Biologists have modified the DNA of a tomato in such a way that the plant no longer converts a precursor of vitamin D into cholesterol. They did this by making a small change in a gene using the DNA modification technique CRISPR.
Biologists have tomatoes genetically engineered in such a way that they are now a vegetable source of vitamin D. Eating two of these tomatoes a day is said to remedy common vitamin D deficiencies. About a billion people worldwide do not get enough vitamin D, especially in the far north where there is little sun. The tomato also offers a vegan alternative to the vitamin D supplements that you can buy in a jar in the supermarket.
The tomatoes still have to overcome a number of technical and economic hurdles before they become widely available.
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In the tomatoes, a gene called Sl7-DR2 has been altered. As a result, the plant no longer produces the enzyme that converts provitamin D3, a precursor of vitamin D, into cholesterol.
Provitamin D3 is found in plant cells and in human skin. When exposed to the sun, it turns into vitamin D3, one of the two main types of vitamin D.
‘We have changed a very small piece in part of the gene,’ says study leader Jie Li of the British John Innes Center in Norwich. ‘In comparison with [gewone] tomato plants, we saw no effect on the growth, development or yield of our modified plant. It just looked like a normal tomato.’
His colleague Cathie Martin says that because of the structure of the gene, it would have been ‘very difficult’ to change the gene through ordinary plant breeding. It would take ten years to achieve the same result that CRISPR-Cas9 has now achieved within a year and a half, she says.
Vitamins for Vegans
For vegans, tomatoes may be a new way to get more vitamin D. Currently, lichen-based vitamin D3 supplements are the only vegan option. These are more expensive than the regular vitamin D3 supplements, which are made with lanolin in sheep’s wool.
It remains to be seen whether the processed tomatoes will be more expensive than regular tomatoes. Martin thinks that shouldn’t be the case, because the growers can get extra income from it in another way. They can use the vitamin D-rich leaves and green shoots to make vitamin D supplements. But research is still needed to prove that it is feasible.
Also read: First CRISPR food hits the shelves: a tomato with altered DNA
The British researchers will start growing the tomatoes outdoors from 1 June to test how much vitamin D3 they produce. Because England sees little sun, artificial light may be needed to boost vitamin production. That would entail more costs and energy. In addition, the commercial sector must embrace the tomatoes before they actually hit the shelves.
Nevertheless, plant biologist Stefan Jansson of Umeå University in Sweden says that the processing offers new possibilities. “They made an important and useful change by changing a few letters in the crucial gene,” he says.