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Cardinal Conversations

Gene Labels: Biology expert Virginia Walbot on Prop 37 and modified food

Courtesy Virginia Walbot

By Kristin Sainani

In the run-up to the 2012 election, California's Prop 37, which would require labeling of foods produced using genetic engineering technology, has gained national attention. Stanford talked to biology professor Virginia Walbot, '67, who can often be found in her on-campus corn field where she researches genotypic and phenotypic diversity in plants. We asked her to explain genetic engineering as it pertains to our food supply.

What are genetically modified organisms?

Genetic engineering involves identifying a gene in one organism—for example, the insulin gene in a human—and then obtaining the physical DNA for that gene and modifying the instructions that turn the gene on and off so that it can be expressed in another organism. The reason it’s called genetic engineering is that you’re combining all of these pieces, kind of like a Lego set, to make a construct that will confer the properties that you think are desirable. And if you’ve done good engineering, you’ll find that that new gene is expressed in the pattern that you designed based on your knowledge.

One really important early example of genetic engineering that illustrates why scientists are so enthusiastic about this as a tool concerns insulin. Until genetic engineering, insulin to treat diabetic humans was attained either from human cadavers or from dead pigs. Diabetics [who were] allergic to pig insulin were required to use cadaver insulin. . . . We were really lucky that the human insulin gene was one of the first cloned; by the time the AIDS epidemic was spreading, we had a source of human insulin produced in bacteria. There were a lot of benefits of this: no human viruses; no pig viruses; it was a perfect, [non-allergenic] replica of the human insulin protein. So diabetics got a safer and more reliable product at a cheaper cost.

How are genetically modified organisms being used in our food supply?

A good example in food is one that most people don’t know about. Cow rennet enzymes for coagulating milk to make cheese used to be obtained from dead calves. These animals’ stomachs were removed and then they were scraped with a knife to get the rennet. You can imagine that there was a lot of variation in the rennet, because people scraped to different extents and different calves had different amounts of the rennet enzyme to begin with. So one of the first food-oriented applications of genetic engineering was to clone the rennet gene from cows and get it expressed in bacteria. So you could have a factory-produced rennet. This has made cheese production much more [consistent].

A lot of food processing is now done using genetically engineered bacteria or genetically engineered yeast. Yeast is important for bread, beer and wine making. And lactobacillus [is used] for making certain dairy products. Most people who are against genetically engineered food don’t even know that many, many, many of the microbes that are responsible for fermentation or other conversions of the food to make it suitable for human consumption, have been genetically engineered for the past 25 to 30 years. We’re very dependent on genetically modified organisms for our food supply.

[When they talk about genetically engineered food] most people are thinking about genetically modified corn or soybeans. So there we are looking at a larger organism. GMO corn and soybeans have been engineered to give farmers biological solutions to weed and pest control. I think this is an important aspect of GMOs. My bottom line is that we’re generally replacing chemistry with biology. Biology is intrinsically softer on the environment. That doesn’t mean it’s perfect or without flaws. But with better engineering we can make it more optimal than it is today, and certainly more optimal than wholesale spraying with chemicals.

Chemical insecticides are a nasty business; just think of DDT. So I’m very enthusiastic about the Bt-transgenic plants because this is a biological insecticide that’s replacing chemical insecticides. So a little bit of background: Bt is the nickname for a gene that comes from the organism bacillus thuringiensis. It is the most widely used organic-farmer solution to insect pests. At least a million tons of this bacterium have been sprayed on organically grown vegetables and fruits in the past 60 years.

What’s absolutely fascinating about this is that it is insect specific. Animals have an acidic stomach; insects have a really alkaline (basic) stomach. . . . The difference in [their pH is about] 100-million-fold. It turns out that the [Bt] protein will only dissolve in a gut if it’s alkaline. So the protein passes right through the gut of all other animals, untouched. But in an insect gut, the protein is cleaved. And one of those pieces aggregates and makes a hole in the lining of the stomach of the insect and . . . kills the insect larvae.

No permanent Bt-resistant insect populations have ever arisen. There’s such a huge biological difference between the insect gut and all other animals. Insects need that alkaline gut to digest all of their other food. So if they evolve a less alkaline gut, they starve to death. So it’s a self-limiting kind of thing. It’s a really interesting comparison to a typical chemical insecticide, which would have a useful lifespan of about 5 to 10 years before the insects evolved resistance to it. With Bt, we’re in year 60 without sustainable resistance in the wild or in the lab.

Genetic engineering of the Bt trait involved taking the gene that encodes the toxin protein, engineering it for expression in plants, and now the plant produces only one of the 5,000 proteins that the bacterium can produce. And that one protein is the insecticidal protein. You can wash [sprayed] Bt organism off your lettuce or potatoes, but it turns out that [on your plate,] the genetically engineered crop plants will have about one-tenth the Bt protein as [a plate of] organic produce, because people don’t wash thoroughly enough. So you’re actually getting more contamination from the organic farm with regard to this one protein.


corn and Walbot
Photo: L.A. Cicero/Stanford News Service
GROWING ENGINEERING: Walbot in the corn field.

Do you think that genetically modified foods should be labeled differently than other foods?

