Biotech

CRISPR Could Domesticate Wild Crops While Avoiding 'Frankenfoods'

Rather than mix the DNA of different species, gene-editing tech could be used to speed the domestication of wild foods by simply editing a plant's existing genetic material.

Around 10,000 years ago in Mesopotamia, our sharp-eyed ancestors noticed an odd stand of wild grass. Instead of scattering its mature seeds at the slightest touch, the plant held its cluster of seminal grains securely in place. Knowing how difficult it is to harvest fragile, windblown grains, the savvy prehistoric man or woman saved those seeds and replanted them.

The mutant grass that resulted - a chance accident of nature - evolved into wheat, the foundation of human agriculture.

This was how plants were domesticated for millennia, a combination of continual genetic mutation and lots of luck. Bathed in ultraviolet light, plants constantly undergo mutations, some more beneficial than others. Ironically, it's the mutations that make a plant less likely to survive and pass on its genes - softer seed husks, more flexible stems, tightly held bundles of grain - that make it more useful for cultivation.

The trick is catching those useful mutations before they're gone.

Of the 300,000 plant species on earth, we've successfully domesticated less than 200 for large-scale agriculture, and most of the world's farmland is dominated by just three: wheat, corn and rice.

But what if we don't have to depend on luck? A team of plant biologists, ethicists and social scientists from the University of Copenhagen proposes to use CRISPR, the precision gene-editing technology, to rapidly domesticate wild plants. Tweaking the genes of wild foods could produce nutritious new grains that are far more sustainable to grow.

In an opinion paper published in Trends in Plant Science, the Danish researchers argue that CRISPR's genetic "scissors," which can snip a single gene within a plant's DNA, represent a more effective and ethical way of genetically modifying food.

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In an interview with Seeker, lead author Michael Palmgren explained that mapping plant genomes has led to exciting new knowledge about how domestication works on the genetic level, including which specific genes were mutated to create the traits we most desire in our agricultural crops.

"But as plant biologists, we're kind of frustrated," said Palmgren. "In the last 10 years or so, there's been a tremendous increase in our knowledge about plants. For us the question has to be, how can we use this knowledge for the benefit of society?"

Part of the frustration is fierce public opposition to anything having to do with genetically modified organisms (GMOs). Palmgren explained that the CRISPR method is different than traditional GMOs, which are often produced by mixing the DNA of different species to produce desired traits in plants. CRISPR can't create so-called "Frankenfoods," because it is limited to editing existing genetic material by shutting off specific genes.

Interestingly, this is exactly how natural domestication works. Almost all mutations that have produced domesticated food crops are called "loss of function" mutations. A single gene stops working, accidentally producing a trait that's attractive to growers and consumers.

"People think that domestication occurs because something new was added, that the plants became 'better' in some way," said Palmgren, "but they have actually lost function."

Take the cauliflower, for example. Each tiny white curd is actually a bud that has failed to flower. The gene that tells the buds to blossom has been turned off, so the plant's energy is redirected to produce more and more buds.

"We think of cauliflower as this wonderful vegetable, as nature's gift, but it's a monstrous mutation," Palmgren said.

Using CRISPR, plant biologists could turn off the same genes in wild plants that have mutated naturally over millennia to produce our favorite domesticated varieties. For instance, scientists know that a gene in rice called sh4 is partly responsible for "seed shattering," the rice plant's natural ability to disperse its mature seeds. Thousands of years ago, plants with a mutated sh4 gene were domesticated because they held onto their seeds.

That very same gene exists in all wild rice plants, including varieties that grow abundantly in poor conditions. Using CRISPR, researchers can select hardier wild rice varieties that require less fertilizer or have a natural pest resistance, and turn off the one "seed shattering" gene that has made them undesirable to growers.

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The Holy Grail of this precision CRISPR method would be to domesticate wild perennial grasses that could be substituted for annual grains like wheat and corn. Annual crops have shallow roots and require continuous irrigation and fertilizer to provide the plant with sufficient nutrients. And since annual fields are left fallow over winter, the bare soil erodes and leaches fertilizer into streams.

Imagine engineering a wild perennial grass to grow the kind of nutrient-rich seed heads that we harvest from annual wheat. Perennial crops would require less fertilizer, less equipment and fuel to replant each season, and would provide year-round ground cover. All with the snip of a single gene.

"Not only could we domesticate perennials, but also grasses that are tolerant to drought or to salt," said Palmgren. "You can go into every marsh or desert or coastal area and find grasses that have adapted to those very harsh conditions. Instead of trying to let our wheat do it all, let's be inspired by nature. That's the idea."

The greatest obstacle to developing more sustainable "CRISPR crops" isn't the science, but public perception. GMO crops have been banned by several European countries - including France, Germany and Italy - and face similar threats in the US largely based on the public's unease with a scientific process that they don't fully understand or trust.

Palmgren blamed some of the backlash against GMOs on "really bad marketing." Companies like Monsanto developed products like corn that was resistant to the herbicide Roundup (glyphosate), which had no clear value to consumers. Farmers loved it because it greatly boosted their yields, and Monsanto loved it because the patented corn greatly boosted the company's profits, but all the consumer saw was an unnatural, genetically altered seed.

For the CRISPR method to win acceptance, biologists and ethicists must learn from Monsanto's mistakes by putting the concerns of the consumer first. If no one is willing to eat these new food crops, after all, no farmers will grow them.

"A much better starting point is to clearly identify the benefit of these crops for society and why they are important to the future of agriculture," Palmgren said. "When you have identified those issues, you can see what's possible to solve through plant biology. But you have to take consumers' concerns seriously, because they're the ones that buy the product."

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