Genome analysis of a novel avian atadenovirus reveals a possible horizontal gene transfer

We report the discovery and characterization of a novel adenovirus, Zoothera dauma adenovirus (ZdAdV), from a wild bird species, Zoothera dauma (Scaly thrush). This new atadenovirus was discovered by metagenomic sequencing without virus cultivation. Analyses of the full genome sequence revealed that this new virus is a distinct member of the genus Atadenovirus and represents a novel species. ZdAdV has a genome of 34,760 bp with 28 predicted genes and 39% GC content. ZdAdV is the first atadenovirus to contain ORF19, a gene previously found only in aviadenoviruses. Phylogenetic analysis of ORF19 suggests that it was acquired by ZdAdV through horizontal gene transfer from an aviadenovirus. By analyzing all orthologous genes of aviadenovirus, mastadenovirus, atadenovirus, and siadenovirus, we also found potential horizontal gene transfer for the E4 gene in Pigeon aviadenovirus B. Our study widens our knowledge concerning the genetic diversity and evolutionary history of atadenoviruses and their potential for cross-species transmission.