The botany of desire: a plant's-eye view of the world (24 page)

The gene gun is a strangely high-low piece of technology, but the main thing you need to know about it is that the gun here is not a metaphor: a .22 shell is used to fire stainless-steel projectiles dipped in a DNA solution at a stem or leaf of the target plant. If all goes well, some of the DNA will pierce the wall of some of the cells’ nuclei and elbow its way into the double helix: a bully breaking into a line dance. If the new DNA happens to land in the right place—and no one yet knows what, or where, that place is—the plant grown from that cell will express the new gene.
That’s it?
That’s it.

Apart from its slightly more debonair means of entry, the agrobacterium works in much the same way. In the clean rooms, where the air pressure is kept artificially high to prevent errant microbes from wandering in, technicians sit at lab benches before petri dishes in which fingernail-sized sections of potato stem have been placed in a clear nutrient jelly. Into this medium they squirt a solution of agrobacteria, which have already had their genes swapped with the ones Monsanto wants to insert (specific enzymes can be used to cut and paste precise sequences of DNA). In addition to the Bt gene being spliced, a “marker” gene is also included—typically this is a gene conferring resistance to a specific antibiotic. This way, the technicians can later flood the dish with the antibiotic to see which cells have taken up the new DNA; any that haven’t simply die. The marker gene can also serve as a kind of DNA fingerprint, allowing Monsanto to identify its plants and their descendants long after they’ve left the lab. By performing a simple test on any potato leaf in my garden, a Monsanto agent can prove whether or not the plant is the company’s intellectual property. I realized that, whatever else it is, genetic engineering is also a powerful technique for transforming plants into private property, by giving every one of them what amounts to its own Universal Product Code.

After several hours the surviving slips of potato stem begin to put down roots; a few days later, these plantlets are moved upstairs to the potato greenhouse on the roof. Here I met Glenda Debrecht, a cheerful staff horticulturist, who invited me to don latex gloves and help her transplant pinkie-sized plantlets from their petri dishes to small pots filled with customized soil. After the abstractions of the laboratory, I felt back on quasi-familiar ground, in a greenhouse handling actual plants.

The whole operation, from petri dish to transplant to greenhouse, is performed thousands of times, Glenda explained as we worked across a wheeled potting bench from each other, largely because there is so much uncertainty about the outcome, even after the DNA is accepted. If the new DNA winds up in the wrong place in the genome, for example, the new gene won’t be expressed, or it will be expressed only poorly. In nature—that is, in sexual reproduction—genes move not one by one but in the company of associated genes that regulate their expression, turning them on and off. The transfer of genetic material is also much more orderly in sex, the process somehow ensuring that every gene ends up in its proper neighborhood and doesn’t trip over other genes in the process, inadvertently affecting their function. “Genetic instability” is the catchall term used to describe the various unexpected effects that misplaced or unregulated foreign genes can have on their new environment. These can range from the subtle and invisible (a particular protein is over- or underexpressed in the new plant, say) to the manifestly outlandish: Glenda sees a great many freaky potato plants.

Starck told me that the gene transfer “takes” anywhere between 10 percent and 90 percent of the time—an eyebrow-raising statistic. For some unknown reason (genetic instability?), the process produces a great deal of variability, even though it begins with a single, known, cloned strain of potato. “So we grow out thousands of different plants,” Glenda explained, “and then look for the best.” The result is often a potato that is superior in ways the presence of the new gene can’t explain. This would certainly explain the vigor of my NewLeafs.

I was struck by the uncertainty surrounding the process, how this technology is at the same time both astoundingly sophisticated yet still a shot in the genetic dark. Throw a bunch of DNA against the wall and see what sticks; do this enough times, and you’re bound to get what you’re looking for. Transplanting potatoes with Glenda also made me realize that it may be impossible ever to conclude once and for all that this technology is
intrinsically
sound or dangerous. For every new genetically engineered plant is a unique event in nature, bringing its own set of genetic contingencies. This means that the reliability or safety of one genetically modified plant doesn’t necessarily guarantee the reliability or safety of the next.

