Genome-wide identification of the WRKY gene family in Angraecum sesquipedale and exploration of its role in cold stress response

Background Angraecum sesquipedale , commonly known as Darwin’s orchid, is a distinctive ornamental species uniquely susceptible to biotic and abiotic stresses, primarily owing to its confinement to specialized habitats. WRKY transcription factors play pivotal roles in plant stress responses, growth and development regulation, and secondary metabolism. However, research on this gene family in A. sesquipedale remains unreported. Results In this study, 70 WRKY genes ( AsWRKYs ) were identified in A. sesquipedale through genome-wide analysis. Phylogenetic analysis, integrating WRKY genes from four model plants ( Arabidopsis thaliana , Solanum lycopersicum , Oryza sativa , and Glycine max ), classified these 70 AsWRKYs into three major groups, with Group Ⅱ further subdivided into five subgroups. Genes within the same group exhibited high conservation in gene structure and motif composition. Tissue expression profiling revealed that several AsWRKYs ( AsWRKY21 and AsWRKY49 ) exhibit root-preferential expression, suggesting their potential involvement in regulating root growth and development in A. sesquipedale . The expression patterns under cold stress showed that 7 genes in roots and 4 genes in leaves exhibited early rapid responses, while 15 genes in leaves and 4 genes in roots exhibited long-term sustained response features. Integrating expression patterns with phylogenetic relationships, key candidate genes potentially implicated in cold stress regulation, including AsWRKY17 , AsWRKY23 , AsWRKY30 , AsWRKY56 , and AsWRKY58 , were identified. Conclusions This study identified 70 WRKY genes in A. sesquipedale , elucidated their classification, evolutionary characteristics, and expression patterns, and unveiled the potential mechanisms of AsWRKYs in cold stress responses. The findings establish a foundation for understanding the evolutionary adaptability of AsWRKYs and the cold regulatory network in A. sesquipedale , and lay a foundation for molecular breeding and genetic improvement of stress resistance in orchids.