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

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.