Foods made with genetically modified organisms (GMO) are called a lot of things, but “healthier” is not usually one of them. Our attitudes toward GMO foods range from outright hostility to, at best, apathy. GMO foods, like pesticide-resistant Roundup Ready soybeans and fast-growing AquAdvantage salmon, seem to exist primarily to pad corporate profits. But the purpose of GMOs is not only restricted to making something more convenient to grow in large quantities; scientists are exploring ways to genetically modify popular foods to make them more nutritious. In the near future, parents concerned about their children’s health may tell their kids to eat their GMO vegetables.
We’re urged to fill our plates with fruits and vegetables in part because they contain a variety of colorful chemicals that are lumped together under the term “antioxidants.” A diet rich in these substances can help prevent cancer and other common diseases. Unfortunately, the fruits and vegetables that we eat most, like apples and tomatoes, don’t have very high levels of antioxidants. Our diets would be healthier if we could make a tomato with the high antioxidant content of a blueberry.
We’re all familiar with the result: pale, tasteless tomatoes that have a lower nutritional value than tomatoes that are allowed to ripen while still on the vine.
This is exactly what a group of scientists at United Kingdom’s John Innes Centre did. Using genetic engineering, they created a blueberry-like purple tomato with high levels of antioxidants. The antioxidants in red tomatoes are found mostly in the skin, but in purple tomatoes antioxidants are present in the entire fruit.
The trick to making a tomato like a blueberry is to transfer two genes from snapdragon plants into normal red tomatoes. These two genes are what molecular biologists call “master regulators” of antioxidant metabolism. Tomatoes naturally possess the metabolic machinery to make antioxidants; the master regulators from snapdragons merely switch this machinery into high gear. The two transferred genes turn on antioxidant production at high levels throughout the entire fruit, and the result is tomatoes that look like deep-purple berries.
Purple tomatoes are not only more nutritious than red ones, but they also have a long shelf life, as researchers recently found. The short shelf life of many fruits and vegetables poses major logistical issues. To get fresh-looking, ripe tomatoes into your local grocery store, tomatoes are harvested while still green, kept in cold storage, and then artificially ripened right before they’re put up for sale. We’re all familiar with the result: pale, tasteless tomatoes that have a lower nutritional value than tomatoes that are allowed to ripen while still on the vine.
Why do purple tomatoes have a longer shelf life? To understand the answer, it’s important to realize that, from the perspective of the tomato plant, rotting of overripe fruit is a feature, not a bug. Tomato plants produce fruit to attract the attention of animals that will spread the seeds via passage through their digestive tracts. If that doesn’t happen, plan B is to disperse the seeds by having the fruit rot. Rotting is an active process; the overripe fruit produces enzymes that break down protective cellular barriers that keep out fungus.
The researchers found that purple tomatoes produce lower amounts of these self-destruction enzymes. As a result, purple tomatoes are less susceptible to fungus, and they remain firm more than twice as long as red tomatoes. This means that purple tomatoes could be harvested later, after they’ve ripened naturally.
For thousands of years, humans have used breeding techniques to extensively modify the genes of crops and livestock in order to create new, desirable traits. We tend to think of GMOs as different and less-natural than new strains of crops and livestock made by breeding, but at a genetic level, it’s not easy to make a clear distinction between the kinds of DNA changes caused by breeding and those achieved by direct genetic engineering. As the technology to make them improves, GMO foods designed to be healthier could become a bigger part of your diet.
