By Herman Brockman OpEd
Two Arctic apple varieties have been in the news recently because of their “approval” by the USDA and FDA. “Approval” is commonly used in the media, but the reality is that the USDA “deregulated” these Arctic apples and the FDA concluded that they “. . . do not raise issues that would require pre-market review or approval by FDA.” These decisions by the USDA and FDA were based mainly on information provided by Okanagan Specialty Fruits, Inc. (OSF), the Canadian company that developed and trademarked these Arctic apples.
Arctic Golden and Arctic Granny were derived by OSF from the popular Golden Delicious and Granny Smith varieties, respectively, using genetic engineering techniques. Thus, Arctic apple trees are genetically modified organisms (GMOs), and their apples are GM food. OSF genetically engineered its Arctic apples so that they do not turn brown when bruised, cut, or bitten—i.e. unlike almost all other apples, they are “nonbrowning.”
OSF posts on its website: “We all love apples! Until they turn brown, that is. Arctic® apples are everything you love about apples, without the “yuck” factor that you don’t. (Now if we could just get rid of the seeds!)” I have eaten many apples, whole and cut up, but I never thought of browning, if I even noticed it, as yucky. And I love seeing the seeds. They remind me of a childhood hero—Johnny Appleseed. They also bring to mind a colleague from the early ‘60s, who, after eating an apple down to the core, would slowly devour the entire core, holding it by its stem—a mesmerizing act of eating.
But most of all, these precious seeds lead me to ponder the upwards of 4.5 million years of evolution by natural selection of a profusion of diverse wild apple forests in the Tian Shan mountains of Kazakhstan. The natives there began at least 4,000 years ago to domesticate these wild apples using artificial selection. This domestication and selection of thousands of varieties continued as apples were spread over the world, including the late event by colonists from Europe to America. Throughout this period, introgressive hybridization with other apple species, notably from the European crab apple, introduced even more genetic diversity into the original wild apple gene pool. This long biological and cultural evolutionary history of domestic apples is far more interesting and inspiring to me than OSF’s genetic engineering of Arctic Golden and Arctic Granny apples. Indeed, the histories of their parent varieties—Golden Delicious since about 1891, and Granny Smith since 1868—are fascinating tales. I doubt that J.M. Mullins and Maria Ann (Granny) Smith would be pleased with OSF’s genetic engineering of the little chance seedling each of them noticed and nurtured. But for them, the world would be poorer—without Golden Delicious and Granny Smith apples.
Almost all domestic apple varieties brown because they have genes that code for enzymes called polyphenol oxidases (PPOs). These enzymes catalyze the oxidation of colorless phenolic compounds, resulting in colored products that form brown complexes called melanins, which we observe as “browning” when an apple is bruised, cut, or bitten. Undamaged apples do not brown because the polyphenols and PPOs are separate in undamaged cells. In a nutshell, OSF used genetic engineering to prevent the synthesis of PPOs in Arctic apples: no PPOs means no melanin and thus no browning.
To begin to crack open that “nutshell,” I will first review some basic molecular biology of DNA, RNA, and protein (enzymes such as PPOs are proteins). The information for the unique sequence of 20 kinds of amino acids in a particular protein (such as a PPO) is encoded in the sequence of the four kinds of nucleotide bases of a gene for that protein. But that information in the DNA is first transferred to the sequence of four kinds of nucleotide bases during synthesis of a messenger RNA (mRNA), which then codes for the synthesis of a unique protein. Thus, the information flows from DNA to RNA (transcription) to protein (translation).
Back to Arctic apples. My main source of information is OSF’s “Petition for Determination of Nonregulated Status: Arctic™ Apple (Malus x domestica) Events GD 743 and GS784” (163 pages) to the USDA. These two “Events” are the two new transgenes introduced into the DNA of Golden Delicious and Granny Smith to produce Arctic Golden and Arctic Granny, respectively. Each of these two transgenes was genetically engineered to initiate a process called RNA interference (RNAi), which prevents the mRNAs coded by the PPO genes from functioning: i.e., transcription of the PPO genes occurs, but translation of those mRNAs to PPOs does not.
I cannot describe all the genetic engineering that OSF used, but they did construct a new gene (transgene) from a piece of each of four PPO genes from a donor apple variety (Golden Delicious or Granny Smith). OSF calls them transgenes, as I did above, but unlike common previous transgenes (such as the one used to make Roundup Ready crops) they do not come from a different species, and do not code for a protein. Other than these two differences and that RNA interference was used, the other biotechnology techniques used were the same or very similar to those used to construct previous GM plants.
How does RNA interference cause nonbrowning in Arctic apples? The transgene noted earlier codes for an RNA molecule, but it is not translated into a protein. Rather, the RNA molecule binds to the mRNAs transcribed from the PPO genes. This RNA complex initiates biochemical events that prevent the mRNA from being translated into PPOs. Thus, no browning.
Concerning the safety of Arctic apples, GMO proponents are saying what they always say about GMOs: they are safe. I do not share that unbridled optimism; rather, I follow the precautionary principle and the scientific literature. I responded to the last person, an Illinois Farm Bureau official, who told me that GMOs are safe: “Try telling that to the Monarch butterflies, try telling that to the earthworms, try telling that to the soil microbes.” I was referring specifically to some of the toxic effects of Roundup (containing the herbicide glyphosate) and Roundup Ready crops combination. More generally, the history of the unrealized positive predictions and the unintended negative consequences of GMOs lead me to a healthy skepticism of the safety claims for new GMOs, including Arctic apples.
OSF claims that its Arctic apples are the first nonbrowning apples. But there are at least two non-GM apple varieties whose white flesh does not brown for hours after cutting. Greenstar’s slow browning is probably due to its exceptionally high vitamin C concentration, up to three times that in most apple varieties. I like that. Apple breeders spent a decade developing Greenstar from a cross between Delbarestival and Granny Smith. The other apple variety is Opal. Ralph Broetie, who grows one million Opal trees in Washington, claims that its white flesh is nonbrowning, but OSF says that it is not completely nonbrowning. Its “nonbrowning” is due to naturally low levels of PPOs. Opal was developed from a cross of Topez and Golden Delicious. Greenstar and Opal demonstrate to me that Arctic apples are not needed, the same conclusion I have reached previously for other GMOs.
Note from the known parents of Greenstar and Opal that Granny Smith and Golden Delicious, respectively, “keep on giving.” Amazingly, as noted earlier, that ability to “give” us new apple varieties goes back millions of years to the vast genetic diversity of the wild apple forests of Kazakhstan. That genetic diversity of apples has decreased due to encroachment of urban development on these forests and to the extinction of many apple varieties developed by humans over thousands of years. Making GM apple varieties pales to insignificance compared to what we should be doing: preserving the invaluable genetic diversity of the remaining wild and domestic apples.
Herman Brockman is a writer and farmer living in central Illinois.