What are some of the DNA strings that scientists put in GMOs?

Expert response from Christopher Barbey

PhD Student, Plant Molecular Genetics and Cell Biology

Friday, 23/03/2018 17:53

Hello, and thanks for your question. Scientists add (and sometimes subtract) DNA from plants all the time, but mostly this is done to learn how plants work. There are relatively few examples of DNA being added to improve crops, but the exceptions are notable as they've had a big impact on agriculture.

The most important strings of DNA are called genes. Two very commonly added genes are 1) insect resistance via a gene called CRY, from Bacillus thuringiensis, and 2) herbicide tolerance via a modification to a plant gene called EPSPS. These two genes make up most of the genetically engineered crops in the U.S., but there are other genes being used as well.

By subtracting a plant gene called PPO, we can prevent a lot of unnecessary food waste by reducing primary browning in crops like apples, potatoes, and mushrooms. This type of injury-induced browning is distinct from natural rotting, and is only triggered when damaged cells are exposed to air. Oxygen naturally degrades many of the plant’s chemical compounds, causing the apple or potato to turn brown. While this process might normally take hours or days, some plants have a gene called PPO which hugely accelerates this chemical reaction. This why apples can turn brown seconds after the first bite, but you can take your time eating a peach or a pear. Damage-induced browning is extremely common during harvesting and shipping, resulting in a huge amount of good food never reaching the market. By turning off the PPO gene, we can make browning proceed at a more normal rate. I’m very proud I actually helped create “non-browning” potatoes!

Virus-resistant Hawaiian papaya is another terrific example of crop genetic engineering. By giving the plant an incomplete piece of papaya virus DNA, we can teach the plant how to recognize that virus and defend itself. It's very much like a plant vaccine! This solution helped a lot of small farmers in Hawaii who were in desperate need. We’ve since used this strategy as a template to invent resistance to many other crop viruses! Unfortunately many of these perfect solutions have been refused by consumers, due to illegitimate concerns regarding their safety.

Ever since humans learned to farm 10,000 years ago, we have artificially directed plants to evolve into what we want. Every time a flower is pollinated, DNA is shuffled around in unpredictable ways to make a new plant that different from its parents. Over ten millennia we have made very dramatic changes. You’d have a very hard time recognizing the wild ancestors of our modern crops. We are still improving crops today, and hopefully always will be.