Happy Sunday scholars and sledders.
I hope everyone is having a merry and mathematical weekend! Did you celebrate Pi Day yesterday? Did you read any of the multitudinous articles about the marvelous irrational ratio of a circle’s circumference to its diameter? Did you bake any pies yourselves?
My favorite flavor of pie is definitely rhubarb, but today I want to discuss a different fruit-filling: apples, specifically, the genetically modified Arctic Apple that was recently approved for sale by the F.D.A.
The arctic apple offers an interesting case study into the ongoing GMO debate. Arctic Apples are cisgenic GMOs- they don’t have any genes from another organism added into them, rather they have been manipulated not to go brown when sliced or bruised (similar to the Simplot potato, that I discussed previously). The trick that allows arctic apples to remain pristine even after hours left out in the air is called gene silencing through RNA interference (RNAi).
RNA interference shuts down an undesirable process by taking advantage of a cell’s own defense mechanisms. As you all remember from basic biology, the cell’s genetic information is stored in the sequence of double-stranded DNA within its nucleus. When a cell wants to make a particular protein, it opens up the corresponding stretch of DNA, then transcribes that region into a single-stranded RNA molecule. That RNA molecule is then sent outside of the nucleus (into the region of the cell called the cytosol, which is where most of the interesting just-and-bolts chemistry takes place to keep us alive).
A machine in the cytosol called a ribosome reads the RNA to make a proteins (which is called translation). Cells are accustomed to their own double-stranded DNA staying in the nucleus, and single stranded RNA floating around the cytoplasm. However, cells are constantly under attack from invading genetic material. Viruses try to take over cells by injecting their own genomes into the mix and hijacking the machinery.
Viruses come in all shapes and sizes, but some store their own genetic information in the form of double-stranded RNA.
Therefore, double-stranded RNA inside a cell’s cytoplasm is a signal that something may be seriously wrong. When a cell senses double-stranded RNA, it quickly grabs onto the offending molecule, and either chews up or sequesters away that piece of RNA, in an effort to avoid inadvertently making viral proteins. This process is pretty similar to how bacteria target invading phages for degradation using CRISPR.
The scientists who created the arctic apple took advantage of RNAi to trick the fruit’s cells into turning off one of their own genes. Apples go brown when cut due to the action of an enzyme called polyphenol oxidase (PPO). Just as the name suggests, PPO oxidizes things; when apple cells rupture, the enzyme reacts with oxygen in the air and phenol compounds inside the fruit, producing the unsightly brown color. Engineers introduced a complementary copy of the PPO gene into the Arctic Apple. The extra copy produces a special single-stranded RNA called a small interfering RNA. The small interfering RNA binds the normal PPO RNA inside the plant’s cytosol, making it double-stranded. The plant’s own defenses then kick in to prevent any PPO protein from ever getting made, effectively squelching the process that causes apples to brown. It’s important to note that, although the RNAi strategy is designed to target four particular copies of the PPO gene, there are ten total versions of PPO within the apple genome. We don’t know WHAT all of these extra copies are doing, or if there’s any cross-talk between the engineered silencing system and these extra alleles.
The Arctic Apple breezed through regulatory approval; as a cisgenic GMO its difficult to make any convincing arguments that the product poses any possible human health risk. I’ve read some breathless claims that double-stranded RNA can be recovered from the digestive tract after being consumed orally. However, given that humans don’t have a PPO gene and the siRNA doesn’t seem to be getting taken up by human cells, I can’t think of any biological reason why a small bit of RNA passing through your intestines (the important word here is THROUGH) would pose any risk at all to human health.
I have to couch my statement with the caveat that human health is incredibly complicated, and we don’t really know anything about what dsRNA does to our systems because the technology just hasn’t been around for very long. It’s controversial whether mammals even use RNA interference to defend themselves from viruses at all! I could potentially imagine a scenario where the dsRNA might shift something in our microbiome, and cause some strange unforeseen consequence (our microbiome does LOTS of things for us, including alter how our liver processes drugs).
However, as I have argued before, the impact on human health is largely beside the point when considering an individual GMO. I sincerely doubt that this technology really poses a threat to anyone’s safety. A more important and more interesting question to consider is: How will large scale implementation of a product influence our food system as a whole?
