Abstract 9514026 Cohen The single-cell sporangiophore of the lower fungus Phycomyces blakesleeanus is very sensitive to blue light, by bending toward the light and growing with exposure to light, and showing a negative growth response to a decrease in light. Phycomyces has great potential for comparing signal processing in lower organisms to those in higher organisms. This investigator has found evidence for the presence of G proteins in the sporangiophore, and G proteins are essential for phototransduction and many types of signal transduction in higher organisms. In this proposal the investigator will seek to establish the role of G proteins in blue light transduction in Phycomyces. Immunoblotting with antibodies to G( subunits and covalent FAD (which is involved in the photoreceptor system of this fungus), will be used in a number of behavioral mutant strains. A cDNA library will be used for cloning of G( subunits and these will be compared to these proteins in other systems, and mRNAs from the mutants will be examined by Northern blotting. These studies will provide important information on how the blue light detection system works at the molecular level and will indicate common elements that exists between signal transduction systems of the lower eukaryotic organisms and vertebrates. ***
