Scientists used CRISPR technology to make a tiny edit in a gene to stop tomato plants producing an enzyme that converts a vitamin D precursor into cholesterol
23 May 2022
By Adam Vaughan
Biologists have created gene-edited tomatoes that offer a new plant-based source of vitamin D, as the UK government prepares to change the law to allow such “precision-bred” food to be sold in supermarkets.
Eating two of the tomatoes a day would address typical deficiencies in vitamin D, which about a billion people globally don’t get enough of, particularly in sun-starved northern latitudes. The engineered fruit also offers a new vegan alternative to typical vitamin D supplements.
However, despite the UK government set to introduce a bill on 25 May to treat gene-edited food differently to genetically modified organisms, the tomatoes face a series of technical and economic hurdles before they can become widely available.
They were made by editing a gene called Sl7-DR2 to stop the plant producing an enzyme that converts provitamin D3, a precursor to vitamin D, into cholesterol. “We altered a very small fragment of a part of this gene,” says Jie Li at the John Innes Centre in Norwich, UK, who led the research. “Comparing with the non-edited tomato plants, we didn’t see any effect on growth, development or yield in our edited plant. It just looked like a normal tomato fruit.”
Cathie Martin, also at the John Innes Centre, says that because of the gene’s structure, it would have been “very difficult” to use traditional plant breeding to arrive at a natural mutation that knocked out the enzyme. Traditional techniques would have taken 10 years to achieve the same result that took 1.5 years using a gene-editing technology known as CRISPR-Cas9, she says.
Vegans may see the tomatoes as a new way to get more vitamin D. Lichen-sourced vitamin D3 supplements are the only existing vegan option and are more expensive than the vast majority of vitamin D3 supplements, which are sourced from lanolin in sheep wool.
It remains to be seen if the edited tomatoes will cost more than conventional ones. Martin believes they shouldn’t, because growers could earn extra revenue from the vitamin D-rich leaves and green shoots to make vitamin D supplements. But more research is needed to show if that production is feasible.
Provitamin D3 is converted to vitamin D3, one of two main types of vitamin D, in plant cells and in human skin if exposed to ultraviolet rays from the sun. The tomatoes are due to be grown outside in government-approved field trials from 1 June to test how much vitamin D3 they produce. Given weak sunlight in the UK, artificial lighting could be required to provide enough UV, meaning more cost and energy. In order to reach shops, the tomatoes will also require a commercial grower to adopt them.
Nonetheless, Stefan Jansson at Umeå University in Sweden says the editing opens up new opportunities. “They have made an important and useful change by changing a few letters in the critical gene,” he says.