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Genetically modified mushroom stirs debate

A lowly fungus has electrified the debate over genetically modified organisms, often referred to as GMOs. Developed by Pennsylvania State University plant pathologist Yinong Yang, the fungus in question is a slight alteration of the common white button mushroom, Agaricus bisporus.

Agaricus bisporus, the common white button mushroom.
Agaricus bisporus, the common white button mushroom.Read more

A lowly fungus has electrified the debate over genetically modified organisms, often referred to as GMOs.

Developed by Pennsylvania State University plant pathologist Yinong Yang, the fungus in question is a slight alteration of the common white button mushroom, Agaricus bisporus.

This is no small matter. The white button is said to be the most popular dinner-table mushroom in the Western world, and it certainly brings money to the Kennett Square area, where mushroom cultivation in the United States began. It is known as the "Mushroom Capital of the World" because of the many mushroom farms there.

Overall, Pennsylvania's 68 mushroom farms produce 63 percent of all U.S. white mushrooms, valued at more than $550 million, according to the industry association, Mushroom Farmers of Pennsylvania.

What's different about Yang's mushroom is that it resists browning, a characteristic that makes mushrooms less attractive. Delaying the browning process would extend the shelf life in grocery stores and shoppers' fridges, which could help reduce food waste.

What's also different is that the U.S. Department of Agriculture, one of the federal agencies regulating GMOs, ruled that the new mushroom does not require its approval before going to market. Therein lies the uproar, as critics call for more scrutiny of GMOs in general, and this "Franken-fungus" in particular.

We recently spoke with Yang about his research.

Tell us about the new mushroom.
The gene-edited mushroom has an anti-browning property, which is slowing down the mushroom browning process that is usually induced by slicing, mechanical injury, or microbial infections.

The change in the mushroom is mainly for appearance and, to some extent, to extend the shelf life. A lot of times you have this browning, even if the food is pretty fresh. I'm not going to say we're going to extend the shelf life for a long time, but it can help.

The research was funded by a Research Applications for Innovation [RAIN] grant from Penn State as well as the Giorgi Mushroom Co. [based in Blandon, north of Reading]. Giorgi donated $100,000 each year to Penn State's College of Agricultural Sciences for general mushroom research. Mine is one of four or five projects. It is not necessarily Giorgi's intent to develop a gene-edited mushroom, but when Giorgi CEO David Carroll visited Penn State to receive an alumni award, he stopped by my office and suggested browning as a trait for improvement. I also talked with a couple of people in the industry, and they said browning is one of the problems.

We used a relatively new technology called CRISPR-Cas9 to make small deletions to a polyphenol oxidase (PPO) gene involved in mushroom browning. It's a very precise and efficient way of editing the genetic material.

Why did the USDA say it did not fall under that agency's purview, as do many other GMO foods?
The Plant Protection Act of 2000 gives the USDA the authority to oversee the management of plant pests or noxious weeds. So a genetically engineered organism would be regulated if it had been engineered using something like a plant pest. Also, if you introduce foreign DNA, that new product would be subject to USDA regulation.

But our mushroom does not contain any introduced genetic material or any foreign DNA. We simply made small deletions to inactivate a gene that causes browning. So it's falling outside of USDA regulatory authority.

However, I have to indicate that in the U.S., food is also subject to regulation by the U.S. Food and Drug Administration. Although crop varieties produced by crossbreeding or radiation and chemical mutagenesis are usually not submitted to FDA for approval, for the gene-edited mushroom it would be prudent for us to get FDA consent before it will be marketed. This could give the public more assurance and peace of mind.

How likely is it that this mushroom will be on grocery store shelves any time soon?
We still have a lot of things to do. Right now, we just knocked out one PPO gene. We need to knock out multiple PPO genes to optimize the anti-browning property. We also need to resolve some intellectual property issues. In addition, we would like to analyze the metabolites and nutritional composition. If we are going to submit the mushroom for FDA approval, we need to demonstrate that the gene-edited mushroom is equivalent to the conventional mushroom in terms of nutritional composition and properties.

We also need to gauge consumer response. There are a lot of people who are concerned about GMOs. From what I heard, Georgi received some negative comments from consumers, although I see that the internet comments are largely positive.

So right now, we don't know when this mushroom will become available. It probably will take a while. It will be years.

Have other foods been developed that are outside USDA purview because they only subtract genetic material, not add it?
Actually, I wasn't too surprised when our mushroom fell outside the regulatory arena, because there are already about 30 crops that have been similarly edited using different technologies. Most involved taking genetic material out or, in some cases, replacing a tiny nucleotide, which is a minor modification. Those also are not subject to USDA oversight. Less than a week after the USDA decision on our anti-browning mushroom, a CRISPR corn variety developed by DuPont was also ruled by the USDA as an unregulated product.

What are the broader implications? Will this change the dialogue about GMOs?
I hope that maybe we can somehow improve the dialogue about GMOs, so it will be more rational and productive. I believe the new technology has a great potential to improve food safety and food security by removing food allergens and toxins and increasing crop yield and quality. The CRISPR technology can also help develop new crop varieties with reduced usage of pesticides, fertilizer, and water, contributing to a more sustainable agriculture and environment.