Expression of Terpenoid Biosynthetic Genes and Accumulation of Chemical Constituents in Valeriana fauriei

Abstract

Valeriana fauriei (V. fauriei), which emits a characteristic and unpleasant odor, is important in traditional medicine. In this study, the expression of terpenoid biosynthetic genes was investigated in different organs that were also screened for volatile compounds including valerenic acid and its derivatives. Specific expression patterns from different parts of V. fauriei were observed using quantitative real-time PCR (qRT-PCR). The highest transcript levels of biosynthetic genes involved in mevalonic acid (MVA) and methylerythritol phosphate (MEP) production were found in the stem. Although the amounts of volatile compounds were varied by organ, most of the volatile terpenoids were accumulated in the root. Gas chromatography mass spectrometry (GC-MS) analysis identified 128 volatile compounds, which represented 65.33% to 95.66% of total volatiles. Certain compounds were only found in specific organs. For example, isovalerenic acid and valerenic acid and its derivatives were restricted to the root. Organs with high transcript levels did not necessarily have high levels of the corresponding chemical constituents. According to these results, we hypothesize that translocation may occur between different organs in V. fauriei.

Keywords: Valeriana fauriei; gene expression; terpenoid; valerenic acid; volatile compounds.

Figure 1

Volatile terpenoid biosynthetic pathways in plants. AACT, Acetoacetyl-CoA thiolase; CMK, 4-(cytidine 5′-diphosphate)-2-C-methyl-d-erythritol kinase; DMAPP, dimethylallyl diphosphate; DXP, 1-deoxy-d-xylulose 5-phosphate; DXR, DXP reductoisomerase; DXS, DXP synthase; FDS, farnesyl diphosphate synthase; FPP, farnesyl diphosphate; GA-3P, glyceraldehyde-3-phosphate; GDS, geranyl diphosphate synthase; GGPP, geranylgeranyl 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-erythritol 4-phosphate cytidylyltransferase; MDS, 2-C-methyl-d-erythritol 2,4-cyclodiphosphate synthase; MEP, 2-C-methyl-D-erythritol 4-phosphate; MK, mevalonate kinase; MVA, mevalonate; MVD, mevalonate diphosphate decarboxylase; PMK, phosphomevalonate kinase; TPS, terpene synthases.

Figure 2

Transcript levels of MVA biosynthetic genes in different organs of V. fauriei (Vf). Genes encode the following enzymes: (a) VfAACT, acetoacetyl-CoA thiolase; (b) VfHMGS, 3-hydroxy-3-methylglutaryl-CoA synthase; (c) VfHMGR, 3-hydroxy-3-methylglutaryl-CoA reductase; (d) VfMK, mevalonate kinase; (e) VfPMK, phosphomevalonate kinase; (f) VfMVD, mevalonate diphosphate decarboxylase; (g) VfFDS, farnesyl diphosphate synthase; and (h) VfIDI, isopentenyl diphosphate isomerase.

Figure 3

Transcript levels of MEP biosynthetic genes in different organs from V. fauriei (Vf). Genes encode the following enzymes: (a) VfDXS, 1-deoxy-d-xylulose 5-phosphate synthase; (b) VfDXR, 1-deoxy-d-xylulose 5-phosphate reductoisomerase; (c) VfMCT, 2-C-methyl-d-erythritol 4-phosphate cytidylyltransferase; (d) VfCMK, 4-(cytidine 5’-diphosphate)-2-C-methyl-d-erythritol kinase; (e) VfMDS, 2-C-methyl-d-erythritol 2,4-cyclodiphosphate synthase; (f) VfHDS, (E)-4-hydroxy-3-methylbut-2-enyl diphosphate synthase; (g) VfHDR, (E)-4-hydroxy-3-methylbut 2-enyl diphosphate reductase; and (h) VfGDS, geranyl diphosphate synthase.

Figure 4

Photographs of two-year-old V. fauriei grown in Pyeongchang, Gangwon-do, South Korea.