PPO Silencing

How we do it

The advantages of Arctic® apples go far beyond simply cosmetic value (though they have that, too!). Nonbrowning apples offer a higher quality eating experience, exceptional convenience, and much more…

Arctic Apple Transformation Process

Hot Potato

Our nonbrowning solution finds its roots in research originally done by CSIRO in Australia, where they mapped the genes associated with PPO after identifying a natural grape sport, Bruce’s Sport, that didn’t go brown. CSIRO then developed PPO-inhibition proof of concept work to address browning in potatoes.

Potatoes suffer enzymatic browning damage like apples, and in both crops browning can result in significant product loss. In 1997, OSF licensed that gene silencing technology, then improved and expanded on it in apples.

Apple-to-apple transformation

Our science team silenced apples’ PPO genes using genes isolated from apples. Arctic® apples produce less than 10 percent of the PPO of their conventional counterparts – not enough to allow apples to brown.

To create nonbrowning Arctic® varieties, our low PPO-producing gene sequence – dubbed GEN-03 – is inserted into the parent cultivar’s DNA. A promoter and terminator gene sequence start and end that transformation process. It is a precise, targeted gene modification that silences the PPO enzyme but does not change any other aspect of the cultivar.

Arctic apple code
Arctic apple leaf tissue

With a little help from our friends

Apples’ own genetic promoters and terminators are too weak to trigger this transformation, so the introduction of Arctic® apples’ nonbrowning trait requires assistance from proven biotechnology tools. A promoter derived from the cauliflower mosaic virus, CaMV, initiates the Arctic® apple transformation, while nopaline synthase terminates it; Agrobacterium tumefaciens aids the process.

The proof is in the PCR

The nptII marker gene, and polymerase chain reaction (PCR) testing confirms the transformation executed properly. The Arctic® apple plantlets are grown in the lab until they can be micrografted to apple rootstock to prepare them for planting. Total time from transformation to a young tree with fruit is approximately 24 months and we have created an infographic that provides a visual overview of the process.

Once planted, Arctic® apple trees grow at the same rate as conventional apple varieties and do not require increased pesticide spraying or other special treatment in the orchard. As the U.S. Department of Agriculture declared in their Environmental Assessment of Arctic® apples, “the agronomic inputs required to cultivate [Arctic® apples] are functionally equivalent to those required for conventional apples”.

OSF Scientist
Arctic Fuji

Easier to judge the fruit’s true quality

An Arctic® apple will decay naturally just like any other apple, but it will not turn brown from bruising, cutting or biting – not in minutes, hours or days. In fact, because Arctic® apples don’t show superficial damage from enzymatic browning, but do show discoloration from fungal or bacterial infections, it is easier to judge the true quality of Arctic® apples than conventional apples.

Giving the Arctic Advantage to existing varieties

Another advantage of our approach is that it allows us to transform, existing, already-popular varieties with the nonbrowning trait. We decided to first enhance two of the most popular apple varieties of all time, Golden Delicious and Granny Smith, to become Arctic® Golden and Arctic® Granny. Next in the queue are Arctic® Gala and Arctic® Fuji.

Arctic apple seedlings

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