Study of cnidarian-algal symbiosis in the “omics” age

Abstract. The symbiotic associations between cnidarians and dinoflagellate algae (Symbiodinium) support productive and diverse ecosystems in coral reefs. Many aspects of this association, including the mechanistic basis of host-symbiont recognition and metabolic interaction, remain poorly understood. The first completed genome sequence for a symbiotic anthozoan is now available (the coral Acro-pora digitifera), and extensive expressed sequence tag re-sources are available for a variety of other symbiotic corals and anemones. These resources make it possible to profile gene expression, protein abundance, and protein localiza-tion associated with the symbiotic state. Here we review the history of “omics ” studies of cnidarian-algal symbiosis and the current availability of sequence resources for corals and anemones, identifying genes putatively involved in symbi-osis across 10 anthozoan species. The public availability of candidate symbiosis-associated genes leaves the field of cnidarian-algal symbiosis poised for in-depth comparative studies of sequence diversity and gene expression and for targeted functional studies of genes associated with symbi-osis. Reviewing the progress to date suggests directions for future investigations of cnidarian-algal symbiosis that in-clude (i) sequencing of Symbiodinium, (ii) proteomic anal-ysis of the symbiosome membrane complex, (iii) glycomic analysis of Symbiodinium cell surfaces, and (iv) expression profiling of the gastrodermal cells hosting Symbiodinium