[Systematic identification of chemical forms of key terpene synthase in Cinnamomum camphora]

Cinnamomum camphora is an important economic tree species in China. According to the type and content of main components in the volatile oil of leaf, C. camphora were divided into five chemotypes, including borneol-type, camphor-type, linalool-type, cineole-type, and nerolidol-type. Terpene synthase(TPS) is the key enzyme for the formation of these compounds. Although several key enzyme genes have been identified, the biosynthetic pathway of(+)-borneol, which has the most economic value, has not been reported. In this study, nine terpenoid synthase genes CcTPS1-CcTPS9 were cloned through transcriptome analysis of four chemical-type leaves. After the recombinant protein was induced by Escherichia coli, geranyl pyrophosphate(GPP) and farnesyl pyrophosphate(FPP) were used as substrates for enzymatic reaction, respectively. Both CcTPS1 and CcTPS9 could catalyze GPP to produce bornyl pyrophosphate, which could be hydrolyzed by phosphohydrolase to obtain(+)-borneol, and the product of(+)-borneol accounted for 0.4% and 89.3%, respectively. Both CcTPS3 and CcTPS6 could catalyze GPP to generate a single product linalool, and CcTPS6 could also react with FPP to generate nerolidol. CcTPS8 reacted with GPP to produce 1,8-cineol(30.71%). Nine terpene synthases produced 9 monoterpene and 6 sesquiterpenes. The study has identified the key enzyme genes responsible for borneol biosynthesis in C. camphora for the first time, laying a foundation for further elucidating the molecular mechanism of chemical type formation and cultivating new varieties of borneol with high yield by using bioengineering technology.