Bread and chocolate are staples of the American diet. And a scientific team in California is working hard to make sure the plants they’re made from are as robust as possible. They’re using a recently discovered bacterial gene-editing tool called CRISPR to create more pest-resistant crops.

CRISPR is a feature of the bacterial defense system. The microbes use it like a molecular pair of scissors, to precisely snip out viral infections in their DNA.

Scientists at the Innovative Genomics Institute in Berkeley, California, are using CRISPR to manipulate plant DNA. Managing director, Susan Jenkins, says the technique is so much faster and precise than other plant transformation methods, it will likely increase the speed of creating new plant varieties by years, if not decades. “What CRISPR is going to allow,” she explains, “is for us to go in and make these changes, and then within one generation of the plant actually have the trait we want.”

Rust-resistant wheat

 

While CRISPR speeds up plant breeding, Jenkins says it’s not a magic wand — changing a plant takes a lot of steps. She points to the Institute’s efforts to develop a wheat variety that resists a fungal rust that can reduce yields by nearly 50 percent.

First, scientists had to figure out just which gene was making the wheat vulnerable to fungal rust. Then they used CRISPR to remove that gene.

“So in this case, we use CRISPR to actually knock out a gene that is in the wheat,” Jenkins says. And because “snipping out” a gene does not add foreign material to a plant, last week, the USDA ruled that gene-changing methods like this do not require special regulatory approval.

 

Plant transformation expert Myeong-Je Cho says they started with a single gene-edited rust-resistant wheat cell, and grew it in the lab into wheat “clones” for further testing. After just over a year, some clones are now stalks of wheat, and Cho adds, “we have grownup plants in the greenhouse,” complete with normal stalks and robust seed heads.

While the Institute introduced no foreign genetic material into the wheat, CRISPR technology can also be used to introduce genes, even genes from other species, as is done with more traditional GMO crops. However, in standard GMO techniques, scientists use a “shotgun” approach to force new genes into a plant’s DNA in random places. Then, they choose which random change is most likely to grow healthy plants. In contrast, CRISPR is used when scientists want to add a specific gene at a specific location in the DNA. CRISPR offers that level of precision.

Protecting cacao trees

The bacterial gene known as Cas9 evolved to snip viruses out of bacterial DNA. Now Institute scientists want to use it to fight a virus that’s attacking cacao trees in West Africa.

The swollen shoot virus evolved in other plants, then, half a century ago, “jumped species” to cacao trees, which it can kill in just three years. So Jenkins says, the Institute is working to add virus resistance to cacao tree DNA, by inserting the Cas9 resistance gene. After all, she says, “If the bacteria have already evolved this to fight this viral infection, we are just going to take that mechanism and put it directly into the plant.”

 

The Institute plans to start growing cacao trees resistant to swollen shoot virus within a year. That is fast, according to Institute Science Director, Brian Staskawicz. He points out, “What this technology can do is to allow us work with the elite cultivars of a plant and basically change them for drought resistance and cold tolerance and disease resistance in a more rapid fashion than classical plant breeding.”

 

Staskawicz says that modifying cacao tree DNA is an exciting project from a technical standpoint, because cacao plants are unusually difficult to clone and genetically transform.

Public attitudes towards genetically modified crops

However, some challenges will go beyond whether the changes are technically possible. Those other challenges become evident at the Diablo Farmer’s market near Berkeley, where vendors like chocolatier Eli Curtis pride themselves on selling craft, organic foods. Curtis suspects we could increase cocoa yields by helping farmers be better stewards of wild cacao trees. He’s not sure consumers will like the idea of gene-edited chocolate, but if CRISPR leads to more pest-resistant crops, he says, “I definitely understand the value. But I also understand consumer apprehension.”

 

Nevertheless, Staskawicz says we need faster plant-breeding techniques like CRISPR because we are in a race, one we need to win, because there are currently 7.3 billion people on earth.

“By 2050 there are going to be nine billion people, and the estimates are that we actually need to increase food production by 70 percent. So we are going to need a way to actually increase the yield of these plants to feed the population of the world.”

CRISPR can help do that. He and his team hope, within a decade, CRISPR’d crops may be ingredients in many things, including bread and chocolate.
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