Im in ur genome, infectin ur flies
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How awesome is this? The bacterium Wolbachia is thought to parasitically infect “70 percent of the world’s invertebrates, coevolving with them”[1] (see previous posting on The Ranger’s Blog). Now research has uncovered an extraordinary and startling phenomenon: Wolbachia has managed to copy its entire genetic code into its host. No, it’s not like Jeff Goldblum in ‘The Fly‘, but it is getting surprisingly close.
Scientists at the University of Rochester and the J. Craig Venter Institute have discovered a full copy of the parasite’s genome in the genome of a Drosophila fly. It’s not unusual for bits of parasitic DNA to get muddled up with host DNA from time to time, but for an entire organism to be transcribed in this way is remarkable – and has far-reaching implications.
Classical evolutionary theory supposes that new features arise by natural variation such as mutations, and that natural selection then ensures that the beneficial features survive. Major changes should therefore take many generations, and very long periods of time. However there has for some time been debate in evolutionary biology about the time that evolution appears to take: there is evidence that it is not a constant, low-level and slow process, but that it sometimes happens in fits and starts.ScienceDaily reports on how this new discovery affects this theory:
The finding suggests that lateral gene transfer – the movement of genes between unrelated species – may happen much more frequently between bacteria and multicellular organisms than scientists previously believed, posing dramatic implications for evolution. Such large-scale heritable gene transfers may allow species to acquire new genes and functions extremely quickly, says Jack Werren, a principal investigator of the study… Werren and [Michael Clark, a research associate at Rochester] are now looking further into the huge insert found in the fruitfly, and whether it is providing a benefit. “The chance that a chunk of DNA of this magnitude is totally neutral, I think, is pretty small, so the implication is that it has imparted some selective advantage to the host,” says Werren. “The question is, are these foreign genes providing new functions for the host?” This is something we need to figure out.”
So, not only has it managed to become an integral part of its host, but it might actually be benefiting it (as Wolbachia is known to do elsewhere). This would obviously provide a way in which evolution could proceed much more rapidly – if one organism is capable of simply adopting the genes of another, fully formed, a mechanism for considerably faster rates of evolutionary change may have been revealed. What other organisms have been absorbed in the past, maybe even into our own genome? It seems inevitable that at some point this will have occurred… and will probably occur again. Perhaps Wolbachia will one day be a part of us too!
Forgive me, this comment is way left field, but I’m wondering if it’s been discovered because Drosophila is so closely studied (and perhaps there are similar phenomena in less easily observable species)… or *as a consequence of* D. being so studied. Might it have been introduced inadvertently by human agency? (dot dot dot)
Doesn’t affect the principle, but the mechanism’s interesting, no?
The Ranger responds: quite right – an implicit part of the interestingness of this discovery is that both Drosophila and Wolbachia are relatively well understood organisms the genome of which is well known. So if this phenomenon were common it would be expected to be discovered somewhere like this.
I’m less sure about the human agency thing – possible, of course, but even if it were, does that make it any less significant? I think not.
Great title! Pop-culture and science merge!