by Jeff Gillman
A short segment of DNA that codes for a particular protein—and hence a trait, like resistance to a disease—can be introduced from one living thing into another by one of a few different processes. None is necessarily better than another, it’s just a matter of which works best with the particular animal or plant that you’re handling. Perhaps the easiest system for introducing DNA into a plant is the gene gun, which is loaded with very small metal particles instead of bullets. These particles adhere to DNA, so when they are mixed in a test tube with the DNA that you want to add to a plant, what you end up with is a bunch of little bullets with DNA glued to them. These DNA-spiked particles are then shot into a plant using compressed air (it’s like a BB gun, but with many very small BBs shot at once) and—voila!—you’re done. You’ve introduced a trait into the plant. The part of the plant that was shot with DNA will then be reproduced using small cuttings, and the resulting plants will be tested to make sure they have the desired DNA.
Another popular method of introducing new DNA into a plant is by putting the DNA into a specific type of bacterium that has the ability to transfer it to another plant. Humans weren’t the first organisms to come up with the idea of moving genes from one living thing to another—these bacteria, called Agrobacterium, have been doing it for millions of years, naturally inserting DNA into plants where it wasn’t found before. In fact, they can even insert their DNA into human cells in certain situations.
Causing plants to produce compounds that they would not normally produce has been a goal of agricultural scientists for as long as there has been agriculture. Genetic engineering is just the newest way to meet an ancient goal. For centuries we have been grafting one plant onto another so that the grafted plant would contain compounds that it would not ordinarily contain. Usually this provides a benefit to the grafted plant (and hence the people who use it), such as insect resistance, but it could also make a perfectly palatable plant extremely dangerous. For example, if you graft a tomato plant onto the roots of jimson weed, the tomatoes will become toxic from poisons manufactured in these roots. Such a graft might actually prove fatal to people who eat the tomatoes. Today, most of our fruit trees are grafted onto roots that imbue the grafted plants with certain traits, such as dwarfing (to increase production and make them easier to harvest) or resistance to certain insects. If you have ever eaten an apple, a peach, or a pear, then it is more than likely you have eaten a fruit from a grafted plant.
By using gene guns, Agrobacterium, and other methods, humans have been able to change animals and plants so that they can do things they had never done before. Many different traits have been transferred to transgenic plants, but the most common are herbicide resistance and resistance to insects, particularly caterpillars. Caterpillar resistance comes from a gene that causes the plant to produce a particular protein called Bt (for Bacillus thuringiensis, the bacteria from which the gene was originally taken). This protein works in the caterpillar’s stomach, basically causing the stomach to split open and the caterpillar to digest itself. This protein is also available as an over-the-counter pesticide commonly called Bt. In the case of herbicide resistance, inserting a particular strand of DNA into plants causes them to be resistant to a particular type of herbicide, most commonly glyphosate, which is the chemical used in Roundup.
It is obvious from the percentage of genetically modified crops grown in this country just how successful genetic engineering has been in the marketplace. Currently, 85 percent of the corn planted in the United States is genetically modified, along with 91 percent of the soybeans, and 88 percent of the cotton.
Americans consume more genetically engineered goods than they probably realize: at least 60 percent of all foods in the United States likely contain some GE material. And in most cases foods containing genetically modified products do not have to be labeled as such. While no GE animals were approved for human consumption (as of 2010, though genetically modified salmon was on its way), dairy products may contain milk produced with GE-BST, the growth hormone for cattle, which comes from genetically engineered bacteria.
There is a great deal of controversy over whether it is moral, ethical, and even safe to transfer genes from one organism to another, and there is no doubt that a lot of money is at stake. Transferring a gene to cotton to make it resistant to a particularly damaging insect transforms that cotton into something very valuable. Likewise, making a crop resistant to a particularly effective herbicide is also extremely valuable. But there are a whole string of concerns that people have about these technologies. First, and perhaps most importantly, is the ethical question of whether it is right to mess with what nature (or God) has created. Second, there is the question of whether altered plants will breed with their unaltered relatives, and whether these new plants become weeds, unresponsive to some of our most effective herbicides because of their new DNA. Third, there is the issue of whether these plants are safe to eat. And finally, there is the concern about whether these plants could negatively affect our environment. Our government needs to take all of these issues into account as it decides what to do, if anything, about the new transgenic organisms we are creating.
Despite extravagant claims, genetically engineered plants tend to have yields similar to their non-GE counterparts.
