Gene Silencing: New Products and New Risks

June 4, 2013
Margaret Mellon
Former contributor

The J.R. Simplot Co. just filed a petition asking the U.S. Department of Agriculture (USDA) to grant non-regulated status to potatoes genetically engineered (GE) to reduce bruising and suppress levels of acrylamide, a neurotoxin occurring naturally in cooked potatoes.

Idaho Potato. Courtesy of Michelle@TNS via Flickr

The Idaho potato which Simplot proposes to improve through gene silencing. Courtesy of [email protected] via Flickr

The Simplot potatoes were produced through a new kind of GE—gene silencing. Simplot’s version of gene silencing, called Innate™ technology, adds genetic fragments derived from cultivated and wild potatoes, but no genetic material from unrelated organisms.

The industry is hoping that the potatoes will get a favorable reception in the marketplace because the potatoes’ benefits—reduced levels of acrylamide and reduced bruising—appeal to consumers as well as potato producers. They also hope that consumers might be less wary of a GE technique that does not cross species lines, but employs only potato genes.

In addition to reducing bruising, the Simplot potatoes also help manage so-called reducing sugars, a substantial benefit to potato growers who can have a much as 20 percent of their crop rejected by food buyers for exceeding acceptable levels of such sugars. Although the potatoes are not initially intended for retail sale, reduced discoloration of after slicing potatoes could be a benefit to consumers.

Reducing acrylamide levels in French fries

Consumers might also benefit from reduced acrylamide concentrations. Acrylamide is a neurotoxin produced by cooking foods discovered by Swedish scientists in 2002. Although acrylamide turns out to present in a variety of heated foods like coffee and baked goods, according to Simplot’s petition for deregulation, French fries and potato chips are the highest per serving sources, accounting for 35 percent of the acrylamide in the U.S. diet.

Scientist have still not fully characterized the ill effects of acrylamide in foods. Some studies find associations with cancer; others do not. But acrylamide is a nasty chemical, and reducing its levels in the diet seems like a good idea.

Many consumers, however, are not aware that French fries or other cooked foods contain acrylamide. So I’m not sure how consumers would become aware that Simplot potatoes provide this benefit. I can’t imagine McDonald’s touting a switch to French fries with reduced levels of a neurotoxin that many consumers had never before associated with their product.

My guess is that many health advocates would prefer consuming fewer French fries to GE as a way of reducing exposure to acrylamide. In fact, nutritionists may worry about a technology that appears to justify eating French fries.

Gene silencing—genetically engineered but not necessarily transgenic

Gene silencing is a relatively new form of GE that turns off particular genes typically by interfering with the protein synthetic machinery of cells. Turning off genes can accomplish many tasks, among them, disabling invading viruses, delaying fruit ripening or altering flower colors.

Gene Silencing. Image courtesy of  Dr. Alper Uzun from

Gene Silencing. Image courtesy of Dr. Alper Uzun from

As noted above, some versions of gene silencing can accomplish desired effects without adding genetic material from unrelated organisms.

But like other forms of genetic engineering, it involves elaborate snipping and rearranging of genetic material to construct cassettes of DNA before being introduced into cells.

Organisms produced by gene silencing are GE, but not necessarily transgenic. Simplot’s Innate™ potato, which is engineered with gene fragments from wild and cultivated potatoes, is an example.

Consumer acceptance?

Will the fact that the genetic material used in the Simplot potato came only from potatoes make a difference in its reception in the marketplace?

Not an easy question. For those who object to crossing species lines from an ethical or philosophical point of view, the all-potato construction might make a big difference.

For those who view transgenesis not as an ethical issue, but as a surrogate for risk, it might not, depending on the other risks of the potato.

Many scientists are concerned about GE that crosses species lines because the resulting trait combinations are generally not possible in nature and so their potential downsides are difficult to predict. From this standpoint, gene silencing using all-potato gene cassettes will probably raise fewer flags than GE that crosses species boundaries.

On the other hand, gene silencing technology is the product of scientific research that shows the cellular regulation of genes to be an immensely complex process. Science has moved far beyond the days of the so-called central dogma in which stretches of DNA (genes) coded for pieces of RNA (messenger RNA) that travelled into the cytoplasm to direct the production of proteins—essentially a one-way flow of information.

The cast of players in protein production now is much, much larger and includes a new alphabet soup of RNA molecules with a plethora of interactions and roles. One of the new players is microRNA (miRNA) that can reduce the amount of protein in a cell by hooking up with special enzymes and destroying the messenger RNA responsible for that protein. But there are many others.

New risks of GE foods

So while some risk-based concern is allayed by confining gene combinations within a species, residual concern based on the complexity and incompletely understood nature of gene silencing and related processes remains. In addition, it appears that gene silencing may pose a previously unrecognized risk of genetic engineering: the risk of turning off non-target genes.

This potential harm, which has been described in a recent paper by Jack Heinemann of the University of Canterbury and colleagues (Environment International 55: 43-55; requires login), depends on one of the many newly recognized kinds of RNA participating in in protein synthesis—double stranded RNA (dsRNA).

DsRNA is an important new topic in food biotechnology and we will discuss it in a later post. But suffice it to say that it represents a potential harm of gene silencing and other forms of GE that merits examination.

So it is too early to say whether the Simplot potato will get a more favorable reception than earlier GE foods based on the all-potato origin of its new genetic material and consumer benefits. But it certainly will become an important test  for how well the FDA handles the potential new risk of  genetic engineering—dsRNAs.