Abstract
Dinoflagellates are ubiquitous marine and freshwater protists. As free-living photosynthetic plankton, they account for ~50% of the primary productivity of oceans and lakes. As photosynthetic symbionts, they provide essential nutrients to corals, the architects of the ecologically and economically hugely important reef ecosystems. Unfortunately, the molecular mechanisms underlying this partnership are still not well understood. In an effort to better understand coral-algal symbioses, we are currently interrogating several lines of research. In an effort to decoding structure and function of the coral metaorganism, we are completing sequencing, assembly, and annotation of a coral hologenome. The availability of the complete gene set encoded in the genomes of a coral animal, its dinoflagellate symbiont, and the associated bacteria promises an unprecedented view on the composition, structure, and function of the coral holobiont. We are also applying deep-transcriptome sequencing to multiple Symbiodinium species at different taxonomic resolutions (i.e. within and between Clades and species) to assess transcriptomic and expression differences at orthologous genes. Further, to better understand the association between stress tolerance of corals and molecular diversity of algal symbionts, we have developed a next-generation sequencing pipeline targeting the ITS2 rRNA gene from Symbiodinium. Besides phylogeny-based analyses, we developed cutoffs to delineate Symbiodinium diversity in an OTU-based framework. This allows us to compare ocean basins and coral genera in a standardized manner. The presentation will highlight results from these efforts and provide an overview over remaining challenges in establishing Symbiodinium as a model organism for marine invertebrate symbioses.