The purple tomato — and why its success is a win for GM food

The USDA has approved a genetically modified purple tomato, clearing the path for the unique fruit to be sold in American stores next year.

The first genetically modified (GM) food ever made commercially available to the public was a tomato, invented in the US in 1994. Since then, a number of different GM foods have been created, including corn, cotton, potatoes and pink pineapple.

Although GM foods still get a bit of a bad rap, there are actually many good reasons why modifying an organism’s genetics may be worthwhile. For example, many breeds of genetically modified foods have made them more resistant to disease.

It’s also possible to modify foods to make them more nutritious. Take for example golden rice. This grain was engineered to have higher levels of vitamin A, in order to tackle deficiencies of this nutrient in impoverished countries.

But despite all the developments in GM foods since 1994, few products have actually made it to the market. The continued ignorance of the general public about GM products alongside the reluctance of government policymakers in some countries have impeded their progress from the lab to the market.

This is why the regulatory approval of purple tomatoes in the US this September is so exciting!

Making a purple tomato

For the last 14 years, Cathie Martin and Eugenio Butelli from the John Innes Centre in Norfolk, England, and their team have been working on developing the purple tomato.

Their aim was to engineer a tomato that contained higher levels of anthocyanins – which can be used alongside unmodified tomatoes to study the benefits of anthocyanins. The team chose to modify a tomato because the fruit is delicious and widely consumed.

Martin and her colleagues published the first results of their research in 2008 in an article in Nature Biotechnology. The results were “stunning,” she said. Cancer-prone mice that ate the purple tomatoes lived around 30% longer than those that ate normal tomatoes, according to the study.

Anthocyanins occur naturally in many fruits and vegetables that have a red, purple or blue flesh or peel – such as blueberries, strawberries, aubergines and red cabbages. In order to produce a purple tomato, the team incorporated genes from snapdragons into the DNA of tomatoes.

A basket of blueberries.
Purple tomatoes contain the same level of anthocyanins as blueberries.

The end result of these experiments was a unique fruit – and not just because of it’s colour. They also succeeded in engineering tomatoes that contained high levels of anthocyanins – comparable to the amount found in blueberries – which is beneficial for a number of reasons.

They actually work to double their shelf life compared to red tomatoes. Anthocyanins help to delay over-ripening and reduce the fruit’s susceptibility to fungus attack post-harvest.

Another benefit is that they attract pollinators and animals to disperse seeds, which increases reproductive success of the plants and their yield.

Anthocyanins also protect plants from UV damage and protect them from pathogens, which maximises their survival.

Anthocyanins may also be good for your health. Studies on other foods containing them have linked them to lower inflammation, lower risk of type 2 diabetes and cancer. They may also protect the brain against disease, such as dementia.

While studies into the benefits of purple tomatoes specifically on humans are still ongoing, one study which fed cancer-prone mice food supplemented with purple tomatoes found they actually lived 30% longer compared to the mice given red tomatoes.

The future of GM

There have been a number of exciting developments in the field of GM foods in the last few years, including the first genome-edited GABA tomatoes in Japan and vitamin D-enriched tomatoes in the UK. Both were developed using CRISPR genome-editing technology.

Genetic modification can offer many benefits. Not only might it help us tackle the challenges of climate change by developing more resilient crops, breeding plants with higher levels of certain vitamins and minerals may potentially allow us to improve health and lower the burden of many common diseases.

And, GM crops may help us ensure that everyone, regardless of where they live, has access to high-quality fresh produce that’s good for them and the environment.

GM foods are also tightly regulated in many countries, which means that any products which are approved for consumption are safe for human, plant and animal health.

The greatest challenge now is getting more governments around the world to approve these GM foods for sale. It’s expected that purple tomatoes will be available for limited sale in the US as soon as 2023.

FDA approval and commercialisation are next steps

Martin has established a spinout company, Norfolk Plant Sciences, to bring the purple tomatoes to market. Nathan Pumplin, the CEO of Norfolk’s US-based commercial business, told CNN that the purple tomato “strikes a cord with people in this very basic way.”

The distinctive purple color means that “it takes no imagination to see that it’s different,” Pumplin said. “It really allows people to make a choice.”

In the past, forays into GM foods have often focused on engineering crops that are more sustainable to produce, he added. But for consumers, the benefits of eating a GM food are murky.

“It’s very abstract, hard to understand,” Pumplin said. “But a purple tomato – you either choose or choose not to consume.” The difference between the GMO (Genetically Modified Organism) product and the non-modified tomato are stark – and the possible health benefits for consumers are also clear.

Pumplin says that consumers are “warming up” to genetically modified foods across the world.

“We look at the problems facing our society as far as sustainability, climate change, health tied to diet and nutrition, and what’s clear from the response from our announcement is that it’s a really important topic to a lot of people,” he said.

“I’m encouraged that a lot of people are starting to relook at biotechnology in light of the important challenges.”

At the same time, “GMOs are not a silver bullet,” he said. “It’s one tool in our toolbox as plant scientists, as scientists, agronomists, to improve the food production system.”

The next steps for the purple tomato are FDA approval and commercialisation, Pumplin said. “We need to breed excellent, delicious purple tomatoes. We need to work with producers to produce them and distribute them.”

Norfolk will begin to launch limited test markets in 2023 to identify which consumers are most interested in purple tomatoes.

As for the taste? The purple tomato is indistinguishable from your standard red tomato, Pumplin said. “It tastes like a great tomato,” he said.

The Conversation, authored by Yang Yue, PhD Candidate in Plants, Food and Health, Quadram Institute, Norwich Research Park, UK;