title: Metabolic diversification of benzylisoquinoline alkaloid biosynthesis through the introduction of a branch pathway in Eschscholzia californica.
abstract: Higher plants produce a diverse array of secondary metabolites. These chemicals are synthesized from simple precursors through multistep reactions. To understand how plant cells developed such a complicated metabolism, we examined the plasticity of benzyl isoquinoline alkaloid biosynthesis in transgenic Eschscholzia californica cells with the ectopic expression of Coptis japonica scoulerine-9-O-methyltransferase (CjSMT). CjSMT catalyzes the O-methylation of scoulerine to produce tetrahydrocolumbamine (THC) in berberine biosynthesis and is not involved in benzophenanthridine alkaloid biosynthesis in E. californica. While a preliminary characterization confirmed that columbamine (oxidized product of THC) was produced in transgenic E. californica cells, many newly found peaks were not identified. Here, we report the identification of novel products, including allocryptopine and 10-hydroxychelerythrine. This result indicates that CjSMT reaction products were further converted by endogenous enzymes to produce double O-methylated compounds instead of a methylenedioxy ring at the 7,8-position of the original benzophenanthridine alkaloids. Further metabolite profiling revealed the enhanced diversification of the alkaloid profile in transgenic cells. Metabolic plasticity and the enzymes involved in metabolic diversity are discussed.
authors.affiliation: Division of Integrated Life Science, Graduate School of Biostudies, Kyoto University, Kyoto, 606-8502 Japan.
authors.forename: Tomoya
authors.initials: T
authors.lastname: Takemura
authors.forename: Nobuhiro
authors.initials: N
authors.lastname: Ikezawa
authors.forename: Kinuko
authors.initials: K
authors.lastname: Iwasa
authors.forename: Fumihiko
authors.initials: F
authors.lastname: Sato
mesh_terms: D000470:Alkaloids / Q000096:biosynthesis*; D044182:Benzylisoquinolines / Q000378:metabolism*; D002851:Chromatography, High Pressure Liquid; D016000:Cluster Analysis; D031675:Eschscholzia / Q000201:enzymology* / Q000235:genetics; D013058:Mass Spectrometry; D055442:Metabolome; D008780:Methyltransferases / Q000235:genetics; D030821:Plants, Genetically Modified / Q000201:enzymology / Q000235:genetics; D018749:RNA, Plant / Q000235:genetics
chemical_list: D000470:Alkaloids; D044182:Benzylisoquinolines; D018749:RNA, Plant; D008780:Methyltransferases; C093217:S-adenosyl-L-methionine - scoulerine-9-O-methyltransferase