Genome-Wide Identification of the WUSCHEL-Related Homeobox (WOX) Gene Family in Barley Reveals the Potential Role of HvWOX8 in Salt Tolerance

The <i>WUSCHEL-related homeobox</i> (<i>WOX</i>) belongs to a plant-specific transcription factor gene family that plays crucial roles in plant growth and development. Barley ranks as the fourth global cereal crop and is recognized as a model crop for the study of cereal genetics. However, genome-wide characterization, functional validation, and stress-related studies of the <i>WOX</i> gene family in barley remain limited, hindering efforts to leverage their potential for improving salt tolerance and regeneration efficiency in breeding programs. In this study, we identified 12 <i>HvWOX</i> genes assigned from chromosome 1 to chromosome 5. Phylogenetic analysis revealed that these <i>HvWOX</i> genes can be classified into three clades (WUS, ancient, and intermediate). Gene structure analysis revealed that the exon numbers of <i>HvWOX</i> genes varied in the WUS and intermediate clades but were highly conserved in the ancient clade. Tissue-specific analysis revealed that the most common <i>HvWOX</i> genes were highly expressed in reproductive tissues such as anthers or ovaries. <i>Cis</i>-element analysis suggested that there were multiple stress- and hormone-responsive elements in the <i>HvWOX</i> gene promoters. In addition, overexpression of <i>HvWOX8</i> in <i>Arabidopsis</i> significantly enhanced root elongation under salt stress (50-100 mM NaCl), suggesting its direct role in salt tolerance. Transcriptomic analysis further revealed that <i>HvWOX8</i> modulates hormone signaling and electron transfer pathways during ATP synthesis under stress conditions. In conclusion, our results provided a comprehensive understanding of the gene characteristics, expression patterns, and potential roles of barley <i>WOX</i> genes.