Identification and functional analysis of the toll-like receptor 20.2 gene in grass carp, Ctenopharyngodon idella

•We characterized tlr20.2 gene expression in grass carp.•Viral and bacterial challenge up-regulated gctlr20.2 in immune-relevant tissues.•LPS, FLA-ST and poly(I:C) resulted in fluctuations of gctlr20.2 expression.•tlr20.2 overexpression induced il1β, il-8 and tnf-α expression via the NF-κB pathway.•Silencing of tlr20.2 inhibited the secretion of il8 and ifn.

We characterized and identified the cDNA sequence of Toll-like receptor 20.2 in Ctenopharyngodon idella (gctlr20.2); it consisted of 3197 bp, with an open reading frame of 2835 bp that encoded a 944 amino acid polypeptide. Relatively, high expression levels of gctlr20.2 were observed in the spleen, head kidney, liver and brain tissues, with lower expression levels in the trunk kidney, intestine and heart tissues. In vivo and in vitro, after being challenged with Aeromonas hydrophila or grass carp reovirus (GCRV), gctlr20.2 expression was induced in C. idella kidney cells stimulated with lipopolysaccharide, flagellin or polyinosinic-polycytidylic acid. Overexpression of gctlr20.2 increased the expression of il1β, il8 and tnf-α, but not ifn, and also increased the activity of the nf-κB signal pathway. Silencing, via siRNA-tlr20.2, inhibited gctlr20.2 transcription by 65.7% and down-regulated the expression of inflammatory cytokine genes, but not tnf-α. This study increases understanding of the immune system in C. idella.