Tomatoes genetically modified with CRISPR could be a new source of vitamin D to prevent health problems associated with deficiency of this micronutrient
Vitamin D is produced in our bodies after exposing the skin to UVB light, but still the main source is food. An estimated 40% of Europeans are vitamin D deficient, and so are nearly a billion people worldwide.
Tomatoes naturally contain in their leaves one of the basic components of vitamin D3, called provitamin D3 or 7-dehydrocholesterol (7-DHC), but in very low levels. Provitamin D3 does not normally accumulate in the fruits of ripe tomatoes.
The researchers from Professor Cathie Martin’s group at the John Innes Center in Norwich, UK, used CRISPR-Cas9 gene editing to introduce changes into the genetic code of tomato plants so that provitamin D3 accumulates in the tomato fruit. The leaves of the edited plants contained up to 600 µg of provitamin D3 per gram of dry weight. Keep in mind that the recommended daily intake of vitamin D is 10 ug for adults.
How to get tomatoes with vitamin D
In previous research, it was studied how 7-DHC is produced in the plant, and if a specific enzyme, Sl7-DR2, is responsible for breaking it down and converting it into other molecules in the fruit, why it was not present. The researchers used CRISPR to deactivate this enzyme in the tomato so that 7DHC builds up in the fruit.
By measuring the amount of 7-DHC, they found that it accumulated in both the flesh and skin of the tomatoes, as well as the leaves. This is interesting because the leaves of these tomatoes are not wasted, but can be reused to make vitamin D3 supplements.
Next, the researchers found that the 7-DHC in tomatoes can be converted into vitamin D3 using UVB light, a process similar to what occurs in human skin. After UVB light treatment, one tomato contained levels of vitamin D3 equivalent to two medium eggs or 28 g of tuna, which are two recommended dietary sources of vitamin D.
This new crop could help millions of people with vitamin D deficiency, a growing problem linked to an increased risk of cancer, dementia and many of the leading causes of death. Studies have also shown that vitamin D insufficiency is linked to greater severity of Covid-19 infection.
Blocking the enzyme in tomato had no effect on the growth, development or yield of tomato plants. Other closely related plants such as eggplant, potato and pepper have the same biochemical pathway, so the method can be applied to these vegetables.