Light-driven regulatory mechanisms in the photosynthetic antenna complex LHCII.

Protection against strong-light-induced photodamage of the photosynthetic apparatus and entire organisms is a vital activity in plants and is also realized at the molecular level of the antenna complexes. Reported recently, the regulatory mechanisms which operate in the largest plant antenna complex, LHCII (light-harvesting complex II), based on light-driven processes, are briefly reviewed and discussed. Among those processes are the light-induced twisting of the configuration of the LHCII-bound neoxanthin, the light-induced configurational transition of the LHCII-bound violaxanthin, the light-induced trimer-monomer transition in LHCII and the blue-light-induced excitation quenching in LHCII. The physiological importance of the processes reviewed is also discussed with emphasis on the photoprotective excitation quenching and on possible involvement in the regulation of the xanthophyll cycle.