A research team is developing genetically engineered tomatoes as a rich source of vitamin D. Turning off a gene aims to increase levels of a precursor to the essential nutrient. Tomatoes usually ripen and taste better in the summer sun. Now, the new research shows that with some help from genetic engineering, sun-ripened tomato varieties can also accumulate a precursor molecule of vitamin D3. This is an essential provitamin normally found primarily in animal products. In addition, the modified tomato plants contain as much provitamin D3 as two eggs or a tablespoon of tuna.
Boosting vitamin D levels with genetically modified tomatoes
According to the scientists, this can be especially true in countries where the Vitamin D deficiency is a problem, be a turning point. Plants modified in this way could also help vegans to get enough of the so-called sun vitamin. Additionally, according to nutritionists, the finding opens up new and exciting 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 a higher risk of cardiovascular disease and other health problems.
Sunlight can prompt the body to synthesize the sun 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 at high latitudes often don’t get enough exposure to UVB, especially in winter, to avoid vitamin D deficiency. Age or darker skin can also slow down vitamin D synthesis. The researchers used gene editing to knock out a specific molecule in the plant’s genome that increased provitamin D3 in both the fruit 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, the new research may help to develop treatment strategies. Such genetically modified tomatoes and such 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 major causes of death.
Scientific studies have also shown that vitamin D deficiency is associated with an increased severity of Infection linked to Covid-19 is. In addition, 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 amounts. However, provitamin D3 does not normally accumulate in ripe tomato fruits.
How a research team was able to develop genetically modified tomatoes
Scientists in Professor Cathie Martin’s group at the John Innes Center used CRISPR-Cas9 gene editing to reengineer 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 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 of the modified tomato plants could be used to make vitamin D3 supplements for vegans or to fortify foods. Previous research has examined the biochemical pathway by which 7-DHC is used in the fruit to make molecules. They discovered that a specific enzyme, Sl7-DR2, is responsible for the conversion into other molecules.
To exploit this, the researchers used CRISPR-Cas 9. This enabled them to turn off the Sl7-DR2 enzyme in tomatoes, allowing the 7DHC to accumulate in the tomato fruit. They measured how much 7-DHC was present in the leaves and fruit of these processed tomato plants. The team found that 7-DHC levels increased significantly in both the leaves and fruit of the processed plants. The 7-DHC accumulates both in the pulp and in the skin of the tomatoes. After exposure to UVB light to convert the 7-DHC into vitamin D3, one tomato contained the same amount of vitamin D as two medium-sized eggs or 28g of tuna – recommended dietary sources of vitamin D.
Future Perspectives
So far, the modified tomatoes have only been grown in laboratory greenhouses. Study authors will begin a field trial in July 2022 and hope to begin this summer. Field testing will be crucial to see if the plants can thrive under real-world stress. The researchers also have to show that the body can absorb the provitamin D3 in the tomatoes and convert it into vitamin D.
Another challenge could be consumer acceptance. Some people may not accept GM tomatoes. If the plants make it to market, however, plant physiologists could mark a leap forward in reducing dependency on animal foods.
This new study states that vitamin D in ripe fruit could be further increased by prolonged exposure to UVB, for example during sun drying. Blocking the enzyme in the tomato had no effect on tomato plant growth, development or yield. Other closely related plants such as aubergines, potatoes and peppers share the same biochemical pathway, so the researchers could apply such methods to these vegetable crops as well.