Nonbrowning GM apple cleared for market

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Mar 08, 2019
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appleThe US Department of Agriculture (USDA) on February 13 approved the first genetically modified (GM) apple developed to resist browning.  The Arctic apple’s go-ahead is a notable achievement for Canadian firm Okanagan Specialty Fruits, as the small biotech is one of the few to have successfully moved a GM plant through the regulatory process on its own. Indeed, two weeks after the apple’s launch, Okanagan announced its acquisition by Germantown, Maryland-based Intrexon, a synthetic biology company. Okanagan’s stockholders will receive $10 million in upfront cash and $31 million in Intrexon common stock. Industry observers now question whether the Arctic apple will carve a niche in the fruit tree industry or get caught up in the GM labeling debate.

Pre-cut fruit and vegetables are a growing trend in the food industry. “The [nonbrowning] trait will enable food service companies to cut and package the apples without adding browning inhibitors such as calcium ascorbate”—an antioxidant that changes the flavor of the apple, says Neal Carter, founder of the Summerland, British Columbia–based Okanagan. About 22,000 trees will be planted in the US this spring, with the resulting fruit available in fall 2016 for product demonstration, he says. Okanagan has also applied for regulatory approval of its apple in Canada.

Browning is caused by polyphenol oxidases (PPOs) naturally present in fruit and vegetables. When fruit is cut or bruised, these enzymes catalyze the oxidation of polyphenols to quinones, causing oxidative browning. The damage is superficial but can affect the taste and texture of the apple as well as its cosmetic qualities. In the Arctic varieties, the GM apples were genetically engineered with a transgene that produces specific RNAs to silence the expression of at least four browning PPO genes. The apple RNA sequences were introduced into Granny Smith and Golden Delicious varieties, where they bound complementary RNA to form a double strand. As RNA is single stranded, the double-stranded sequence is read as a mistake, and the plant’s naturally occurring Dicer enzymes are sent to chop it up, resulting in no or significantly fewer PPO proteins being produced.

RNA interference (RNAi) was also used by JR Simplot of Boise, Idaho to silence PPO production in nonbrowning potatoes, which were approved by the USDA in November (Nat. Biotechnol. 33, 12–13, 2015). For that product, fragments of a single potato PPO gene were re-introduced into potato, activating the RNAi pathway. But unlike the apple, the potato’s double-stranded RNA is formed by an inverted repeat transcribed in the tuber and processed into small interfering RNAs that ultimately silence their targets. JR Simplot’s crop was also modified to have reduced acrylamide, which was achieved by using RNAi to silence the asparagine synthetase-1 gene (ASn1).

Apples that won’t brown could make them more appealing to consumers and could also reduce waste by minimizing discarded apple due to bruising. But at least three growers associations urged US and Canadian regulatory agencies to reject Okanagan’s petitions for approval. Their objections were not made because of human health or safety concerns. In separate letters, the US Apple Association, the Northwest Horticultural Council and the BC Fruit Growers Association said GM apples may cause severe market disruptions, particularly in apple export markets averse to genetically modified organisms (GMOs). US Apple, however, changed its tune once USDA approval became imminent. “We are confident from the assurance we’ve received from Okanagan that they intend to stand by their pledge to clearly identify their apples in all marketing and packaging,” enabling consumers to choose between GM and non-GM apples, says Wendy Brannen, director of consumer health and public relations at US Apple.

Okanagan’s apples will not be labeled ‘GM’, but packaging will include the ‘Arctic’ name and logo. “It will be highly recognized as a GM product, given the amount of media attention we’ve had,” says Carter at Okanagan. The company has not yet decided whether the packaging will use other descriptive words, such as ‘nonbrowning’, which will partly depend on guidance from the US Food and Drug Administration, Carter says.

The GM apple may get caught up in the GMO labeling debate and used as an example, given its cachet as a family friendly, wholesome food, says Chris Schlect, president of the Northwest Horticultural Council in Yakima, Washington. “Apples are a symbolic product. It’s a fruit that a mother gives to a child going to school,” he says. “It’s going to be used in the media and by Congress in issues over the national labeling initiative.” Indeed, the Washington, DC–based Environmental Working Group put out a press release in February saying the approval of Arctic apples “underscores the need for a transparent and consistent national labeling standard.”

Other consumer groups argued against the safety of Okanagan’s apple. The Center for Food Safety (CFS) said USDA’s environmental assessment was inadequate—a complaint the Center has made for nearly every biotech crop assessment USDA has conducted in recent years. In its 61-page comment, the Center said that proper characterization of the PPO genes, their functions and the impacts of silencing them in the apple tree as a whole was not conducted. “I was floored by that,” says Martha Crouch, former professor of biology at Indiana University in Bloomington and a consultant for CFS. “It seems like that would be the minimum you would want to know before you start an assessment.” The Center noted that PPO genes have been shown in other plants to be associated with pathogen resistance, and that silencing them could lead to more susceptibility to disease and pests.

Okanagan says it conducted pest- and disease-resistance studies, and supplied the data to the USDA upon the agency’s request. “We have not seen any difference in disease susceptibility or plant pest risk between Arctic and control apple fruit or trees,” says Carter. “As summarized and analyzed in our petition document, we monitored all common orchard pests and diseases, including storage rot, over multiple years and multiple sites and saw no difference.”

Emily Waltz, Nashville, Tennessee 

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