Carotenoid biosynthetic pathway (adapted from Lu et al. 2008). The isopentenyl diphosphate (IPP) is synthesized via the 2-C-methyl-D-erythritol 4-phosphate (MEP) pathway. IPP and DMAPP form the central intermediate geranylgeranyl diphosphate (GGDP) for carotenoid biosynthetic pathway. Phytoene synthase (PSY) acts at the condensation of two molecules of GGDP to form the phytoene, the first step of the carotenoid pathway. Names of compounds are highlighted in black and of enzymes in red. Abbreviations: G3P, glyceraldheyde-3-phosphate; DXP, 1-deoxy-D-xylulose 5-phosphate; HMBPP, 1-hydroxy-2-methyl-2-butenyl 4-diphosphate; ABA, abscisic acid; DXR, 1-deoxy-D-xylulose 5-phosphate reductoisomerase; DXS, 1-deoxy-D-xylulose 5-phosphate; IPI, isopentenyl diphosphate isomerase; GGPS, geranylgeranyl diphosphate synthase; PDS, phytoene desaturase; Z-ISO, ζ-carotene isomerase; ZDS, ζ-carotene desaturase; CRTISO, carotene isomerase; LCYB, β-cyclase; LCYE, ϵ-cyclase; ZEP, zeaxanthin epoxidase; VDE, violaxanthin de-epoxidase; NSY, neoxanthin synthase; NCED, 9-cis-epoxycarotenoid dioxygenase.