Artificial horizontal gene transfer (HGT)

January 2016

"Genetically modified” or "GM" is the term settled on by politicians to describe the artificial creation of genes (genetic engineering) and the artificial change of DNA in an organism (genetic transformation). 

Even in the earliest days, GM DNA was never as simple as a single protein-coding 'gene'.  Scientists soon realised that their isolated DNA needed all manner of adjustments and extra bits if it were to work at all in its new environment, and some of their creations don't code for a protein at all but were found to alter the function of the natural genome around them in useful (to man) ways. 

For twenty years the public have been listening to claims that 'GM' is 'safe', but the proof of GM safety shifts with the tides.  And consumer distrust has continued unabated. 

The big new propaganda event of last year was the 'discovery' of a "naturally GM" food crop [1]. 

In spring 2015, a paper was published documenting an ancient horizontal gene transfer from a bacterium into all domesticated sweet potatoes.  Such transfers have "long been recognised as a natural phenomenon" and modern molecular methods are increasingly detecting them in all types of organism. 

The bacterium involved is thought to be an ancient relative of Agrobacterium spp.  Modern strains of these bacteria are plant pathogens which insert their own DNA to induce cell proliferation and, thus, create a bacterium-friendly environment for themselves.  GM versions of Agrobacterium have been widely used as vectors to create GM crop plants. 

The ancient DNA was found to be expressing at very low levels in the sweet potatoes and seemed to be conferring neither advantage nor disadvantage to the plants.  This finding isn't unusual as sequestration of pathogen-derived DNA in the genome of healthy organism is well recognised. 

Sadly for science, this interesting study was used as a vehicle for blatant pro-GM propaganda. 

Even in its title, the paper itself plugged the notion that sweet potatoes are 'naturally transgenic' and that (somehow) this could allay consumer distrust of unnaturally transgenic food, by (somehow) changing consumer perception of GM crops as being "unnatural". 

Press coverage at the time allowed the author for correspondence, Jan Kreuze, to plug the further idea that human-made GM is better than natural because we "know exactly" what we're putting in.  Other pro-GM writers declared sweet potatoes could now no longer be considered organic and that all EU regulations on GM would now have to be changed. 

In the event, the naturally GM sweet spuds don't seem to have changed any minds or regulations. 

However, it recently became apparent that the 'naturally GM' PR spin machine kept on rolling. 

In July 2015, another batch of articles about the study popped up.  These hinted heavily that the ancient bacterial gene must have conferred some 'positive' or 'interesting' or 'important agricultural' trait which was selected for by farmers.  The implication being that natural GM is beneficial and therefore so is unnatural GM.

COMMENT. The possibility that the sweet potatoes might be the remnants of the few plants to survive some ancient bacterial plague due to their ability to sequester the pathogen instead of succumbing to it has never been voiced. 
Since sweet potatoes reproduce vegetatively there will have been limited scope for the bacterial DNA to be eliminated through the corrective processes of sexual reproduction or through selective breeding.
GM Freeze has pointed out that sweet potatoes are known to be one of the oldest domesticated crops, and that there has been some 8,000 years for the bacterial gene-containing spuds to be selected for safety: put another way a 90-day animal feeding study (if you're lucky) of a food with a man-made DNA construct doesn't compare. 

In October 2015, a letter to the Editor popped up in the Guardian newspaper confidently repeating all the same propaganda, and adding the apparently novel notion that the ancient bacterial genes caused the roots to swell resulting in bigger sweet potato roots which the ancient farmers favoured. 

And the reason for all this unscientific scientific innuendo? 

Who knows, except that in November 2015, Jan Kreuze was awarded a grant from the Bill and Melinda Gates "Grand Challenges Explorations" for research on RNA silencing (the GM fad du jour [2,3]) to combat viral infection in common Developing World crops including sweet potatoes.  The Grand Challenges Exploration grants are $100,000 with follow-on grants for successful projects of up to $1 million. 


It seems scientists have to look after their own, even at the expense of science? 

'Natural GM' is, of course, more public-friendly than that old political hot potato, 'horizontal gene transfer', which not even a sweet potato can make politically correct. 

Perhaps to avoid confusion regarding 'natural GM' we need to re-name what used to be 'GM' as 'unnatural-' or 'artificial-' horizontal gene transfer.  Or even call it what it actually is: DNA conceived by humans (HC) and placed by human contrivance (also HC) in an organism to create a humanly-conceived, humanly-contrived organism (HCCO)? 


[2] RNA MODIFIED FOOD - July 2013

[3] RNAi RISKS SUPRESSED - June 2014

  • Tina Kyndt, et al., 2015, The genome of cultivated sweet potato contains Agrobacterium T-DNAs with expressed genes: An example of a naturally transgenic food crop, PNAS, 112:18 5.05.15
  • Ghent University, Horizontal gene transfer: Sweet potato naturally 'genetically modified', Science Daily 21.04.15
  • Sweet Potato Is a Natural GMO, Genetic Engineering News, 22.04.15
  • Kevin Folta, Discovery of naturally transgenic sweet potato poses conundrum: Will it be labelled or banned? Genetic Literacy Project, 23.04.15
  • Jonathan Jones, Sweet!  A naturally transgenic crop, Nature Plants 1, 2.06.15
  • Tina Kyndt, GMOs are not a human invention: sweet potato is a naturally transgenic food crop, The Science Breaker, 6.07.15
  • Jan F. Kreuze, Sweetpotato Is a Naturally Transgenic Crop, Information Systems for Biotechnology News Report,, July 2015
  • Prof. Anthony Trewavas, Eaten sweet potato? Then you've had a GM meal, Letter to the Editor, The Guardian 22.10.15
  • International Potato Center Receives Grand Challenges Explorations Grant for Groundbreaking Research in Global Health and Development, International Potato Center (CIP) Press Release, 23.11.15
  • Sweet potato's 8,000 years of natural selection, GM Freeze Press Notice, 23.10.15

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