Abstract
X-cells are alveolate protists related to the economically important shellfish parasite Perkinsus, amphibian parasites, and more distantly to the human malaria pathogen Plasmodium. X-cells parasitise fish and are known from five teleost Orders, including cod and salmonids, and are likely to represent elevated risks in aquaculture conditions. Molecular studies suggest that X-cells are much more diverse, and are likely to affect many more fish groups, than currently known. Our project will use molecular bio logy techniques and bioinformatics to construct a far more realistic picture of X-cell diversity than current available. We will use these results to determine which environmental factors are the best predictors of X-cell presence and infection, the bioge ography of X-cell lineages, and to improve the phylogeny of the perkinsids so that their evolutionary position with respect to other parasites is clarified. We will also screen fish samples from a range of species and sampling sites so that new X-cell par asites can be firmly associated with their host species. These results will provide a new baseline for making aquacultural decisions with respect to fish disease. We will also use comparative transcriptomics to understand the mechanisms by whi ch X-cells infect cod, and describe the parasitic interaction in terms of gene expression levels in both X-cell and cod. The recent publication of the cod genome and importance of cod aquaculture in Norway make this a research priority. Our results will h ave broader implications as related work is currently underway for other alveolate parasites, so subsequent comparative genomics analyses will show how parasitism evolved in alveolates as a whole. The genome-wide sequence data from the transcriptomes will also enable us to include X-cells in phylogenomic (multi-gene) analyses, which can be highly resolving and show exactly where in the tree of life X-cells belong.
Norway