Comprehensive genome-wide characterization of NAC transcription factors in Barley influence insights into stress tolerance and evolutionary dynamics.

Barley (Hordeum vulgare L.), a crucial cereal crop known for its resilience to harsh environmental conditions, relies on complex genetic networks to withstand abiotic stressors such as drought, salinity, and extreme temperatures. In this study, a comprehensive genome-wide identification and characterization of the NAC (NAM, ATAF, and CUC) transcription factor family in barley was conducted, revealing 26 HvNAC genes. Detailed analyses included assessments of gene structure, conserved motifs, cis-regulatory elements, chromosomal localization, and evolutionary relationships with other species. The findings demonstrated significant diversity in the physicochemical properties and structural features of HvNAC proteins, with several genes harboring stress-responsive elements linked to Abscisic acid (ABA), Methyl jasmonate (MeJA), auxin, and gibberellin pathways. Phylogenetic analysis revealed six distinct clades of NAC genes, indicating the evolutionary divergence of HvNACs from related species, such as wheat, rice, and Arabidopsis thaliana. Additionally, gene duplication events and synteny analysis highlighted the evolutionary forces shaping this gene family. The investigation of microRNA (miRNA) interactions identified miRNA164 and Hvu-miR156 as key regulators of HvNAC expression under drought stress, underscoring the functional importance of these genes in stress adaptation. Under drought and salt stress, HvNAC2 and HvNAC6 were significantly upregulated in barley roots, highlighting their key roles in stress adaptation, while leaves showed minimal expression changes. Additionally, under temperature stress, HvNAC4, HvNAC5, and HvNAC3 were upregulated in leaves during heat stress, whereas HvNAC6 and HvNAC6-C were more active in roots during cold stress, indicating tissue-specific responses to environmental conditions. This study offers valuable insights into the molecular mechanisms governing stress tolerance in barley and provides a foundation for breeding programs aimed at enhancing barley's resilience to environmental challenges.