Journal Article

Metabolic Diversification of Benzylisoquinoline Alkaloid Biosynthesis Through the Introduction of a Branch Pathway in <i>Eschscholzia californica</i>

Tomoya Takemura, Nobuhiro Ikezawa, Kinuko Iwasa and Fumihiko Sato

in Plant and Cell Physiology

Published on behalf of Japanese Society of Plant Physiologists

Volume 51, issue 6, pages 949-959
Published in print June 2010 | ISSN: 0032-0781
Published online April 2010 | e-ISSN: 1471-9053 | DOI: http://dx.doi.org/10.1093/pcp/pcq063
Metabolic Diversification of Benzylisoquinoline Alkaloid Biosynthesis Through the Introduction of a Branch Pathway in Eschscholzia californica

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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.

Keywords: Eschscholzia californica; Isoquinoline alkaloid; Metabolic diversity

Journal Article.  4487 words.  Illustrated.

Subjects: Biochemistry ; Molecular and Cell Biology ; Plant Sciences and Forestry

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