A Potato Made with Gene Editing
Dan Voytas is a plant geneticist at the University of Minnesota. But two days a week he stops studying the fundamentals of DNA engineering and heads to a nearby company called Cellectis Plant Sciences, where he applies them.
His newest creation, described in a plant journal this month, is a Ranger Russet potato that doesn’t accumulate sweet sugars at typical cold storage temperatures. That will let it last longer, and when it’s fried it won’t produce as much acrylamide, a suspected carcinogen.
What’s different about the potato is that it was bred with the help of gene editing, a new kind of technique for altering DNA that plant scientists say is going to be revolutionary for its simplicity and power. The technology could also be a way to engineer plants that avoid the stigma, and the regulations, normally associated with genetically modified organisms (GMOs).
In the case of the Ranger Russet, Voytas’s gene-editing technique, known as TALENs, left behind no trace other than a few deleted letters of DNA. The edit disabled a single gene that turns sucrose into glucose and fructose. Without it, Voytas thinks, the potatoes can be stored far longer without loss of quality.
The potato is a prototype of what plant scientists say is a rapidly arriving new generation of genetically modified plants. With gene editing, small companies think they can very quickly develop new crops for a fraction of the typical cost—even in species so far mostly untouched by biotechnology, like avocados, sorghum, and decorative flowers.
Most genetically modified crops that have been grown commercially so far incorporate genes from bacteria to make them produce insecticides or resist weed killers. Public opposition and regulatory requirements make these transgenic plants expensive to develop. That is why nearly all biotech plants are lucrative, big-acreage crops like soy, corn, and cotton and are sold by just a few large companies, like Monsanto and DuPont.
In August, the U.S. Department of Agriculture told Cellectis that unlike transgenic plants, its potato wouldn’t be regulated. That means instead of being grown in fenced-in test plots and generating folder upon folder of safety data, the Ranger Russet may go quickly to the market. Two years ago the agency reached a similar conclusion when it considered a DNA-edited corn plant developed by Dow AgroSciences, although it isn’t being sold yet.
Scientists say products like the potato are just the start for gene-editing techniques in plants. The same technologies are going to allow far more sophisticated engineering, including manipulation of photosynthesis to make plants grow faster and yield more food. “It’s an enormous opportunity, an unfathomable opportunity,” says Martin Spalding, a plant researcher at Iowa State University.
For now, the techniques are being used to modify plants in more modest ways. “The first wave of this technology is just removing a few base pairs,” says Yinong Yang, a professor of plant pathology at Penn State University, referring to the combinations of DNA letters—A, G, C, and T—that make up a genome. By “knocking out” just the right gene, as researchers did with the potato, it’s possible to give a plant a few valuable properties.
The next step, Yang says, will be to change the DNA letters of plant genes, swapping one plant’s version of a gene for that of another known to offer, say, resistance to disease. Yang says there is a blight-resistant form of rice that differs from commercial species by only a few DNA letters. “I could just change that over to resistance,” he says. “It’s like gene therapy in humans.” He says he’s negotiating a contract to produce the gene-edited rice now.
As for Voytas, this isn’t the first time he has set out to gene-edit plants. A decade ago he started a company called Phytodyne based on an earlier technology, called zinc finger nucleases, but it folded after Dow AgroSciences paid more than $50 million for exclusive rights to use that type of gene editing in plants.
Voytas teamed up with the French biotechnology company Cellectis in 2010 after it offered to install him as science chief of a new plant engineering division. But initial efforts ran into difficulty when another gene-editing system, meganucleases, proved challenging to work with and also got tied up by patent disputes.
Eventually, Voytas returned to the lab and coinvented a new way to edit genes, using specially engineered proteins called TALENs. That technology was used to make Cellectis’s potato, as well as a soybean with improved oil. Since then, Voytas and Cellectis have also worked with a newer technique, called CRISPR (see “Genome Surgery”).
Voytas says the potato took only about a year to create. “If you did it via breeding it would take five to 10 years,” he says.
Altogether, says Luc Mathis, CEO of Cellectis Plant Sciences, developing the potato cost a tenth of what it does to create and bring to market a transgenic plant, like corn or soy. “We will still need to generate some data, but it will not be a huge process,” says Mathis, who continues to meet with regulators to determine what steps remain before the potato can be sold.
Cellectis will move ahead with preliminary planting as soon as warm weather arrives in Minnesota. The first crops will determine whether the potatoes have the commercial benefits seen in greenhouse tests. “We need to check that we can store the potato in the cold,” says Mathis. “Once we have the commercial proof of concept, we can discuss with farmers what the interest level is.”
Kevin Folta, a professor of horticultural sciences at the University of Florida, says about 50 experts, including scientists and lawyers, met in Arizona earlier this year to discuss gene editing and how to orchestrate the industry’s approach to regulators in the United States and abroad. “Anyone who works in any kind of plant engineering is vigorously pursuing these technologies, especially with crops that have complex genomes or that you can’t breed easily,” he says. “There are lots of plants that need solutions.” He says gene editing will allow citrus trees to be modified in ways that would take 150 years with conventional breeding.
Folta says opponents of GMOs were not included in the planning meeting. “To invite people who view things nonscientifically would clog the discussion,” says. “There is no technology they are happy with.”
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