Pattern-recognition receptors in duck (Anas platyrhynchos): identification, expression and function analysis of toll-like receptor 3

ABSTRACT

1. Innate immunity provides the first line of defence against pathogenic organisms through a myriad of germline encoded receptors called pattern-recognition receptors (PRRs). Toll-like receptor (TLR) 3, as an important member of PRRs, is indispensable for host defence against viral infection by recognising virus-derived RNAs. However, little is known about the structure and function of TLR3 in ducks (Anas platyrhynchos), a natural host for the avian influenza virus.

2. This study cloned the full-length cDNA of duck TLR3 using reverse transcription polymerase chain reaction (RT-PCR) with rapid amplification of cDNA ends (RACE). The cDNA sequence of duck TLR3 was 4046 bp in length and encoded 895 amino acids. Multiple sequence alignment showed that duck TLR3 shared high similarity with that from other vertebrates.

3. Quantitative real-time PCR (qRT-PCR) analysis suggested that TLR3 mRNA was constitutively expressed in all tissues tested, having higher levels in the kidney, liver, breast muscle, ovary and heart. After stimulation with viral- or bacterial-mimics, including LPS, poly(I:C), pam3CSK4, FLS-1, FLA-ST and R848, the TLR3 transcript was significantly upregulated. Meanwhile, overexpression of duck TLR3 significantly promoted the transcription of IFN-β, IRF7, TRIF, Mx, STAT1 and STAT2 mRNA after stimulation with poly(I:C).

4. These results suggested that TLR3 play an important role in resistance against viral and bacterial infections in ducks.

KEYWORDS:

• Duck
• toll-like receptor 3
• antivirus
• expression
• poly(I:C)

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

This study was supported by the Key R&D Program of Zhejiang Province [2018C04014], the Natural Science Foundation of Zhejiang Province [LQ17C170003], the Natural Science Foundation of China [31702106 and 31872982], and the earmarked fund for Modern Agro-industry Technology Research System [CARS-42-6].