Putting Birds In Their Place On The Tree Of Life

A study of 48 bird species sheds light on the relatively compact and virus-free genome of birds.

AsianScientist (Dec. 16, 2014) – In a contribution to an extraordinary international scientific collaboration, the University of Sydney found that genomic ‘fossils’ of past viral infections are up to thirteen times less common in birds than mammals. This research has been published in Science.

“We found that only five viral families have left a footprint in the bird genome (genetic material) during evolution,” said Professor Edward Holmes, from the University of Sydney’s Charles Perkins Center, School of Biological Sciences and Sydney Medical School.

“Our study therefore suggests that birds are either less susceptible to viral invasions or purge them more effectively than mammals. The results shed light on virus-host interactions across 100 million years of bird evolution,” he said.

After four years of collaboration, an international team of scientists has successfully sequenced, assembled and compared the full genomes of 48 bird species.

“One of the most striking findings is the small size of bird genomes, and the small number of fossil viruses seems to match this,” said Holmes.

Together with his postdoctoral student Jie Cui, now at Duke-NUS in Singapore, Holmes screened 48 avian genomes for ‘viral fossils’; that is, copies of viruses that have been incorporated into the avian genome and then passed on through generations.

“Using comparative genomics we have shown that birds carry far fewer of these viral or genomic fossils than mammals. Only five viral families have visited during bird evolution, with retroviruses and hepadnaviruses (like hepatitis B virus) the most common,” said Holmes.

“Clearly, our next question is whether the small genomes carried by birds somehow favour a reduction in the number of these viral fossils?”

The article can be found at: Zhang et al. (2014) Comparative Genomics Reveals Insights into Avian Genome Evolution and Adaptation.

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Source: University of Sydney; Photo: Anita Ritenour/Flickr/CC.
Disclaimer: This article does not necessarily reflect the views of AsianScientist or its staff.

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