title: Tryptophan decarboxylase plays an important role in ajmalicine biosynthesis in Rauvolfia verticillata.
abstract: Tryptophan decarboxylase (TDC) converts tryptophan into tryptamine that is the indole moiety of ajmalicine. The full-length cDNA of Rauvolfia                         verticillata (RvTDC) was 1,772 bps that contained a 1,500-bp ORF encoding a 499-amino-acid polypeptide. Recombinant 55.5 kDa RvTDC converted tryptophan into tryptamine. The K                         (m) of RvTDC for tryptophan was 2.89 mM, higher than those reported in other TIAs-producing plants. It demonstrated that RvTDC had lower affinity to tryptophan than other plant TDCs. The K                         (m) of RvTDC was also much higher than that of strictosidine synthase and strictosidine glucosidase in Rauvolfia. This suggested that TDC might be the committed-step enzyme involved in ajmalicine biosynthesis in R. verticillata. The expression of RvTDC was slightly upregulated by MeJA; the five MEP pathway genes and SGD showed no positive response to MeJA; and STR was sharply downregulated by MeJA. MeJA-treated hairy roots produced higher level of ajmalicine (0.270 mg g(-1) DW) than the EtOH control (0.183 mg g(-1) DW). Highest RvTDC expression level was detected in hairy root, about respectively 11, 19, 65, and 109-fold higher than in bark, young leaf, old leaf, and root. Highest ajmalicine content was also found in hairy root (0.249 mg g(-1) DW) followed by in bark (0.161 mg g(-1) DW) and young leaf (0.130 mg g(-1) DW), and least in root (0.014 mg g(-1) DW). Generally, the expression level of RvTDC was positively consistent with the accumulation of ajmalicine. Therefore, it could be deduced that TDC might be the key enzyme involved in ajmalicine biosynthesis in Rauvolfia.
authors.affiliation: Key Laboratory of Eco-environments in Three Gorges Reservoir Region (Ministry of Education), Laboratory of Natural Products and Metabolic Engineering, Chongqing Engineering and Technology Research Center for Sweetpotato, School of Life Sciences, Southwest University, Chongqing, 400715, China.
authors.forename: Wanhong
authors.initials: W
authors.lastname: Liu
authors.forename: Rong
authors.initials: R
authors.lastname: Chen
authors.forename: Min
authors.initials: M
authors.lastname: Chen
authors.forename: Haoxing
authors.initials: H
authors.lastname: Zhang
authors.forename: Meifang
authors.initials: M
authors.lastname: Peng
authors.forename: Chunxian
authors.initials: C
authors.lastname: Yang
authors.forename: Xingjia
authors.initials: X
authors.lastname: Ming
authors.forename: Xiaozhong
authors.initials: X
authors.lastname: Lan
authors.forename: Zhihua
authors.initials: Z
authors.lastname: Liao
mesh_terms: D000595:Amino Acid Sequence; D001142:Aromatic-L-Amino-Acid Decarboxylases / Q000378:metabolism*; D018076:DNA, Complementary; D015971:Gene Expression Regulation, Enzymologic; D018506:Gene Expression Regulation, Plant; D017343:Genes, Plant; D005959:Glucosidases / Q000378:metabolism; D024301:Plant Bark / Q000378:metabolism; D018515:Plant Leaves / Q000378:metabolism; D018517:Plant Roots / Q000378:metabolism; D030821:Plants, Genetically Modified; D011926:Rauwolfia / Q000201:enzymology* / Q000235:genetics*; D046948:Secologanin Tryptamine Alkaloids / Q000378:metabolism*; D014364:Tryptophan / Q000378:metabolism
chemical_list: D018076:DNA, Complementary; D046948:Secologanin Tryptamine Alkaloids; C005709:raubasine; D014364:Tryptophan; D005959:Glucosidases; D001142:Aromatic-L-Amino-Acid Decarboxylases