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Scientists found a species of wheatgrass that is resistant to fungus, but how it became resistant is both surprising and unclear.

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Go to Brilliant.orgscishow to check out their course on Math History. [♪ INTRO]. It’s pretty fair to say that people love bread.

And cookies, and pasta. And beer. So it’s unfortunate that billions of dollars worth of wheat, barley, and other grain go to waste every year due to a fungus called Fusarium graminearum.

The fungus produces toxins that cause a disease called Fusarium head blight, or FHB. The family of fungal toxins that cause FHB mess with protein synthesis in all kinds of organisms, including plants and humans. This both shrivels the grain and sickens people who eat it.

One of these toxins is sometimes known as vomitoxin -- we’ll let you guess why. It can also cause dizziness, headache, and fever. People have been dealing with FHB for thousands of years, and it’s very much still a problem.

In a 2020 study, however, scientists made a discovery that could help. They’ve identified a protective gene in a wild species of wheatgrass called Thinopyrum elongatum. Researchers were already aware that this plant, which is native to Africa and Eurasia, is resistant to the blight.

The researchers sequenced the wild wheatgrass genome, but that was just the start. They systematically bred the resistant wheatgrass with other plants and compared the DNA of the various offspring with resistance to those that weren't resistant to the blight. Eventually, they identified a gene called Fhb7, which codes for an enzyme that breaks down the fungal toxins before they can cause any harm.

Now, the way you’d expect this to happen is for a gene that plays some other role in the plant to eventually evolve the ability to detoxify the FHB toxins. Except it’s not what happened here, at all. The Fhb7 gene appears to have made the jump to plants… from another fungus.

The researchers found that Fhb7 is 97 percent the same as a gene in the fungal genus Epichloë, which lives on grass. And it’s not present in any other grass genomes outside of those in the Thinopyrum genus. If Fhb7 had originated in plants, then it would exist in other species that share a common ancestor with Thinopyrum.

They don’t know how it happened. But they think that the gene somehow slipped from Epichloë to the grass about 5 million years ago via what’s called horizontal gene transfer. That’s basically when one species somehow acquires genetic material from another, even though they can’t reproduce with one another.

Scientists know that horizontal gene transfer happens pretty regularly in bacteria and other simple organisms, but it’s less clear how often it happens in multicellular organisms like plants. What Epichloë is doing with this gene is uncertain. The researchers think that it might help the fungus compete with Fusarium to colonize wild grasses.

Whatever its original function, the gene seems to have given the plant an edge in dealing with fungal threats. And here’s the incredibly convenient thing: If you were an agricultural researcher looking to solve the problem of FHB, you might want to genetically engineer a gene like Fhb7 into wheat. But nature’s already done that for us.

All researchers would have to do is cross Thinopyrum with commercial strains of grain. In fact, the authors of this study have already done so on a small scale. Now, researchers are hoping to take this finding one step further and identify other, similar genes.

Then they could breed crops with several of them at a time to make them even more resistant to the blight. All in all, this is one natural feat of genetic engineering that bodes well for the future of bread, pasta, and all of that other good stuff. This gene came from somewhere totally unexpected -- and that’s why it helps to draw from a bunch of other different fields when trying to understand the universe.

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