Integrative Multi-Omics Analysis Identified Tissue-Specific Volatile Metabolites in <i>Populus koreana</i>

<i>Populus koreana</i> emits a wide array of volatile organic compounds (VOCs) with potential ecological functions; however, the tissue-specific distribution and underlying regulatory mechanisms of these compounds remain poorly understood. This study employed an integrated approach combining gas chromatography-mass spectrometry (GC-MS)-based metabolomics and RNA-seq to systematically profile VOC composition and gene expression in terminal buds, stems and leaves of <i>P. koreana</i>. A total of 207 VOCs were identified, predominantly terpenes and aromatic compounds, exhibiting distinct tissue-specific accumulation patterns. Terminal buds were enriched in limonene and caryophyllene, while leaves showed higher concentrations of alcohols and phenolic aldehydes. Transcriptomic analysis revealed 12,733 differentially expressed genes (DEGs) among the three organs, with substantial enrichment in terpenoid and phenylpropanoid biosynthetic pathways. Notably, key upregulated genes in buds, including TPS21 and PAL1, correlated with observed VOC profiles. Weighted gene co-expression network analysis (WGCNA) further identified 6365 genes strongly associated with bud-specific VOC biosynthesis. Integrated omics analyses indicated coordinated regulation of phenylalanine metabolism and transcription factors in VOC production. These findings illuminate the molecular mechanisms underlying tissue-specific VOC accumulation in <i>P. koreana</i>, enhancing our understanding of metabolic specialization and ecological adaptation in woody plants.