“There’s still a lot we don’t understand about gene expression,” Starck acknowledged. A great many factors, including the environment, influence whether, and to what extent, an introduced gene will do what it’s supposed to do. In one early experiment, scientists succeeded in splicing a gene for redness into petunias. In the field everything went according to plan, until the temperature hit 90 degrees and an entire planting of red petunias suddenly and inexplicably turned white. Wouldn’t this sort of thing—these Dionysian jokers rearing up in the ordered Apollonian fields—rattle one’s faith in genetic determinism a
little
? It’s obviously not quite as simple as putting a software program into a computer.

• • •

July 1.
When I got home from St. Louis, my potato crop was thriving. It was time to hill up the plants, so, with a hoe, I pulled the rich soil from the lips of the trenches down around the stems to protect the developing tubers from the light. I also dressed the plants with a few shovelfuls of old cow manure: potatoes seem to love the stuff. The best, sweetest potatoes I ever tasted were ones that, as a teenager, I helped a neighbor dig out of the pile of pure horse manure he’d planted them in. I sometimes think it must have been this dazzling example of alchemy that sold me—not just on potato growing but on gardening as a quasi-magical, quasi-sacramental thing to do.

My NewLeafs were big as shrubs now, and crowned with slender flower stalks. Potato flowers are actually quite pretty, at least by the standards of a vegetable: five-petaled lavender stars with yellow centers that give off a faint roselike perfume. One sultry afternoon I watched the bumblebees making their rounds of my potato blossoms, thoughtlessly chalking themselves with yellow pollen grains before lumbering off to appointments with other blossoms, other species.

Uncertainty
is the theme that unifies most of the questions now being raised about agricultural biotechnology by environmentalists and scientists. By planting millions of acres of genetically altered plants, we’re introducing something novel into the environment and the food chain, the consequences of which are not completely understood. Several of these uncertainties have to do with the fate of the grains of pollen these bumblebees are carting off from my potatoes.

For one thing, that pollen, like every other part of the plant, contains Bt toxin. The toxin, which is produced by a bacterium that occurs naturally in the soil, is generally thought to be safe for humans, yet the Bt in genetically modified crops is behaving a little differently from the ordinary Bt that farmers have been spraying on their crops for years. Instead of quickly breaking down in nature, as it usually does, genetically modified Bt toxin seems to be building up in the soil. This may be insignificant; we don’t know. (We don’t really know what Bt is doing in soil in the first place.) We also don’t know what effect all this new Bt in the environment may have on the insects we
don’t
want to kill, though there are reasons to be concerned. In laboratory experiments scientists have found that the pollen from Bt corn is lethal to monarch butterflies. Monarchs don’t eat corn pollen, but they do eat, exclusively, the leaves of milkweed (
Asclepias syriaca
), a weed that is common in American cornfields. When monarch caterpillars eat milkweed leaves dusted with Bt corn pollen, they sicken and die. Will this happen in the field? And how serious will the problem be if it does? We don’t know.

What is remarkable is that someone thought to ask the question in the first place. As we learned during the glory days of the chemical paradigm, the ecological effects of changes to the environment often show up where we least expect to find them. DDT in its time was thoroughly tested and found to be safe and effective—until it was discovered that this unusually long-lived chemical travels through the food chain and happens to thin out the shells of birds’ eggs. The question that led scientists to this discovery wasn’t even a question about DDT, it was a question about birds: Why is the world’s population of raptors suddenly collapsing? DDT was the answer. Hoping not to encounter that sort of surprise again, scientists are busy trying to imagine the sorts of questions to which Bt or Roundup Ready crops might someday prove to be the unexpected answer.

