AUTHOR=Guo Shengtao , Gao Wenxue , Zeng Mengsha , Liu Fenglin , Yang Qingzhuoma , Chen Lei , Wang Zesong , Jin Yanjun , Xiang Peng , Chen Hanxi , Wen Zhengyong , Shi Qiong , Song Zhaobin 

TITLE=Characterization of TLR1 and expression profiling of TLR signaling pathway related genes in response to Aeromonas hydrophila challenge in hybrid yellow catfish (Pelteobagrus fulvidraco ♀ × P. vachelli ♂)

JOURNAL=Frontiers in Immunology

VOLUME=14

YEAR=2023

URL=https://www.frontiersin.org/journals/immunology/articles/10.3389/fimmu.2023.1163781

DOI=10.3389/fimmu.2023.1163781

ISSN=1664-3224

ABSTRACT=<p>Toll‐like receptor 1 (TLR1) mediates the innate immune response to a variety of microbes through recognizing cell wall components (such as bacterial lipoproteins) in mammals. However, the detailed molecular mechanism of TLR1 involved in pathogen immunity in the representative hybrid yellow catfish (<italic>Pelteobagrus fulvidraco ♀ × P. vachelli ♂</italic>) has not been well studied. In the present study, we identified the <italic>TLR1</italic> gene from the hybrid yellow catfish, and further comparative synteny data from multiple species confirmed that the <italic>TLR1</italic> gene is highly conserved in teleosts. Phylogenetic analysis revealed distinguishable TLR1s in diverse taxa, suggesting consistence in evolution of the TLR1 proteins with various species. Structural prediction indicated that the three-dimensional structures of TLR1 proteins are relatively conserved among different taxa. Positive selection analysis showed that purifying selection dominated the evolutionary process of TLR1s and TLR1-TIR domain in both vertebrates and invertebrates. Expression pattern analysis based on the tissue distribution showed that <italic>TLR1</italic> mainly transcribed in the gonad, gallbladder and kidney, and the mRNA levels of <italic>TLR1</italic> in kidney were remarkably up-regulated after <italic>Aeromonas hydrophila</italic> stimulation, indicating that TLR1 participates in the inflammatory responses to exogenous pathogen infection in hybrid yellow catfish. Homologous sequence alignment and chromosomal location indicated that the TLR signaling pathway is very conserved in the hybrid yellow catfish. The expression patterns of TLR signaling pathway related genes (<italic>TLR1</italic>- <italic>TLR2</italic> - <italic>MyD88</italic> - <italic>FADD</italic> - <italic>Caspase 8</italic>) were consistent after pathogen stimulation, revealing that the TLR signaling pathway is triggered and activated after <italic>A. hydrophila</italic> infection. Our findings will lay a solid foundation for better understanding the immune roles of TLR1 in teleosts, as well as provide basic data for developing strategies to control disease outbreak in hybrid yellow catfish.</p>