The Role of Metacaspases in Mediating Cell Fate During Viral Infection of Unicelluar, Marine Phytoplankton

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Phytoplankton, microscopic photoautotrophs that drift with the currents, account for 1% of the Earth's biomass, yet they are responsible for nearly 50% of global annual carbon-based primary productivity. Steady-state maintenance of such a high production to biomass ratio implies that, on average, these organisms grow, die, and are replaced weekly. The primary mechanism used by biological oceanographers to explain the high lysis rates of phytoplankton has been infection by viruses. However, the molecular mechanisms regulating infection have been virtually ignored, even though they have important ecosystem consequences, such as coupling primary productivity to microbial foodwebs and short-circuiting carbon export to the deep ocean. This project will investigate whether metacaspases, putative programmed cell death (PCD) proteases, mediate the fate of marine phytoplankton by executing PCD upon viral infection. Proposed research will specifically elucidate whether the regulation of metacaspase expression and activity controls susceptibility or tolerance to viral infection. By integrating concepts in biochemistry, molecular biology, and cell communication, results will provide unprecedented insight into phytoplankton PCD from organismal, ecological, and evolutionary contexts. Experiments will utilize an algal-virus model system, consisting of the coccolithophore, Emiliania huxleyi, and its specific Coccolithoviruses (EhV). Experiments will employ a variety of physiology, biochemistry, and molecular biology techniques including immunoprecipitation, genetic transformation, polymerase chain reaction, Western blot analysis, enzyme activity assays, microscopy, and flow cytometry. This project will provide excellent hands-on training for development of graduate and undergraduate students, broaden the participation of women, and provide a platform for researchers with different levels of training to interact and develop. It will build both on established national and international collaborations and foster new ones. Research activities will interface with the Mid-Atlantic Center for Ocean Science Education Excellence (MA-COSEE), by participating in K-12 teacher workshops and in outreach programs at New Jersey's Liberty Science Center that introduce urban, largely minority, children and families to marine science. Specific goals are to stimulate awareness of the immense diversity and large-scale importance of marine microbes to ocean function.