Genome-wide identification of WRKY gene family members in Populus trichocarpa and their response to biotic stresses

Background WRKY transcription factors (TFs) are key regulators of plant stress resistance. Despite their importance, the regulatory mechanisms of WRKY s in Populus trichocarpa under biotic stress remain insufficiently explored. This study presents a comprehensive bioinformatic characterization of the WRKY gene family in P. trichocarpa . Methods The most recent P. trichocarpa genome was employed to identify all WRKY genes in the species. Detailed analyses, including molecular characterization, phylogenetic relationships, gene structure, motif and promoter composition, chromosomal localization, and syntenic relationships, were conducted. Real-time quantitative polymerase chain reaction (RT-qPCR) was utilized to assess the expression profiles of PtWRKY genes under insect stress. Results A total of 139 WRKY genes were identified, unevenly distributed across 18 chromosomes and classified into three principal groups. Conserved motif analysis showed that all PtWRKY proteins contained motifs 1, 2, and 4, with members of the same subgroup exhibiting highly similar motif architectures. Collinearity analysis identified 91 homologous gene pairs within the PtWRKY family, suggesting potential functional redundancy. Examination of the 2,000 bp upstream promoter regions revealed diverse cis-acting elements associated with light responsiveness, phytohormone signaling, and stress regulation. Moreover, several PtWRKY genes responded to feeding stress caused by Hyphantria cunea . Conclusion Collectively, these findings elucidate the genomic organization and potential regulatory roles of the WRKY gene family in P. trichocarpa , highlighting their involvement in insect-induced defense and offering insights for future agricultural improvement strategies.