With the latest gene editing techniques, scientists can now insert capsaicinoids, the molecules that give peppers their spiciness, into tomatoes – introducing the spicy tomato.
From an evolutionary perspective, the chilli pepper is the tomato’s long-lost cousin, they split off from a common ancestor 19 million years ago but still share similar DNA. While the tomato plant developed to have a fleshy, nutrient-rich fruit yielding bountiful harvests, the more agriculturally difficult chilli plant went defensive, developing capsaicinoids, the molecules that give peppers their spiciness, to ward off predators. And now with the latest gene editing techniques, it could be possible to make a spicy tomato by altering a tomato to produce capsaicinoids as well.
Making a spicy tomato
The objective of the study was not to start a hot, new culinary craze, but to have an easier means of mass-producing large quantities of capsaicinoids for commercial purposes. The molecules have nutritional and antibiotic properties and are used in painkillers and pepper spray.
Senior author Agustin Zsögön, a plant biologist at the Federal University of Viçosa, Brazil explains: “Engineering the capsaicinoid genetic pathway to the tomato would make it easier and cheaper to produce this compound, which has very interesting applications.”
“We have the tools powerful enough to engineer the genome of any species; the challenge is to know which gene to engineer and where.”
What do you know about capsaicinoids?
The spicy taste that capsaicinoids add isn’t a taste, but a reaction to pain. The molecules activate nerve cells in the tongue that deal with heat-induced pain, which the brain interprets as a burning sensation. Evidence suggests that the evolution of capsaicinoids helped chilli peppers deter small mammals from eating their fruit, however birds, which are much better seed dispersers, show no pain response to the molecules.
There are at least 23 different types of capsaicinoids, which originate from the pith of the chilli pepper.
The spiciness of a pepper is determined by the genes that regulate capsaicinoid production, and less pungent peppers have mutations affecting this process. Previous gene sequencing work has shown that tomatoes have the genes necessary for capsaicinoids but don’t have the machinery to initiate them.
Gene editing to activate the spicy tomato
“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 sequencing of the chilli pepper genome and the discovery that the tomato has the genes necessary for pungency paves the way for engineering a spicy tomato. The researchers write that not only will this endeavour help better understand the evolution of this unique botanical trait and allow for the development of tomato capsaicinoid bio factories, but perhaps enable new varieties of produce to be sold in the grocery aisle.
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