Abstract
Wild birds harbour a large number of adenoviruses that remain uncharacterised with respect to their genomic organisation, diversity, and evolution within complex ecosystems. Here, we present the first complete genome sequence of an atadenovirus from a passerine bird that is tentatively named Passerine adenovirus 1 (PaAdV-1). The PaAdV-1 genome is 39,664 bp in length, which was the longest atadenovirus to be sequenced, to the best of our knowledge, and contained 42 putative genes. Its genome organisation was characteristic of the members of genus Atadenovirus; however, the novel PaAdV-1 genome was highly divergent and showed the highest sequence similarity with psittacine adenovirus-3 (55.58%). Importantly, PaAdV-1 complete genome was deemed to contain 17 predicted novel genes that were not present in any other adenoviruses sequenced to date, with several of these predicted novel genes encoding proteins that harbour transmembrane helices. Subsequent analysis of the novel PaAdV-1 genome positioned phylogenetically to a distinct sub-clade with all others sequenced atadenoviruses and did not show any obvious close evolutionary relationship. This study concluded that the PaAdV-1 complete genome described here is not closely related to any other adenovirus isolated from avian or other natural host species and that it should be considered a separate species.
Highlights
Adenoviruses are medium-sized, non-enveloped, linear, double-stranded DNA viruses within the family Adenoviridae [1]
The passerine adenovirus 1 (PaAdV-1) genome contained a central conserved coding region bounded by two identical inverted terminal repeat (ITR) regions
Using the same set of concatenated protein sequences, we found that the maximum inter-lineage sequence identity values between the novel PaAdV-1 and other atadenoviruses were >63% (PaAdV-1 vs. duck atadenovirus (DAdV)), >62.5%
Summary
Adenoviruses are medium-sized, non-enveloped, linear, double-stranded DNA (dsDNA) viruses within the family Adenoviridae [1]. The family Adenoviridae contains five accepted genera [1]. One of these genera, the Atadenovirus, was added in 2002, to include adenoviruses that were previously assigned to the genus Mastadenovirus, but varied significantly based on genomic size, structure, genes, and gene arrangement. Atadenoviruses have a set of core genes shared with the other adenovirus genera plus genus-specific genes. A feature of adenoviruses is their ability to acquire genes from their hosts, bacteria, fungi, and other viruses. The Atadenoviruses appear to be adept at this and all Viruses 2020, 12, 1036; doi:10.3390/v12091036 www.mdpi.com/journal/viruses
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