My personal opinion is to always favor people having more information. So that, to me, is principle number one. No matter how safe I think GMOs are, I do think people have the right to know. On the other hand, it’s very strange to me that what [Prop 37] does is ask about the food processing technology—not about the [food’s] content. What people need to be concerned about [are the components] if they’re worried about allergies or getting a balanced diet. So let’s imagine in a supermarket that we required very extensive labeling that dealt with process. You pick up a package of hamburger and it says: “This meat was produced after shooting a cow in the head with a gun.” That was the process of generating the meat. GMO is a technology; it’s not an ingredient. So I think that the proposition is attacking a technology rather than focusing on what people really need to know—which is a complete ingredient list. I find the focus on the technology to be troubling, because it’s not focused on what the real issue is in my mind.

When you express a new protein in a different organism or in any organism, you run the small risk that that protein will be allergenic. So, this is a real concern. As someone who is actually allergic to a specific [natural] food additive, I know that what we need to be concerned with in the food supply is the actual content of the material. . . . So I think for all labeling the focus should be on what proteins or other carbohydrates or other constituents have been added, potential allergens.

You recently gave a lecture entitled, “Are you afraid of genetically modified food?” What do you tell people who are afraid?

There are always people who are very conservative—if not absolutely opposed—to every new technology. But I would like to visit their house, and I would particularly like to visit their outdoor bathroom. Those of us who are old alums of Stanford realize that the Stanfords were afraid of indoor plumbing. We’re actually sitting in the last building built at Stanford with outdoor restrooms (Herrin labs, built in 1968). Alums from ’67 and before will recall that all of the bathrooms on the Quad were in little separate houses. The Stanfords thought that sewer gases and other things . . . might inadvertently poison the students or cause an explosion. So that’s a reflection of smart people’s thoughts in the 1880s and 1890s. Today we’re more concerned if someone would have an outhouse. We’ve all accepted indoor plumbing and running water as necessities of modern life.

It takes maybe 20 to 40 years—one or two generations—for the scary technology of today to become so engrained that we don’t even think of it as cool technology anymore.

In 1900, half of all Americans lived and worked on farms and ranches; and today [less than 1 percent claim farming as an occupation]. Each farmer and rancher is several hundred times more productive today. Various revolutions in agriculture, like mechanization, commercial fertilizer, and the introduction of chemical pesticides and herbicides, these technologies basically saved labor on the farm. We can look at the adoption of genetically modified organisms as a progression, another step in labor saving and increasing efficiency.

So people who want handmade cookies or who want very small-batch cheese, I need to ask them: If we were like France, 15 percent of the population would live and work on farms. Are we prepared to have 15 percent of Stanford undergraduates go to work on the farm? Or is our future a different kind of technology? We may need to live with factory-produced food. We can make a lot of those things better, nutritionally. But I don’t think most Americans want to move back to the farm or want their children to move back to the farm.

Is there a particular piece of misinformation about GMOs about which you would like to set the record straight?

The first misconception that always kind of blows me away is that people think that they are going to get a new gene by eating a GMO product. That it will somehow get incorporated into their body. But every time they eat raw fruit or raw vegetables, they’re eating a whole lot of DNA. And they have never turned into a stalk of celery. All organisms have DNA. You cannot turn into a tomato by eating a raw tomato, even though you eat all the genes in the tomato. So you should not be afraid of the DNA in genetically modified organisms.

What are the potential risks of GMO foods to health or the environment? And what steps do you recommend that biotech and agriculture companies take to mitigate these risks?

One of the risks is the adoption of monoculture: using just a single strain of corn or soybeans across a large land area. We could readily reduce the risk by requiring those who sell GMO seed to sell at least a dozen or more varieties suitable for major farming areas. Monoculture makes the crop susceptible to a new disease or climate variables. Biological diversity is an insurance policy against disease pressure, drought or other factors that can reduce farm yield. We could readily reduce the risk by requiring those who sell GMO seed to sell at least a dozen or more varieties suitable for major farming areas. If we are sophisticated enough to design and generate GMO crops, we (the public and scientists) should demand sophistication in deployment as well.

There’s a lot of room for improvement in the use of GMOs. Thoughtful scientists who look at, say, the way we deploy Bt, are afraid to [criticize] because they’re afraid of being misquoted in the media as being anti-GMO. But let’s combine something that we talked about a long time ago, those regulatory signals that allow for the precise expression pattern of a new gene, the genetically engineered gene. [Currently, genetically engineered plants express the Bt protein in each and every cell.] We don’t need that. If you were working in corn, and you were concerned primarily with root nematodes, [one possibility] would be to express the protein in the roots where the nematodes are feeding. If you were concerned with a leaf insect in tomato plants, you’d express the protein in the leaves. We have the technology to do that. You tell me where and when you want it expressed, and I could design a promoter. That’s much better genetic engineering. The switch away from using a sledge hammer of chemistry to kill everything to the specificity—and with better genetic engineering, exquisite specificity—to only kill the insects that are actually chewing on the crop, this would be great engineering.

I think one of the tragedies of the polarization of the debate is we’re not concentrating on better engineering. We’re concentrating on a yes/no.

Because the debate has been so raucous, I would say that the USDA has been reluctant to do much that’s innovative. I think this is an area where an informed public could be demanding more. Demand better gene regulation—so that each GMO gene is targeted as precisely as science knows how. Demand more biodiversity in the products. These are things that would address a number of consumer concerns.

Interview has been condensed and edited.


Kristin Sainani, MS '99, PhD '02, is a freelance writer and clinical assistant professor in the department of health research and policy.


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