Function of Phospholipase C Encoded by the norpA Gene of Drosophila
Randall Shortridge Principal Investigator
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The process of phototransduction captures the energy of light by cells in the retina of the eye, converting it into a nerve signal to the brain. A useful model system for studying this aspect of vision is the fruitfly Drosophila, because its genetics are extremely well known and many mutant strains are available. One of the mutations in a gene called "norpA" abolishes a step in phototransduction, making the animal blind. This gene normally produces an enzyme called PLC (for phospholipase-C), which is an important effector enzyme for one of the largest classes of biochemical pathways for cellular signaling. There are at least two subtypes of PLC encoded by norpA. One occurs only in the eye, but the norpA gene also is expressed in other tissues in the body unrelated to phototransduction, suggesting its use in other cellular signaling pathways. This work uses biochemical and molecular biological techniques to examine how the norpA-encoded PLC functions in the normal phototransduction pathway, during states of adaptation to light and to dark. The two protein subtypes are tested to see whether the non-retinal subtype can function adequately in vision if the retinal subtype is absent. Genetic deletion studies produce altered genes to identify which domains of the PLC encoded by the norpA gene are important for the visual function, and tissue-specific expression of the norpA gene is examined to see where else in the body the PLC is activated in non-visual signaling pathways. The work is an important step not only for understanding the molecular basis of vision, but also for a variety of fundamental signals involved in cell growth, differentiation, and cellular secretion in both animals and plants.