Abstract
Proliferative kidney disease is an emerging disease among salmonids in Europe and North America caused by the myxozoan parasite Tetracapsuloides bryosalmonae. The decline of endemic brown trout (Salmo trutta) in the Alpine streams of Europe is fostered by T. bryosalmonae infection. Toll-like receptors (TLRs) are a family of pattern recognition receptors that acts as sentinels of the immune system against the invading pathogens. However, little is known about the TLRs’ response in salmonids against the myxozoan infection. In the present study, we identified and evaluated TLR1, TLR19, and TLR13-like genes of brown trout using data-mining and phylogenetic analysis. The expression pattern of TLRs was examined in the posterior kidney of brown trout infected with T. bryosalmonae at various time points. Typical Toll/interleukin-1 receptor protein domain was found in all tested TLRs. However, TLR13-like chr2 had a short amino acid sequence with no LRR domain. Phylogenetic analysis illustrated that TLR orthologs are conserved across vertebrates. Similarly, a conserved synteny gene block arrangement was observed in the case of TLR1 and TLR19 across fish species. Interestingly, all tested TLRs showed their maximal relative expression from 6 to 10 weeks post-exposure to the parasite. Our results suggest that these TLRs may play an important role in the innate defense mechanism of brown trout against the invading T. bryosalmonae.
Highlights
Tetracapsuloides bryosalmonae, a cnidarian myxozoan endoparasite belonging to the class malacosporea is responsible for causing proliferative kidney disease (PKD) in salmonids [1]
Phylogenetic, and syntenic analysis showed that TLR1, TLR19, and TLR13-like genes of brown trout are conserved across fish species
This is the first study on brown trout to evaluate and provide fundamental information regarding Toll-like receptors (TLRs) expression patterns in response to myxozoan infection
Summary
Tetracapsuloides bryosalmonae, a cnidarian myxozoan endoparasite belonging to the class malacosporea is responsible for causing proliferative kidney disease (PKD) in salmonids [1]. In the summer of 2016, an outbreak of T. bryosalmonae infection at the Yellowstone river in the state of Montana, USA resulted in the mass mortality of salmonids, predominantly mountain whitefish (Prosopium williamsoni) [6]. This incident led to the temporary emergency closure of a section of the river to the public, resulting in a significant economic impact on the local tourism and recreational industry [7]
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