Cloning and functional analysis of novel terpene synthase genes from Aquilaria sinensis and insights into the biosynthesis of sesquiterpene

Aquilaria sinensis (Lour.) Gilg is one of the most important plant resources that produce agarwood, a fragrant resinous wood of high commercial value. Sesquiterpenes, the predominant constituents and important criterion for the quality of agarwood, play an essential role in stress and defence responses. However, the biosynthesis mechanisms of volatile sesquiterpenes and genes involved in these processes have not been comprehensively studied in Aquilaria . In this study, four sesquiterpene synthase genes were cloned from 3-year-old A. sinensis and identified using a yeast expression system as novel genes critical for sesquiterpene biosynthesis. AsTPS14, which catalyses the production of equal amounts of 4,11-selinadiene and α-selinene, is the first selinene synthase identified in Aquilaria . AsTPS13 can catalyse the production of three oxygenated sesquiterpenes, namely, β-eudesmol, γ-eudesmol and hinesol. AsTPS3 and AsTPS10 are two α-humulene synthases that can catalyse the production of α-humulene, and AsTPS3 is the most efficient α-humulene synthase in A. sinensis . Findings in this study reveal the diversity of sesquiterpene synthases and their multi-faceted functions, and offer further insights into the molecular mechanism of agarwood sesquiterpene biosynthesis. This work provides a solid theoretical and experimental foundation for molecularly assisted breeding of A. sinensis and efficient synthesis of sesquiterpenes.