Role of Phosphodiesterase and G-Protein in the Response System of Phycomyces

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One of the leading problems in the study of vision, and of sensory systems in particular, is to discover the mechanism(s) by which environmental stimuli cause the receptor cells to discharge action potentials (nerve impulses). It is these impulses which are eventually interpreted by the brain as the basis for sensations. The conversion of information in the environment (for example, light energy) into nerve impulses in receptor cells is known as transduction. Although fungi do not have nerves, and therefore do not have sensory systems in the strict interpretation of the term, some fungi do respond to light. It is widely believed that the mechanism by which light elicits responses in these organisms is similar to that by which light elicits responses in visual receptor cells. Since fungi are amenable to genetic and biochemical manipulations that are impossible or extremely difficult in true visual receptors the elucidation of transduction in these organisms can be done far more easily than in visual receptor cells. Testing visual receptors for the mechanisms shown to occur in fungi can be accomplished fairly readily once the pathways are known in the fungi. In this project the investigator will explore the roles of various enzymes and proteins involved in metabolism of compounds called cyclic nucleotides in the responses of fungi to light. There are already reasons for suspecting that these compounds are common constituents of sensory transducing cells, and one of the enzymes that metabolizes them in the fungus under study is known to be sensitive to light.