Molecular cloning, expression and mimicking antiviral activity analysis of retinoic acid-inducible gene-I in duck (Anas platyrhynchos)

ABSTRACT

Intracellular double-stranded RNA (dsRNA) is a chief sign of replication for many viruses. Pattern recognition receptors (PRRs) of the innate immune system detected the dsRNA and initiate the antiviral responses. Retinoic acid-inducible gene I (RIG-I), a member of PRRs, plays an essential regulatory role in dsRNA-induced signalling. In this study, the full-length complementary DNA (cDNA) of duck RIG-I (duRIG-I) was cloned using the reverse transcription-polymerase chain reaction (RT-PCR) and rapid amplification of the cDNA ends (RACE). The cDNA of duRIG-I contained 97-bp 50 UTR, 141-bp 30 -UTR and 2802 bp complete open-reading frame (ORF) encoding 933 amino acids. Multiple sequence alignments showed that duRIG-I shared high similarity with RIG-I from other vertebrates. Quantitative real-time PCR (qRT-PCR) analysis revealed that duRIG-I mRNA was expressed in all tested tissues, with high levels in the liver, heart, spleen, kidney and thymus, while lower in the duodenum. duRIG-I could be induced by treatment with poly(IC). Further, overexpression of duRIG-I significantly activated the transcription of poly(IC)-induced IFN-b, IRF7, TRIF, Mx, STAT1 and STAT2 mRNA, and duRIG-I knockdown showed the opposite results. Overall, our results suggested that duRIG-I could be an important receptor for mimicking antiviral state in duck, which warrant further studies to show the possible mechanism.