#GMOFAQ: Transferring genes from one species to another is neither unnatural nor dangerous

Last week I wrote about the anti-science campaign being waged by opponents of the use of genetically modified organisms in agriculture. In that post, I promised to address a series of questions/fears about GMOs that seem to underly peoples’ objections to the technology. I’m not going to try to make this a comprehensive reference site about GMOs and the literature on their use and safety (I’m compiling some good general resources here.)

I want to say a few things about myself too. I am a molecular biologist with a background in infectious diseases, cancer genomics, developmental biology, classical genetics, evolution and ecology. I am not a plant biologist, but I understand the underlying technology and relevant areas of biology. I would put myself firmly in the “pro GMO” camp, but I have absolutely nothing material to gain from this position. My lab is supported by the Howard Hughes Medical Institute, the National Institutes of Health and the National Science Foundation. I am not currently, have never been in the past, and do not plan in the future, to receive any personal or laboratory support from any company that makes or otherwise has a vested interest in GMOs. My vested interest here is science, and what I write here, I write to defend it.

S0, without further ado:

Question 1) Isn’t transferring genes from one species to another unnatural and intrinsically dangerous

The most striking thing about the GMO debate is the extent to which it contrasts “unnatural” GMOs against “natural” traditional agriculture, and the way that anti-GMO campaigners equate “natural” with “safe and good”. I’ll deal with these in turn.

The problem with the unnatural/natural contrast is not that it’s a mischaracterization of GMOs – they are unnatural in the strict sense of not occurring in Nature – rather that it is a frighteningly naive view of traditional agriculture.

Far from being natural, the transformation of wild plants and animals into the foods we eat today is – by far – the single most dramatic experiment in genetic engineering the human species has undertaken. Few of the species we eat today look anything like their wild counterparts, the result of thousands of years of largely willful selective breeding to optimize these organisms for agriculture and human consumption. And, in the past few years, as we have begun to characterize the genetic makeup of crops and farm animals, we are getting a clear picture of the extent to which traditional agricultural practices have transformed their DNA.

Let’s take a few examples. This is a Mexican grass known as teosinte and its seed.

Thousands of years of selection transformed this relatively nondescript plant into one of the mainstays of modern agriculture – corn. The picture below – which shows the seeds of teosinte on the left, and an ear of modern corn on the right – gives a pretty good sense of the scope of change involved in the domestication and improvement for agriculture of teosinte.

Thanks to the pioneering work of geneticist John Doebley, and more recently an international consortium who have sequenced the genome of maize and characterized genetic variation in teosinte and maize, we now have a good picture of just what happened to the DNA of teosinte to accomplish the changes in the structure of the plant and its seed: a recent paper that characterized the DNA of 75 teosinte and maize lines identified hundreds of variants that appear to have been selected during the process of domestication. And maize is not weird in this regard – virtually all agriculturally important plants have a similar story of transformation from wild ancestors as generations of farmers adapted them to be easier to grow, safer to eat, more nutritious, resistant to pests and other stresses, and tastier.

For most of history this crop domestication and improvement has been a largely blind process, with breeders selecting crossing individuals with desired traits and selecting the offspring who have inherited them until they breed true – unaware of the molecular changes underlying these traits and other changes to the plants that may have accompanied them.

Modern genetics has fundamentally altered this reality. It has increased the power breeders have to select for desirable traits using traditional methods, and makes it far easier ensure that undesirable have not come along for the ride. And it also gives us the ability to engineer these changes directly by transferring just the DNA that confers a trait from one individual in a species to another. There are many ways to accomplish this – the most common involves extracting the DNA you want to transfer from the donor, placing it into a bacterium whose natural life-cycle involves inserting its DNA into that of its host, and then infecting the target individual with this bacterium. But recently developed technologies make it possible to effectively edit the genome in a computer and then make the desired changes in the living organism.

When applied to transfer genetic information from one individual in a species to another, this is an intrinsically conservative form of  crop improvement around since is all but eliminates the random genetic events that accompany even the most controlled breeding experiment.

The only difference between this and the generation of GMOs is that the transfered DNA comes not from a member of the same species, but from somewhere else on the tree of life. I understand why some people see this is a big difference, but modern molecular biology has shown us that all living things share a remarkably similar molecular toolkit, with the distinct properties of each species coming more from how these pieces are wired together than which ones are where.

Transferring a gene from a fish into a plant does not make the plant swim any more than stealing the radio from someone’s Maserati and putting it into my Honda Civic would turn it into a high-performance sports car. Indeed, scientists routinely use genes from mice, fungi, plants and even bacteria to substitute for their human counterparts, and vice-versa – which they often do perfectly.

And this doesn’t just happen in the lab. There are countless examples of genes moving naturally between species. Microorganisms swap DNA all the time – this is how antibiotic resistance spreads so quickly between species. Our own genome contains genes that got their start in bacteria and were subsequently taken up by one of our ancestors.

