Biotechnology: Tomatoes engineered to produce vitamin D

Tomatoes can be engineered to produce more provitamin D3 — a precursor to vitamin D3 — by blocking the action of an enzyme that normally converts this vitamin to cholesterol, according to a study published in Nature Plants. These tomatoes could represent a new dietary source of vitamin D3, with potential public health implications.

Vitamin D deficiency is a major global health issue that affects approximately one billion people worldwide and can lead to an increased risk of developing diseases such as cancer, Parkinson’s disease and dementia. Although humans can synthesize vitamin D3 on exposure to sunlight, most of this vitamin comes from our diets. However, dietary sources are limited, especially those from plants.

Cathie Martin and colleagues edited a gene in tomatoes that encodes an enzyme (7-dehydrocholesterol reductase) that normally converts provitamin D3 into cholesterol. By editing the gene, the authors were able to block this pathway, leading to the substantial accumulation of provitamin D3 in the tomatoes’ fruits and leaves, without affecting plant growth, development or yield. Provitamin D3 can then be converted to vitamin D3 by treatment with UV-B light, or can be used by the human body to synthesize vitamin D3 on UV-B exposure. The authors find that the amounts of provitamin D3 in one tomato fruit — if converted to vitamin D3 — would equal levels present in two medium-sized eggs or 28 grams of tuna. Eating the tomato fruits, they state, could help satisfy child and adult daily requirements for vitamin D3.

The authors conclude that this strategy could inspire further research into crop engineering to increase levels of vitamin D3 in plants.