The strategy is called “antisense.” “It’s pretty straightforward,” says Hiatt, a microbiologist who speaks only half-jokingly of tomatoes as “higher organisms.” “You just make a reverse copy of the gene. Genes have a start and a stop switch, and the gene itself lies in between. So you take the DNA, cut the gene out from between the start and stop points, turn it around, reinsert it and then put the whole thing back together. Now you have the start signal at the gene’s tail and the stop signal by its head. It’s backwards.”
The reverse version of the gene is then put into the cells of tomato leaves in a laboratory dish. The beast of burden for this task is a common soil microbe that has the ability to insert DNA into plant chromosomes. Once the backwards version of the gene is in the leaf cells, it starts gumming up the works. Its signals cancel out the signals from the normal gene, making it all but impossible for the cell to make PG. Calgene scientists say they have reduced the amount of PG in a ripe tomato by 99 percent, more than enough to greatly slow down softening.
Why go to all this trouble?
First of all, because it’s not much trouble anymore. The leaves from those early experiments were allowed to regenerate into tomato plants, from which seed was extracted and planted again. Then more plants and more seeds, over and over. By 1990, when the company first filed submissions with the FDA, it had a large volume of Flavr Savr seed on hand, each seed armed with the antisense PG gene. No one need do any more laboratory gymnastics.
And second of all, because when you slow down the rotting process, you can leave tomatoes on the vine longer and can take more time delivering them, making refrigeration unnecessary. All of which enhances taste.
“We gain 7 to 10 days of firmness,” Benoit says. “That allows us to leave the tomatoes on the vine an extra three to four days, during which time they’ll pick up much more flavor. We wouldn’t leave them on any longer than that because it’s during those crucial three or four days when the balance of sugars and acids are absorbed. After that, there is no gain, and you risk damage from bugs and fungus.”
Farmers have always faced the problem of pestilence. Most of the time, it can be dealt with. But those who would grow and sell the products of recombinant DNA face a new kind of foe, whose true strength is as yet hard to gauge. That foe is a loose latticework of activist groups that have made it their top priority to stop bioengineered agriculture in its tracks.
One of these organizations, the Washington, D.C.-based Foundation on Economic Trends, has declared virtual war on the Calgene tomato, saying, in effect, a plague on all your hothouses. Founded by Jeremy Rifkin, author, scholar and unremitting enemy of most, if not all, things recombinant, the Foundation on Economic Trends has initiated a movement it calls the Pure Food Campaign: An International Boycott Against Genetically Engineered Foods.
Like other “green” movements, the foundation is concerned about the tomato primarily because it is the wedge for a huge array of gene-modified foods to follow. Some of the more than 30 foods waiting in the wings involve exotic combinations of genes from different species. DNA Plant Technology in New Jersey, for example, is attempting to put a copy of a frost-resistance gene from the Arctic flounder into a tomato so that it will be able to undergo refrigeration without harm. Trout genes have been placed into carp, firefly genes into tobacco, and chicken genes into potatoes, all with the blessing of the U.S. Department of Agriculture, which has cleared them for field testing. The government itself has experimented with putting human liver genes into pigs in an attempt to produce leaner pork.
Calgene itself has plans to extend its Flavr Savr technology to such items as melons, peaches, bananas and berries. This is in addition to work it is undertaking in genetically engineering potatoes, rapeseed oil and cotton.
Ron Cummins is the Pure Food Campaign’s point man in the fight against the Flavr Savr and its ilk. He is a voluble fellow who has spent a quarter of a century as a grass-roots organizer, including a number of years in Central America promoting peace and social justice. He joined Rifkin’s group about a year ago and has been at the forefront of the campaign ever since.
“Our basic position,” he says, “is that although genetic engineering appears to have some promise in terms of medical research and environmental cleanup, we are opposed to all genetically engineered food products. We haven’t seen any proposals for such products that offer us a reason to support them, and the Flavr Savr is a perfect example of what we’re talking about.”
Cummins’ arguments revolve around the theme of a technology-crazed society driven by the compulsion to add ever more layers of complexity to daily life, and doing so at its peril.
“The bottom line for a company like Calgene is that corporate tomatoes taste like hell,” says Cummins, who, like many in the movement, uses the word “corporate” to distinguish the bounty of agribusiness. “Any company that comes out with something that tastes good will have a definite competitive advantage.
“The solution to the taste problem is simple, as anyone who’s ever grown tomatoes in the back yard or eaten organic tomatoes knows. But Calgene says they’re not going to take the low-tech solution of organic farming. Their solution is a high-tech, genetically engineered tomato, which is a false solution to the problem.
“And,” he adds portentously, “it adds a new health risk.”
The alleged risk is one raised by a number of Flavr Savr critics. As the argument goes, the antisense PG gene itself may not be a menace to health. In fact, most authorities agree that it’s not. But inside each cell of a Flavr Savr tomato is a “marker” gene lashed tightly to the antisense gene. It is this marker that some think may be injurious to humans.
