Toll-like receptor 3 regulates Mx expression in rare minnow Gobiocypris rarus after viral infection

Abstract

Toll-like receptor 3 (TLR3) plays a key role in activating immune responses during viral infection. To study the genes involved in the regulatory function of TLR3 in the rare minnow Gobiocypris rarus after viral infection, a full-length cDNA of TLR3 (GrTLR3) with a splice variant (GrTLR3s) was identified by homologous cloning and RACE techniques. The antiviral effector molecule Mx gene was cloned and partially sequenced. The mRNA expression levels of GrTLR3, GrTLR3s, and Mx were studied in different tissues before and after virus infection by real-time quantitative RT-PCR. The transcripts of all three genes in liver were significantly increased following GCRV infection (P<0.05). The mRNA levels in liver were upregulated at 24 h post-injection for GrTLR3 and GrTLR3s, and at 12 h for Mx. The upregulated expression levels were several folds for GrTLR3s, tens of folds for GrTLR3, and hundreds of folds for Mx. By semiquantitative RT-PCR, GrTLR3 and Mx expressed at all the developmental stages, whereas GrTLR3s could only be detected at later developmental stages. Using RNAi and transgenic techniques, GrTLR3 mediated Mx expression but GrTLR3s did not. The time-dependent upregulation of receptor and effector, and the Mx over-expression dependent on TLR3, indicated that GrTLR3 regulated Mx expression in viral infection through a configuration change in rare minnow, and its splice variant did not contribute to the process.

Genomic organization and expression analysis of Toll-like receptor 3 in grass carp (Ctenopharyngodon idella)

“…TLR3 gene expressions in zebrafish, rainbow trout and rare minnow were also modulated during viral infection [14,16,23]. The kinetics of up-regulation in zebrafish, rainbow trout and rare minnow differed from the present study and may be due to differences in viral kinetics or host factors.…”

β-Glucan-supplemented diets increase poly(I:C)-induced gene expression of Mx, possibly via Tlr3-mediated recognition mechanism in common carp (Cyprinus carpio)

“…Although these diverged more than 500,000 years ago [40] both are commonly used in aquaculture and laboratory research. tlr3 gene expression has been detected in a wide range of tissues of different cyprinid species, with high levels of expression being recorded in skin, liver, gut, gills and spleen [16], [35], [36], [38] and [41]. Studies on the tlr3 genes reported here have confirmed this differential gene expression in organs, for example carp tlr3.1 is highly expressed in mid gut, head kidney and mid kidney, spleen and thymus whilst carp tlr3.2 is predominantly expressed in mid gut, liver and PBLs.…”

“…TLR3 is one of the most studied TLRs and several homologues have been found and characterized in different fish species, i.e. zebrafish [34] and [35], rare minnow (Gobiocypris rarus) [36], grass carp [37], common carp [16], rohu (Labeo rohita) [38] and catfish [21]. TLR3 seems to play an important role in the antiviral defense in all vertebrates studies including fish where it has been reported that polymorphisms/haplotypes of Tlr3 in grass carp have significant association with resistance/susceptibility to GCRV [39].…”

RNA-seq profiles from grass carp tissues after reovirus (GCRV) infection based on singular and modular enrichment analyses

“…In addition, intestine and liver tissues are susceptible to GCRV (Su et al, 2008), while the spleen is an important immune-organ in this fish species (Fänge and Nilsson, 1985;Press and Evensen, 1999). Therefore, in this present study, RNA-seq sequencing was performed on these four tissues in grass carp before GCRV infection and at six time points post-challenge.…”