EVOLUTIONARY CONVERGENCE OF LIGHT PERCEIVING SYSTEMS - VISION-LIKE CASCADE PROCESS STARTED BY PHYTOCHROME IN LICHENS

Modern research on the photobiology of both higher and lower plants in dicates that these organisms have been able to develop light-perceivin g systems for which the signal transduction process operates in a simi lar way to that described for animals. Signal transduction from phytoc hrome in higher plants involves a phosphatidyl inositol cascade almost identical to that described for cholinergic agonist-receptor interact ions. Phytochrome in lichens activates adenylate cyclase. The increase in the amount of intracellular cyclic AMP initiates a cascade mechani sm similar to that effected by rhodopsin in vertebrates, although cycl ic AMP rather than cyclic GMP seems to be involved in the activation o f a protein kinase that is responsible for the opening of membrane ion channels.