Tomatoes naturally produce vitamin D precursors.Closing the pathway to convert it into other chemicals can lead to precursor accumulation.
Gene-edited tomato plants that produce vitamin D precursors could one day provide an animal-free source of key nutrients.
An estimated 1 billion people don’t get enough vitamin D — a condition that can lead to a variety of health problems, including immune and neurological disorders.Plants are often a deficient source of nutrients, and most people get vitamin D from animal products such as eggs, meat, and dairy.
When the gene-edited tomatoes described in Nature Plants on May 23 were exposed to ultraviolet light in the lab, some precursors called vitamin D3 were converted into vitamin D3.But these plants have not yet been developed for commercial use, and it is not known how they will behave when grown outdoors.
However, says plant biologist Johnathan Napier of Rothamsted Research in Harpenden, UK, this is a promising and unusual example of using gene editing to improve the nutritional quality of crops.It requires an in-depth understanding of tomato biochemistry.”You can only edit what you understand,” he said.”And it’s only because we understand the biochemistry that we can do this type of intervention.”
Gene editing is a technique that allows researchers to make targeted changes to an organism’s genome and has been hailed as a potential way to develop better crops.While genetically modified crops made by inserting genes into a plant’s genome typically must undergo extensive scrutiny by government regulators, many countries have streamlined the process of genome-editing crops—provided the editing is relatively simple and the resulting mutations may also have naturally-occurring mutations .
But Napier said there are relatively few ways to use this kind of gene editing to improve the nutritional content of crops.While gene editing can be used to shut down genes in ways that are beneficial to consumers—for example, by removing plant compounds that can cause allergies—it’s much harder to find a gene mutation that results in a gene.new nutrients.”For actual nutritional enhancement, you have to step back and think, how useful would this tool be?” Napier said.
While some plants naturally produce a form of vitamin D, it is usually later converted into a chemical that regulates plant growth.Blocking the transformation pathway leads to accumulation of vitamin D precursors, but also to stunted plant growth.”This is a very important consideration if you want to make high-yielding plants,” says Cathie Martin, a plant biologist at the John Innes Centre in Norwich, UK.
But nightshades also have a parallel biochemical pathway that converts provitamin D3 into defensive compounds.Martin and her colleagues took advantage of this to engineer plants that produce vitamin D3: They found that shutting down the pathway led to the accumulation of vitamin D precursors without interfering with plant growth in the lab.
Dominique Van Der Straeten, a plant biologist at Ghent University in Belgium, said researchers must now determine whether blocking the production of defense compounds when grown outside the laboratory affects the ability of tomatoes to cope with environmental stress.
Martin and her colleagues plan to study this and have already received permission to grow their gene-edited tomatoes in the field.The team also wanted to measure the effect of outdoor UV exposure on the conversion of vitamin D3 to vitamin D3 in plant leaves and fruits.”In the UK, it’s almost doomed,” joked Martin, referring to the country’s notoriously rainy weather.She said that when she contacted a collaborator in Italy to ask if he could conduct the experiments in full sun, he replied that it would take about two years to get regulatory clearance.
If tomatoes do well in field studies, they may end up joining a limited list of nutrient-fortified crops available to consumers.But Napier warns that the road to market is long and fraught with complications involving intellectual property, regulatory requirements and logistical challenges.Golden Rice — an engineered version of a crop that produces a vitamin A precursor — took decades to move from lab benches to farms, before it was approved for commercial cultivation in the Philippines last year.
Van Der Straeten’s lab is growing genetically modified plants that produce higher levels of a variety of nutrients, including folate, vitamin A and vitamin B2.But she is quick to point out that this fortified crop can only address malnutrition.”It’s just one of the ways we can help people,” she said.”Obviously it will take a variety of measures.”
Post time: May-25-2022