Transcriptional regulation of carotenoid biosynthesis pathway (CBP) genes in photosynthetic tissues. The regulation of CBP genes in response to light (sun), senescence (leaf), and high temperature (thermometer) and by epigenetic controls (DNA) is shown. The carotenoid biosynthesis pathway is in black, with carotenoid biosynthesis genes indicated in dark blue. Carotenoid regulators discussed in the paper are shown in light blue, with other regulators in purple. Green arrows indicate positive regulation, while blunt red arrows indicate negative regulation. Solid lines show direct interactions, while dotted lines show indirect/unknown interactions. GGPP, geranylgeranyl pyrophosphate; PSY, phytoene synthase; PDS, phytoene desaturase; Z-ISO, 15-cis-zeta-carotene isomerase; ZDS, zeta-carotene desaturase; CRTISO, carotene isomerase; LCYB, lycopene beta-cyclase; CYCB, chromoplast-specific lycopene beta-cyclase; BCH, beta-carotene hydroxylase; ZEP, zeaxanthin epoxidase; VDE, violaxanthin deepoxidase; NSY, neoxanthin synthase; LCYE, lycopene epsilon-cyclase; CYP97A3, cytochrome P450–type beta-hydroxylase; CYP97C1, cytochrome P450–type epsilon-hydroxylase.