Comprehensive Analysis of the TLP Gene Family in Pine and Functional Implications in Response to Pine Wood Nematode Infection

Pine wilt disease, caused by Bursaphelenchus xylophilus, poses a serious threat to global pine forest ecosystems and forestry production. Thaumatin-like proteins (TLPs), which belong to the PR-5 family, are known to participate in plant defense, but their roles in pine have not been well characterized. In this study, a comprehensive genome-wide analysis of the TLP gene family was conducted in Pinus taeda. A total of 116 TLP genes were identified and classified into four major clades based on phylogenetic analysis. Gene structure and conserved motif analyses revealed that members within the same clade generally exhibited similar exon–intron organization patterns and conserved motif compositions. Promoter analysis identified numerous cis-regulatory elements associated with stress responses and phytohormone signaling. Transcriptome data from different stages of pine wood nematode infection identified eight TLP genes that exhibited continuous differential expression, and their expression patterns were further confirmed by qRT-PCR. A multilayer regulatory network highlighted MYB and other transcription factors as key upstream regulators, and yeast one-hybrid assays confirmed MYB-mediated regulation. Together, these findings improve our understanding of the TLP gene family in P. taeda and offer valuable candidate genes and regulatory information for future studies on pine resistance to pine wilt disease.