Metabolic engineering of the mevalonate and non‐mevalonate isopentenyl diphosphate‐forming pathways for the production of health‐promoting isoprenoids in tomato

Summary The genetic manipulation of both the mevalonic acid (MVA) and methylerythritol‐4‐phosphate (MEP) pathways, leading to the formation of isopentenyl diphosphate (IPP), has been achieved in tomato using 3‐hydroxymethylglutaryl CoA ( hmgr‐1 ) and 1‐deoxy‐ d ‐xylulose‐5‐phosphate synthase ( dxs ) genes, respectively. Transgenic plants containing an additional hmgr‐1 from Arabidopsis thaliana , under the control of the cauliflower mosaic virus (CaMV) 35S constitutive promoter, contained elevated phytosterols (up to 2.4‐fold), but IPP‐derived isoprenoids in the plastid were unaltered. Transgenic lines containing a bacterial dxs targeted to the plastid with the tomato dxs transit sequence resulted in an increased carotenoid content (1.6‐fold), which was inherited in the next generation. Phytoene and β‐carotene exhibited the greatest increases (2.4‐ and 2.2‐fold, respectively). Extra‐plastidic isoprenoids were unaffected in these lines. These data are discussed with respect to the regulation, compartmentalization and manipulation of isoprenoid biosynthetic pathways and their relevance to plant biotechnology.