Large and rapidly increasing areas of salt-affected soils are posing major challenges for the agricultural sector. Most fields used for the important food crop Triticum aestivum (wheat) are expected to be salt-affected within 50 years. To counter the associated problems, it is essential to understand the molecular mechanisms involved in salt stress responses and tolerance, thereby enabling their exploitation in the development of salt-tolerant varieties. The myeloblastosis (MYB) family of transcription factors are key regulators of responses to both biotic and abiotic stress, including salt stress. Thus, we used the Chinese spring wheat genome assembled by the International Wheat Genome Sequencing Consortium to identify putative MYB proteins (719 in total). Protein families (PFAM) analysis of the MYB sequences identified 28 combinations of 16 domains in the encoded proteins. The most common consisted of MYB_DNA-binding and MYB-DNA-bind_6 domains, and five highly conserved tryptophans were located in the aligned MYB protein sequence. Interestingly, we found and characterized a novel 5R-MYB group in the wheat genome. In silico studies showed that MYB transcription factors MYB3, MYB4, MYB13 and MYB59 are involved in salt stress responses. qPCR analysis confirmed upregulation of the expression of all these MYBs in both roots and shoots of the wheat variety BARI Gom-25 (except MYB4, which was downregulated in roots) under salt stress. Moreover, we identified nine target genes involved in salt stress that are regulated by the four MYB proteins, most of which have cellular locations and are involved in catalytic and binding activities associated with various cellular and metabolic processes.

Climate change is dramatically increasing the overall area of saline soils around the world, which is increasing by approximately two million hectares each year. Soil salinity decreases crop yields and, thereby, makes farming less profitable, potentially causing increased poverty and hunger in many areas. A solution to this problem is increasing the salt tolerance of crop plants. Transcription factors (TFs) within crop plants represent a key to understanding salt tolerance, as these proteins play important roles in the regulation of functional genes linked to salt stress. The basic leucine zipper (bZIP) TF has a well-documented role in the regulation of salt tolerance. To better understand how bZIP TFs are linked to salt tolerance, we performed a genome-wide analysis in wheat using the Chinese spring wheat genome, which has been assembled by the International Wheat Genome Sequencing Consortium. We identified 89 additional bZIP gene sequences, which brings the total of bZIP gene sequences in wheat to 237. The majority of these 237 sequences included a single bZIP protein domain; however, different combinations of five other domains also exist. The bZIP proteins are divided into ten subfamily groups. Using an in silico analysis, we identified five bZIP genes (ABF2, ABF4, ABI5, EMBP1, and VIP1) that were involved in regulating salt stress. By scrutinizing the binding properties to the 2000 bp upstream region, we identified putative functional genes under the regulation of these TFs. Expression analyses of plant tissue that had been treated with or without 100 mM NaCl revealed variable patterns between the TFs and functional genes. For example, an increased expression of ABF4 was correlated with an increased expression of the corresponding functional genes in both root and shoot tissues, whereas VIP1 downregulation in root tissues strongly decreased the expression of two functional genes. Identifying strategies to sustain the expression of the functional genes described in this study could enhance wheat’s salt tolerance.

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.