Back Article

Figure 1. 

The pathway of carotenoid biosynthesis and its transcriptional regulation. The pathway in the rectangle above represents the production of substrates for carotenoid synthesis through the MEP pathway. The pathway in the lower ellipsis represents the synthesis and decomposition of carotenoids in plastids. Enzymes are shown in blue. Blue arrows denote positive regulation, whereas red arrows denote negative regulation. DXS, 1-deoxy-D-xylulose-5-phosphate synthase; GGPP, geranylgeranyl pyrophosphate; DXR, 1-deoxy-d-xylulose 5-phosphate reductoisomerase; MCT, 2-C-methyl-d-erythritol 4-phosphate cytidylyltransferase; CMK, 4-(cytidine 5′-diphospho)-2-C-methyl-d-erythritol kinase; MDS, 2-C-methyl-d-erythritol 2,4-cyclodiphosphate synthase; HDS, (E)-4-hydroxy-3-methylbut-2-enyl diphosphate synthase; HDR, (E)-4-hydroxy-3-methylbut-2-enyl diphosphate reductase; IDI, isopentenyl diphosphate isomerase; GPPS, geranyl diphosphate synthase; PSY, phytoene synthase; PDS, phytoene desaturase; ZDS, ζ-carotene desaturase gene; ZISO, ζ-carotene isomerase; CrtISO, carotene isomerase; LCY, lycopene beta-cyclase; HYDB, β-carotene hydroxylase; CYP97C, cytochrome P450-type monooxygenase 97C; VDE, violaxanthin de-epoxidase; ZEP, zeaxanthin epoxidase; NXS, neoxanthin synthase.

Figure 2. 

Overview of the synthesis and metabolism framework of polyphenols in tomato. Enzymes are shown in red. Different colored rectangles represent the synthesis of different polyphenols. PAL, phenylalanine ammonia-lyase; C4H, cinnamate-4-hydroxylase; C3H, coumarate 3-hydroxylase; 4CL, 4-coumarate CoA ligase; COMT, catechol-Omethyl transferase; CHS, chalcone synthase; CHI, chalcone isomerase; F3H, flavanone 3-hydroxylase; DFR, dihydroflavonol reductase; ANS, anthocyanidin synthase; FOMT, flavonoid O-methyltransferase; F3'5'H, flavonoid-3,5-hydroxylase; A3GlcT, anthocyanin-3–O-glucosyltransferase; A3G6''RhaT, anthocyanin-3–O-glucoside-6′′–O-rhamnosyltransferase; ACT, Acylase; HCT, hydroxycinnamoyl-CoA shikimate/quinate hydroxycinnamoyltransferase; HCGQT, hydroxycinnamoyl glucose quinate hydroxycinnamoyl transferase; SGT, Solanidine: UDP-glucosyltransferase; HQT, hydroxycinnamoyl-Co A quinate hydroxycinamoyl transferase; F3'H, flavonoid 3-Hydroxylase; FLS, flavonol synthase.

Figure 3. 

Biosynthetic pathways of L-ascorbic acid in plants. PMI, mannose-6-phosphate isomerase; PMM, phosphomannomutase; GMP, GDP-mannose pyrophosphorylase (mannose-1-phosphate guanylyltransferase); GME, GDP-mannose-3′,5′-epimerase; GGP, GDP-L-galactose phosphorylase; L-GalDH, L-galactose dehydrogenase; L-GalLDH, L-galactono-1,4-lactone to produce ascorbate; AO, ascorbate oxidase; APX, ascorbate peroxidase; DHAR, dehydroascorbate reductase; MDHAR, monodehydroascorbate reductase; GPP, L-galactose-1-phosphate phosphatase.

Figure 4. 

Important intermediates in plant sugar metabolism. RuBP, ribulose-1,5-bisphosphate; 1,3-BPG, 1,3-bisphosphoglycerate; GAP, glyceraldehyde3-phosphate; Ru5P, Ribulose 5-phosphate; PRK, phosphoribulokinase; Glu, glucose; Fru, fructose; SAI, soluble acid invertase; NI, neutral invertase; CWI, cellwall invertase; G6P, glucose-6-phosphate; SUS, sucrose synthase; G1P, glucose-1-phosphate; F6P, fructose-6-phosphate; F1,6BP, fructose-1,6-bisphosphate; 6PG, 6-phosphogluconate; G6PH, glucose 6-phosphatedehydrogenase; 6PGH, 6-phosphogluconate dehydrogenase; PGM, Phosphoglucomutase; ADP-Glu, ADP-glucose; UDP-Glu, UDP-glucose; SS, Starch synthase; SPS, sucrose phosphate synthase; SPP, sucrose phosphate phosphatase;

Figure 5. 

Citric acid and malic acid metabolic pathways in fruit. TCA, tricarboxylic acid cycle; ACO, aconitase; ATP-CL, ATP-citrate lyase; CS, citrate synthase; ICL, isocitrate lyase; MS, malate synthase; NAD-MDH, NAD-malate; dehydrogenase; NAD-ME, NAD-malic enzyme; NAD-IDH, NAD-isocitrate dehydrogenase; NADP-ME, NADP-malic enzyme; OAA, oxaloacetate; NADP-IDH, NADP-isocitrate dehydrogenase; PDH, pyruvate dehydrogenase; PEPC, phosphoenolpyruvate carboxylase; PEPCK, phosphoenolpyruvate carboxykinase; PPDK, pyruvate orthophosphate dikinase.