Why the marker is there in the first place illustrates the limits of genetic engineering, which in many ways is an appallingly crude technology. Scientists know that only a small percentage of target cells-say, on the order of 30 percent-will take up any new gene they are trying to insert. They also know it’s impossible to tell by looking at cells which fraction of them has acquired the new gene. So they insert a so-called marker gene alongside the real payload to help them sort things out.
The marker employed by Calgene is a commonly used one called the kanamycin resistance gene. Naturally occuring, it makes certain micro-organisms immune to the antibiotic kanamycin. To determine which tomato cells have taken up the marker gene and its mate, the antisense PG gene, all one does is add kanamycin to the test medium in which the cells are floating. Those cells that do not have the kanamycin resistance gene inside them will die, and those that have it will survive.
The trouble, Cummins contends, is that anyone who eats a Flavr Savr tomato may also become immune to kanamycin and to its sister antibiotic, neomycin. “This is potentially a serious problem, especially for infants and children, because they are often treated with these antibiotics,” Cummins says.
Kanamycin and neomycin are, in fact, not used as often as formerly, partly because the bacilli they once routinely wiped out have grown progressively resistant to them. Also, kanamycin is associated with hearing loss and kidney damage. It is, however, contained in certain topical creams used to treat eye infections and is frequently given prior to bowel surgery to prevent postoperative infection. It also is used to treat infants suffering from intestinal tract infections and patients in comas due to liver disease.
Cummins issues a further health alarum about Flavr Savrs in particular and about tomatoes in general. “There are tremendous problems out there right now, from an environmental and human health standpoint, with corporate tomatoes,” he says, citing a disturbing report issued last summer by the National Academy of Sciences that expressed “potential concern” that children may be ingesting unsafe amounts of pesticides in their food.
The report, based on a four-year study commissioned by Congress, noted that children are more sensitive to pesticide residues than adults. It urged parents to wash and peel fruits and vegetables before serving and called on government to revise its current “one size fits all” policy of using adult body weights alone to compute acceptable tolerance levels.
Tomatoes, Cummins asserts, are particularly dangerous because, he believes, they soak up pesticide like a sponge. “Because of the texture of the tomato and the amount of liquid it absorbs, it’s an unusually contaminated vegetable,” he says. “And there’s not a lot you can do about it. You can’t cut away the skin like you can with some other vegetables. Tomatoes rank right up there with corporate beef in terms of having to watch the amount you ingest.
“The Flavr Savr will be full of pesticide residues too. So now you’ll get pesticides along with novel genetic material,” Cummins says, making the new tomato sound more like a hand grenade than a foodstuff.
Thomas Churchwell takes these charges in stride. He is the president of Calgene Fresh and a veteran of skirmishes with foodies, having been vice president of sales for NutraSweet when that company was fighting for its life with opponents who challenged the safety of its sweetener.
“We know it’s not possible to confer resistance by oral intake of a resistance gene because that gene is metabolized by the stomach,” Churchwell said one recent afternoon. He was sitting in his smallish office overlooking the production line in Calgene Fresh’s packing plant on Chicago’s Far South Side.
Calgene Fresh was founded two years ago to give Calgene a vehicle for distributing and marketing its genetically engineered produce. For most of those two years, it has been practicing for the big time by supplying supermarkets with premium conventional tomatoes sold under the brand name MacGregor’s Tomatoes. When Flavr Savr hits the market, the conventional tomatoes will be phased out over a matter of months until Calgene Fresh is selling nothing but Flavr Savrs, but still under the MacGregor’s name, at a premium price of $2 to $3 a pound, compared to 50 cents to $1.50 for regular tomatoes.
As Churchwell spoke, an avalanche of tomatoes was rolling down a system of belts in an endless stream. They had originated in Mexico, Florida and California on farms that have contracts with Calgene to grow tomatoes to its specifications. Then they were shipped in Calgene’s specially cushioned “air ride” trailer trucks, which are driven night and day by two-man teams, and are satellite-controlled so that the company knows exactly where a truck is at any given time and can control interior temperature remotely. Now the tomatoes were being graded by hand and by computer, only one out of four qualifying for the MacGregor’s label. The rest would be sold for other uses, such as salsa.
“The ultimate answer on kanamycin,” Churchwell said, apologizing for his layman’s understanding of science, “is not going to come from me, but from the FDA.”
Calgene has been conspicuous about taking the high road with the FDA. The agency is still formulating its policy toward genetically engineered foods, much like a child learning to walk. Its first ruling, handed down in May 1992 in response to Calgene’s petition, was that DNA inserted in a product from another source did not constitute a food additive, and thus the product would not need extensive safety studies-unless it contained greatly elevated levels of toxins or allergens. Nor would it need to be labeled in stores as “genetically engineered.” The FDA could have ruled otherwise, that a genetically engineered tomato was a processed food and would require prolonged review and labeling. But it chose to find that a tomato with a gene inside that does not occur in nature was a tomato nonetheless. Thus, the use of genetic engineering was seen to be merely another step in traditional plant breeding.