What’s Good About Genetic Engineering
Despite extravagant claims, genetically engineered plants tend to have yields similar to their non-GE counterparts. Often, a company selling GE plants will claim that farmers can increase yield by using transgenic plants. Usually, what they really mean is that using GE plants will reduce their losses to the insect pest that the crop has been engineered to resist, or to the weeds that can be controlled by using a more effective herbicide that the crop is now resistant to. It’s a subtle but very real difference that is often more pronounced in developing countries. In these poorer countries, farmers make fewer pesticide applications, while here in the United States farmers generally have the freedom to apply whatever is needed whenever it is needed. Hence, in poorer countries GE crops will often show greater yields because of a reduction in losses, but in the United States, yield numbers are usually similar to non-GE crops because of our ability, through pesticides as well as other, more natural, means, to control pests in non-GE crops very effectively. A more established benefit of transgenic plants is a reduction in pesticide use. The use of transgenic cotton has resulted in a substantial decrease in the use of pesticides for this crop in the United States as well as in China, Australia, and other countries. Chinese farmers reduced their pesticide inputs by almost 80 percent when they used rice varieties genetically modified to resist insects. On the other hand, some people argue that there is actually a net increase in pesticide use, at least in crops modified to be herbicide resistant, because the herbicide that these crops are resistant to, Roundup, is used more frequently. But there is a consequent reduction in the use of other herbicides (like atrazine) that are usually considered more environmentally damaging than Roundup. Indeed, this reduction in pesticide use can have a profound impact on preserving our natural ecosystems in certain sensitive locations near farmland. If a crop suffers an outbreak of pests, in many cases the only choice for a farmer is to spray pesticides. Pesticides often drift, or can be used incorrectly, causing damage to lake or stream ecosystems, or even to forests or rainforests. A genetically altered plant seems like a good choice because it will often preclude, or at least drastically reduce, the need for environment-damaging pesticides.
A more established benefit of transgenic plants is a reduction in pesticide use.
Today’s biotechnology allows us to do things that were impossible just a few years ago. On the surface this may seem entirely positive, but what if there are complications that we never thought of? Opponents of biotechnology claim that new chemicals could be introduced into food that would cause it to become poisonous, but that just hasn’t happened, and it seems unlikely (unless it is done purposely by some malicious person or government, which is not ou
t of the question). True, soybeans have been transformed using Brazil nut plants, which caused the GE soybeans to contain an allergen, but the problem was discovered before the plants were released and no human was ever affected. As of the writing of this book, we don’t know of a single case where a transgenic food was proven to have made someone physically sick because it was transgenic. In contrast, traditional breeding and selection processes have been know to cause injury. For example, people who were handling a new variety of insect-resistant celery developed a reaction when they were exposed to sunlight because of the increased levels of chemicals called psoralens that the plants contained. And lima beans are a crop in which new varieties need to be screened very carefully because of their tendency to have high levels of cyanide.
We don’t know of a single case where a transgenic food was proven to have made someone physically sick because it was transgenic.
Despite the lack of evidence that humans are harmed by genetically modified plants, a few studies have shown that other animals may be affected by certain transgenic foods. For example, in one isolated experiment, certain genetically modified potatoes were been shown to be potentially damaging to the digestive system of rats. Other studies have shown that the addition of a bean protein into peas caused mice to exhibit an immune response that could, potentially, be dangerous in humans. More studies on mice have shown that, when fed diets of transgenic foods (corn and soybeans) over many generations, or when older mice were fed transgenic foods, they developed abnormalities in some of their organs. These studies do not provide conclusive evidence that transgenic plants can affect our health, however, and the preponderance of studies show that transgenic plants are safe. But these experiments do support the fear that someday a food that is not safe will sneak by or—just as bad—that some of the transgenic foods that we currently eat will have a negative effect on us that will not be evident for years to come.
There are additional reasons to be concerned about the use of transgenics. One of the greatest fears of farmers and the companies that produce transgenic plants is that their genetically engineered crops will escape cultivation and create races of superweeds. After all, most transgenic plants were created to have resistance to one problem or another, so the idea that these crops could breed with wild crops and make superweeds isn’t really that far-fetched. In fact, there is a case of a transgenic crop breeding with a wild relative: transgenic corn grown in Mexico has passed its DNA on to native corn, including the Roundup Ready gene. This is potentially the worst gene that could escape because it allows the plant to resist the most powerful herbicide in our pesticide arsenal, glyphosate, which kills almost anything green.
Though this introgression of the gene for Roundup resistance into wild corn is a bit scary, what is even scarier is that it is not the only case of this type of introgression. Glyphosate-resistant creeping bent grass, a grass used for lawns, was identified in Oregon in 2006, and the gene for glyphosate resistance was found in field mustard in 2007, apparently transferred from transgenic canola. These are just a few cases of the many where genes have escaped into wild populations, and there are likely more to come.
