A new opinion article in the journal Trends in Plant Science has outlined how tomatoes could be genetically engineered to produce capsaicinoids, the spicy compound found in chilies. The scientists suggest the innovation would be geared towards an efficient and easier way to mass produce capsaicinoids for commercial purposes.
The hypothetical proposal, presented by an international team of scientists, suggests capsaicinoids have significant nutritional and commercial uses. From painkillers to weaponized pepper sprays, capsaicinoids are increasingly becoming valued commercial compounds. A modified version of the compound has most recently demonstrated compelling anti-obesity effects.
The hurdle presented by the researchers is that growing high yields of the crops containing capsaicinoids is proving challenging. Hot chili peppers are difficult to cultivate in large quantities, and often result in inconsistent levels of capsaicinoids. So the solution could be to activate capsaicinoid pathways in a crop that is easier to grow, such as tomatoes.
"Engineering the capsaicinoid genetic pathway to the tomato would make it easier and cheaper to produce this compound, which has very interesting applications," explains Agustin Zsögön, senior author on the new article. "We have the tools powerful enough to engineer the genome of any species; the challenge is to know which gene to engineer and where."
The article suggests that while tomatoes and chili peppers diverged genetically over 19 million years ago, tomatoes still hold all the genes necessary to produce capsaicinoids.
"In theory you could use these genes to produce capsaicinoids in the tomato," says Zsögön. "Since we don't have solid data about the expression patterns of the capsaicinoid pathway in the tomato fruit, we have to try alternative approaches. One is to activate candidate genes one at a time and see what happens, which compounds are produced. We are trying this and a few other things."
The scientists also hypothesize more imaginative ways tomatoes may be used as "chassis" housing biofactories that produce other valuable metabolites. The plant could be modified to produce high levels of a natural food coloring called bixin, or tomatoes could be engineered to hold massive levels of beta carotene, an important antioxidant.
Of course, all of these discussions into genetically modified foods remain resolutely hypothetical, with debate still raging over how to regulate CRISPR gene-edited foods. Over the past few decades regulatory bodies have established control over foods that have been manipulated through the addition of foreign genes, but CRISPR gene editing now allows for a different kind of plant engineering.
Switching on an already present gene that potentially has been silenced for millions of years, a process called mutagenesis, is not the same as transgenesis, the introduction of foreign genes into an organism. Last year the EU and the US came to opposing decisions on how to classify these newer forms of gene-edited plants.
So, while the prospect of genetically modified spicy tomatoes may excite some people, it realistically will be a long time before these products reach our supermarket shelves. In the short term we will still have to mix tomatoes and chili peppers together manually to make a spicy red sauce or salsa.
The new article was published in the journal Trends in Plant Science.
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