Biological Networks in Barley (Hordeum vulgare L.): From Molecular Interactions to Systems-Level Understanding

Barley ( Hordeum vulgare L.) is an important model organism for studying stress tolerance, development, and yield formation. Recent advances in multi-omics approaches, including genomics, transcriptomics, proteomics, and metabolomics, have shown that these complex biological processes are governed by intricate molecular networks, challenging traditional linear or single-gene models. This review synthesizes the latest insights into barley's biological networks, such as protein–protein interaction (PPI) networks, gene co-expression networks, metabolic pathways, and signaling cascades, providing a systems-level understanding of how genes, proteins, and metabolites work together to regulate physiological functions. Through a comparative analysis of transcriptomic, proteomic, and metabolomic studies, we highlight how network-based approaches and integrated pathway modeling have identified key hub genes, regulatory modules, and their roles in stress adaptation. We also discuss how systems biology has enhanced our understanding of barley’s adaptive complexity, particularly in response to environmental stressors, and examine emerging research directions, including dynamic network modeling, pan-genomic integration, and multi-layer omics strategies. This review highlights the potential of network biology to advance predictive modeling and molecular breeding, providing new strategies for developing barley cultivars with improved resilience, yield, and quality in response to environmental challenges.