Abstract

Toll-like receptors (TLRs) play essential roles in the innate immune system and have been extensively studied in mollusks . In this study, through a genome-wide search, TLR genes were identified as 29 in Haliotis discus hannai , 33 in H. rufescens , and 16 in H. laevigata . Domain analysis indicated that these TLR genes contain leucine-rich repeat (LRR) and Toll/IL-1 receptor (TIR) domains and exons ranging from 1 to 5. Polymorphism analysis showed that the TLRs in abalones did not have high diversities with 143 SNPs and no Indel in H. discus hannai , 92 SNPs and 3 Indels together with 6 missense mutations in H. rufescens , and no SNP or Indel in H. laevigata. The expression of 8 TLR genes in H. discus hannai was confirmed in the hepatopancreas , gill, hemolymph, gonads , intestine, muscle, and mantle. The expression of five TLR genes (out of 8) in gills (p < 0.05), three in hepatopancreas (p < 0.05), and three in hemolymph (p < 0.05) was upregulated separately in response to the infection caused by Vibrio parahaemolyticus . The findings in this study would contribute to a better understanding of the molecular immune mechanism of H. discus hannai against stimulation by V. parahaemolyticus and provide a basis for the study of TLRs in abalones.