Orthologs of the archaeal isopentenyl phosphate kinase regulate terpenoid production in plants

Abstract

Terpenoids, compounds found in all domains of life, represent the largest class of natural products with essential roles in their hosts. All terpenoids originate from the five-carbon building blocks, isopentenyl diphosphate (IPP) and its isomer dimethylallyl diphosphate (DMAPP), which can be derived from the mevalonic acid (MVA) and methylerythritol phosphate (MEP) pathways. The absence of two components of the MVA pathway from archaeal genomes led to the discovery of an alternative MVA pathway with isopentenyl phosphate kinase (IPK) catalyzing the final step, the formation of IPP. Despite the fact that plants contain the complete classical MVA pathway, IPK homologs were identified in every sequenced green plant genome. Here, we show that IPK is indeed a member of the plant terpenoid metabolic network. It is localized in the cytosol and is coexpressed with MVA pathway and downstream terpenoid network genes. In planta, IPK acts in parallel with the MVA pathway and plays an important role in regulating the formation of both MVA and MEP pathway-derived terpenoid compounds by controlling the ratio of IP/DMAP to IPP/DMAPP. IP and DMAP can also competitively inhibit farnesyl diphosphate synthase. Moreover, we discovered a metabolically available carbon source for terpenoid formation in plants that is accessible via IPK overexpression. This metabolite reactivation approach offers new strategies for metabolic engineering of terpenoid production.A ll living organisms produce terpenoids, directing a considerable amount of their available carbon to the biosynthesis of one of the most structurally and functionally diverse classes of primary and secondary metabolites in nature (1). These molecules play essential and specialized roles in their hosts in photosynthesis and respiration (the phytyl side-chain of chlorophyll, quinones), modulating membrane fluidity (sterols), regulating growth and development (hormones), photoprotection and energy transfer (carotenoids), and communication, environmental adaptation, and chemical defense (mono-, sesqui-, and diterpenes) (2, 3). Some compounds, like quinones, chlorophylls, and certain proteins, which require targeting to membranes for their functions, are anchored by terpenoid structures. In addition to their vital biological roles, terpenoids are also widely used by humans as nutritional supplements, flavors, fragrances, biofuels, and pharmaceuticals (4-6). Multiple metabolic pathways operate in parallel, often intersect, and routinely exchange intermediates, leading to one of the most chemically complex groups of natural products in the biosphere. Therefore, achieving a complete understanding at both genetic and biochemical levels of the underlying regulatory networks that coordinate and homeostatically govern these biosynthetic systems is of paramount importance to fully capitalize on the utility of terpenoids to natural ecosystems and humans.All terpenoids originate from C5 building blocks, isopentenyl diphosphate (IPP) and its isomer dimethylallyl diphosphate (DMAPP), which are ...

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