MOLECULAR CLONING AND EXPRESSION ANALYSIS OF TOLL-LIKE RECEPTOR 3 GENE IN BARBEL CHUB SQUALIOBARBUS CURRICULUS

To investigate whether the toll-like receptor 3 (ScTLR3) gene involve in antiviral immune response, TLR3 full-length cDNA in barbel chub (Squaliobarbus curriculus) was cloned and characterized with RACE technique and grass carp reovirus (GCRV) infection was used The method of real-time qPCR was used to examine the expression of ScTLR mRNA in 10 different tissues and the relative expression in liver, spleen, trunk kidney and, head kidney after infection at different times. The results showed that the full-length cDNA of ScTLR3 was 4043 bp including a 216 bp 5'-terminal untranslated region (UTR), an 1112 bp 3'-terminal untranslated region (UTR) and a 2715 bp open reading frame (ORF) encoding a polypeptide of 904 amino acid residues. The putative isoelectric point (pI) and molecular weight (Mw) of ScTLR3 were 8.76 and 102.67 kD, respectively. The ScTLR motifs were consisted of N-terminal signal peptide (SP), 14 leucine-rich repeats (LRRs), transmembrane domain (TM), and the Toll/IL-1 Receptors domain (TIR) in C-terminal. ScTLR3 mRNA was expressed in all tested tissues, and its expression in liver was extremely significant higher than other tested tissues in health barbell chub (P0.01). GCRV infection induced the ScTLR expression in liver, spleen, trunk kidney, and head kidney. Compared with the control group, the ScTLR mRNA expression levels in liver, spleen and trunk kidney tissues of barbel chub was induced 5-, 7-, and 6-fold at 24h post infection, respectively. These results suggest that ScTLR3 may play an important role in the immune response of barbel chub against GCRV infection.