Plant & Animal Genomes XVII Conference

January 10-14, 2009
Town & Country Convention Center
San Diego, CA

Repertoire And Divergence Of Toll-Like Receptors In Teleost Fish

Tomokazu Takano , Seong Don Hwang , Hidehiro Kondo , Ikuo Hirono , Takashi Aoki

  Laboratory of Genome Science, Graduate School of Marine Science and Technology, Tokyo University of Marine Science and Technology, Konan 4-5-7, Minato, Tokyo 108-8477, Japan

Toll-like receptors (TLRs) identified in mammals orchestrate innate and acquired immune responses following specific recognition of their ligands. On the other hand, many types of TLR orthologues have been reported from teleost fish genome databases. Interestingly, teleost fish possess numerous number of TLR repertoires than mammals and there are novel TLRs in teleost fish, which have not been identified in mammals. To date, a total of twelve types of puffer fish (Takifugu rubripes) TLRs (TLR1, TLR2, TLR3, soluble form TLR5, TLR5, TLR7, TLR8, TLR9, TLR14, TLR21, TLR22 and TLR23) and thirteen types of TLRs (TLR1, TLR2, TLR3, TLR4, TLR5, TLR7, TLR8, TLR9, TLR14, TRL19, TLR20, TLR21 and TLR22) from zebrafish (Danio rerio) have been reported or predicted. Particularly in zebrafish, there are paralogues of TLR4, TLR5, TLR8 TLR19 and TLR20 that have been generated by gene duplications. A total of eleven types of Japanese flounder (Paralichthys olivaceus) TLRs (TLR1, TLR2, TLR3, soluble form TLR5, TLR5, TLR7, TLR8, TLR9, TLR14, TLR21 and TLR22) have been identified by our research. The Japanese flounder TLRs were predominantly expressed in immune-related tissues and some of the TLRs were up-regulated following the stimulation of mitogen and pathogens. Taken together, these results suggest that teleost TLRs are indeed involved in fish immunity. Moreover, the highly diverged TLRs in teleost fish may exert unique TLR-mediated immune responses not seen in mammals. Here, the repertoires and divergence of teleost TLRs compared with that of mammals are discussed.