Characterization and expression analysis of common carp Cyprinus carpio TLR5M.

TLR5 is responsible for the recognition of bacterial flagellin in vertebrates. In this study, we cloned the TLR5M gene of common carp using the rapid amplification of cDNA ends (RACE) method. The TLR5M cDNA was 3182 bp in length and contained a 2658-bp open reading frame, which encoded a protein of 885 amino acids (aa). The entire coding region of the TLR5M gene was successfully amplified from genomic DNA and contained a single exon. The aa sequence of carp TLR5M showed the highest similarity (84.46%) to Cirrhinus mrigala. Tissue-specific expression analysis of the TLR5M gene by quantitative real-time polymerase chain reaction revealed its broad distribution in various organs and tissues; however, the highest level of TLR5M expression was noted in the liver. TLR5M gene expression was examined after flagellin stimulation and showed highly significant (p<0.01) induction in the spleen, heart, liver and kidney. The induction of TLR5M was analyzed in various organs infected with Aeromonas hydrophila. TLR5M gene expression in the kidney and spleen was significantly (p<0.01) increased. Concurrently, modulation of TLR5M gene expression and the induction of IFN-γ, IL-1β, IL-10 and TNF-α4 were analyzed in peripheral blood leucocytes after lipopolysaccharide, concanavalin A, and flagellin stimulation. In the treated group, significant induction of these genes was noted, although the intensity varied between the tissues. These findings may indicate a crucial role for TLR5M in the innate immunity of common carp in response to pathogenic invasion.