Molecular mechanisms of lignin biosynthesis in Chimonanthus praecox: Morphological, physiological, transcriptomic,...

Chimonanthus praecox, an economically important tree species that is native to China, is widely cultivated as a woody cut flower and is highly demanded by consumers worldwide. The development and utilization of lignin can further enhance its economic value. However, there is currently no research on lignin biosynthesis in C. praecox branches. This study investigated two C. praecox varieties that exhibit significant differences in branch lignin content. Physiological characteristics of the xylem and the content of lignin, auxin, and four types of gibberellins were evaluated, and transcriptomic analysis of the differential expression of genes involved in lignin biosynthesis was performed. CpCAD4 was identified as a key functional gene, and its sequence characteristics were analyzed. Then, the gene was transferred to Nicotiana tabacum plants for further functional validation. Histological analysis and lignin content measurements of transgenic N. tabacum showed a significant increase in lignin content compared with that in wild-type N. tabacum. RT-qPCR analysis of the genes involved in the lignin biosynthesis pathway in transgenic N. tabacum revealed a significant increase in the expression of relevant genes, indicating that CpCAD4 is closely related to lignin biosynthesis in C. praecox. This study provides the first comprehensive exploration of the molecular mechanisms underlying lignin biosynthesis in C. praecox by integrating morphological, physiological, transcriptomic, and functional gene analyses. These findings provide valuable references for the further development and utilization of C. praecox and offer insights into the lignin biosynthesis mechanisms in woody plants.