A research team is developing genetically modified tomatoes as a rich source of vitamin D. Deactivating a gene aims to increase the levels of an essential nutrient precursor. Tomatoes usually ripen and taste best in the summer sun. Now, new research shows that with the help of genetic engineering, sun-ripened tomato varieties can also accumulate a vitamin D3 precursor molecule. This is an essential provitamin that is normally found mainly in animal products. Additionally, modified tomato plants contain as much provitamin D3 as two eggs or a tablespoon of tuna.
Increase Vitamin D Levels With Genetically Modified Tomatoes
Scientists say this could be a game changer, especially in countries where vitamin D deficiency is a problem. Plants modified in this way could also help vegans get enough of the so-called sunshine vitamin. Additionally, according to nutritionists, the discovery opens up exciting new opportunities for people with vitamin deficiencies. For example, vitamin D helps regulate how the body uses calcium, which leads to stronger bones. There is also evidence that low levels are associated with an increased risk of cardiovascular disease and other health problems.
Sunlight can cause the body to synthesize the solar vitamin, as ultraviolet B (UVB) radiation converts a precursor in the skin into a form that the liver and kidneys convert into usable vitamin D. People living in high latitudes often don’t get enough UVB exposure, especially in winter, to avoid vitamin D deficiency. Age or darker skin can also slow down vitamin D synthesis. Researchers have used gene editing to eliminate a specific molecule in the plant genome that increased provitamin D3 in both the fruits and leaves of tomato plants. It was then converted to vitamin D3 by exposure to UVB light.
Potential medical benefits
Since the main source of vitamin D is diet, new research can help develop treatment strategies. Such genetically modified tomatoes and fortified plants could help millions of people with vitamin D deficiency. As mentioned above, this is a growing problem linked to an increased risk of cancer, dementia and many of the leading causes of death.
Scientific research has also shown that vitamin D deficiency is associated with greater severity of Covid-19 infection. Furthermore, tomatoes that produce vitamin D could be a simple and sustainable innovation to address a global health problem. They naturally contain one of the building blocks of vitamin D3, called provitamin D3 or 7-dehydrocholesterol (7-DHC), in their leaves in very small quantities. However, provitamin D3 does not normally accumulate in ripe tomato fruits.
How a research team managed to develop genetically modified tomatoes
Scientists from Professor Cathie Martin’s group at the John Innes Center used CRISPR-Cas9 gene editing to redesign the genetic code of tomato plants so that provitamin D3 accumulates in the tomato fruit. The leaves of the processed plants contained up to 600 µg (micrograms) of provitamin D3 per gram of dry weight. The recommended daily intake of vitamin D is 10 µg for adults. When growing tomatoes, the leaves are usually waste material, but those from modified tomato plants could be used to make vitamin D3 supplements for vegans or to fortify foods. Previous research has looked at the biochemical pathway by which 7-DHC is used in the fruit to make molecules. They found that a specific enzyme, Sl7-DR2, is responsible for converting into other molecules.
To take advantage of this, the researchers used CRISPR-Cas 9. This enabled them to deactivate the Sl7-DR2 enzyme in the tomatoes, allowing 7DHC to accumulate in the tomato fruit. They measured the amount of 7-DHC present in the leaves and fruits of these processed tomato plants. The team found that 7-DHC levels increased significantly in both the leaves and fruits of the processed plants. 7-DHC accumulates in both the pulp and skin of tomatoes. After exposure to UVB light to convert 7-DHC to vitamin D3, one tomato contained the same amount of vitamin D as two medium-sized eggs or 28g of tuna – recommended food sources of vitamin D.
So far, modified tomatoes have only been grown in laboratory greenhouses. The study authors will begin a field trial in July 2022 and hope to begin this summer. Field tests will be crucial to see if plants can thrive under real-world stress. Researchers also need to show that the body can absorb provitamin D3 in tomatoes and convert it into vitamin D.
Another challenge could be consumer acceptance. Some people may not accept GM tomatoes. If plants hit the market, however, plant physiologists could mark a leap forward in reducing dependence on animal foods.
This new study suggests that vitamin D in ripe fruit could be further increased by prolonged UVB exposure, such as during sun drying. Blocking the enzyme in the tomato had no effect on the growth, development or yield of the tomato plants. Other closely related plants such as eggplant, potatoes and peppers share the same biochemical path, so researchers could apply those methods to these horticultural crops as well.