Genetically modified foods: would you eat a purple tomato?

In the past week there has been a lot of press coverage about genetically modified foods. The first of these was a proposal made by Rothamsted Research in Hertfordshire to carry out field trials on plants engineered to produce the omega-3 oils that are usually found in fish. The second of these was a farm in Canada who had produced 1,200 litres of juice from‘purple tomatoes’ – a genetically modified tomato developed here at the John Innes Centre. With all the buzz around these genetically modified foods, it made sense to write a post about the potential that genetic modification (GM) has for increasing the benefit of our foods.

GM is a type of plant breeding that has been used to improve crops, and has been in global commercial use for 18 years. These GM organisms, or GMOs, contain a DNA sequence that does not occur naturally in its own genome and has not been created by conventional breeding. GM has been used to create more efficient and improved crops, for instance increasing food production or creating herbicide-resistant plants.

Genetic modification is usually carried out using one of two systems. Both systems begin with identification of a desired gene. The gene is then inserted into a circular piece of DNA called a plasmid. This plasmid is then transferred into a bacterium which reproduces to create several copies of the gene. The gene is then transferred to the plant by one of two ways. The first is to attach the DNA sequence to particles of gold or tungsten and firing the particles into plant tissue. The second is to use an infective soil bacterium called Agrobacterium tumefaciens which has been modified so that it takes the chosen gene into the plant tissue but does not become active once inside the plant. These processes are usually done involving an antibiotic marker to allow detection of successful GMOs, although new technologies are being developed that work without an antibiotic marker1.

The first commercial GMOs were grown in North America in the late 1990s. Globally over 12% of arable land is now used for GM crops. Soya is the world’s leading GM crop imported for both feed and human products, with GM maize, oilseed rape and cotton being other important GM crops.

Most GM crops that are commercially grown are modified to improve their yields or pest/disease resistance. However, in more recent years, the potential of GM has been directed to improving the crops to make them more beneficial to health or to provide nutrients that are more difficult to get into the diet otherwise. Here I will briefly highlight three examples of this to show the potential that this technology can have.

Golden Rice vs Normal Rice
(Image from Wikimedia Commons)

Golden Rice:
Golden rice is a strain of rice that has been engineered with higher levels of vitamin A than normal rice. It was developed to combat childhood vitamin A deficiency – a common problem in developing countries such as India, which can lead to a compromised immune system and even blindness. This golden rice was developed with the aim that it would be freely available to developing countries without the demand for payment or licences which they simply could not afford. Engineering this sort of crop could make a huge difference to the lives of children in developing countries, and golden rice has had a lot of positive publicity behind it2.

If you are more interested in Golden Rice, there is an event at JIC this week, which will be streamed online and open to questions on twitter. More information here.

purple tomatoes

Only the purple tomatoes are GM.
The rest are natural varieties

Purple tomatoes:
These tomatoes produced here at the Norwich Research Park have two new genes from the snapdragon plant. These genes increase the levelsof anthocyanins in the tomatoes. These anthocyanins are the antioxidants found in blackberries and cranberries, and it is thought that these anthocyanins offer protection against some cancers, cardiovascular disease and age-related diseases. Considering that in 2012 32% of UK deaths were caused by circulatory disease, and 29% from cancer, developing foods that could combat these diseases is a top priority3. Tomatoes and their by-products such as tomato sauce are a widely produced and consumed food in the UK, and are more commonly consumed than the berries with naturally high anthocyanins. These purple tomatoes have been shown to extend the lifespan of cancer-susceptible mice4, leading to possible application in human cancer treatment/prevention. As mentioned previously, a farm in Canada has recently grown and juiced a crop of these tomatoes. This juice can now be used for further research on its benefits, as well as used to attract new investors. To find out more about the new advances in this, check out this video or this press release
People may be put off by the purple colour of the tomatoes – but humans have been breeding to change the colour of vegetables for centuries. Ancestral carrots were once purple – but the Dutch bred them to be orange, and those are the carrots we eat today.

Many people take fish oil capsules as a supplement (Image from Wikimedia Commons)

Omega-3 oils in plants:
Some fatty acids that we need in our diet are found in oily fish – which gain these oils by consuming marine algae. Eating these fish allows the fatty acids into our diets, and there are also dietary supplements that can be bought. Increasing omega-3 oil consumption is putting pressure on rapidly diminishing fish stocks, and fish farming relies on feeding fish existing omega-3 oils rather than the marine algae that they would get them from in nature adding furtherpressure on the industry. Researchers at Rothamsted Research in Hertfordshire have inserted algal genes into oil-producing crops (such as Camelina sativa, or false flax) to enable them to produce these oils in a more sustainable setting5. The crops that they have produced are currently awaiting approval for field trials of these GM crops.

As you can see from these three examples, there is a huge potential for using genetic modification to improve the crops that we grow and improve our diets for the better (and possibly cheaper too!). GM still has its skeptics, as well as a large amount of regulation at the EU and government level. We won’t be growing any of these crops for consumption here in the UK in the near future, but as even more developments come in the science, maybe changes will be made in the regulation and we might finally get the chance to try these exciting new products. I’d certainly like to try a purple tomato – would you?

To read about our experiences talking about GM at Science Festivals, check out our post from a few months ago here


  2. Am J Clin Nutr 2009; 89:1776–83; 7. Nature Biotechnology 26, 1301 – 1308 (2008)
  3. Deaths Registered in England and Wales (Series DR), 2011, ONS
  4. Nature Biotechnology 26, 1301 – 1308 (2008)
  5. Plant Biotechnology 7: 704-716 (2009)

By Izzy Webb – a second year PhD student in Phil Poole’s group


2 thoughts on “Genetically modified foods: would you eat a purple tomato?

Leave a Reply

Fill in your details below or click an icon to log in: Logo

You are commenting using your account. Log Out / Change )

Twitter picture

You are commenting using your Twitter account. Log Out / Change )

Facebook photo

You are commenting using your Facebook account. Log Out / Change )

Google+ photo

You are commenting using your Google+ account. Log Out / Change )

Connecting to %s