Disobedient cells

May 2015

Twenty years of commercial use seems a very long time to profit from something that only works sometimes.

Genetic engineers are very good at cobbling together DNA. Once they've built a gene, attached a DNA 'on-switch' to it and popped it into a plant, the switch can't help but drive the gene, the gene can't help but send out messages to the cell to make a novel protein and the cell can't help but do what it's told. If the gene codes for a 'Bt' insecticidal protein, the GM plant can't help but douse itself with insecticide and make a lot of money for the biotech industry.

What could possibly go wrong?

Well, it was realised some time ago that the amount of Bt protein actually produced by GM plants varied unpredictably with tissue type, age, and environmental conditions such as soil quality, pesticide use and nitrogen application. That's a lot of variation. The insecticide just might not be in the same place at the same time as the pest, or in the right quantity to be lethal.

Recent research has added a few more disturbing variables to the GM outcome.

The Bt gene may be churning out messages to the cell to make insecticide, but a stressed plant just might not do what it's told, or might unaccountably shift into hyper-production (73-fold if you like figures).

Two varieties of the same plant with the same DNA construct make different amounts of Bt protein and the Bt they produce under stress can be wildly different.

And then, the artificial gene might not bother to send out too many messages to the cell, but somehow the Bt protein just keeps coming anyway.

The authors of this study point out that the assumption that genetic engineers can force a plant to do their bidding is fundamental not only to the creation of GMOs in the first place but to the subsequent level of safety testing required. They also voice concerns about the implications for pharmaceutical or nutrient-enhanced GM crops which are planned to be the next big biotech money-maker: minimum doses clearly can't be guaranteed, and high doses could be harmful.

OUR COMMENT

Who knows what other unpredictable and unusual things are happening in the physiology of these GM plants, and since nothing else about them is predictable who knows what toxins just might be there too.

SOURCES

• Miluse Trtikova, et al., 2015, Transgene Expression and Bt Protein Content in transgenic Bt Maize (MON810) under Optimal and Stressful Environmental Conditions, PLOS ONE 8.04.15
• Gene expression and content of insecticidal toxins cannot be reliably predicted, Testbiotech 10.04.15
• Effects of stress on GM maize: Researcher answers questions, GM Watch 10.04.15