A mushroom that's resistant to browning has become the first CRISPR-edited food to get green lit by the US government. Here's how this mutated fungus managed to escape USDA oversight — and why this agency needs to upgrade its regulatory guidelines.
White button mushrooms. (Image: Böhringer Friedrich/CC BY 2.5.)
Penn State geneticist Yinong Yang created the browning-defying mushroom (Agaricus bosporus) by targeting the family of genes that encodes an enzyme that makes it turn brown as it ages. Using the CRISPR/cas9 gene-editing tool, he managed to knock out a bunch of base pairs in the mushroom's genome, reducing the enzyme's activity by upwards of 30 per cent. It was addition by subtraction; unlike many GMOs, this new fungus doesn't contain genetic information derived from another organism, or what's called transgenes.
Back in October, the USDA's Animal and Plant Health Inspection Service (APHIS) was asked to consider the new mushroom. Half a year later, it released its decision in a letter: "APHIS does not consider CRISPR/Cas9-edited white button mushrooms as described in your October 30, 2015 letter to be regulated." This means the mushroom can be grown and sold without any further oversight. As Nature News explained, the reason has to do with a certain loophole:
Yang's mushroom did not trigger USDA oversight because it does not contain foreign DNA from 'plant pests' such as viruses or bacteria. Such organisms were necessary for genetically modifying plants in the 1980s and 1990s, when the US government developed its framework for regulating GMOs. But newer gene-editing techniques that do not involve plant pests are quickly supplanting the old tools.
This isn't the first time a genetically tweaked organism has escaped regulation. The mushroom is now one of about 30 GMOs that have evaded regulation in the past five years. What makes this particular food unique is that it's the first to be modified by CRISPR, the current cause célèbre of the biotech world. Previous plants have been modified with pre-existing genetic tools, including ZFN and TALENS.
The problem with the USDA's current set of guidelines is that it doesn't consider the end product, but rather the processes used to make the product. Just because a modified crop doesn't contain any transgenes doesn't mean it should be immune to questions about its safety and efficacy. As this particular mushroom attests, sometimes novel function can be imbued by the removal of genes. What's more, CRISPR is extremely versatile, and we've only scratched the surface of what it can do.
"The regulation of gene-edited crops is a work in progress right now, [because] the technology has moved faster than the regulatory aspect has," said Joyce Van Eck, an assistant professor at Boyce Thompson Institute.
The USDA is reviewing its guidelines, known as the Coordinated Framework for Regulation of Biotechnology. But until they fix this regulatory problem, labs around the US will undoubtedly try to take advantage of the loophole to accelerate the development of new foods.
"The mushroom is likely to be the first of an ongoing pipeline," said Rodolphe Barrangou, a food scientist at North Carolina University. "I would be surprised if the number of labs looking to develop CRISPR food products wasn't well into the hundreds. Everyone I talk to who is doing any genetics research is using CRISPR. The first instance is always compelling, but in six months the number will be much higher." [Nature News]