Mechanism of Terpene Formation in Pogostemon cablin cv. Jing Huoxiang Revealed by Metabolome and Transcriptome Analysis

Pogostemon cablin (Blanco) Benth. cv. ‘Jing Huoxiang’, is a valuable medicinal plant widely studied for its aboveground tissues, which are rich in bioactive compounds such as patchouli alcohol. However, systematic investigations into the biosynthesis of sesquiterpenes in its underground parts (roots) remain limited, with several critical knowledge gaps: (1) the metabolic basis of root-specific accumulation of polycyclic sesquiterpenes is unclear; (2) key terpene synthase (TPS) gene resources remain underexplored; and (3) the regulatory network of terpenoid biosynthesis is poorly understood. Addressing these questions is essential for the rational design and efficient production of terpene synthases. In this study, we integrated metabolomic and transcriptomic approaches to systematically characterize terpenoid profiles across different tissues of P. cablin and elucidate their biosynthetic regulation. Using GC-MS analysis, we identified distinct terpenoid compositions in roots, stems, leaves, flowers, and glandular trichomes. Notably, patchouli alcohol and pogostone accounted for over 60% of the total volatile oil content, while roots specifically accumulated polycyclic sesquiterpenes such as β-caryophyllene and α-humulene. Through transcriptome sequencing and bioinformatic analysis, we comprehensively annotated the TPS gene family, revealing that the TPS-a subfamily (34 genes) was the most abundant in P. cablin, with several members exhibiting root-predominant expression. Co-expression network analysis further identified candidate genes encoding potential high-efficiency polycyclic sesquiterpene synthases and uncovered a β-caryophyllene/α-humulene-regulated tertiary metabolic pathway. Our findings not only fill a critical gap in understanding sesquiterpene biosynthesis in the underground tissues of P. cablin but also provide a foundation for synthetic biology-based optimization of terpenoid production. This research paves the way for the efficient biosynthesis of sesquiterpenes to meet industrial demands in pharmaceuticals, fragrances, and biofuels.