A non-mammalian Toll-like receptor 26 (TLR26)gene mediates innate immune responses in yellow catfish Pelteobagrus fulvidraco

• Published in: Fish & shellfish immunology Vol. 95; pp. 491 - 497
• Main Authors: Liu, Qiu-Ning, Yang, Ting-Ting, Wang, Cheng, Jiang, Sen-Hao, Zhang, Dai-Zhen, Tang, Bo-Ping, Ge, Bao-Ming, Wang, Jia-Lian, Wang, Dong, Dai, Li-Shang
• Format: Journal Article
• Language: English
• Published: England Elsevier Ltd 01.12.2019
• Subjects: Animals; Catfishes - genetics; Catfishes - immunology; Cloning, Molecular; Expression analysis; Fish Diseases - immunology; Gene Expression Profiling; Gene Expression Regulation; Immune response; Immunity, Innate; Lipopolysaccharides - pharmacology; Pelteobagrus fulvidraco; Poly I-C - pharmacology; RNA, Messenger; Toll-like receptor 26; Toll-Like Receptors - genetics; Toll-Like Receptors - immunology; Pelteobagrus fulvidraco; Expression analysis; Toll-like receptor 26; Immune response
• ISSN: 1050-4648; 1095-9947
• DOI: 10.1016/j.fsi.2019.11.005

In this study, we identified a fish-specific Toll-like receptor (TLR) in Pelteobagrus fulvidraco, an economically important freshwater fish in China. This TLR, PfTLR26, was shown to be encoded by a 3084 bp open reading frame (ORF), producing a polypeptide 1027 amino acids in length. The PfTLR26 protein contains a signal peptide, eight leucine-rich repeat (LRR) domains, two LRR_TYP domains in the extracellular region, and a Toll/interleukin (IL)-1 receptor (TIR) domain in the cytoplasmic region, consistent with the characteristic TLR domain architecture. This predicted 117.1 kDa protein was highly homologous to those of other fish, with phylogenetic analysis revealing the closest relation to TLR26 of Ictalurus punctatus. Real-time quantitative reverse transcription-PCR (qRT-PCR) analysis showed that the PfTLR26 gene was expressed in all tissues tested, with the highest expression levels seen in the head kidney and blood, and the lowest seen in muscle. PfTLR26 exhibited significant upregulation in liver, spleen, head kidney, and blood at different time points following challenge with the common TLR agonists lipopolysaccharide (LPS) and polyriboinosinic polyribocytidylic acid (Poly I:C). Taken together, these results suggest that PfTLR26 may be an important component of the P. fulvidraco innate immune system, participating in the transduction of TLR signaling under pathogen stimulation. •A TLR26 gene was cloned from yellow catfish Pelteobagrus fulvidraco.•TLR26 mRNA levels were detected in a wide range of P. fulvidraco tissues.•The mRNA expression levels of PfTLR26 were up-regulated in response to Poly I:C or LPS challenge.