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Fig. 1 | Plant Methods

Fig. 1

From: Isotope ratio-based quantification of carbon assimilation highlights the role of plastidial isoprenoid precursor availability in photosynthesis

Fig. 1

Involvement of the 2C-methyl-d-erythritol-4-phosphate (MEP) pathway in the biosynthesis of photosynthetic co-factors. The MEP pathway produces isopentenyl and dimethylallyl diphosphate (IDP and DMADP, boxed) in the plastid, which supplies PQ (plastoquinone), Chl (chlorophyll a and b), and PhyQ (phylloquinone) biosynthesis. Mutants (blue italics) and herbicides (red, bold) used in this study are shown next to the affected steps. Enzymes are shown in bold on the left. The mevalonate pathway, which yields IDP and DMADP in the cytosol, is enclosed in the solid box. The MEP pathway is directly linked to the formation of photosynthetic machinery by providing IDP and DMADP which are condensed into geranylgeranyl diphosphate (GGDP) by the prenyl transferase GGDP synthase (GGDS). GGDP undergoes three subsequent reductions to form phytyl diphosphate through dihydrogeranylgeranyl diphosphate and tetrahydrogeranylgeranyl diphosphate. Phytyl diphosphate provides the phytyl tail for phylloquinone and chlorophyll. The MEP pathway further supports photosynthesis through 8 total step-wise condensations of IDP with DMADP to form SDP, which becomes the hydrocarbon tail for plastoquinone. Herbicide abbreviations are as follows: CLZ, clomazone; FSM, fosmidomycin; NFZ, norflurazon; MEV, mevinolin. Biosynthetic intermediates are as follows: GAP, d-glyceraldehyde-3-phosphate; DXP, 1-deoxy-d-xylulose 5-phosphate; MEP, 2C-methyl-d-erythritol 4-phosphate; CDP-ME, 4-(cytidine 5′-diphospho)-2-C-methyl-d-erythritol; CDP-MEP, 4-(cytidine 5′-diphospho)-2-C-methyl-d-erythritol-2-phosphate; MEcDP, 2C-methyl-d-erythritol-2,4-cyclodiphosphate; HMBDP, 1-hydroxy-2-methyl-2-(E)-butenyl-4-diphosphate; SDP, solanesyl diphosphate; GGDP, geranylgeranyl diphosphate; AcCoA, acetyl-CoA; HMG-CoA, hydroxymethylglutaryl-CoA; FDP, farnesyl diphosphate. Enzymes abbreviations are as follows: DXS, 1-deoxy-d-xylulose 5-phosphate synthase; DXR, 1-deoxy-d-xylulose 5-phosphate reductoisomerase; MCT, 2C-methyl-d-erythritol 4-phosphate cytidyltransferase; CMK, 4-(cytidine 5′-diphospho)-2C-methyl-d-erythritol kinase; MDS, 2C-methyl-d-erythritol-2,4- cyclodiphosphate synthase; HDS, 4-hydroxy-3-methylbut-2-enyl diphosphate synthase; HDR, 4-hydroxy-3-methylbut-2-enyl diphosphate reductase; PSY, phytoene synthase; PDS, 15-cis-phytoene desaturase. Dotted arrows represent multiple steps

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