Mechanism of photoregulation of carotenoid biosynthesis in plants

It is a well known phenomenon that in plants both development and metabolism are highly dependent on external factors, in particular on light. Biosynthesis of various compounds starts only after illumination; such a regulation has been reported also for carotenoids in different groups of plants. The main problem in the photoregulation of carotenoid biosynthesis is — like in the photoregulations of other processes — how can the organism translate the physical signal"light"into a biochemical signal and finally into physiological and biochemical events. The sequence of reactions in— volved includes the photoreception by a receptor pigment, the signal trans— duction and the regulatory level of the activity of carotenogenic enzymes. This review concentrates on the elucidation of these problems. The present state of knowledge is reported and discussed for three groups of plants — algae, higher plants and fungi — which might represent different mechanism types.