Integrated physio-chemical, transcriptomics and metabolomics analyses reveal the potential roles of flavonoids biosynthesis pathway in drought response of barley

Drought stress significantly reduces yield and quality of barley. Flavonoids (FLVs) are important antioxidants metabolites associated with drought adaptation in the crop. However, the molecular mechanisms associated with FLVs-mediated drought responses in barley remain incompletely understood and require further functional investigation. This research guided review integrates physiological, transcriptomic, metabolomics, and computational evidence to translate current knowledge of FLVs-associated drought responses in purple barley into future research directions. Experimental evidence indicates that drought stress increases FLVs accumulation, antioxidant enzyme activities, and osmolyte content while optimizing stomatal parameters associated with efficient water conservation. Transcriptome analyses identified 826 upregulated genes enriched in phenylpropanoid and FLVs biosynthesis pathways. Metabolomic analyses detected 3,335 differentially accumulated metabolites with significant enrichment of FLVs-synthesizing pathways. Integrated multi-omics analyses suggest coordinated changes in expression of enzymes involved in FLVs biosynthesis (CHS, CHI, F3H, FLS, DFR) and representative FLVs metabolites under drought stress. Twenty highly interactive proteins comprising ten enzymes of FLVs biosynthesis pathway and ten transcription factors (ERF, MYB, bZIP, WRKY, NAC) exhibited significant upregulation during drought stress, whose promoter regions contain notable drought-responsive cis -elements. Molecular docking with key FLVs metabolites also predicted favorable binding affinities, and identified candidate protein–ligand interactions for future functional validation. Overall, these findings provide valuable insights into the molecular mechanisms of FLVs-mediated drought response in barley to direct future research in developing drought-tolerant barley varieties.