Characterization, evolution, and expression analysis of TLR7 gene subfamily members in Mastacembelus armatus (Synbranchiformes: Mastacembelidae)

• Published in: Developmental and comparative immunology Vol. 95; pp. 77 - 88
• Main Authors: Han, Chong, Li, Qiang, Liu, Jinmei, Hao, Zhiqiang, Huang, Jianrong, Zhang, Yong
• Format: Journal Article
• Language: English
• Published: United States Elsevier Ltd 01.06.2019; Elsevier Science Ltd
• Subjects: Aeromonas veronii; Aeromonas veronii - immunology; Aeromonas veronii - pathogenicity; Amino acid sequence; Amino Acid Sequence - genetics; amino acid sequences; Amino acids; Animals; Biological Coevolution - genetics; Biological Coevolution - immunology; coevolution; eel; Evolution; Evolution, Molecular; Fish Diseases - immunology; Fish Diseases - microbiology; Fish Proteins - genetics; Gene expression; genes; Gram-Negative Bacterial Infections - immunology; Gram-Negative Bacterial Infections - microbiology; Host-Pathogen Interactions - genetics; Host-Pathogen Interactions - immunology; Immunity, Innate - genetics; kidneys; Leucine; Mastacembelus armatus; Monopterus albus; pathogen-associated molecular patterns; Pathogens; Pattern recognition; Pattern recognition receptors; Phylogeny; Positive selection; Protein Domains - genetics; Protein Domains - immunology; quantitative polymerase chain reaction; Receptors; Selection, Genetic; Seriola lalandi; Smegmamorpha - genetics; Smegmamorpha - immunology; Smegmamorpha - microbiology; Spleen; statistical analysis; Synbranchiformes; tissues; TLR7 protein; TLR7 subfamily; TLR9 protein; Toll-like receptor 7; Toll-Like Receptor 7 - genetics; Toll-Like Receptor 7 - immunology; Toll-like receptor 8; Toll-like receptor 9; Toll-like receptors; PBS; PP; ORF; Positive selection; FUBAR; TLR7 subfamily; qRT-PCR; Mastacembelus armatus; FEL; LRR; LRT; PRR; PAMP; Aeromonas veronii; UTR; MEME; NLR; RLR; TM; TLR; TIR; SLAC
• ISSN: 0145-305X; 1879-0089; 1879-0089
• DOI: 10.1016/j.dci.2019.02.002

TLR7 subfamily members are important pattern recognition receptors participating in the recognition of pathogen-associated molecular patterns. In this study, we successfully identified 3 members of TLR7 subfamily from the spiny eel Mastacembelus armatus (MaTLR7, MaTLR8 and MaTLR9). The amino acid sequence identities of MaTLR7 and MaTLR8 with Monopterus albus TLR7 were 87.2% and 76.5%, respectively and the identity of MaTLR9 with Seriola lalandi TLR9 was 74.7%. The phylogenetic analysis revealed MaTLRs showed close relationship to other species in Synbranchiformes or Perciformes. Quantitative real-time PCR analysis revealed that they were expressed in all tested tissues and higher expression was found in spleen or gill. After infection with Aeromonas veronii, expression of MaTLR7, MaTLR8 and MaTLR9 were all significantly downregulated in spleen and kidney. Evolutionary analysis suggested that the ancestral lineages of teleost TLR8 and TLR9 had been subject to positive selection pressures and multiple Maximum likelihood methods recovered 3 positively selected sites in teleost TLR7, 4 in TLR8 and 8 in TLR9. Domain distribution revealed most positively selected sites were located in leucine-rich repeat domain. Our results will contribute to better understanding the antibacterial mechanism of TLRs and their co-evolution with pathogens. •Three new TLRs (MaTLR7, MaTLR8 and MaTLR9) were cloned and characterized from the Zig-zag eel Mastacembelus armatus.•TLR7 subfamily members were expressed in all tested tissues of Mastacembelus armatus.•Expression of three new TLRs significantly downregulated after bacterial infection.•Many positively selected sites were found in teleost TLR7 members especially in LRR domain.