Transcriptomic analysis reveals the significant effects of fertilization on the biosynthesis of sesquiterpenes in Phoebe bournei

Phoebe bournei is a potential medicinal plant. Its essential oils (Eos) are mainly composed of sesquiterpenes that has potential activities of anti-bacteria and anti-tumors. In this study, we evaluated the effects of compost and compound fertilizer on the total amount and main components of Eos in P. bournei, we also studied the molecular mechanism undergoing this process by deep sequencing the genes involved in the biosynthesis of sesquiterpenes. Fertilization enhanced the total amount of main components in Eos from both leaves and twigs. Bicyclo-germacrene, the primary sesquiterpene in the leaf EO, was significantly increased under compost treatment, while bicyclogermacrene and delta-cadinene (the second most abundant sesquiterpene) were decreased under compound fertilizer treatment. The two fertilizers had no significant effect on the abundance of the primary (+)-delta-cadinene in the twig EO, but had a positive effect on the second most abundant sesquiterpene copaene. Sig-nificant differences were observed in the number of differentially expressed genes (DEGs) with the leaves showing greater number of DEGs as compared to the twigs after compost treatment. Terpenoid backbone biosynthesis (TBB) is a key pathway of sesquiterpenes synthesis. The expression of genes regulating several important enzymes in TBB was altered after fertilization. After the compost treatment, the expression of the leaf DXS gene (ACQ66107.1), being closely related to the sesquiterpene biosynthesis in P. bournei leaves, was decreased. Compost and compound fertilizer altered the expression of the two important branch-point enzymes (FPPS and GGPPS) genes (ART33314.1 and ATT59265.1), which contributed to the changes of the total amount and components of P. bournei sesquiterpenes. This study provides a new insight into the future use of P. bournei for Eos.

Automated summary

In this study, the effects of compost and compound fertilizer on the total amount and main components of essential oils (Eos) in Phoebe bournei were evaluated. The study also investigated the molecular mechanism underlying the biosynthesis of sesquiterpenes in P. bournei. Fertilization was found to enhance the total amount of main components in Eos from both leaves and twigs. Different effects of compost and compound fertilizer were observed on the abundance of specific sesquiterpenes. The study provides new insights into the future use of P. bournei for essential oil production.