Abstract
The myxozoan Tetracapsuloides bryosalmonae is a widely spread endoparasite that causes proliferative kidney disease (PKD) in salmonid fish. We developed an in silico pipeline to separate transcripts of T. bryosalmonae from the kidney tissue of its natural vertebrate host, brown trout (Salmo trutta). After stringent filtering, we constructed a partial transcriptome assembly T. bryosalmonae, comprising 3427 transcripts. Based on homology-restricted searches of the assembled parasite transcriptome and Atlantic salmon (Salmo salar) proteome, we identified four protein targets (Endoglycoceramidase, Legumain-like protease, Carbonic anhydrase 2, Pancreatic lipase-related protein 2) for the development of anti-parasitic drugs against T. bryosalmonae. Earlier work of these proteins on parasitic protists and helminths suggests that the identified anti-parasitic drug targets represent promising chemotherapeutic candidates also against T. bryosalmonae, and strengthen the view that the known inhibitors can be effective in evolutionarily distant organisms. In addition, we identified differentially expressed T. bryosalmonae genes between moderately and severely infected fish, indicating an increased abundance of T. bryosalmonae sporogonic stages in fish with low parasite load. In conclusion, this study paves the way for future genomic research in T. bryosalmonae and represents an important step towards the development of effective drugs against PKD.
Highlights
Tetracapsuloides bryosalmonae is an obligate endoparasite that causes proliferative kidney disease (PKD) in salmonid fish
This study reports the first annotated transcriptome of T. bryosalmonae derived from wild, infected brown trout using dual RNA sequencing
By employing multi-step filtering of parasite reads followed by de novo assembly, our work provides new insights into the differentially expressed T. bryosalmonae genes in the fish and identifies six proteins that could act as potential targets for the development of antiparasitic drugs against PKD
Summary
Tetracapsuloides bryosalmonae is an obligate endoparasite that causes proliferative kidney disease (PKD) in salmonid fish. PKD is considered as one of the most serious emerging temperature-dependent parasitic freshwater diseases of salmonids in the Northern Hemisphere, causing significant losses on farms and in natural populations (Okamura et al, 2001, 2011). The parasite has a two-host life-cycle, alternating between an invertebrate host (several species of freshwater bryozoans) and a fish host (salmonids) (Okamura et al, 2011). Sporogonic development takes place in the kidney of permissive fish hosts, and spores infective to bryozoans are released in fish urine (Hedrick et al, 2004). The decline of native salmonid fish populations in several countries has been linked with a combination of increasing temperatures and emergence of PKD (Wahli et al, 2002; Okamura et al, 2011; Sudhagar et al, 2020)
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