Complementary chromatic adaptation: photoperception to gene regulation.

Many photosynthetic organisms can acclimate to the quantity and quality of light present in their environment. In certain cyanobacteria the wavelengths of light in the environment control the synthesis of specific polypeptides of the light harvesting antenna complex or phycobilisome. This phenomenon, called complementary chromatic adaptation, is most dramatically observed in a comparison of cyanobacteria after growth in green light and red light. In red light-grown cells the phycobilisome is largely composed of phycocyanin and its associated linker polypeptides (the latter are important for the assembly of the phycocyanin subunits and their placement within the light harvesting structure); the organisms appear blue-green in color. In green light-grown cells the phycobilisome is largely composed of phycoerythrin and its associated linker polypeptides; the organisms appear red in color. The ways in which these cyanobacteria sense their changing light environment and the regulatory elements involved in controlling the process of complementary chromatic adaptation are discussed in this review.