Genetically engineering a spicy tomato
Conversation about tomatoes with a twist started to heat up after a paper in Trends in Plant Science made the case for engineering tomatoes that could produce capsaicinoids, the metabolites that give chili peppers their heat.
Could we even do that?
Chili peppers and the other domesticated deliverers of the capsaicinoids we crave come from the Capsicum genus. But they actually share a common ancestor with today’s tomatoes. The two diverged at least 19 million years ago.
It turns out, the tools of the chili pepper’s spicy genome still exist in tomatoes. Every one of the necessary genes for producing capsaicinoids all appear in tomato DNA.
You might wonder why tomatoes aren’t already spicy then.
Studies of sweet peppers have revealed that the amount of capsaicinoids produced — and how spicy the resulting peppers turn out to be — stems from gene regulation. Genes have what amount to dimmer switches built-in, meaning they can essentially be turned up and down, a process called gene regulation. What we’re saying here is that spiciest peppers have the genes that contribute to capsaicinoids turned up to eleven, while sweet and mild peppers have those same genes, but they’re toned down to one or two.
Since tomatoes appear to still have their spice-making factories intact, we theoretically just need to figure out a way to turn them on again. The scientists who penned the paper suggest this could be accomplished using various gene-editing tools such as CRISPR.
Would we really go through all that just for spicy tomatoes?
This might depend on who you ask? Strictly speaking though, it’s unlikely that culinary curiosity could spark such an undertaking.
Capsaicinoids have demonstrated a number of promising qualities. For example, they’ve been documented to have anti-inflammatory, antioxidant, antitumoral and weight loss properties. With all of those benefits packed into one group of metabolites, we’re met with the suggestion that regularly eating capsaicinoids could give your health a boost. Not to mention that capsaicinoids have also been documented as a topical pain-management treatment.
Tomatoes on the other hand . . .
Take this statistic from the Trends in Plant Science paper:
Yields of hot pepper seldom exceed 3 tons per hectare on the field in about 4–5 months of culture. For tomato, on the other hand, it is not uncommon to reach 110t/ha on the field over a 120 day cropping cycle.
That means that tomatoes produce roughly 35x the yield of hot peppers.
Suddenly the spicy tomato makes a lot more sense as a source of capsaicinoids.
And the case only gets stronger.
The tomato is already one of the main horticultural crops in the world, but it’s also a “model species,” meaning it’s amenable to biotechnological manipulation. Essentially, scientists might be able to make tomatoes spicy, but they also stand a good chance of making them larger or smaller or more heat resistant or less water dependent or more pest resilient. There are already cultivars for tiny tomatoes, which can be grown quickly and in large numbers with limited space.
If you could make tomatoes into capsaicinoid factories, Italian food would never be the same, but we’d also get an unprecedented opportunity to further explore known health benefits and medical uses without nearly as much concern about supply.
But is there a catch?
There always is, right?
For one, none of the methods mentioned for turning the capsaicinoid genes in the tomato back on are certain to work. For example, maybe the necessary genes come back on, but they aren’t functioning to the degree they would need to to really kick up the heat. It’s also possible that they overexpress the capsaicinoid producers to the point where the rest of the genome shuts it down and silences the genes altogether.
Also, manufacturing capsaicinoids through tomatoes is part of a practice called biopharming, where medical compounds are genetically engineered into crops in order to mass-produce them. The aim is to dramatically reduce the cost of producing many valuable medicines. For example, tobacco is being looked to for producing necessary proteins to create everything from ebola vaccines to cancer treatments, because of its ability to grow robustly in relatively inhospitable conditions. Tomatoes could be used in much the same way for capsaicinoids.
However, regulations for these types of transgenic crops are still incredibly strict. The rules themselves are from another age of genetic research, and a real question remains of how these rules should be updated, if at all, given our ever-increasing capabilities.
The red hot future of genomics
We can do more with plant life on the genetic level than ever before, which empowers us to meet many of the challenges of the coming age. Between a growing world population and changing climate, scientists have a lot to figure out to produce the crops of tomorrow.
The same can be said for medicines — not just in terms of discovering them — but also in how they are produced.
We have real questions to ask ourselves about what methods we will endorse and even rely on going forward.
The spicy tomato may just be on that menu.
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