How ancient virus species helped each other by exchanging DNA

Ancient virus species infecting the same plant helped each other by exchanging DNA, according to a new study.

Researchers at Hokkaido University in Japan made the discovery by analyzing ancient viral footprints in the rice genome, according to the study published in the journal PLOS Pathogens.

The team led by Yuji Kishima analyzed the sequences of PRVs in 20 grass genomes including Oryza sativa, also known as rice. The team found DNA of five non-autonomous PRVs lacking some essential genes and therefore incapable of functioning on their own. All previously identified PRVs have been autonomous.

Viruses including “pararetroviruses” can insert their DNA into their host’s genome, the study said. For some viruses, this is a required step for replication, while in others, the DNA is inserted accidently and is passed from one generation to the next.

Inherited viral DNA sequences serve as fossil records for ancient viruses and studying them has revealed valuable data about the evolutionary dynamics of host-virus interactions, the authors said. However, little is known about the evolution of virus-virus interactions.

The study suggests that non-autonomous PRVs adopted two strategies to maintain their life cycles. One involves a “commensal” partnership with another species of autonomous PRV. The other strategy involves a “mutualistic” partnership with another species of non-autonomous PRV in which both PRVs compensate for a function they are each lacking.

“In both strategies, exchanging DNA between the virus species plays an important role in establishing the partnership,” said Kishima  “We suggest that the exchange of noncoding regulatory sequences is an important mechanism driving concerted evolution of the viruses.”

The same type of partnerships could be used in existing non-autonomous PRVs, Kishima added.

“Whether plant or human, further studies are needed to better understand the mechanisms of viral evolution and pathology.”

Image Credit: Chen S. et al., PLOS Pathogens, June 29, 2017

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By: David Beasley, Earth.com Staff Writer

Source: Hokkaido University

Image Credit: Chen S. et al., PLOS Pathogens, June 29, 2017