Reasons to sequence the genome of the dinoflagellate Symbiodinium

Dinoflagellates are ubiquitous marine and freshwater protists. As free-living photosynthetic plankton, they account for much of the primary productivity of oceans and lakes. As photosynthetic symbionts, they provide essential nutrients to all reef-building corals and numerous other marine invertebrates, supporting coral reefs, the most diverse marine ecosystem, a rich food source, and a potential source of future pharmaceuticals. When the dinoflagellate symbionts are expelled from their coral hosts during mass coral bleaching events, coral reefs and the surrounding ecosystems rapidly decline and die. Population explosions of dinoflagellates are the cause of red tides, extensive fish kills, and paralytic shellfish poisoning. As parasites and predators, they threaten numerous fisheries, but are also an important check on the very dinoflagellates that cause red tides. As bioluminescent organisms, they are a spectacular feature of nighttime oceans and a model for the study of luminescence chemistry. Dinoflagellates are alveolates and a sister group to the apicomplexans–important human and animal pathogens. The apicomplexans are obligate intracellular parasites, e.g. Plasmodium spp. the agents of malaria. Describing the genome of a dinoflagellate that is an intracellular symbiont will aid us in understanding the capacities, weaknesses and evolution of the apicomplexans, and will inform the apicomplexan genomes in a way directly relevant to the development of antimalarial and antiapicomplexan drugs. Dinoflagellates, because of these roles, impact human health and life on many levels. We propose that a dinoflagellate genome be completely sequenced, to increase our understanding of these important organisms. We propose that the primary symbiont of marine invertebrates, Symbiodinium, is the preferred subject for such a project. Symbiodinium is a well studied dinoflagellate, has a very small genome for a dinoflagellate (the vegetative cells are haploid and contain ~2 x 10 bp of DNA), and is representative of the metabolic capabilities of dinoflagellates as a group. We propose to sequence a set of Symbiodinium species to various extents. A high-coverage closed sequence of one species will serve to anchor the assembly of three other low-coverage genome sequences of other species within the genus. This combined data set, together with large on-going EST projects, will allow the identification of most ORFs and many regulatory sequences.