Genomic and transcriptomic analyses highlight evolutionary and functional characteristics of WRKY genes in Asterids

WRKY transcription factors regulate development, dormancy, germination, senescence, and reactions to abiotic and biotic stress. Asterids, a major group of eudicots, are commercially and pharmacologically important. However, large-scale WRKY gene family analyses in Asterids are lacking. We performed genome-wide re-annotation and downstream analyses of WRKY genes in nine Asterid species in addition to Arabidopsis thaliana and Beta vulgaris. We identified a total of 1,013 WRKY genes, 91 of which were newly annotated in our analysis. These were divided into six subgroups based on domain structure, phylogeny, and motif composition. Duplication analysis revealed increased copy numbers of WRKY genes belonging to specific subgroups in Helianthus annuus (sunflower), Actinidia chinensis (kiwifruit), and Olea europaea var. sylvestris (wild olive). Both H. annuus and A. chinensis displayed recent duplications of the WRKY gene after their divergence, whereas O. europaea var. sylvestris showed ancient duplication of WRKY genes. Transcriptome analyses suggested that potential function of WRKY genes in responses to abiotic and biotic stresses in H. annuus and A. chinensis, respectively. Our data shed light on the evolutionary and functional characteristics of WRKY genes, especially among Asterid plant species.