Terpenoids play important roles in productivity and product quality in tea(Camellia sinensis),not only because volatile terpenoids contribute significantly to the aroma of teas,but terpenoid-derived light harvesting pigments and phytohormones such as strigolactones implement photosynthesis and branching in plants.All terpenoids are derived from isopentenyl diphosphate(IPP),dimethylallyl diphosphate(DMAPP) produced by methyl-erythritol-phosphate(MEP) and mevalonate(MVA) pathways,the early steps of isoprenoid biosynthesis.For the purpose to determine key genes in the MEP and MVA pathways in C.sinensis,five genes with complete coding sequence and three with partial sequence were obtained based on previously attained transcriptome data and polymerase chain reaction approach in this study.In silico analyses suggested that the five genes with full coding sequence individually encoded acetyl-CoA C-acetyltransferase(CsAACT),3-hydroxy-3-methylglutaryl-CoA synthase(CsHMGS),4-(cytidine 5'-diphospho)-2-C-methyl-D-erythritol kinase(CsCMK),1-hydroxy-2-methyl-2-(E)-butenyl-4-diphosphate synthase(CsHDS),and farnesyl pyrophosphate synthase(CsFPS).Additionally,studies on metabolite-mediated gene expression were performed using tea cell suspensions and leaf-disc cultures.Our data showed that the addition of acetyl-CoA increased the transcript level of CsAACT and CsHMGS by 1.5- and 3-fold,respectively.The addition of deoxy-D-xylulose 5-phosphate(DXP) induced the expression of CsCMK and CsHDS by 2.3- and 1.5-fold,respectively.The CsFPS expression was approximately 2-fold higher when treated with DXP,IPP or DMAPP than the untreated control,but this induction was not observed with the acetyl-CoA treatment.Our studies indicated that expression of CsAACT,CsHMGS,CsCMK,CsHDS,and CsFPS were metabolite-mediated in a different extent.
