Apples are not farmed by planting a seed and waiting for the tree to grow, as seeds contain a mixture of genetic information from two parents. An apple is formed from a flower fertilized by another tree’s pollen, so its seeds will contain a random mix of both parents’ genes. To consistently reproduce the same breed, apple trees are cloned through grafting to preserve the qualities of the original variety. When people want to make a new apple variety, they will typically cross-breed with existing varieties, which mixes the genes of two existing types. If a certain trait is desired, genes that code for the trait must already exist in at least one of the parents, and several daughter trees must be planted to create apples with the desired combination of traits. However, with genetic engineering, scientists can make precise edits to the apple trees’ genome and introduce or alter traits in ways that aren’t seen in any existing varieties. Without genetic engineering, the only way to induce a trait that was previously nonexistent is hope for the right mutation, which is extremely unlikely and would require a great deal of time and resources.

One disadvantageous trait all apples have is browning, which occurs when the polyphenols react with oxygen through the activity of PPO (polyphenol oxidase) enzymes. Normally, PPO enzymes are physically separated from polyphenols, but when the tissues of an apple are damaged, the structures that separate PPOs from polyphenols are ruptured, and oxidation proceeds. If PPO enzyme activity was prevented, browning would not occur, which would protect texture, flavor, and nutritional value, and even reduce food waste, as consumers are less likely to discard otherwise perfect apples that have browned due to bruising or oxidation. This would be extremely impactful, as almost “half of the produce that’s grown in the United States is thrown away,” which is bad for the environment and feeds fewer people.

As a result, researchers have developed the Arctic Golden apple, a genetically engineered Golden Delicious apple that has been edited to inhibit PPO enzyme activity. Arctic apples were created by using RNAi (RNA interference), which is a natural biological process that identifies and deletes certain RNA sequences. Scientists implemented genes that code for RNA sequences that seek out PPO enzyme RNA and destroy it before the it is translated into the enzymes that catalyze browning. A protein called NPTII was also inserted with the transgene, serving as a marker so that researchers knew if genetic engineering was successful. NPTII is not detectable in Arctic apples, but it has been approved by the FDA for being nontoxic and nonallergenic. Other than that, Arctic apples are identical to Golden Delicious apples, as they contain the exact same nutritional value and the anti-PPO RNA is swiftly digested without any notable difference from regular Golden Delicious apples.

The Arctic apple project began in 1996 and they were approved for human consumption in 2015 by the USDA and FDA. As of 2018, Arctic Granny Smith, Fuji, and Gala apples have been under development with the first two already approved by the FDA, and Arctic Goldens have been sold pre-sliced in some regions of the US. These creative additions to agriculture and biotechnology are profitable while eliminating food waste, paving the path for similar innovations to follow suit.

I’m curious to know what purpose the PPO enzyme in apples normally serves, because you’d think it evolved for a reason. Yet, there doesn’t seem to be a downside to inhibiting its activity. Muyyy interesante.

I was surprised to see that this article was written in 2018, as it seems like a really promising advancement that seems relatively simple to implement into other varieties. I visited their site and they’ve commercialized Arctic Goldens and Granny Smiths, but it seems as though they’re exclusively sold pre-cut and in plastic packaging. Not exactly eco-friendly. I really wish this advancement could be more broadly applied, because if we were able to replace the varieties we already eat, we could reduce the amount of waste produced due to browning. If apples didn’t take so long to grow, I would honestly be really interested in doing an experiment on applying these findings to another variety if I ever got the chance. Who knows, maybe one day. Stay tuned to learn with me!

Baker, Allison. “Arctic Apples: A Fresh New Take on Genetic Engineering.” Science in the News, 15 Jan. 2018, sitn.hms.harvard.edu/flash/2018/arctic-apples-fresh-new-take-genetic-engineering/.

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