One of those questions has to do with “gene flow”: What might happen to the Bt genes in the pollen my bumblebees are moving from blossom to blossom around my garden? Through cross-pollination those genes can wind up in other plants, possibly conferring a new evolutionary advantage on that species. Most domesticated plants do poorly in the wild; the traits we breed them for—fruit that ripens all at once, say—often render them less fit for life in the wild. But biotech plants have been given traits, such as insect or pesticide resistance, that render them
more
fit in nature.

Gene flow ordinarily occurs only between closely related species, and since the potato evolved in South America, the chances are slim that my Bt genes will escape into the wilds of Connecticut to spawn some kind of superweed. That’s Monsanto’s contention, and there’s no reason to doubt it. But it is interesting to note that while genetic engineering depends for its power on the ability to break down the genetic walls between species and even phyla in order to freely move genes among them, the environmental safety of the technology depends on precisely the opposite phenomenon: on the integrity of species in nature and their tendency to reject alien genetic material.

Yet what will happen if Peruvian farmers plant Bt potatoes? Or if I plant a biotech crop that does have local relatives? Scientists have already proved that the Roundup Ready gene can migrate in a single generation from a field of rapeseed oil plants to a related weed in the mustard family, which then exhibits tolerance to the herbicide; the same has happened with genetically modified beets. This came as no great surprise; what did is the discovery, in one experiment, that transgenes migrate more readily than ordinary ones; no one knows why, but these well-traveled genes may prove to be especially jumpy.

Jumping genes and superweeds point to a new kind of environmental problem: “biological pollution,” which some environmentalists believe will be the unhappy legacy of agriculture’s shift from a chemical to a biological paradigm. (We’re already familiar with one form of biological pollution: invasive exotic species such as kudzu, zebra mussels, and Dutch elm disease.) Harmful as chemical pollution can be, it eventually disperses and fades, but biological pollution is self-replicating. Think of it as the difference between an oil spill and a disease. Once a transgene introduces a new weed or a resistant pest into the environment, it can’t very well be cleaned up: it will already have become part of nature.

In the case of the NewLeaf potato, the most likely form of biological pollution is the evolution of insects resistant to Bt, a development that would ruin one of the safest insecticides we have and do great harm to the organic farmers who depend on it.
*
The phenomenon of insect resistance offers an object lesson in the difficulties of controlling nature, as well as the problem with using a linear machine metaphor to deal with a process as complex and nonlinear as evolution. For this is a case where the more thorough our control of nature is, the sooner natural selection will overthrow it.

According to the theory, which is based on classical Darwinism, the new Bt crops add so much Bt toxin to the environment on such a continuous basis that the target pests will evolve resistance to it; the only real question is how long this will take to happen. Before now resistance hasn’t been a worry, because conventional Bt sprays break down quickly in sunlight and farmers spray only when confronted with a serious infestation. Resistance is essentially a form of coevolution that occurs when a given population is threatened with extinction. That pressure quickly selects for whatever chance mutation will allow the species to change and survive. Through natural selection, then, one species’ attempt at total control can engender its own nemesis.

I was surprised to learn that the specter of Bt resistance has forced Monsanto to temporarily lay aside its mechanistic habits of thought and approach the problem more like, well, a Darwinian. Working with government regulators, the company has developed a “Resistance Management Plan” to postpone Bt resistance. Farmers who plant Bt crops must leave a certain portion of their land planted in non-Bt crops in order to create “refuges” for the targeted bugs. The goal is to prevent the first Bt-resistant Colorado potato beetle from mating with a second resistant bug and thereby launching a new race of superbugs. The theory is that when that first Bt-resistant insect does show up, it can be induced to mate with a susceptible bug living on the refuge side of the tracks, thereby diluting the new gene for resistance. The plan implicitly acknowledges that if this new control of nature is to last, a certain amount of no-control, or wildness, will have to be deliberately cultivated. The thinking may be sound, but an awful lot has to go right for Mr. Wrong to meet Miss Right. No one can be sure how big the refuges have to be, where they should be located, and whether farmers will cooperate (creating safe havens for your most destructive pests is counterintuitive, after all)—not to mention the bugs.