You Say Potato, I Say Double-Stranded RNA

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You Say Potato, I Say Double-Stranded RNA
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You Say Potato, I Say Double-Stranded RNA
Amidst the outrage, puzzlement and theories caused by the finding of genetically-modified wheat in an Oregon field, USDA is considering whether to commercialize another dinnertime staple--the potato.

Last month, Idaho-based J.M. Simplot asked the Agriculture Department to grant a deregulated status for a new variety of potatoes genetically engineered to reduce bruising and develop lower levels of acrylamide, a neurotoxin and possible carcinogen, when cooked.

Unlike the transgenic crops thatt use genetic material from other organisms - like the genes from a bacterium that makes Bt corn, soybeans and cotton - Simplot's Innate (TM) potatoes only use genetic material from other varieties of potatoes. Instead of adding genetic material for desirable traits, certain undesirable traits are "silenced" by inhibiting RNA from carrying the genetic base pairs from the DNA to synthesize proteins.

Simplot has taken genetic fragments from wild and domestic potatoes and arranged them in a way that results in silencing of two genes, one that lead to browning and the other that makes the amino acid that oxidizes to create acrylamide.

Simplot speeds up a process that has been "painfully slow" through conventional breeding, wrote Walter Stevenson, a professor emeritus in plant pathology at the University of Wisconsin, Madison, in a letter to USDA in support of deregulating Innate potatoes.

The technology promises to bring both health and economics benefits. Bruising costs the potato industry about $298 million per year. As for acrylamide, there is not enough information to date to set a reliable threshold for how much is safe, but it's a good idea to keep levels low -- from both a safety and business standpoint.

Margaret Mellon of the Union of Concerned Scientists wrote about Simplot's potatoes in UCS's The Equation blog. Although she welcomes the possibility of safer potatoes with lower acrylamide levels, she warns of the unknowns of gene silencing, referring to a recent paper from the University of Cantebury that warns of the biosafety risks. The papers' authors, led by John Heinemann, warn that small interfering RNA (siRNA) used to silence genes could disrupt human cells. siRNA is a type of double stranded RNA (dsRNA).

The author stirred fears down under last year with well-publicized warnings around the development of genetically-modified wheat by the CSIRO, Australia's national science agency. The wheat is being tested for a variety of nutritional and resilience traits. This gene silencing wheat, said the authors, could turn off human genes and lead to ailments like glycogen storage disease, which causes liver malfunction. RNA engineered to maintain toxic traits could also enter the natural environment to harm plants and animals, Heinemann argued.

The paper was lambasted by the Food Standards Australia New Zealand, which assesses food safety risks:

"In formulating their hypothesis, the authors have not taken into account the fact that small dsRNAs are ubiquitous in the environment and in the diverse range of organisms we consume as food, including plants and animals. This establishes a long history of safe human consumption which pre-dates the use of such techniques in GM plants," the agency responded, adding that the study underestimated the strengths of the food safety regulatory system to detect possible unintended effects.

"There is no scientific basis for suggesting that small dsRNAs present in some GM foods have different properties or pose a greater risk than those already naturally abundant in conventional foods," the agency concluded.

To provide clarity to a thoroughly confused population, afraid of gene-altering bread in the sandwiches of the future, the New Zealand Science Media Centre called on scientists to provide some feedback to FSANZ's conclusion. Three scientists defended the agency, saying that Heinemann's suggestions to tighten scrutiny on gene silencing would create an unnecessary burden to regulators and unfounded anxiety in consumers.

The only voice to reject FSANZ's conclusion? Heinemann himself.

There is undoubtedly much more to learn about dsRNA, a field that only began in the early 1990s. But a panicked reaction to technology only promotes a volley of contradictory messages for people who want safe, healthy food.

At the same time, Simplot is marking its distance from trangenic crops by explicitly promoting the fact that the Innate (tm) genes come from good, old-fashioned potatoes. As USDA mulls its decision to deregulate the potatoes, it will be interesting to see if the company can successfully disassociate from one M -- Monsanto -- while pleasing the customers of another M -- McDonalds.

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