Characteristics and Expression Profiles of Identified WRKY Genes in Barley Landraces Under Cold Stress

The <i>WRKY</i> gene family comprises important transcription factors widely distributed in plants and plays significant roles in the growth and development, diverse (biotic and abiotic) stress responses, and various biological processes. In the current study, 96 identified <i>HvLWRKY</i> genes were classified into three groups and seven subgroups. Among these, 89 genes possessed the conserved domain WRKYGQK. A total of ten motifs were harbored in <i>HvLWRKY</i> genes with two to four introns. Fragmental duplication was suggested to be the prime force that drove the evolution of <i>HvLWRKY</i> genes. A high degree of collinearity was observed between barley and <i>Triticum spelta</i>. <i>Cis</i>-elements of HvLWRKYs were closely associated with abiotic stress, light response, and hormone response; however, there were differences in the numbers among groups. <i>HvLWRKY</i> genes, even the paralogous gene pairs, from different clades were differentially regulated under cold treatments in two landraces. <i>HvLWRKY33</i>, <i>43</i>, <i>44</i>, <i>57</i>, <i>65</i>, and <i>77</i> were homologous with the relative <i>AtWRKY</i> genes in <i>Arabidopsis thaliana</i>. They are suggested to regulate abiotic and pathogen resistance of two barley landraces via SA and JA pathways. Meanwhile, some genes (for example, <i>HvLWRKY1</i> and <i>HvLWRKY32</i>) were specifically expressed in either cold-tolerant or cold-sensitive landraces. Under cold stress, different cold-responsive patterns occurred in different barley landraces. These findings provide a foundation for further studies on cold resistance in barley landraces and offer new insights for application of <i>WRKY</i> genes in barley breeding.