Expression of Terpenoid Biosynthetic Genes and Accumulation of Chemical Constituents in _Valeriana fauriei_  
[PERSON]  
1 Department of Crop Science, Chungnam National University, 99 Daehak-ro, Yuseong-gu, Daejeon 34134, Korea; [EMAIL_ADDRESS]  
[PERSON]  
2 Department of Botany and Microbiology, Addiriyah Chair for Environmental Studies, College of Science, King Saud University, P. O. Box 2455, Riyadh 11451, Saudi Arabia; [EMAIL_ADDRESS] (M.V.A. ); [EMAIL_ADDRESS] (N.A.A.-D.)  
[PERSON]  
4 Department of Food and Nutrition and Institute of Natural Medicine, Hallym University, Chuncheon 200-702, Korea; [EMAIL_ADDRESS]  
[PERSON]  
1 Department of Crop Science, Chungnam National University, 99 Daehak-ro, Yuseong-gu, Daejeon 34134, Korea; [EMAIL_ADDRESS]  
Footnote 1: email: [EMAIL_ADDRESS]; [EMAIL_ADDRESS]; yel1004@korea. chologogic, analgesic, and spasmolytic effects of volatile compounds [7]. Volatile compounds determine a plant's chemotype and can influence its ecological relevance by shaping interactions with pollinators and herbivores [8]. Diverse volatile compounds are synthesized by different biochemical pathways in plants. There are lipoxygenase pathways including oxylipins, green leaf volatiles, isoprene and other terpenoids, some carotenoid derivatives, indoles, and phenolics, such as methyl salicate [9]. Terpenoids, which constitute the largest class of volatiles from plants, are synthesized from isoprenoid pathways (Figure 1) [1]. There are three basic phases of volatile terpenoid biosynthesis [10]. First, C\({}_{5}\)-isoprene units are formed from isopentenyl pyrophosphate (IPP) and its isomer dimethylallyl pyrophosphate (DMAPP) via two compartmentsally separated pathways, the mevalonic acid (MVA) pathway in the cytoplasm and the methylerythntol phosphate (MEP) pathway in the chloroplast. These precursors are then catalyzed by short-chain preyltransferase to form prenyl diphosphates, including geranyl diphosphate (GPP), farnesyl diphosphate (FPP), and geranylgeranyl pyrophosphate (GGPP) [11; 12]. Finally, many terpene synthases (TPS) synthesize prenyl diphosphates and build primary representatives of each type of terpenoid skeleton. Many volatile terpenoids are directly catalyzed by TPS, but others are modified by oxidation, dehydrogenation, acylation, and other types of reactions [10]. The MVA pathway is thought to provide three C\({}_{5}\) units for volatile sesquiterpenes (C\({}_{15}\)), while the MEP pathway gives rise to volatile hemiterpenes (C\({}_{5}\)), monoterpenes (C\({}_{10}\)), and diterpenes (C\({}_{20}\)) [13]. However, metabolic cross talk has been demonstrated, regulated by exchange of isoprenes like IPP between cytosolic and chloroplastic pathways [14]. Figure 1: Volatile terpenoid biosynthetic pathways in plants. _AACT_, Acetoacetyl-CoA thiolase; _CMK_, 4-(cytidine 5′-diphosphate)-2-C-methyl-D-erythntol kinase; _DMAPP_, dimethylallyl diphosphate; DXP, 1-deoxy-D-xylulose 5-phosphate; _DXR_, DXP reducoisomerase; _DXS_, DXP synthase; _FDS_, farnesyl diphosphate synthase; FPP, farnesyl diphosphate; GA-3P, glyceraldehyde-3-phosphate; _GDS_, geranyl diphosphate synthase; GGPP, geranyldiganyl diphosphate; GPP, geranyl diphosphate; _HDR_, _(E)_-4-hydroxy-3-methylbut 2-enyl diphosphate reductase; _HDS_, _(E)_-4-hydroxy-3-methylbut-2-enyl diphosphate synthase; HMG-CoA, 3-hydroxy-3-methylglutaryl-CoA; _HMGR_, HMG-CoA reductase; _HMGS_, HMG-CoA synthase; _IDI_, isopentenyl diphosphate isomerase; IPP, isopentenyl diphosphate; _MCT_, 2-C-methyl-D-erythntol 4-phosphate cytidylyltransferase; _MDS_, 2-C-methyl-D-erythntol 2,4-cyclodiphosphate synthase; MEP, 2-C-methyl-D-erythntol 4-phosphate; _MK_, mevalonate kinase; MVA, mevalonate; _MVD_, mevalonate diphosphate decarboxylase; _PMK_, phosphomevalonate kinase; _TPS_, terpene synthases. The genus _Valeriana_ L. belongs to Caprifoliaceae (honeysuckle family), and includes approximately 250 perennial herbaceous species with malodorous root stalks [15], and grows in temperate areas around the world [16].