Fig. 8

Plausible biosynthetic pathway and expression of unigenes involved in the biosynthesis of anthraquinones in Polygonum cuspidatum. The expression levels of unigenes encoding the enzymes of each step are shown. MenF, isochorismate synthase; MenD, 2-succinyl-5-enolpyruvyl-6-hydroxy-3-cyclohexene-1-carboxylate synthase; MenH, 2-succinyl-6-hydroxy-2,4-cyclohexadiene-1-carboxylate synthase; MenC, O-succinylbenzoate synthase; MenE, O-succinylbenzoic acid-CoA ligase; MenB, naphthoate synthase; DXS: 1-deoxy-D-xylulose-5-phosphate synthase; DXR: 1-deoxy-D-xylulose-5-phosphate reductoisomerase; ISPD, 2-C-methyl-D-erythritol 4-phosphate cytidylyltransferase; ISPE, 4-diphosphocytidyl-2-C-methyl-D-erythritol kinase; ISPF, 2-C-methyl-D-erythritol 2,4-cyclodiphosphate synthase; HDS, (E)-4-hydroxy-3-methylbut-2-enyl diphosphate synthase; HDR, 4-hydroxy-3-methylbut-2-enyl diphosphate reductase. AACT, acetyl-CoA C-acetyltransferase; HMGS, hydroxymethylglutaryl-CoA synthase; HMGR, hydroxymethylglutaryl-CoA reductase; MVK, mevalonate kinase; PMVK, phosphomevalonate kinase; MVD, diphosphomevalonate decarboxylase; IDI, isopentenyl-diphosphate delta-isomerase. The anthraquinone metabolism pathway was drawn using ChemDraw software according to map 00900 and map 00130 in KEGG pathway database; the copyright permission of use and modification of the above pathways has been granted