Evolution of mammalian and avian bornaviruses.

Recently, Avian Bornavirus (ABV) was identified to be a new member of the Bornaviridae family consisting solely of the mammal-infecting Borna disease virus (BDV). Here, to gain more insights into the evolution of these bornaviruses, the time-stamped N gene sequences of BDV genotype 1 (BDV1) and ABV were subjected to Bayesian coalescent analyses. The nucleotide substitution rates and the divergence times were estimated. Age calculations suggested that the first diversification event of the analyzed BDV1 isolates might have taken place about 300years ago, and revealed that ABV was an old virus newly recognized. Great differences were observed in the rate of nucleotide substitution and the pattern of codon usage bias between BDV1 and ABV. Moreover, the analyzed bornaviruses might be descended from an AT-rich ancestor.