Gene-edited tomatoes may wipe out $1.6 billion Vitamin D business

 Gene-edited tomatoes could become a source of Vitamin D

Approximately 1 billion persons worldwide suffer from Vitamin D deficiency. Insufficient Vitamin D affects the immune system and inflammation and is connected to several medical conditions such as rickets in children, weak bones, diabetes, high blood pressure, cancer and autoimmune diseases such as multiple sclerosis.
The source of Vitamin D in humans is threefold:

1. Skin. Humans synthesise Vitamin D from 7-dehydrocholesterol (7-DHC, provitamin D₃) after exposure to sunlight, specifically ultraviolet B or UVB radiation emitted by the sun. Over-exposure to sunlight, however, can cause skin cancer for which reason people wear protective clothing and use sunscreens and this in turn can result in Vitamin D insufficiency. Vitamin D synthesis also decreases with age and therefore affects the elderly.

1. Foods such as fatty fish (e.g., salmon, tuna or mackerel), beef liver, dairy products (cheese, milk), mushrooms and egg yolks. With few exceptions, plants and vegetables are a very poor source of Vitamin D and this puts vegans in particular at risk of suffering from Vitamin D insufficiency.

1. Supplements. Several companies sell Vitamin D supplements to compensate for its deficiency in humans. Vitamin D sales attained $1.1 billion in 2020 and are expected to reach $1.6 billion in 2025.

All this could change after scientists have found a way of boosting the presence of provitamin B₃ in tomatoes through gene-editing using CRISPR-Cas9 technology.
Genetically modified crops are made by inserting extraneous genes into the genomes of the plants and thereby make them e.g. resistant to damage or destruction by insects or viruses and so on. Crops thus modified using extraneous genes are submitted to intense scrutiny by government regulators though in recent times the rules have been relaxed somewhat and approval is granted if the editing is relatively simple and the mutations could have occurred naturally as for example in the case of the sweet potato.
Although some plants do produce isoforms of the precursors of Vitamin D, these are subsequently converted to chemicals that regulate the plant’s growth and altering these chemicals make the plants stunted and yields decrease substantially.
7-DHC or provitamin D₃ has been identified in tomato leaves but it does not accumulate in the tomato fruit. In an article published recently, scientists working on this project (Li, J., Scarano, A., Gonzalez, N.M. et al. Biofortified tomatoes provide a new route to vitamin D sufficiency) discovered that solanaceous plants such as tomato exhibit a duplicate pathway by which specific isoforms of some enzymes responsible for the biosynthesis of phytosterol and brassinosteroid produce cholesterol for the formation of steroidal glykoalkoloid SGA. A specific form of 7-DHC reductase Sl7-DR2 then converts 7-DHC to cholesterol. The researchers turned off the activity of 
Sl7-DR2 using CRISPR-Cas9 technology, leading to an accumulation of 7-DHC in the tomato fruit. They also found that this procedure does not affect the growth, development or yield of the plant.
The next step will be to obtain regulatory approval to grow the gene-edited tomato plants outside the laboratory and test how they fare in this environment. If they perform well in field studies, they will still have to face the scrutiny of the regulatory authorities before they can be cultivated on a large scale. Keeping in mind that no extraneous genes are introduced into the tomato plant genome in the technique used and the gene-editing performed by the researchers could have occurred naturally, regulatory approvals should in theory be less stringent. But it could be years before the general public can switch from Vitamin D supplements to the gene-edited tomatoes.

Sources:

• Li, J. et al. Nature Plants https://doi.org/10.1038/s41477-022-01154-6 (2022).
• doi: https://doi.org/10.1038/d41586-022-01443-2
• https://www.nature.com/articles/d41586-022-01443-2?utm_source=Nature+Briefing&utm_campaign=9784ac12ed-briefing-dy-20220524&utm_medium=email&utm_term=0_c9dfd39373-9784ac12ed-47096220