Horizontal Gene Transfer in Higher Eukaroyotes

A Role for Host–parasite Interactions in the Horizontal Transfer of Transposons Across Phyla

http://www.nature.com/nature/journal/v464/n7293/abs/nature08939.html

Horizontal gene transfer is a process that geneticists have mostly studied in bacteria, and is offered as a possible explanation to how bacteria are able to quickly become antibiotic resistant. But only recently has this same process been documented in higher organisms, thanks to the work Gilbert et al. The findings in this article pose an interesting question: do higher organisms transfer genes to other species more often than originally thought?

Simply put, this article argues that there is a type of parasitic blood-sucking bug that feasts on tetrapods in many different phylas, and is causing horizontal gene transfer (HGT). Although we haven’t gone over this extensively in class, many of us have heard about HGT in other classes we have taken. In HGT, an organism incorporates genetic material to another organism without being the offspring or a mate of that organism. This phenomenon is noted mostly in unicellular organisms, and so I found it really interesting that this bug could inflict HGT on animals of higher complexity.

The authors of the article uses a few different phylogenies to show how the animals affected by the mites are not closely related and are from different regions of the world, and therefore should not have too much similar DNA. To give an idea, some of the animals included are opossums, squirrel monkeys, frogs, lizards, and chickens. Then, from these dispersed animals, the researchers sequenced genomes and found a portion of genes shared amongst all of the animals and the mites. They therefore concluded that this is proof of HGT within these phyla. HGT mechanisms are still not clearly understood, and so how genes are transferred is not specifically talked about in this paper. Because of this and the fact that there may be other factors causing similar sequences (such as unknown distant relatives), I’m not really sure if I believe this paper or not. It seems too far-fetched that the authors randomly chose species and they all had the sequences in common with the mite. I feel like there is a lot missing from the article, and I would like to see data on animals that are more closely related to all of the species. I feel like I need proof that related species to the ones in the study who are not parasitized by the bug do not also have the same sequence. If I saw this data, I might be more inclined to believe that HGT can be caused by a parasitic bug across many multicellular phyla. All in all, this article leaves me wanting more information on just how common HGT is in higher organisms and it will surely be interesting to learn.

Clement Gilbert1*, Sarah Schaack1*, John K. Pace II1, Paul J. Brindley2 & Cedric Feschotte1

“A role for host–parasite interactions in the horizontal transfer of transposons across phyla”

Nature Vol 464 April 2010 (p 1347-1352)