The US Department of Agriculture (USDA) will not regulate a mushroom genetically modified with the gene-editing tool CRISPR–Cas9. This long-awaited decision means that the mushroom can be cultivated and sold without passing through the agency’s regulatory process. Making it the first CRISPR-edited GMO mushroom organism to receive a green light from the US government.
CRISPR – a revolutionary new technique
The first term of CRISPR–Cas9 is an acronym for “clustered regularly interspaced short palindromic repeats,” a description of the genetic basis of the method. Cas9 is the name of a protein that makes it work. Technical details aside, Crispr-Cas9 makes it easy, cheap, and fast to move genes around. Any genes, in any living thing, from bacteria to people.
Yinong Yang, a plant pathologist at Pennsylvania State University (Penn State) in University Park, engineered the common white button (Agaricus bisporus) mushroom to resist browning. The effect is achieved by targeting the family of genes that encodes polyphenol oxidase (PPO). This enzyme that causes browning. By deleting just a handful of base pairs in the mushroom’s genome, Yang knocked out one of six PPOgenes — reducing the enzyme’s activity by 30%. Yang’s GMO 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. In the meantime, Yang is mulling over whether to start a company to commercialize his modified GMO mushroom. Fruits and vegetables that resist browning are valuable. Because they keep their color longer when sliced, which lengthens shelf life. In the past 18 months, biotech companies have commercialized genetically engineered non-browning apples and potatoes.
Source: NATURE
