Researchers Engineering Spicy Tomatoes

Spices are an important part of our life. They are used in the preparation of many recipes all over the world.

Recently researchers at the Federal University of Viçosa in Brazil have found that the capsaicinoids are responsible for the pungent taste. There are at least 23 different types of capsaicinoids that originate from the pith of the chilli pepper. The spiciness of a pepper is determined by the genes that regulate capsaicinoid production, and less spicy peppers have mutations affecting this process. Earlier gene sequencing work has shown that tomatoes have the genes necessary for capsaicinoids but don't have the machinery to turn them on. 

An article published in the journal "Trends in Plant Science" came into the lime light on the 7th January. 

The chili pepper, from an evolutionary perspective, is the tomato's long-lost spitfire cousin. They split off from a common ancestor 19 million years ago but still share some of the same DNA. While the tomato plant went on to have a fleshy, nutrient-rich fruit yielding bountiful harvests, the more agriculturally difficult chili plant went defensive, developing capsaicinoids, the molecules that give peppers their spiciness, to protect against predators. 

With the latest gene-editing techniques, it could be possible, although challenging, to make a tomato produce capsaicinoids as well, Their objective isn't to start a hot, new culinary fad--although that's not completely off the table--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. 

The sequencing of the chili 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 allow for the development of some new varieties of produce in the grocery aisle. 

"Engineering the capsaicinoid genetic pathway to the tomato would make it easier and cheaper to produce this compound, which has very interesting applications," says senior author Agustin Zsögön, a plant biologist at the Federal University of Viçosa in Brazil whose group is working toward this goal. "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 spicy taste that capsaicinoids add isn't a taste, but a reaction to pain. They 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 chili peppers deter small mammals from eating their fruit. Birds, which are much better seed dispersers, show no pain response to the molecules. 

"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."