title: Molecular insights of the first gastropod TLR counterpart from disk abalone (Haliotis discus discus), revealing its transcriptional modulation under pathogenic stress.
abstract: Toll-like receptors (TLRs) are well-characterized pattern recognition receptors of innate immunity, known to induce immune responses against the pathogens by interacting with evolutionarily conserved pathogen-associated molecular patterns (PAMPs). In this study, a novel TLR homolog from disk abalone (Haliotis discus discus) was identified and characterized at molecular level. The open reading frame (ORF) of AbTLR is 3804 bp in length and encodes a 1268 amino acid peptide with a calculated molecular mass of 143.5 kDa. The deduced protein shows typical TLR domain architecture, with leucine rich repeats (LRR) and the toll-interleukin receptor (TIR) domain. Phylogenetic analysis revealed a close evolutionary relationship for AbTLR to its invertebrate counterparts, with close clustering to the molluscan homologs. Quantitative real-time PCR detected ubiquitous transcription of AbTLR in healthy tissues, but with highest levels in hemocytes. Differential transcriptional modulation of AbTLR was observed in abalone hemocytes and gills upon immune challenge, whereby Vibrio parahaemolyticus and purified lipopolysaccharide (LPS) enhanced the transcript level prominently. In addition, the viral hemorrhagic septicemia virus induced AbTLR transcription in hemocytes and gills, representing the first evidence of viral-induced immune response in mollusks to date. Collectively, our findings support a putative role for AbTLR in abalone antiviral and antibacterial defense.
authors.affiliation: Department of Marine Life Sciences, School of Marine Biomedical Sciences, Jeju National University, Jeju Self-Governing Province 690-756, Republic of Korea.
authors.forename: Don Anushka Sandaruwan
authors.initials: DA
authors.lastname: Elvitigala
authors.forename: H K A
authors.initials: HK
authors.lastname: Premachandra
authors.forename: Ilson
authors.initials: I
authors.lastname: Whang
authors.forename: Bo-Hye
authors.initials: BH
authors.lastname: Nam
authors.forename: Jehee
authors.initials: J
authors.lastname: Lee
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D018076:DNA, Complementary / Q000235:genetics / Q000378:metabolism; D005786:Gene Expression Regulation; D008070:Lipopolysaccharides / Q000502:physiology; D008969:Molecular Sequence Data; D029141:Novirhabdovirus / Q000502:physiology; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D060888:Real-Time Polymerase Chain Reaction / Q000662:veterinary; D056910:Republic of Korea; D016415:Sequence Alignment / Q000662:veterinary; D012908:Snails / Q000235:genetics* / Q000276:immunology / Q000378:metabolism; D014018:Tissue Distribution; D051193:Toll-Like Receptors / Q000737:chemistry / Q000235:genetics* / Q000276:immunology; D014736:Vibrio parahaemolyticus / Q000502:physiology
chemical_list: D018076:DNA, Complementary; D008070:Lipopolysaccharides; D012333:RNA, Messenger; D051193:Toll-Like Receptors
keywords: Disk abalone; Novel TLR homolog; Phylogenetic relationship; Spatial expression of mRNA; Transcriptional profiles under pathogenic stress