Expressions of Toll Like Receptor (TLR) Genes in Paralichthys olivaceus After Induced by Different Extracts of Edwardsiella tarda

Toll like receptors (TLRs) are the main innate immune ‘pattern recognition receptors’ of animals, which play a central role in host cell recognition and responses to invasive pathogens, particularly common structures of microbial pathogens. In this study, the gene expression profiles of TLRs in the spleen, head kidney, gill, small intestine, liver, muscle, and heart of healthy Paralichthys olivaceus were detected by real-time quantitative PCR (qPCR). The TLR family members were widely expressed in different tissues with different basic expression profiles. The highest expressions of TLR1, 5m, 7, 8, 9, 14, and 21 were found in the spleen; the highest expressions of TLR3 and TLR21 were found in the gill; the highest expressions of TLR2 and 5s were found in the small intestine. The second highest expressions of TLR3, 7, and 8 were found in small intestine. The gene expression profiles of TLRs stimulated with Edwardsiella tarda DNA, RNA, and lipopolysaccharide (LPS) were also detected in spleen, head kidney and gill. TLR9 and TLR21 were sensitive to E. tarda DNA; TLR 8 and TLR21 were sensitive to E. tarda RNA; and TLR1 and TLR14 were sensitive to E. tarda LPS. The expressions of the other TLR genes showed no significant changes. The results imply that the expressions of these TLR genes in P. olivaceus are differently regulated in the whole body and play important roles in the immune response against E. tarda infection.