Brief description: Study the evolution and specific adaptations to parasitism in Ascetosporea, an emerging threat in marine environments that has remained beyond reach of modern molecular tools. Ascetosporea is a collection of poorly characterized microbial eukaryote parasites of marine invertebrates. It is best-known for including deadly pathogens of oysters and mussels, costing millions of dollars to the growing aquaculture industry. To date, however, Ascetosporea is absent from models describing the evolution of parasites because comparative genomic data is lacking. This is due to multiple factors, including minute cell size, obligate intracellular lifestyle, lack of suitable host cell lines, and techniques for in vitro culture. Here, we propose to overcome these challenges by using micromanipulation and single-cell genomic/transcriptomic methods. We will sequence de novo the genome and transcriptome of several uncultured parasites encompassing the diversity of Ascetosporea, as well as their closest free-living outgroups. With these data, we will broadly look at the evolution of parasitism in Ascetosporea, i.e. identify pre-parasitic conditions, ancestral parasitic innovations, and lineage-specific adaptations using comparative genomics.
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