I personally strongly object to GMOs that promote increased pesticide usage and poor farming practices. I also worry that a single monolithic company holds proprietary patents over the majority of our agricultural products. Round Up Ready corn and soybeans are two of the most egregious GMO offenders, responsible for a steady flow of glyphosphate onto the ground and coins into Monsanto’s coffers.
An orchard of Arctic Apples, by contrast, would be indistinguishable from any other arboretum. Non-organic apples are among the most pesticide-sprayed snacks on the market, but that’s incidental to the discussion of this particular product. The company that developed The Arctic Apple, Okanagan Specialty Fruits, is a small biotechnology and agriculture firm based in British Columbia. Okanagan specialty fruits was recently acquired by the Maryland based company Intrexon, which I see as an encouraging shift away from the
evil empire of Monsanto single-corporation market-dominance currently in place.
I’m ambivalent about what the GMO trait itself does for the apple. There’s some evidence that the activity of PPO helps protect plant seeds from pathogens, but apple trees seem to be able to grow juts fine when the gene is silenced. In terms of human health, a brown apple is JUST as nutritious and delicious as a pristine, just-sliced fruit. PPO activity merely causes cosmetic defects, why did Okenagan Specialty Fruits spend YEARS developing a way to turn off this gene? Representatives at the company are optimistic that Arctic Apples will help reduce food waste. Food waste comprises a massive proportion of the material languishing in landfills across America. Each year up to 1.3 million tons of food gets thrown away, uneaten. Fruits and vegetables are the most commonly wasted food items, and most of the waste arises simply because of cosmetic defects. American are throwing away 40% of the food we purchase; we toss to 1,700 calories per day of perfectly edible products in the trash. The marketing team behind the Arctic Apple claims that a non-browning fruit will reduce food waste. The apples don’t bruise, so supermarkets will throw away less fruit inadvertently blemished during shipping. They company conducted a market survey which found that 55% of consumers rate apple browning as “a big issue.” They also hope that this product will sell like gangbusters in the pre-sliced fruit market.
I think that food waste is a travesty, although I’m a more than a little skeptical that a non-browning apple will really significantly halt the flow of fruits and veggies into landfills. I think that strong messaging about buying less, and not rejecting fruits just because they look funny will do more to reduce food waste than this one GMO. The biggest success stories in food waste reduction (like Harvard’s efforts in its dining halls) come from changing consumer habits, not necessarily the food itself.
Additionally, there are other effective ways to prevent the PPO enzyme in apples from turning them brown. The acidity in lemon juice does the trick; coumarin (which naturally occurs in cinnamon) will work as well. I even found a paper that isolated a PPO inhibitor from Blue Mussels. Whether a brown apple is more objectionable than an apple covered in eau-de-mollusk remains an ongoing topic of debate.
I don’t believe that the Arctic Apple is really going to do much for food waste (though it would be great if it does). However, I think it is an important development, even though it hits supermarket shelves in 2017, and the public appears to have already lost interest.
Primarily, I hope that the Arctic Apple can start to shift the national conversation about GMOs, by introducing consumers to a familiar, non-threatening, photogenic product.
I hope that eventually we can become sophisticated enough in our discourse to really discuss the merits of a particular GMO individually, rather than falling back on blanket statements. Right now we seem stuck shouting either: “ALL GMOs ARE EVIL AND MONSANTO WILL MURDER OUR CHILDREN” or “GMOs ARE USEFUL AND SAVE FARMERS MILLIONS OF DOLLARS AND YOU’RE A DIRTY HIPPY IF YOU DISAGREE.”
The Arctic Apple, a likely harmless, but potentially not very useful, GMO is interesting because it shifts the script to a conversation about food waste. I’m rooting for the product to hit supermarket shelves, and for consumers to realize that, indeed, this GMO is likely largely indistinguishable from any other apple. Starting a conversation about WHY we throw away so much food every year would be an added benefit. Finally, I’m more than a little excited about the prospect of a small Canadian upstart unseating king-corn Monsanto from its GMO throne.
I’ll be following Okanagan specialty fruits and Intrexon as they move forward with this product. If nothing else, it’s a clever application of genome editing technology. Hopefully we can start paying more attention to what GMOs actually DO and spend less time deciding whether they are universally BAD or GOOD.
What do you think about the Arctic Apple?
What do you think about food waste? Isn’t it atrocious how much we throw away?