Molecular profile and expressional modulation of a Toll like receptor-1 homolog from rock bream (Oplegnathus fasciatus)

Abstract

Toll-like receptors (TLRs) are well-described pattern recognition receptors that recognize different pathogen-associated molecular patterns (PAMPs) to activate innate immune responses. TLR1 forms a heterodimer with TLR2 that works to identify PAMPs including bacterial components. In the present study, we identified a TLR1 homolog from rock bream Oplegnathus fasciatus (RbTLR1) and characterized it at the genomic level. The complete coding sequence of RbTLR1 was 2406 bp in length and encoded an 802 amino acid protein possessing a calculated molecular mass of 90.7 kDa and typical TLR domain architecture. A single exon spanned the genomic length (2931 bp) of RbTLR1. Phylogenetic analysis showed a close evolutionary relationship between RbTLR1 and its fish orthologs. Using quantitative real time polymerase chain reaction, we detected RbTLR1 mRNA in all the tissues examined, suggesting its merely universal tissue expression. RbTLR1 was expressed strongly in the spleen, kidney, and liver. Following immune stimulation by bacterial pathogens and mitogens, RbTLR1 transcript levels were elevated at various time points post stimulation. Moreover, injection of a viral stimulant, polyinosinic:polycytidylic acid, and rock bream iridovirus altered the basal transcription of RbTLR1. Collectively, these data showed that RbTLR1 is transcriptionally regulated in response to bacterial and viral stimulation, suggesting its putative importance in host immune defense.