights into four NAC TFs and identify potential molecular targets for improving wheat salt tolerance. By targeting key tolerance genes at the DNA level offers greater precision and can significantly reduce breeding time.