Metabolic Engineering of Tropane Alkaloid Biosynthesis in Plants

Abstract

Over the past decade, the evolving commercial importance of so-called plant secondary metabolites has resulted in a great interest in secondary metabolism and, particularly, in the possibilities to enhance the yield of fine metabolites by means of genetic engineering. Plant alkaloids, which constitute one of the largest groups of natural products, provide many pharmacologically active compounds. Several genes in the tropane alkaloids biosynthesis pathways have been cloned, making the metabolic engineering of these alkaloids possible. The content of the target chemical scopolamine could be significantly increased by various approaches, such as introducing genes encoding the key biosynthetic enzymes or genes encoding regulatory proteins to overcome the specific rate-limiting steps. In addition, antisense genes have been used to block competitive pathways. These investigations have opened up new, promising perspectives for increased production in plants or plant cell culture. Recent achievements have been made in the metabolic engineering of plant tropane alkaloids and some new powerful strategies are reviewed in the present paper.

Tropane alkaloids production in transgenic Hyoscyamus niger hairy root cultures over-expressing Putrescine N-methyltransferase is methyl jasmonate-dependent

“…Some researches have already been done on the genetic engineering of pharmaceutically important tropane alkaloids (Zhang et al 2005;Oksman-Caldentey and Arroo 2000). Because the conversion of hyoscyamine to the much more valuable scopolamine is the major goal of these studies, more workers paid their attention to the h6h gene coding for the last enzyme involved in the tropane alkaloid biosynthesis ( Fig.…”

Engineering secondary metabolite production in hairy roots

“…The production of secondary metabolites is under strict regulation in plant cells owing to coordinated control of the biosynthetic genes by transcription factors. The use of specific transcription factors would avoid the time-consuming step of acquiring knowledge about all the enzymatic steps of a poorly characterized biosynthetic pathway and transcription factors could be used to increase the level of a series of enzymes in a pathway, avoiding the need to overexpress each individual pathway gene (Zhang et al 2005b). In Arabidopsis, it has been found that over-expression of the MYB transcription factor PAP1 (production of anthocyanin pigment-1) leads to transgenic plants with higher anthocyanin levels due to the co-ordinated up-regulation of genes in the anthocyanin biosynthetic pathway.…”

“…Strategies should include fortification of multiple steps by overexpressing multiple biosynthetic genes (Fig. 3I), manipulating regulatory genes that control the expression of multiple pathway enzyme genes, or both (Zhang et al 2005b). Simultaneous introduction and overexpression of genes encoding the ratelimiting upstream enzyme putrescine N-methyltransferase (PMT) and the downstream key enzyme hyoscyamine 6 b hydroxylase (H6H) of scopolamine biosynthesis in transgenic henbane (H. niger) hairy root cultures have been studied by Zhang et al (2004).…”

Increasing Scopolamine content in Hairy Roots of Atropa belladonna using Bioreactor

“…Atropa belladonna L. (solonacea), generally referred to as the "deadly nightshade," is a perennial herbaceous plant used for commercial production of tropane alkaloids in the pharmaceutical industry (Zhang et al 2005). Among tropane alkaloids, scopolamine is a more valuable secondary metabolite due to its fewer side-effects, usefulness in the treatment of Parkinson"s disease, and relaxing and hallucinogenic properties.…”