Andrew Masterson
Andrew Masterson is a former editor of Cosmos.
Geneticists have suggested editing the genome of the humble tomato to turn it into a factory producing the compounds that give chillies their heat – and capsicum spray its immobilising power.
In a paper published in the journal Trends in Plant Science, a team led by Agustin Zsögön of the Federal University of Viçosa in Brazil point out that chillies – the source of the fiery capsaicinoids popular with gourmets and law-enforcement personnel alike – are challenging to grow in large amounts.
Their distant evolutionary cousins, tomatoes, on the other hand, grow easily in a wide range of conditions.
The two species split from a common ancestor some 19 million years ago and pursued different evolutionary strategies. Tomatoes developed rich, mild fruits, attractive to many animals, and are thus distributed abundantly via myriad digestive systems.
Chillies took a different and essentially defensive route, developing capsaicinoids as a way of discouraging predation.
The full genome of the chilli plant (Capsicum annuum) was sequenced in 2014, and that of the tomato a couple of years earlier.
Given the distant similarities between the two species and the development of gene editing techniques such as CRISPR-Cas9, Zsögön and colleagues argue, it should be possible to add capsaicinoid-producing genes into tomatoes.
This, in turn, would enable a massive increase in global production – and, not entirely coincidentally, a rather fun new ingredient for the world’s cooks.
“Engineering the capsaicinoid genetic pathway to the tomato would make it easier and cheaper to produce this compound, which has very interesting applications,” says Zsögön.
The process, however, is not without its challenges.
“In theory you could use these genes to produce capsaicinoids in the tomato,” he adds.
“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.”
