Enhanced resistance to Botryosphaeria dothidea through upregulation of the lignin biosynthesis regulator WRKY11 in poplar

The outbreak of poplar canker caused by <i>Botryosphaeria dothidea</i> poses a severe threat to poplar growth. Its resistance mechanisms are closely linked to the regulation of plant secondary metabolism and transcription factor-mediated defense pathways. However, as a plant-specific regulatory factor family, the functional mechanisms of the WRKY transcription factor (TF) family in poplar resistance to <i>B. dothidea</i> remain unclear. This study systematically elucidated the evolutionary characteristics of the WRKY gene family in <i>Populus trichocarpa</i> and their roles in disease resistance regulation in <i>P. davidiana</i> × <i>P. alba</i> var. <i>Pyramidalis</i> (Pdpap) through integrated genome-wide identification and molecular functional validation. Using BLASTp and Hidden Markov Model screening, 102 <i>PtrWRKYs</i> were identified. Phylogenetic analysis classified them into seven subfamilies based on <i>Arabidopsis thaliana</i> classification criteria. Functional diversification of this family was driven by plasticity in motif combinations, segmental duplication events, and subfamily-specific cis-regulatory elements. <i>PdpapWRKY11</i>, selected via RNA-seq and gene family analysis, significantly enhanced resistance to <i>B. dothidea</i> in transgenic Pdpap lines. Using the Pdpap-<i>B. dothidea</i> interaction system as a model, we further propose that <i>PdpapWRKY11</i> may activate key phenylpropanoid pathway genes (<i>PdpapPAL</i> and <i>PdpapCAD</i>), promoting lignin accumulation and thereby enhancing pathogen resistance. This research provides foundational insights into WRKY TF functions in poplar and establishes a theoretical basis for improving disease resistance for controlling canker disease.