Figure 1

Biosynthesis of β-carotene via both the MEP and MVA pathways used in this study. DMAPP and IPP, precursors for β-carotene biosynthesis are synthesized via both the MEP and MVA pathways. The MVA pathway was divided into two portions, the upper (acetyl-CoA to MVA) and lower (MVA to IPP and DMAPP). The upper portion is composed of the mvaE (acetyl-CoA acetyltransferase), mvaS (HMG-CoA synthase) and mvaE (HMG-CoA reductase) genes, which are from E. faecalis, while the lower is composed of the Erg12 (mevalonate kinase), Erg8 (phosphomevalonate kinase), Erg19 (diphosphomevalonate decarboxylase) and idi1 (IPP isomerase) genes, which are from S. cerevisiae. DMAPP and IPP are converted to GPP by IspA (GPP/FPP synthase) from E. coli and by GPPS2 (GPP synthase) from A. grandis. FPP is transformed into β-carotene via the foreign carotenoid synthesis pathway which includes crtE (GGPP synthase), crtB (phytoene synthase), crtI (phytoene desaturase) and crtY (lycopene cyclase) from E. herbicola. dxs (DXP synthase) and fni (IPP isomerase) genes from B. subtilis. Abbreviations: G-3-P, glyceraldehyde-3-phosphate; DXP, 1-deoxy-d-xylulose-5-phosphate; MEP, 2-C-methyl-d-erythritol-4-phosphate; HMG-CoA, 3-hydroxy-3-methylglutaryl-CoA; IPP, isopentenyl diphosphate; DMAPP, dimethylallyl diphosphate; GPP, geranyl diphosphate; FPP, farnesyl diphosphate; GGPP, geranylgeranyl diphosphate.