August 1, 2007-January 31, 2013
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Photosynthesis plays a fundamental role in understanding plant growth and productivity. The chloroplast, the organelle of photosynthesis, evolved following the endosymbiotic uptake of a cyanobacterium and massive gene transfer. As a result, the chloroplast is highly dependent upon nuclear genes to provide essential chloroplast proteins. A special form of endosymbiosis, kleptoplasty, has evolved in the marine mollusc Elysia chlorotica. This green, leaf-like animal carries out photosynthesis for its entire ten month life-cycle, as if it were a plant, by using chloroplasts it steals and retains from the alga Vaucheria litorea. It is highly likely that horizontal gene transfer (HGT) has occurred between these two unrelated multi-cellular organisms, to support the long-term activity of the chloroplasts in the sea slug. The overall approach of this study is to combine cellular and molecular analyses with studies of whole animal biology to understand how such an endosymbiotic association can form and be sustained, and also influence the evolution of photosynthesis in an animal. These studies will identify specific examples of HGT from the alga to the sea slug, where and how the genes are integrated into the animal DNA, the mechanism of recognition and uptake of the chloroplasts, and the specificity of the association. The broader impact of these studies is seen at many levels. Fascinating organisms can transform the teaching of basic principles in biology; hence, the ""solar-powered"" sea slugs will be exploited in developing multimedia educational materials for students of all ages. Kleptoplastic sea slugs also potentially have a direct bearing on human health, through their production of anti-cancer compounds. The ability to culture the sea slugs will provide a supply of this unusual organism for classrooms and laboratories, marine hobbyists, and contributes to protection of a rare species and its native habitat.
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Rumpho, Mary E., "Sea Slug—Algal Chloroplast Symbiosis: Towards an Integrated Understanding of Long-Term Chloroplast Functioning in an Animal" (2012). University of Maine Office of Research and Sponsored Programs: Grant Reports. 308.