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Influence of Precursor Availability on Alkaloid Accumulation by Transgenic Cell Line of Catharanthus roseus1

Serap Whitmer, Camilo Canel2, *, Didier Hallard, Cecilia Gonçalves, and Robert Verpoorte

Department of Pharmacognosy, Gorlaeus Laboratories, Leiden University, P.O. Box 9502, 2300 RA Leiden, The Netherlands

We have used a transgenic cell line of Catharanthus roseus (L.) G. Don to study the relative importance of the supply of biosynthetic precursors for the synthesis of terpenoid indole alkaloids. Line S10 carries a recombinant, constitutively overexpressed version of the endogenous strictosidine synthase (Str) gene. Various concentrations and combinations of the substrate tryptamine and of loganin, the immediate precursor of secologanin, were added to suspension cultures of S10. Our results indicate that high rates of tryptamine synthesis can take place under conditions of low tryptophan decarboxylase activity, and that high rates of strictosidine synthesis are possible in the presence of a small tryptamine pool. It appears that the utilization of tryptamine for alkaloid biosynthesis enhances metabolic flux through the indole pathway. However, a deficiency in the supply of either the iridoid or the indole precursor can limit flux through the step catalyzed by strictosidine synthase. Precursor utilization for the synthesis of strictosidine depends on the availability of the cosubstrate; the relative abundance of these precursors is a cell-line-specific trait that reflects the metabolic status of the cultures.

1   This work was supported by the National Science Foundation under a grant awarded to C.C. in 1995.
2   Present address: U.S. Department of Agriculture, Agricultural Research Service, Natural Products Center, Room 2021, University, MS 38677.
*   Corresponding author; e-mail CCanel{at}olemiss.edu; fax 1-601-232-1035.

Plant Physiol. (1998) 116: 853-857
Copyright Clearance Center:   0032-0889/98/116/0853/05
© 1998 American Society of Plant Physiologists




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[Abstract] [Full Text]


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