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

The outbreak of poplar canker caused by Botryosphaeria dothidea 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 B. dothidea remain unclear. This study systematically elucidated the evolutionary characteristics of the WRKY gene family in Populus trichocarpa and their roles in disease resistance regulation in P. davidiana × P. alba var. Pyramidalis (Pdpap) through integrated genome-wide identification and molecular functional validation. Using BLASTp and Hidden Markov Model screening, 102 PtrWRKYs were identified. Phylogenetic analysis classified them into seven subfamilies based on Arabidopsis thaliana classification criteria. Functional diversification of this family was driven by plasticity in motif combinations, segmental duplication events, and subfamily-specific cis-regulatory elements. PdpapWRKY11 , selected via RNA-seq and gene family analysis, significantly enhanced resistance to B. dothidea in transgenic Pdpap lines. Using the Pdpap– B. dothidea interaction system as a model, we further propose that PdpapWRKY11 may activate key phenylpropanoid pathway genes ( PdpapPAL and PdpapCAD ), 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.