Written by Kevin Folta



We are currently witnessing the USDA public commentary period on the Arctic Apple, a transgenic apple that does not exhibit browning upon injury or cutting. The anti-browning trait was installed by scientists at Okanagan Specialty Fruits. A copy of the apple gene for polyphenol oxidase (PPO) was overexpressed, which triggers a plant response to silence the over-expressed gene. The same process also suppresses the apple’s endogenous PPO genes. Without this protein, the apple flesh will not brown when you cut it.

After a decade of assessment and testing for over a decade, the trees are poised for widespread adoption. But like clockwork, the critics have now emerged against this non-browning apple. They say that the apples are untested in humans, that the pollen will contaminate other plants. They say that it is unnatural and will need more pesticide. There is a feeling of reaching for any excuse to be anti-Arctic Apple.

The same criticisms were strangely silent against a parallel genetic alteration in grape. A genetic alteration damaged the normal expression of the PPO gene in the ‘Sultana’ grape, a genetic change that was unknown, uncharacterized and un-investigated. All the scientists knew is that the grape didn’t brown. The resulting grape exhibited the same anti-browning properties as the current Arctic Apple, and gained rapid favor for the production of light-colored raisins and low-oxidation wines. Unlabeled and untested, this genetic aberration spread quickly throughout the dried-grape industry, as consumers and farmers realized great gains from the sweet, white and golden raisins.

Worse, it turns out that scientists later deciphered the molecular basis for the disorder. The normal PPO protein was unprocessed, a new protein created! Just like the anti-GMO folks warn us about all the time, the new protein, untested for allergenicity and long-term feeding consequences, accumulated in the modified Franken-fruit background. This new freakish protein was the unnatural reason that the grapes did not brown, and the raisins remained white or golden.

The Punchline: You’ve likely eaten them. You might have even bought them at an organic market. You never cared.

In fact, the PPO mutant occurred spontaneously in 1962 in a grape line called “Sultana”. A mutation in the grapevine changed a gene so that the PPO oxidase protein (the one suppressed in Arctic Apple) could not be processed and made functional. The fruits were pale and exhibited a significant decrease in PPO activity.

Why? The active PPO enzyme is about 40 kilodaltons in size, but in ‘Bruce’s Sport’, the ppo mutant, the protein was not processed from its original 60 Kd size. The modified protein was not a functional PPO. A new protein was formed and caused the lack of browning. How did this mutant atrocity ever escape regulation? Surely Monsanto ram-rodded this through the FDA and USDA!

Not so much.

In fact, not at all.

The PPO mutant was found in 1962. Nobody cared about why the grapes didn’t brown, they just knew was a great trait for farmers and consumers. In 1992 scientists finally figured out that the non-browning trait was caused by the fact that a new unprocessed protein was formed in the plant, an unprocessed form of PPO that could not participate in the browning process.

1962. New changes in genes, new proteins formed. All untested, unlabeled, and accepted as perfectly fine; happy golden raisins to go with your granola. De-lish.

Turn ahead to 2012. The exact same gene is suppressed in apples with great precision. A group of people object to the process. They worry about allergies, cross-pollination and GMO Franken-dangers.

Questions

Why was this process completely acceptable when unknown, unpredictable and untested back in the 1960’s?

Why is the process decried when it is understood, documented and tested now?

These two questions frame an intellectual inconsistency of the anti-GMO movement that I cannot understand, and show that it is not the product, but the process that activists find objectionable.

References

Antcliff, A. & Webster, W. (1962). Bruce’s sport — a mutant of the sultana, Australian Journal of Experimental Agriculture, 2 (5) DOI: 10.1071/EA9620097

Dry, I.B. & Robinson, S.P. (1994). Molecular cloning and characterisation of grape berry polyphenol oxidase, Plant Molecular Biology, 26 (1) 502. DOI: 10.1007/BF00039560

Rathjen, A.H. & Robinson, S.P. (1992). Aberrant Processing of Polyphenol Oxidase in a Variegated Grapevine Mutant, PLANT PHYSIOLOGY, 99 (4) 1625. DOI: 10.1104/pp.99.4.1619

Written by Guest Expert

Kevin Folta has studied biology and agricultural biotechnology for over thirty years. His research examines the role of light in controlling plant traits, especially those relevant to agriculture. His group is known for using innovative genomics approaches to identify genes associated with fruit quality, especially flavors and aromas.