Researchers have identified a pair of 'David and Goliath' viruses that sheds light on the evolutionary origin of some jumping genes.
The small virus Mavirus that attacks another virus more than 100 times its own size (marine zooplankton Cafeteria roenbergenesis and CroV), rescuing the infected zooplankton from certain death.
"It's a microbial version of the David and Goliah story where, after infecting Cafeteria roenbergeneis, Mavirus protects it against infection by CroV, while ensuring its own survival," said Curtis Suttle of University of British Columbia.
"What makes this interaction significant to evolutionary biology is that the closest genetic relatives to Mavirus are mobile genetic elements found in single-celled and higher organisms," said Suttle.
"This implies that over evolutionary time, organisms have co-opted the DNA from ancient relatives of Mavirus into their own genomes, presumably so that they could acquire immunity against giant viruses like CroV."
Transposons, or jumping genes, are bits of DNA that can move or "transpose" themselves to new positions within an organism's genome.
Researchers think that a subset of transposons - called Maverick transposons - have a viral origin because of the nature of their DNA sequences.
"Because they've sequestered the virophage DNA into their own genomes, organisms probably don't need to rely on being infected by a second virus to protect themselves," says Suttle.
The study is published online today in Science Express.