Integrated transcriptomic, untargeted metabolomic, and lignin-targeted metabolomic insights into vascular cambium development in Osmanthus fragrans

Osmanthus fragrans wood is valued for its hardness, fine texture and wear resistance, making it particularly suitable for high-end furniture and intricate woodcarving. However, the molecular mechanisms underlying vascular development remain poorly understood. Here, we integrated transcriptomic, untargeted metabolomic, and lignin-targeted metabolomic analyses across five developmental stages of the vascular cambium. Untargeted metabolomic profiling identified 1837 differentially synthesised metabolites (DSMs), primarily enriched in the zeatin and phenylpropanoid biosynthesis (PB) pathways. Lignin-targeted metabolomics detected 11 metabolites, nine of which exhibited significant variation and represented eight key phenylpropanoid-derived compounds. Transcriptome sequencing generated 631.473 million high-quality clean reads and revealed 10,895 differentially expressed genes (DEGs), predominantly enriched in plant hormone signal transduction, zeatin biosynthesis, and PB pathways. During the active cambium phase, 15 PB-related structural genes—including PAL , C4H , 4CL , CCR , COMT , and CCoAOMT —were upregulated, likely facilitating the accumulation of lignin precursors such as coniferaldehyde, sinapyl alcohol, sinapic acid, and sinapinaldehyde. Transcription factors from the MYB , NAC , ERF , and HSF families may regulate the PB pathway. Hormone signalling analysis revealed that indole-3-acetic acid plays a central role in the transition from dormancy to active growth, whereas cytokinin, jasmonic acid, ethylene, and brassinosteroids promote cambial activity. In contrast, salicylic acid and abscisic acid were primarily associated with the induction of cambial dormancy. Several hormone-related potential hub transcription factors—including C2H2 , TCP , TGA , WRKY , bZIP , NAC , bHLH , and HD-ZIP —were identified. These findings may provide new insights into the transcriptional and metabolic regulation of cambial development and establish a molecular foundation for improving wood properties in O. fragrans .