The exasperating issue of GM plants

25-11-2016 - A little pre-script from a 10-year older Mike: Although I haven't done any deep research on the matter, there seem to be diverging opinions on the safety of glyphosate. The Roundup-resistant GM plants themselves are harmless though (unless of course they are an invasive species, which is a completely different ecological matter).

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As I have reached my revision period, I might as well contribute to public education and write about some of the topics I tackled in this year's lectures. One of the most prominent and controversial issues in the modern era of genetic engineering revolves around genetically modified organisms, mainly plants.

The public debate is going nowhere, because protesters always have the loudest voices, usually only spreading their misinformed ideologies of general devastation and death. Yes, if we are not getting killed by an upcoming ice-age, volcano eruption or nuclear fallout triggered by a bunch of terrorists, plants are going to wipe us off the planet. Nature is cruel.

Now that we considered and ignored the general gobbledygook [1], we can face the facts. Genetically modified plants hardly differ from their «normal» pendants' genotype; meaning that they typically carry one to a couple of additional genes. The big advantage to conventional breading is the possibility to introduce specifically a single gene, which may be of any species as long as one can get a grasp on the cDNA and it can be expressed in plants.

The most frequent traits embrace herbicide tolerance, insect resistance, virus and fungal resistance, modified nutritional value and several other traits that exploit plants as bioreactors for the production of e.g. pharmaceuticals [2,3].

A widely used herbicide is glyphosate that interferes with plants' shitimake pathway, which is responsible for the production of many aromatic metabolites, including some amino acids [4]. As animals don't have this pathway, glyphosate only exhibits low toxicity for animals; it is also cleared quite rapidly by soil bacteria. The herbicide has found extensive application in e.g. killing plants off rail tracks even in the pre-GM era. In GM plants tolerant to glyphosate, an additional EPSPS gene from the soil bacterium Agrobacterium tumefaciens has been introduced which isn't affected by the chemical. This allows selective growth of the GM crops, decreased the use of herbicides applied in tillage, improved the soil quality and therefore enabled crop rotations [5]. Other common herbicide traits include tolerance against bromoxynil and gluphosinate, whereby both approaches rely on the detoxication of the compounds by the transgene product.

Herbicide tolerance has been engineered into many crops and is by far the most successful GM trait. To show some figures: 81% of the USA's soybean crops in 2003 was glyphosate-tolerant [6], facilitating effective cost-cuts in herbicide expenditures (and therefore environmental burden) which easily amortise the additional technology costs for GM seeds.

More about GM later.

[1] Thanks Dr Colquhoun for that great word.
[2] I haven't heard anyone crying out that we abuse Escherichia coli for the production of insulin.
[3] This list is not supposed to be comprehensive in any way and only provides a rough outline.
[4] The exact target is EPSPS, 5-enolpyruvylshikimate-3-phosphate synthase.
[5] Normal herbicides are not cleared quickly enough from the soil and would kill crops different to the ones grown.
[6] Benbrook, CM. 2003. Impacts of Genetically Engineerd Crops on Pesticide Use in the United States: The First Eight Years. BioTech InFo Net Technical Paper Number 6.

My apologies for not providing all the references, but this is merely a blog, not a scientific journal.