چکیده : 

Mammalian Toll-like receptor (TLR) 7 and 8 are responsible for recognizing viral single-stranded RNA

(ssRNA) and are activated by anti-viral imidazoquinoline compounds, leading to a series of defensive

mechanisms being launched to protect the host against viruses. In this study, we identified two TLR7

(with one probably a pseudogene) and three TLR8 genes, namely TLR8a2, TLR8b1 and TLR8b2 from Atlantic

salmon (Salmo salar) whole-genome shotgun (WGS) contigs. Bioinformatics analysis showed that salmon

TLR7 and TLR8a2 are closely related to the corresponding trout orthologs, however, salmon TLR8b1 and

TLR8b2 share the highest amino acid sequence similarity to zebrafish TLR8b and formed a subfamily of

the piscine TLR8 molecules in phylogenetic tree analysis. A conserved gene synteny was found with

the salmon TLR7/8a members as seen in other vertebrate loci. Deduced domain organisation of salmon

TLR7 and TLR8 molecules showed similar structural features, with equal numbers of leucine-rich repeats

(LRRs) and insertion motifs. Individual TLR molecules were expressed in a similar pattern between parr

and post-smolts, with a high expression level in immune tissues. Promoter analysis predicted several

transcription factor binding sites in the TLR8a1/2 and TLR8b1 50 flanking regions, namely C/EBP, AP-1,

STAT, NFjB, and IRF family, suggesting cytokine regulation of the genes. Hence, three recombinant cytokines,

type I IFN, IFNc and IL-1b were used to study the regulation of the salmon TLR gene expression

levels in primary head kidney cells and the Salmon Head Kidney-1 (SHK-1) cell line. Salmon TLR7 and

TLR8a1 gene expression was more sensitive to type I IFN and IFNc treatment in primary head kidney cells

and SHK-1 cells respectively, with no significant up-regulation of TLR8a2 and TLR8b2 by any of the treatments.

On the other hand, salmon TLR8a1 and TLR8b1 were most sensitive to IL-1b treatment in SHK-1

cells and primary head kidney cells, respectively. TLR8b2 was undetectable in SHK-1 cells under these

same conditions.

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چکیده : 

Mammalian Toll-like receptor (TLR) 7 and 8 are responsible for recognizing viral single-stranded RNA

(ssRNA) and are activated by anti-viral imidazoquinoline compounds, leading to a series of defensive

mechanisms being launched to protect the host against viruses. In this study, we identified two TLR7

(with one probably a pseudogene) and three TLR8 genes, namely TLR8a2, TLR8b1 and TLR8b2 from Atlantic

salmon (Salmo salar) whole-genome shotgun (WGS) contigs. Bioinformatics analysis showed that salmon

TLR7 and TLR8a2 are closely related to the corresponding trout orthologs, however, salmon TLR8b1 and

TLR8b2 share the highest amino acid sequence similarity to zebrafish TLR8b and formed a subfamily of

the piscine TLR8 molecules in phylogenetic tree analysis. A conserved gene synteny was found with

the salmon TLR7/8a members as seen in other vertebrate loci. Deduced domain organisation of salmon

TLR7 and TLR8 molecules showed similar structural features, with equal numbers of leucine-rich repeats

(LRRs) and insertion motifs. Individual TLR molecules were expressed in a similar pattern between parr

and post-smolts, with a high expression level in immune tissues. Promoter analysis predicted several

transcription factor binding sites in the TLR8a1/2 and TLR8b1 50 flanking regions, namely C/EBP, AP-1,

STAT, NFjB, and IRF family, suggesting cytokine regulation of the genes. Hence, three recombinant cytokines,

type I IFN, IFNc and IL-1b were used to study the regulation of the salmon TLR gene expression

levels in primary head kidney cells and the Salmon Head Kidney-1 (SHK-1) cell line. Salmon TLR7 and

TLR8a1 gene expression was more sensitive to type I IFN and IFNc treatment in primary head kidney cells

and SHK-1 cells respectively, with no significant up-regulation of TLR8a2 and TLR8b2 by any of the treatments.

On the other hand, salmon TLR8a1 and TLR8b1 were most sensitive to IL-1b treatment in SHK-1

cells and primary head kidney cells, respectively. TLR8b2 was undetectable in SHK-1 cells under these

same conditions.

?>