Abstract: The Interferons(IFN, interferon) are a family of cytokines which have various biological functions, such as anti-virus, anti-tumor, and immune regulation. Interferon-α belongs to type I interferon, encoded by Z-linked gene IFNA. In this study, the sequences of IFNA in eight avian species of anseriformes were amplified and sequenced by PCR. Combined with the data retrived from GenBank, the sequence characterization, the evolutionary rate and the physicochemical properties of IFNA in seventeen species of Galloanserae were analyzed using bioinformatic methods. To discuss the phylogenetic implications of IFNA, we reconstructed the evolutionary trees using maximum parsimony(MP), maximum likelihood(ML) and bayesian inference(BI) methods. Results demonstrated that the CpG islands were existed in nucleotide sequences of IFNA in majority of Galloanserae species, and detected that the Interferon-α(IFN-α) was unstable hydrophilic secreted proteins. The evolutionary rate of IFNA in Galloanserae was faster than that of three mitochondrial coding genes(nad2, cytb and atp6) with higher dN/dS. In addition, a positive selection site of IFNA was found in Galloanserae species in this study. The molecular phylogenetic analysis indicated that IFNA had some phylogenetic informations within Galloanserae. Phylogenetic tree based on multiple genes could reveal the evolutionary history of species.

Key words: IFNA, Galloanserae, sequence characterization, evolutionary rate, phylogeny