Using CRISPR to design superior foods

By Jenna Gallegos

May 1, 2018

Photo: Ashley Katz

Scientists are now using a pioneering technology called CRISPR to edit a plant’s own genes, ushering in a host of new crop traits that directly benefit consumers.

Produce that doesn’t bruise or brown

In 2015, scientists at Pennsylvania State University described the first CRISPR-edited food: a mushroom that doesn’t brown.

Browning in plants is like swelling in humans. When we get injured or sick, we swell up. When plants are cut, dropped, munched by insects, or infected, they brown. Browning helps the plant resist further attacks or infection, but as with any uncontrolled swelling, there are consequences. Tissue dies.

Browning is mainly caused by polyphenol oxidase (PPO) genes. The scientists at Penn State used CRISPR to turn off a PPO gene in mushrooms. Previously, a different approach was used to inactivate PPO genes in apples and potatoes.

Non-browning apples, potatoes and mushrooms still rot eventually. They simply do not brown. That means they are less likely to become damaged during shipping or harvest and will keep longer on store shelves and home refrigerators, which can help address the huge problem of food waste.

Non-browning mushrooms, potatoes and apples are just the beginning. Injury and infection activate PPO genes in tomatoes, pineapples, wheat, pears, cucumbers, grapes, cherries, mangos and more, making them all possible candidates for gene editing fixes to minimize bruising.

Hypoallergenic wheat and nuts

Allergens are typically caused by proteins like gluten. Theoretically, scientists could use CRISPR to turn off the genes that lead to allergenic proteins.

For many allergenic plants, there are dozens of genes responsible for allergies. In order to make wheat safe for people with Coeliac disease, scientists would have to turn off 45 genes. So far, scientists have managed to take out 35 of them using CRISPR.

Prior to the CRISPR revolution, older genetic engineering methods were used to make progress towards hypoallergenic rice, soybeans, apples, birch trees, tomatoes, carrots and peanuts.

Unfortunately, some of the genes that cause allergic reactions are also important for regular growth of the plant, so knocking them out has consequences. The 13 genes responsible for allergens in peanuts make up a significant proportion of the peanut’s total protein content, so engineering hypoallergenic peanuts will be particularly challenging.

If successfully generated, hypoallergenic foods would have to be kept carefully separated from their allergenic counterparts. It is unlikely that this will ever be executed well enough to give severely allergic individuals the confidence to let their guard down. But for those with minor allergies, CRISPR-edited hypoallergenic foods could provide an extremely welcome relief.

Healthier produce

The nutritional value of a crop can be improved in three main ways: increasing the activity of genes that produce healthy compounds; turning off genes that produce unhealthy compounds; or adding new genes to introduce nutrients that do not occur naturally or are not absorbed very well from a given food.

The third approach, called biofortification, has largely been the focus of genetic engineers seeking to improve nutrition. Using more traditional genetic modification techniques, humanitarian scientists have biofortified crops like rice and cassava with nutrients like vitamin A, iron, folate, and zinc. Projects like these help address malnutrition in low-income communities.

But nutrient deficiencies are not the only food-related health concerns. Gene-edited plants could also be used to combat obesity and heart disease.

Rice and other carb-heavy crops contain multiple kinds of starches. Some starches are readily digested into sugars. Others, like amylose, pass through without being digested and serve as a dietary fiber. Scientists have already used CRISPR to produce high-amylose rice, a healthier option for overweight or diabetic individuals. CRISPR is also being used to produce oils enriched with healthier fat profiles, including more omega-3 fatty acids.

Molecules like the tannins and antioxidants found in dark-colored produce have been associated with heart health and protection against cancer. CRISPR has also been used to generate antioxidant-rich purple tomatoes. Although the health benefits of these compounds are debated, this project demonstrates the potential for using CRIPSR to enrich plants with protective molecules.

Future prospects: sweeter peas, seedless tomatoes, glowing flowers and more.

Any trait that is controlled by one or a few genes potentially could be tweaked to create crops with all kinds of consumer benefits. In some cases, taste could also be improved. For instance, sweetness in peas and bitterness in cucumbers are largely controlled by a small number of genes.

The USDA’s decision not to impose new regulations on CRISPR-edited crops spared the omega-3 enriched oils from having to undergo six years and nearly $50 million worth of testing. With that price tag, only traits that dramatically benefited farmers previously could afford to get to market, and only large companies could afford to develop them. CRISPR gene-editing in plants could thus usher in a new era of university-produced food crops with vast consumer benefits.