CRISPR to Boost Tomatoes’ Vitamin D Levels

By making a few genetic tweaks using CRISPR technology, scientists have designed a special sun-dried tomato packed to the leaves with vitamin D. The flesh and peel of the fruit were genetically engineered to contain the same vitamin D levels as two eggs or 28 grams of tuna, both of which are currently recommended sources of the vital nutrient.

Researchers used gene editing to turn off a specific molecule in the plant’s genome which increased provitamin D3 in both the fruit and leaves of tomato plants. It was then converted to vitamin D3 through exposure to UVB lightVitamin D is created in our bodies after skin’s exposure to UVB light, but the major source is food. This new biofortified crop could help millions of people with vitamin D insufficiency, a growing issue linked to higher risk of cancer, dementia, and many leading causes of mortality. Studies have also shown that vitamin D insufficiency is linked to increased severity of infection by Covid-19.

Tomatoes naturally contain one of the building blocks of vitamin D3, called provitamin D3 or 7-dehydrocholesterol (7-DHC), in their leaves at very low levels. Provitamin D3, does not normally accumulate in ripe tomato fruits. Researchers in Professor Cathie Martin’s group at the John Innes Centre (in UK) used CRISPR-Cas9 gene editing to make revisions to 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 ug of provitamin D3 per gram of dry weight. The recommended daily intake of vitamin d is 10 ug for adults. When growing tomatoes leaves are usually waste material, but those of the edited plants could be used for the manufacture of vegan-friendly vitamin D3 supplements, or for food fortification.

We’ve shown that you can biofortify tomatoes with provitamin D3 using gene editing, which means tomatoes could be developed as a plant-based, sustainable source of vitamin D3,” said Professor Cathie Martin, corresponding author of the study which appears in Nature Plants. “Forty percent of Europeans have vitamin D insufficiency and so do one billion people world-wide. We are not only addressing a huge health problem, but are helping producers, because tomato leaves which currently go to waste, could be used to make supplements from the gene-edited lines.”

Previous research has studied the biochemical pathway of how 7-DHC is used in the fruit to make molecules and found that a particular enzyme Sl7-DR2 is responsible for converting this into other molecules. To take advantage of this the researchers used CRISPR-Cas 9 to switch off this Sl7-DR2 enzyme in tomato so that the 7DHC accumulates in the tomato fruit. The researchers then tested whether the 7-DHC in the edited plants could be converted to vitamin D3 by shining UVB light on leaves.

After treatment with UVB light to turn the 7-DHC into Vitamin D3, one tomato contained the equivalent levels of vitamin D as two medium sized eggs or 28g tuna – which are both recommended dietary sources of vitamin D. The study says that vitamin D in ripe fruit might be increased further by extended exposure to UVB, for example during sun-drying.

Source: https://www.jic.ac.uk/