Monday, August 5, 2013

Yes Mom, I do study GMOs

Reading Amy Harmon's great piece on GMOs and citrus greening inspired me to write this post. What follows is a slightly fictionalized account of a conversation I had with my mom. Don't worry, these conversations actually happened pretty much how I describe. I recently stopped home for a couple of days (my favorite conference to attend is but 2 hours away from my parent's house in VT) and eventually found myself arguing with her about the benefits of genetically modified organisms (GMOs). Her main comment was something along the lines of "How do you know what happens when you stick a lemon gene into corn. There could be horrible side effects". I found myself making the case that substantial scientific evidence exists concerning on the safety of GMOs and human health as well as describing how corn was completely different from it's non-domesticated (and hence non-genetically modified) ancestor teosinte. Standard stuff really, and the conversation ended in rhetorical standstill as is par for the course when I disagree with my parents.

A few hours later my mom asked me about my own research program. I started to tell her about horizontal gene transfer (HGT) in microbes, how the transfer of such genes is a driving force for microbial evolution, and finished by describing how we know very little about the side effects of HGT. Then it hit me, my research links up perfectly with the discussion about the side effects of GMOs. HGT is a natural process that is effectively indistinguishable from the creation of GMOs. At a forest through the trees level specific genes start out in species A and are transferred to species B. In the case of HGT, the vector for transfer can be a plasmid/phage/transposon/etc whereas for GMOs the vector can be a plasmid/phage/transposon/etc. In the former, random chance (and many other factors such as environmental proximity) determine which HGT events occur, whereas in the latter it's humans that determine which occur. The only (arguably subtle) difference between HGT and GMOs is what structures selection pressures. In the case of HGT, natural selection culls out unproductive combinations of genes and backgrounds whereas with GMOs humans directly select and screen for the most "productive" combinations. You could even argue, thinking about the selection pressures on the movement of antibiotic resistance genes in microbial pathogens, that there is substantial overlap even in selection pressures. If you just focus on the movement of genes and don't worry about the how, the natural process of HGT and artificial process of GMO creation are exactly the same. What we learn about the side effects of HGT will be directly applicable to understanding the side effects of GMOs, i.e. for figuring out how badly a single lemon gene would screw up your tasty corn. My research can actually be able to address my mom's original question.

"Ahh...but Dave", you might say, "microbes are different than corn". Well, it turns out that HGT occurs much more frequently in multicellular eukaryotes (like corn) than we previously thought. Aphids come in different colors because they have acquired carotenoids from fungus. A substantial portion of the genome that codes for your steak is potentially derived from snakes (arguing about the precise percentage can get a little hand-wavy since this may only be one HGT event). Michael Douglas may have gotten oral cancer because of viral HGT. Perhaps most relevant to this discussion, there is a gene in sorghum and rice that is has been acquired from a parasitic plant. The list goes on and on and will only grow as more genomes are sequenced. Yes mom, even though I study the transfer of microbial genes, I'm still studying nature's GMOs.

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