Fig. 2.

Photoregulation of chlorophyll (Chl) biosynthesis by blue (B), red (R), green (G), ultraviolet A (UV-A) and B (UV-B) light. Light-activated UV-B receptor (UVR8), cryptochromes (crys) and phytochromes (phys) inhibit COP1-based E3-ubiquitin-ligase and thus rescue HY5 transcription factor from proteolysis. Light-activated phys also inhibit PIF transcription factors. HY5 induces and PIFs repress Chl biosynthesis-related nuclear genes. Photoreceptor Zeitlupe (ztl) controls some of these genes via regulation of circadian clock. Chl biosynthesis depends on local lipid membrane composition. R and G promote lipid peroxidation (POL) in thylakoid membranes, probably via imperfectly formed PSA, which produces an excessive ROS amount. Dashed arrow — unknown mechanism, probably negative influence. Carotenoids (Cars) modulate Chl synthesis, because proper functioning of some Chl synthesis enzymes also needs the presence of carotenoids in their environment. Double line matches regulation on transcription level