A rose by any other name…


Biofortified, a group blog I read sometimes, is carrying a piece today called Crop Plants with DNA Deletions are not GMOs. The piece is largely about exciting new technology used to examine disease resistance in rice. But the title comes from this passage:

Instead of adding a sentence or two to the genome book, as is done by standard genetic modification (GM) approaches, they removed a few letters; the rice varieties they generated lack anywhere from 3 to 57 bases in their genomes (as in the Figure to the right from the Li paper). Thus, the rice plants generated by Li et al. do not contain extraneous DNA and cannot by any reasonable definition be considered “GMOs.”

Figure 1e from Li. The top row is a DNA sequence in the gene that makes wild type rice susceptible to blight. Each of the other rows have deletions (marked by dashed) or additions (red letters) induced by the TAL-nuclease.

I regularly explain to non-scientists, or school kids on STEM visits, that while GMO may stand for Genetically Modified Organism, that’s rarely what it is understood as. Because of course a plant with a deletion is a GMO. Its genome has been modified! And yet in the minds of the public and policy makers and just about anyone else GMO has become a surrogate for transgenic*. (Irrelevant aside: I have a very fine t-shirt acquired from Plant Biotechnology Journal with the slogan ‘Proud to be transgenic on the back’. I wore it to Freshers’ Fair last year and was asked where one could find LGBT…)

The lay public are often wary of ‘GM technology’ as a concept, rather than specific concerns about the genes being transferred. So I suppose there are several reasons why they might be more wary of transgenics than deletion lines. The idea that a transgenic protein may have an incompletely understood effect upon the transformed organism, or that the protein might somehow be horizontally transferred to a weed… these concerns don’t seem so relevant to deletion lines in the public mind.

But I wonder if that should really be the case. Here’s a (hugely simplified) example:

  • The 1960s Green Revolution was powered by gai (giberellic acid insensitive) mutations that lead to short plants.
  • Short plants expend less energy on vegetative growth, therefore producing higher yield (aka more seed)
  • Gai crop plants then outcross with nearby weeds. (This is next to impossible, since crops and the weeds that grow around them are usually so phylogenetically distant from one another, but is often the cornerstone in people’s GM fears, and I’m trying to make this roughly equivalent)
  • Weeds then also grow shorter, use less energy, produce more seed and are therefore able to spread further and faster.

There’s a lot wrong with the analogy. (For one thing, I imagine that the shorter weed would be outcompeted for resources by its wild type relatives.) But I suppose my point is, what some people fear in terms of GM crops outbreeding is not a mysterious ethereal gene crossing over to a different species. It’s the phenotype**: it’s what the plant actually looks like. And while most mutations will be recessive, while the presence of a new gene is more likely to be dominant, a deletion line is no less able to pass on this phenotype than a transgenic plant.

What I’m arguing about is really just semantics. For the moment deletion lines can be grown far less stringently than transgenic plants, but they’re also more of a tool than an end product. I just find it faintly ridiculous that anyone can publish something saying ‘this plant in which the genome has been modified is not a genetically modified organism’.

Rant for today over.

* Transgenic = an organism containing foreign DNA from another species. E.g. Roundup Ready corn or Bt corn or Golden Rice or the new aphid-scaring wheat from Rothamsted

** Phenotype = what an organism looks like, as opposed to its genotype, which is what its genetic code says.  

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9 responses to “A rose by any other name…

  1. Thanks for your post. Yes, you are arguing semantics because in the mind of the public GMO=transgenics. Otherwise, pretty much every single plant we eat is a genetically modified organism.

    • Oo hello! Thank-you for replying. I agree: I was recently asked in a talk why my own (DL) approach was different or better than transgenics to which all I could answer was ‘Daily Mail readers seem to mind deletion lines less…’ But I dislike giving in and using terminology the way the public have when it actually means something else. Does that make sense?

  2. It just shows how fully “GMO” has been co-opted to mean “transgenic” that it didn’t even occur to me to interpret the term literally when we were writing this.

    • I really don’t like using the term GMO but we seem to be stuck with it. Transgenic is so much more specific but then we are creating a potentially false distinction between safety of transgenic and cisgenic… when we all know that some cisgenic could be unsafe while some (most) transgenic is safe!

  3. “Short plants expend less energy on vegetative growth, therefore producing higher yield (aka more seed) ”

    The reason shortness was selected for was for better utilization of high levels of fertilizer – tall plants, under high fertilization, will lodge (fall over) short plants don’t – thus short plants allowed increased fertilizer use – at least according to the plant physiologists I know.

    • Like I said, I was simplifying. Short plants do lodge less (but still plenty!) So yes, the yield increase can be partially attributed to less grain being lost pre-harvest, but grain filling is also increased. I’m guessing that lodging is less relevant to weed species though.

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