Figure 2. Schematic gene expression profiles of photosynthesis-associated nuclear genes and photoreceptors.

Expression patterns describing the mRNA expression levels at continuous white light (CWL), after 48 h dark treatment (D48) and re-exposure to white light (WL) for 0.5, 6, and 24 h. A) Light-responsive expression patterns common for category 1 genes representing the majority of the PhANGs characterized by low transcriptional activity in darkness, modest induction by 0.5 h re-exposure to WL and generally high expression when exposed to WL for longer periods of time. I: Gene expression peaking after 6 h of re-exposure to WL. II: Gene expression stabilizing at CWL level after only 6 h of re-exposure to WL. III: Gene expression steadily increasing during 24 h of re-exposure to WL, but never reaching CWL levels. B) Expression pattern representative for category 2 genes including several genes belonging to the LHC family encoding proteins believed to have a photoprotective function, as well as for the POR4 gene and two photoreceptor genes. Genes are characterized by being strongly, but transiently induced by WL exposure for 0.5 h. C) Expression pattern representative for the category 3 genes including a few PhANGs and a photoreceptor gene characterized by high transcriptional activity in darkness and a gradual reduction towards CWL levels during 24 h of WL re-exposure.