Calcium ions (Ca²⁺) play a crucial role as a key messenger in various adaptive and developmental processes. In plants, the calcineurin B-like protein (CBL) family is a unique calcium sensor, which plays a key role in regulating plant growth and development as well as responding to external environmental stimuli throughout the Ca²⁺ signaling pathway. However, the CBL gene family in poplar has not been systematically described. In this study, thirteen CBL genes were identified from the Populus trichocarpa genome using bioinformatics methods. Multiple sequence alignment showed that all PtrCBLs contained four conserved EF-hand domains. Promoter cis-acting elements revealed that PtrCBL promoters contained at least one abiotic-related or hormone response element. A protein–protein interaction network revealed that PtrCBLs interacted with various CIPK proteins to participate in growth and development or respond to environmental stimuli in poplar. Transcriptome data demonstrated that numerous PsnCBLs were involved in the response to alkaline stress in Populus simonii × Populus nigra. RT-qPCR and RNA-seq analyses implied that PsnCBLs exhibited complex expression patterns in poplar under alkaline stress at different time points. These results provide comprehensive information for future research on the CBL gene function and lay a research foundation for studying alkaline stress in poplar.

Populus koreana 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 P. koreana. 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 P. koreana, enhancing our understanding of metabolic specialization and ecological adaptation in woody plants.