The relatively low rate of such “horizontal gene transfer” in multicellular organisms like plants and animals compared to bacteria is more a reflection of reproductive barriers and the defenses they have evolved to prevent viruses from hitchhiking in their DNA, than from a fundamental molecular incompatibility between species.

This is why I do not find the process of making GMOs unnatural or dangerous – certainly no more so than traditional breeding. And why I find the obsession with, and fearmongering about, GMOs to be so bizarre and irrational.

Of course the fact that making GMOs is not inherently dangerous does not mean that every GMO is automatically safe. I can think of dozens of ways that inserting a single gene into, say, soybeans could make them lethal to eat. But it would be because of what was inserted into them, not how it was done.

For what its worth, it would also be relatively easy to make crops plant dangerous to eat by strictly non-GM techniques. Essentially all plants make molecules that help them fight off insects and other pests. In the foods we eat regularly, these molecules are present at sufficiently low levels that they no longer constitute a threat to humans eating them. But it is likely that the production of these molecules could be ramped up when crossing crop varieties with wild stocks, or by introducing new mutations, and selecting for toxicity, much as one would do for any other trait. Indeed, there have been reports of potatoes that produce toxic levels of solanines and celery that produce unhealthy amounts of psoralens, both chemicals present at low levels in the crops. Which segways nicely into the next topic.

NEXT: Question 2) Maybe GMOs aren’t automatically bad, but isn’t it obvious that it’s dangerous to consume crops that produce their own pesticides and can tolerate high doses of herbicides?

 

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14 Comments

  1. Peter Combs
    Posted June 10, 2012 at 9:26 am | Permalink

    Even granting the somewhat dubious point that GMOs are qualitatively different than artificially selected crops, this is still a great place to point out the Appeal to Nature fallacy: http://www.fallacyfiles.org/adnature.html In short, unless you believe that rampaging infections, unstable food supplies, and no access to any of the many marvels of technology is “good”, what is natural is not always good, and what is good is not always natural. This is worth bearing in mind in all kinds of arguments today.

  2. algernon
    Posted June 10, 2012 at 11:04 am | Permalink

    I guess you can argue that everything is “natural” because nature comprises space/time and the world within it. You could also say that “transferring genes” from one species to another isn’t dangerous because at that point all you are doing is transferring genes (not eating the end product). Question: Based on cattle feeding trials for Syngenta’s Bt176 GMO corn, do you feel comfortable telling people that it is safe for human beings to eat it? I sure don’t.

    • Posted June 10, 2012 at 11:19 am | Permalink

      As I said, I am arguing here that all GMOs are, a priori, safe – just that the process of making GMOs is not intrinsically dangerous and that there is no good reason to fear a new GMO any more than a new conventionally bred organism.

      As for the specific case you mention, the mechanisms of action of Bt suggests that it would not be toxic to mammals, and I have not seen any compelling evidence that convinces me otherwise. I will deal with this further later on.

  3. Posted June 10, 2012 at 11:31 am | Permalink

    Dude, I can’t believe you (1) drive a fucken Honda Civic and (2) linked to an article in Nature Reviews Genetics!

  4. Ewan R
    Posted June 11, 2012 at 6:58 am | Permalink

    It’d probably be useful if you linked the study you were concerned about algernon – there seems to be quite a bit of literature out there on Bt 176 all of it perfectly boring thus far.

  5. Diana Y.
    Posted June 11, 2012 at 7:36 am | Permalink

    Thank you for this! Somebody needs to explain this and I’m glad you’re doing it so well. Keep it up!

  6. Posted June 11, 2012 at 10:49 am | Permalink

    The UN Consensus document on the safety of Plants expression Insecticidal Proteins is an excellent source of information on Bt proteins. Here is a little quote from page 34:

    4. Human Risk Assessment
    65. The acute oral toxicity data on Cry1Ab, Cry1Ac, Cry9C, Cry3A, Cry1F, Cry2Ab2, Cry3Bb1,
    Cry34Ab1, and Cry35Ab1 supports the prediction that the Cry proteins would be non-toxic to humans.
    When proteins are toxic, they are known to act via acute mechanisms and at very low dose level (Sjoblad
    et al., 1992). Therefore, since no effects were seen in the acute tests, even at relatively high dose levels,
    these δ-endotoxin proteins are not considered toxic to humans. Both the long history of safe use of B.
    thuringiensis and the acute oral toxicity data allow for a conclusion that these and other δ-endotoxins pose
    negligible toxicity risk to humans.

  7. Posted June 11, 2012 at 8:55 pm | Permalink

    Wonderfully well done. It will clearly not sway those who have an paranoic aversion to the very thought of GMO’s but at least it tires to set the record straight, as I myself have tried to do in other venues, that the so-called “natural” breeding methods used by generations of sophisticated farmers and so on, has produced crosses that are every bit as non-natural as anything a vector-based gene transfer is doing. And in fact often with far more trial and error.

