Viewpoint

Potatoes, frogs and Nandor Tanczos

Gareth Wilson

The advance of science and technology has made some strange changes in familiar institutions. Take Green party candidate and Wild Greens spokesperson Nandor Tanczos for example. He would be utterly familiar 30 years ago. A "green" activist with an unconventional appearance, defending an act of sabotage against something he says is damaging the environment. What would puzzle our hypothetical observer from 1969, however, is the target of the sabotage. Not a logging truck or a pollution-belching factory, but a plot of potatoes.

When questioned about this, Nandor would explain the potatoes are genetically engineered, carrying a gene from the African clawed frog. Our time-traveler would be disgusted at this revelation and wonder what possible reason could there for such a bizarre product. It seems that many present-day New Zealanders share his views.

The Green party has gone from semi-obscurity to national prominence as a result of their opposition to genetically modified food, of which the "frog potato" is just one of the most lurid examples. Even though they remain somewhat vague about what health or environmental effects such products would actually have, they have successfully exploited the instinctive "ick" reaction to the extent that even the Labour party has called for a moratorium on field trials of genetically engineered plants.

Sadly, there has been very little coverage in the media of the actual purpose of the genetic modification, or the rather subtle reality behind the words "frog gene".

The frog in question is the African clawed frog. The story of its "union" with the humble spud starts in the United States, where Michael Zasloff, a geneticist at the National Institute of Health, was working with frog ovaries. The ovaries were surgically removed and the frogs were returned to their tanks with sewn-up incisions. Despite the rather unsanitary condition of the murky tank water, the incisions always healed quickly and never became infected. Zasloff was intrigued by the frogs' resistance to disease, and eventually isolated two compounds with antimicrobial properties from the skin of the frogs. He named them "magainins", after the Hebrew word for "shield". A modified magainin may become available soon for use on skin ulcers and to accelerate the healing of wounds.

The potato enters this story through the disease "soft rot". When potatoes are damaged in harvesting or by insects, the bacterium Erwinia can infect them, leading to rotten, inedible tubers. There have been several attempts to breed a soft rot resistant potato, with little success. Some strains are resistant to the bacterium but none are immune. Behind the recent controversy is an attempt by the Crop and Food Research Institute to use genetic engineering to produce a soft rot-immune strain of potato. The gene which produces a magainin in the frog is inserted into the potato plant, which will hopefully produce the magainin, kill the bacterium and prevent the disease.

Now we know the reason behind the insertion of the "frog gene" it's worth looking into why it seems so disturbing. There are three potential concerns one might have about the project.

The first is whether something dangerous from the frog might contaminate the potato. This is the easiest concern to dispel, because nothing from the frog itself is ever put into the potato plant. The sequence of amino acids in the magainin is studied, and the gene that will produce that sequence is built up from totally synthetic components.

The second concern is that the genetic engineering might alter the potato in some way to make it dangerous to eat. This cannot be ruled out at this stage, since no safety testing has been carried out on the potato. But the magainin gene is one of the simpler types of genetic engineering. The magainin is a peptide, which means that the potato plant will directly synthesise it from the inserted gene without any other alteration of the plant's metabolism. The magainin is not toxic itself (indeed it has suggested as an anti-plaque additive in toothpaste) and it is difficult to see how the new gene could pose any danger. In any case the potato will have to undergo rigorous safety trials before being sold to the public.

The third concern is a more nebulous one. Many people believe there is something intrinsically wrong about inserting foreign DNA into an organism, regardless of whether it causes any health or environmental problems. In this particular case it's possible to debate just how "foreign" the magainin gene really is. Although it's based on the original frog gene, it has been heavily modified to help it operate in the potato plant. The gene as inserted in the plant contains promoter and terminator regions (the genome's start and stop codes) which are specific to plants and not found in the frog gene. Even the sequence of bases in the entire gene is altered. The code which translates bases in a strand of DNA into amino acids in a peptide contains some redundancy; some amino acids are coded for by more than one sequence of bases. The protein synthesis mechanisms in cells tend to prefer some of the alternative sequences to others, synthesising peptide chains more efficiently if the genetic message is worded in one particular way.

Frog cells and potato cells have different preferences, and the magainin gene is designed to be expressed most efficiently by the potato. The new gene is also designed to add a short "signal portion" to the original 23 amino acids of the magainin. This small peptide chain signals the potato to transport the entire peptide to the extracelluar space, and then is cleaved off by potato enzymes, leaving just the original magainin.

To many opponents of genetic engineering, this means little. They remain opposed in principal to all types of manipulation of the genome, whether the new genes come from well-known animals, obscure bacteria, or are totally synthetic. This argument would be more impressive if it was actually spelt out to the consumers and voters that are the targets of their campaigns. Anti-GM food campaigners know that the average shopper will hardly be convinced by a kind of moral argument about the sanctity of the genome. They'll be concerned mostly about health and environmental effects, and the campaign literature tends to reflect this. The only group to explicitly spell out a "moral" or "spiritual" objection to genetic engineering is the Natural Law party.

The March 1999 attack by the Wild Greens was carried out on a field trial of the new potato strain. Laboratory tests had already confirmed that the new strain produced magainins that killed bacteria, but the field trial was needed to test the strain's response to real-world conditions. The destruction of the 1999 crop has delayed the project by at least one year, also delaying the PhD programmes of three students working for the Institute. The Crop and Food Institute has been forced to tighten security at a significant cost. Despite this no prosecution is possible because the actual saboteurs are unknown. Nandor Tanczos has only defended the attack, not personally claimed responsibility.

Without further attacks the trials may be complete within six years, at which point a commercial potato cultivar containing the gene may be developed. It's also possible that the technology could be applied to other crops. If this is successful there will finally be a solution to the ancient scourge of Erwinia, and it'll be a great pity if we're still too scared to use it.

Gareth Wilson graduated from Canterbury University with a Master's Degree in Chemistry in 1997 and is studying at Christchurch Polytechnic for a diploma in Laboratory Technology.