The genes that we release do not always stay where we place them. None of these crosses, however, have yet produced weeds that impede crop production. Furthermore, though these hybrid plants are resistant to Roundup, they are not resistant to the many other available herbicides, so they are still easily controlled. Besides, it’s not as though plants can’t be naturally resistant to glyphosate. The Asiatic dayflower, once an ornamental, is now a glyphosate-resistant weed that threatens Roundup Ready corn and soybeans because it can survive exposure to this herbicide. This resistance didn’t develop in a vacuum, however, and it can easily be argued that the presence of the Roundup Ready gene in crops accelerated the process.
In addition to the ability of genes to escape boundaries by breeding with related plants, there is also the issue of the genes that we move from one organism to another becoming ineffective. A weed can develop resistance to an herbicide because it acquired this resistance from a genetically engineered relative, but there is also another way: natural selection. If a particular pesticide is used too frequently, then pests will develop resistance to it. For example, cotton bollworm, a pest of cotton, has developed resistance to the Bt gene because of that gene’s pervasive use in transgenic cotton. Similarly, the increased use of Roundup to support Roundup resistant crops means that weeds have been under a lot of pressure to adapt. In a nutshell, that’s what natural selection does: select for the organisms that can survive certain hardships. In this instance the hardship is Roundup, and natural selection favors the weeds that can cope with the herbicide. Hence, with increased Roundup applications weeds develop resistance to this product faster than they might have otherwise. Fortunately, we already have crops that have been genetically engineered to be resistant to another herbicide, glufosinate ammonium, which can be used very similarly. And when weeds start to develop resistance to that …
What happens if nonpest insects are damaged by these transgenic plants? Will our natural ecology be turned on its head? It’s already known that pollen from transgenic plants can poison the monarch and many of our most beautiful butterflies. If pollen from transgenic corn plants falls on the milkweed that these butterflies eat while they are larvae, it can kill them. Despite this example, we have yet to see any widespread calamity from transgenic pollen.
Many people understandably feel as though we’re just waiting for the biotechnology industry to make a wrong decision in creating a transgenic plant or animal. If this occurs, we could suddenly see problems that we cannot now imagine. Could it occur with an animal rather than a plant? It’s possible. Currently there are experimental catfish that have a gene inserted into their DNA that causes them to grow rapidly. If these catfish escaped into the wild, would they have a radical effect on the environment? Some research shows that they wouldn’t survive, but the truth is, until it happens, we won’t really know.
And then there is the fact that pests tend to be able to get around some of our best laid plans. In many ways, all we’re doing when we control pests with pesticides, biotechnology, or any other method is trying to hold our own. Aristotle wrote that nature abhors a vacuum, and that is very true in the case of insects and the resources available to them. When we stop one pest, another rushes in to fill the void. When we inserted the Bt gene into cotton to control caterpillar pests like the cotton bollworm, we opened the door for other insects. Stink bugs are immune to the effects of Bt, so they found the cotton bolls, now relatively free of their competitor, the cotton bollworm, a good place to feed. In other crops the same thing is happening: the damage formerly caused by the larvae of butterflies and moths is being traded for damage caused by stink bugs and flea beetles. Furthermore, the reductions in pesticide applications realized by the use of transgenic plants are very crop specific. This means that with some crops, major reductions in pesticide use are possible, but with other crops the reductions are minor, or there may even be an increase in pesticide use. Transgenic plants may have changed the battle lines, but they have not won the war.
Government Policy
Currently, federal policy treats products created with biotechnology the same as products created with conventional processes. Put another way, products are regulated based on the features of the product (such as disease resistance or color), not the method by which they were produced. Genetically engineered products must meet the same safety and health standards as their traditional counterparts. No more, and no less. This policy was articulated by the White House Office of Science and Technology Policy in 1986, and Congress has never modified it.
Following this policy, the Food and Drug Administration determined in 1992 that no special label would be required for GE foods, since the foods were substantially equivalent to their traditional counterparts. In 2001, the FDA invited public comments on whether to issue new rules on GE labeling but has not, as of 2010, changed its
original stance. The FDA has, however, required intensive review of GE foods if the genetic modification causes the food to have a different composition, nutrients, or toxicity than conventional products. Review is also required if the plant that is the source of one of more of the genes produces allergic reactions; if the modified plants are used to make substances like pharmaceuticals or polymers in addition to food; or if the gene transfer has produced unexpected genetic effects. Simply put, this means that the FDA requires a lot of testing of genetically engineered plants before they can be planted on farms.
In cases where a product (such as an oil) obtained from the genetically engineered organism is sufficiently different from its conventional counterpart, the FDA requires that the modified product be given a different name, but it does not require an identification of its GE production method. For example, the FDA required the renaming of a soybean oil whose fatty acid composition had been altered by genetic engineering. The new name is “high oleic acid,” which, while it may be descriptive of the oil’s chemistry, does little to tell consumers about the source of this oil.
