Types I to IV IFNs and their receptors in white spotted bamboo shark (Chiloscyllium plagiosum)

Interferons (IFNs) are a class of proteins with significant antiviral and antibacterial functions. To date, four distinct types of IFNs have been identified in vertebrates, including types I, II, III and IV IFNs. However, all these IFNs have not been reported together from any species of cartilaginous fish. In this study, types I, II, III and IV IFNs have been identified in white spotted bamboo shark (Chiloscyllium plagiosum). Type I IFNs were distributed in a conserved locus as reported in amphibian and zebrafish with seven duplicated genes. IFN-γ and IFN-υ genes were located in conserved loci as reported in other vertebrates, but four copies of IFN-υ genes were found in the bamboo shark as compared with a single gene in other vertebrates. However, a single IFN-λ gene was found in the bamboo shark, but not in the conserved gene locus as reported in other vertebrates. It is obvious that all these IFN genes were constitutively expressed in examined organs/tissue, and were induced following poly(I:C) stimulation. The findings of four types of IFNs in bamboo shark fill up the gap in relation with the composition of IFNs in cartilaginous fish, and contributes to the understanding of IFN system from an evolutionary point of view.