Transposons and symbiosis

There are a pair of really interesting articles in this week's Science. First, Fischer and Suttle report the discovery of a virophage (like a "virus" for viruses) that is a connecting link between double-stranded DNA viruses and the eukaryotic DNA transposon Maverick/Polinton. You might recall Liu and Soper's exogenization hypothesis that I discussed previously. One of my concerns about their idea was that it could account only for retroviruses rather than comprehensively explaining all viruses. This new virophage discovery doesn't rectify that problem, but it does suggest that there are more connections between viruses and genomic elements than we had previously guessed.

Fischer and Suttle. 2011. A Virophage at the Origin of Large DNA Transposons. Science 332:231-234.

Next, Himler et al. report on amazing fitness gains in an invasive fly due to the spread of a rickettsial endosymbiont. I've previously emphasized the role of transposons and other genome modifications as possible explanations for rapid speciation [PDF], but I'm beginning to wonder whether symbiosis might play a more prominent role. Food for thought.

Himler et al. 2011. Rapid Spread of a Bacterial Symbiont in an Invasive Whitefly Is Driven by Fitness Benefits and Female Bias. Science 332:254-256.

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