Vitamin D from tomatoes? Researchers have found a way to produce vitamin D3 (cholecalciferol) in tomatoes, according to the article in Nature Plants.
It is well known that plants are a very poor source of vitamin D. A weak form of the vitamin, vitamin D2, can be produced by fungus infected plants. But vitamin D3 (cholecalciferol) is produced in animals, and humans, by exposure of the provitamin 7-dehydrocholesterol to ultraviolet rays (UVB) of the sun. Other than this source, the vitamin should be supplied by the diet, which is a problem for vegans.
Researchers found that there are two pathways for steroidogenesis in tomatoes, one for production of phytosterols and the other for production of little amounts of cholesterol used for synthesis of steroidal glycoalkaloids (SGA). They aimed at knocking out the gene of 7-dehydrocholesterol reductase enzyme responsible for conversion of 7-dehydrocholesterol to cholesterol. Their goal was to accumulate the provitamin in the plant, which can be converted to vitamin D3 by UVB, thus getting vitamin D from tomatoes.
Using CRISPR-Cas9 editing technique, they could knock out the targeted gene. The tomato plant accumulated the provitamin in its leaves, and in the fruits, with no bad effect on the growth of the plant. UV irradiation produced the desired vitamin, vitamin D from tomatoes. One tomato fruit could have vitamin D equivalent to two medium-sized eggs or 28 g of tuna, the recommended sources of vitamin D. The leaves, which are a waste product, could be a vegetable source for manufacturing the vitamin supplements.
Related plants, like potatoes, eggplant, and pepper can be modified the same way. There is no need to say that these plants should be grown in sunny areas to get the desired vitamin. More work to knock out substances that reduce the penetration of UV may be beneficial. The production of such genetically modified crops still must go through governmental regulations.
Source: Li, J., Scarano, A., Gonzalez, N.M. et al. Biofortified tomatoes provide a new route to vitamin D sufficiency. Nat. Plants (2022). https://doi.org/10.1038/s41477-022-01154-6
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