Scientists have created genetically edited tomatoes, each containing as much provitamin D3 – the precursor to vitamin D – as two eggs or a tablespoon of tuna.
Outdoor field trials of the tomatoes are expected to begin in the UK next month, and if successful, could provide an important new dietary source of vitamin D.
Approximately 13-19% of Britons have low levels of vitamin D, which is needed to keep bones, teeth and muscles healthy. Our main source of this nutrient comes from exposing the skin to sunlight, which converts provitamin D3 into an active form of vitamin D that our bodies can use.
However, in the UK there is only enough sunlight to achieve this between April and September, meaning we have to rely on dietary sources – such as oily fish, red meat, egg yolks and mushrooms – or supplements. This is particularly challenging for vegans, as many supplements contain lanolin from sheep’s wool.
“Gene-editing tomatoes to accumulate provitamin D3 at levels above recommended dietary guidelines could result in better health for many especially as tomatoes are a widely accessible and readily eaten food,” said Guy Poppy, a professor of ecology at the University of Southampton.
The tomato plants were created by making tiny changes to an existing tomato gene using an editing technique called Crispr-Cas9. “It’s like a pair of molecular tweezers, which you can use to precisely snip out a very small fragment of the gene to enhance a desirable trait in plants a lot quicker than traditional breeding process, and without introducing any foreign DNA from other species,” said Jie Li at the John Innes Centre in Norwich, who led the research.
In this case, their focus was an enzyme found in tomato plants that normally converts provitamin D3 into cholesterol. By altering this enzyme, the researchers managed to block this pathway, meaning provitamin D3 accumulated in the tomatoes’ fruits and leaves.
They calculated that the amount of provitamin D3 in one tomato fruit – if converted to vitamin D3 – would be equivalent to levels present in two medium-sized eggs or 28 grams of tuna. To convert this into active vitamin D3, the fruit would still need to be exposed to UVB light, or they could potentially be grown outdoors, something the researchers plan to test in upcoming field trials. The research was published in Nature Plants.
“It’s a nice example of the use of gene-editing technologies to make a very specific change to a crop,” said Prof Gideon Henderson, the chief scientific adviser at the Department for Environment, Food and Rural Affairs.
Such “precision-edited” crops are the subject of a bill, set out in the Queen’s speech, which will allow gene-edited plants to be treated differently to genetically modified organisms (GMOs) – the cultivation of which is governed by strict European rules that the UK hopes to move away from.
“It’s an example of the type of product that could pass through traditional GMO legislation, but would do so very slowly under the present regulatory environment and could take decades to navigate the system,” said Henderson.
Unlike GMOs, the tomato plants do not contain genes from other organisms and could theoretically have been created through selective breeding – albeit much more slowly. Such crops would be allowed under the proposed genetic technology (precision breeding) bill, which the environment secretary has predicted will be passed into law this year, potentially enabling the first gene-edited foods to be available by 2023.
Prof Cathie Martin at the John Innes Centre, who supervised the study, said it demonstrated the potential for gene editing to be used to enhance the nutritional properties of foods, and that same technique could generate similar alterations in any elite tomato variety. “This means that companies could introduce this trait into their patent-protected cultivars, or it could be introduced into [the tomato variety] Gardener’s Delight, where there’s no [patent] protection,” she said.
“[The technique] could also probably work well in other solanaceous food crops such as peppers, chillis, potatoes and aubergines.”
A further benefit to growers was that they could potentially sell the leaves or unripe fruits to supplement manufacturers for processing into vitamin D tablets, said Martin.