    I think the main reason for this disconnect is that anti-GMO folks see the vector-based genetic manipulation as the products of big geed-driven companies (often whose polices are indeed not very defensible at all – a very different matter – I am not defending the companies like Monsanto, for e.g.) but see the poor farmer in his/her field as somehow a less sophisticated benevolent soul who is the salt of the earth, literally and figuratively.

    Too many people have no idea how sophisticated the genetic crossing of livestock and plant crops is and how very unnatural the products are.

    Your piece debunks that, or tries to. Thank you.

  8. Geoff
    Posted June 13, 2012 at 12:32 pm | Permalink

    Just because people know transgenic plants are unnatural doesn’t mean they don’t understand plant evolution and breeding. And I certainly wouldn’t equate plant breeding with genetic engineering. As you say, there’s no “engineering” involved whatsoever. One can’t be an engineer if he’s not even aware of the existence of DNA.

    It’s not surprising that people have trouble with the idea that “[t]housands of years of selection” of traits from the same species is the same as a 40-year-old technology that can combine genes from very different parts of the genetic universe. Even highly educated people feel nervous about language like “inserting its DNA into that of its host, and then infecting the target individual with this bacterium.” Especially when they hear that it’s totally safe, but that lateral gene transfer is rare in nature because “reproductive barriers and the defenses they have evolved to prevent viruses from hitchhiking in their DNA”. This reinforces peoples’ idea that “nature knows best” (otherwise, if transgenic organisms were beneficial, they would have already been widespread without our help), and that scientists don’t know enough about how genomics really works yet (e.g., we don’t call it “junk DNA” anymore).

    There’s probably no hope for the people from the “GMOs are an abomination!” crowd, but better communication from scientists is crucial for widespread acceptance. Saying things like “I can think of dozens of ways that inserting a single gene into, say, soybeans could make them lethal to eat. But it would be because of what was inserted into them, not how it was done” doesn’t really help the cause!

    • Rick
      Posted September 25, 2013 at 1:18 pm | Permalink

      I agree that it is understandable that those with only lay knowledge of the science and techniques can be skeptical and suspicious. What infuriates me is that those with the sophistication and wherewithal to be a conduit of accurate information, i.e. Greenpeace, Food and Water Watch, etc. do not fulfill that role, instead they merely exploit and cultivate the ignorance of the average joe with self-serving dung to advance an idealogical agenda. Up until about 7 months ago, I would describe my knowlege about the science and application of biotech as passive. Although I was generally trusting in the competence of science, and my familiarity with biotech was from observation of its actual use and benefits to farmers and farming, I would say that I too was uncertain about whether some aspects had been fully thought out. Today, I am more convinced than ever in the logic and soundness of the technology and the competency of science to enable us to utilize biotech responsibly and in ways that are benificial and to avoid unintended results. My questions are no longer about safety (I am convinced that the anti side has provided no quality, honest, compelling evidence that “proves” enhancing a plant’s genetic endowment in part through biotech tools presents any new or inherent health, environmental or risk that is not presented by any other breeding method to improve plants utility or performance, nutritional content or resiliance to disease and pests) but more regarding the best and appropriate applications of the technology. What are your thoughts on how to overcome the biases and barriers to public understanding? Where is the transparency lacking?

  9. David J james
    Posted June 14, 2012 at 3:46 pm | Permalink

    Geoff does’nt now much about plant breeding. As someone who worked professionally in a government sponsored plant research organisation for many years I can categorically state that plant breeders would include mutation breeding, polyploid induction, somaclonal variation, embryo rescue and other techniques as valid parts of the plant breeding spectrum and would certainly rank as ‘genetic engineering techniques ‘. Many crop plants today are their legacy. e.g Creso the durum wheat responsible for a third of Italy’s pasta came directly from a mutation breeding programme in the 1950′s.

  10. Geoff
    Posted June 16, 2012 at 8:01 am | Permalink

    Since you don’t know me, Mr. james, I’d appreciate it if you didn’t make statements about what I know and don’t know. The techniques you list have been in use for less than a century, and so hardly equate to the thousands of years of non-GE plant breeding that we are talking about. Are they in the armamentarium of modern plant breeding? Of course. But I was making a distinction between pre-scientific breeding and molecular biology-based transgenic GE, since that’s what I interpreted Mr. Eisen equating in his original post.

  11. chelsea tornade-hoe
    Posted June 25, 2014 at 4:05 pm | Permalink

    “The relatively low rate of such “horizontal gene transfer” in multicellular organisms like plants and animals compared to bacteria is more a reflection of reproductive barriers and the defenses they have evolved to prevent viruses from hitchhiking in their DNA, than from a fundamental molecular incompatibility between species.”

    When you say “viruses” don’t you mean ‘bacteria’ or possibly ‘disease’ ??

  12. Posted August 6, 2014 at 10:47 am | Permalink

    Lovely piece of writing, explanation. I will link to it when trying to explain to my readers that the activities of molecular biologists don’t require exorcism. :)

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