Four Mx Genes Identified in Andrias davidianus and Characterization of Their Response to Chinese Giant Salamander Iridovirus Infection

SIMPLE SUMMARY: Andrias davidianus is one of the largest amphibian species in the world. To improve our understanding of Myxovirus resistance (Mx) genes in amphibians, particularly their function in virus infection, we cloned four full-length A. davidianus (adMx) cDNA sequences and characterized these genes by bioinformatics analysis and quantitative expression techniques. The four adMx genes ranged from 2008 to 2840 bp in length, and their conserved protein domains included the signature architectural feature of the dynamin superfamily. Deduced amino acid sequences exhibited relatively high sequence identity with Mx proteins from other vertebrates and phylogenetic analysis revealed close clustering with fish. The four adMx genes were broadly expressed in healthy A. davidianus, but differentially expressed in the spleen following Chinese giant salamander iridovirus (GSIV) infection. These findings imply that the adMx genes share major sequence and protein structures and similar functions with those of other species. ABSTRACT: Amphibians, including Andrias davidianus, are declining worldwide partly due to infectious diseases. The Myxovirus resistance (Mx) gene is a typical interferon (IFN)-stimulated gene (ISG) involved in the antiviral immunity. Therefore, knowledge regarding the antiviral immunity of A. davidianus can be used for improved reproduction in captivity and protection in the wild. In this study, we amplified and characterized four different A. davidianus Mx genes (adMx) and generated temporal mRNA expression profiles in healthy and Chinese giant salamander iridovirus (GSIV) infected A. davidianus by qualitative real-time PCR (qPCR). The four adMx genes ranged in length from 2008 to 2840 bp. The sequences revealed conserved protein domains including the dynamin superfamily signature motif and the tripartite guanosine-5-triphosphate (GTP)-binding motif. Gene and deduced amino acid sequence alignment revealed relatively high sequence identity with the Mx genes and proteins of other vertebrates. In phylogenetic analysis, the adMx genes clustered together, but also clustered closely with those of fish species. The four adMx genes were broadly expressed in healthy A. davidianus, but were differentially expressed in the spleen during the GSIV infection. Our results show that the adMx genes share major structural features with their homologs, suggesting similar functions to those in other species.