Metabolic Engineering of Terpenoid Biosynthesis in Plants

Abstract

Metabolic engineering of terpenoids in plants is a fascinating research topic from two main perspectives. On the one hand, the various biological activities of these compounds make their engineering a new tool for improving a considerable number of traits in crops. These include for example enhanced disease resistance, weed control by producing allelopathic compounds, better pest management, production of medicinal compounds, increased value of ornamentals and fruit and improved pollination. On the other hand, the same plants altered in the profile of terpenoids and their precursor pools make a most important contribution to fundamental studies on terpenoid biosynthesis and its regulation. In this review we describe our recent results with terpenoid engineering, focusing on two terpenoid classes the monoterpenoids and sesquiterpenoids. The emerging picture is that engineering of these compounds and their derivatives in plant cells is feasible, although with some requirements and limitations. For example, in terpenoid engineering experiments crucial factors are the subcellular localisation of both the precursor pool and the introduced enzymes, the activity of endogenous plant enzymes which modify the introduced terpenoid skeleton, the costs of engineering in terms of effects on other pathways sharing the same precursor pool and the phytotoxicity of the introduced terpenoids. Finally, we will show that transgenic plants altered in their terpenoid profile exert novel biological activities on their environment, for example influencing insect behaviour.Abbreviations: DMADP -dimethylallyl diphosphate; FDP -farnesyl diphosphate; GDP -geranyl diphosphate; GGDP -geranylgeranyl diphosphate; IDP -isopentenyl diphosphate; MEP -methylerythritol 4-phosphate; TPSs -terpene synthases.

Two nearly identical terpene synthases catalyze the formation of nerolidol and linalool in snapdragon flowers

“…The presence of substrate for monoterpene and sesquiterpene biosynthesis in both plastids and cytosol, although at different levels (high GPP/trace FPP in plastid and vice versa in cytosol), would allow a dual functional enzyme to produce monoterpenes and sesquiterpenes in both compartments, but at a ratio representative of that of the precursors. Indeed, overexpression of strawberry FaNES1 in plastids of Arabidopsis and potato resulted in the formation of small quantities of nerolidol, which was 100-to 300-fold lower than the quantity of linalool that was produced (Aharoni et al, 2003(Aharoni et al, , 2006. Here, we show that snapdragon flowers emit linalool and nerolidol, the levels of which are developmentally regulated, and are of a similar order of magnitude (Figure 7d).…”

“…Thus, compartmental separation of precursors for monoterpene and sesquiterpene biosynthesis would prevent a bifunctional monoterpene/ sesquiterpene synthase from using both of its activities, unless it is localized in both compartments. However, recent metabolic engineering in Arabidopsis, tobacco and potato revealed the existence of small levels of FPP in plastids and GPP in the cytosol (Aharoni et al, 2003(Aharoni et al, , 2006Wu et al, 2006). The presence of substrate for monoterpene and sesquiterpene biosynthesis in both plastids and cytosol, although at different levels (high GPP/trace FPP in plastid and vice versa in cytosol), would allow a dual functional enzyme to produce monoterpenes and sesquiterpenes in both compartments, but at a ratio representative of that of the precursors.…”

Systematic significance and pharmaceutical potentials of trichomes in accessions of Sesamum indicum L. Pedaliaceae

“…Glandular trichomes have in common the capacity to produce, store and secrete large amounts of different classes of secondary metabolites (Fahn, 2000;Schilmiller et al, 2008). Many of the specialized metabolites that can be found in glandular trichomes have become commercially important as natural pesticides, but also have been found to be used as food additives or pharmaceuticals (Duke et al, 2000;Aharoni et al, 2006). For instance, plants of the Lamiaceae, comprising species such as Mint (Mentha × piperita), Basil (Ocimum basilicum), Lavender (Lavandula spica), Oregano (Origanum vulgare) and Thyme (Thymus vulgaris), are cultivated for their glandular trichomeproduced essential oils (Schilmiller et al, 2008).…”

Isolation of Viable Multicellular Glands from Tissue of the Carnivorous Plant, <i>Nepenthes</i>

“…It should be emphasized that the production and secretion capacities of many secreting glands identified them as prime targets for metabolic engineering in plants with potential applications in a wide range of areas including human health or durable crop protection 13,14 . In addition, secretions by these different structures play important roles in the interactions of the plants with their abiotic and biotic environment in particular with insects.…”