Tropic to launch non-browning bananas in March

[Disclosure: AgFunderNews’ parent company AgFunder is an investor in Tropic ]

UK-based plant biotech co Tropic is gearing up to launch non-browning bananas in March and bananas with extended shelf-life by the year end—innovations it says will open up the cut fruit market, cut food waste, unlock new export markets, and reduce shipping costs.

Separately, it is expanding field trials of Cavendish bananas resistant to the devastating fusarium wilt fungal disease (TR4) that is decimating crops around the world.

Founded in 2016 by Gilad Gershon and Eyal Maori, Tropic is best-known for its proprietary Gene Editing Induced Gene Silencing (GEiGS) technology, which activates gene silencing machinery (RNAi) naturally found in plants to combat threats such as fungi and viruses.

However, the first two innovations—non-browning bananas and extended shelf-life bananas—have been developed using more traditional CRISPR gene editing techniques, Gershon told AgFunderNews.

As commercial Cavendish bananas are sterile and lack seeds, they are reproduced asexually via cloning, whereby new plants are grown from parts of an existing plant. This means that traditional methods of selecting genetic variation for desirable traits  and subsequent cross breeding are very challenging.

This leaves researchers to rely on inducing genetic variations via mutagenesis (using chemicals or radiation), deploying genetic modification (introducing foreign DNA), somaclonal variation (spontaneous mutations in tissue culture that happen naturally), or gene editing techniques.

Non-browning bananas

According to Gershon: “People have been trying to improve the Cavendish for years with very little success. We spent the first few years of our existence focusing on gene editing in bananas, which is a far from trivial task.

“After several years of development, we started production of [non-browning] seedlings about a year ago, and we’re now starting to offer significant quantities of these banana plants to farmers.

“The bananas have the same taste, smell, sweetness profile, the same everything, except that the flesh doesn’t go brown as quickly, which means you can add them to fruit salads and cut fruit products, opening up a huge new market.”

Browning is not the same as ripening, he noted, and doesn’t impact sweetness. It is triggered by polyphenol oxidase, an enzyme that catalyzes the oxidation of phenolic compounds in the banana, which causes the brown color. This is the same process that happens in apples and potatoes when they are cut and left out in the air, he added.

“This is very exciting to the industry, as historically, you wouldn’t include bananas, which are very popular fruits, in a prepared fruit selection in a store, because they go brown too quickly.”

So how is Tropic doing it?

“It’s very simple,” claimed Gershon. “I would categorize it as a gene knock out, even though there’s a lot of unique IP behind it, as no one as far as we know can do gene editing in bananas with this level of efficiency, all in a non GMO manner.”

Put simply, he said, “We know which genes are responsible for the production of that enzyme, and we disable them.”

To date, Tropic has secured regulatory approvals for the bananas in the Philippines, Colombia, Honduras, the USA, and Canada, with more territories likely coming on line later this year, he said.

Bananas with extended shelf life

Meanwhile, bananas with an extended shelf-life will be hitting the market later in the year, said Gershon.

“Bananas are picked when they are green, very like tomatoes. The intention is to keep them in this kind of pre-ripened state while they are being shipped from the country of the production to the country of consumption.”

But there is a limit to how far the bananas can travel, he said. “So you can harvest in Ecuador, but it is challenging to ship those bananas to Japan or to the Middle East.

“What we’re doing is knocking out the genes that are responsible for the production of ethylene,” a plant hormone which activates enzymes that break down starch into sugar, softens the fruit by breaking down cell walls, and changes the peel color from green to yellow by breaking down chlorophyll.

If bananas can stay greener for longer, you can harvest them later, ship them for longer, and reduce packaging and chilled transportation costs, claimed Gershon.

Tropic isn’t preventing ripening altogether, which would clearly be undesirable, but “buying companies at least 10 extra days, which is huge for the banana industry,” he said.

Bananas resistant to fusarium wilt

Another banana-related project from Tropic relates to the fungal disease—fusarium wilt, or TR4—that has been devastating Cavendish crops around the world, said Gershon.

In this case, Tropic is deploying its signature Gene Editing Induced Gene Silencing (GEiGS) technology, which effectively triggers the banana plant’s own RNAi [RNA interference] capabilities to target the genes in fungi that are attacking the plant.

According to Gershon: “We filed patents around GEiGS, which basically combines RNAi with gene editing in a way that, in our view, brings forward both of these technologies’ benefits while overcoming their unique disadvantages.”

How does GEiGS work?

In bananas, and in any other organism, said Gershon, there are thousands of coding genes that contain instructions to make proteins that perform functions in the cell, for examples enzymes such as polyphenol oxidase. Non-coding genes, by contrast, do not make proteins but regulate gene activity.

According to Gershon: “For gene knockouts, usually the approach is to disable coding genes. But this has its limitations. Say you want to make a banana resistant to a fungal disease. You might have to go through more than 30,000 genes to identify the one that, if you stop it from working, will help the banana fight off the disease. And then you might also find you’ve caused other problems.”

GEiGS, by contrast, takes a more nuanced approach, he said. “We use traditional gene editing tools like CRISPR, but instead of editing coding genes, we edit non-coding genes, the ones that produce natural RNAi for example, which are used to regulate other genes.

“We make very small changes in these non-coding genes to repurpose them and redirect their functionality. So if that non-coding gene was used to regulate one gene in the banana, we redirect it to start regulating another gene in the banana, or a family of genes in the banana, or actually inhibit genes in a virus, a pest or a fungus.

“In the case of TR4, we’re redirecting a banana non-coding RNA to attack a gene within the fusarium strain causing the disease. Instead of regulating a gene in the banana, this unique GEiGS RNA attacks a gene in the fungus.”

GEiGS allows for greater specificity 

Stepping back, he said, Tropic’s patented GEiGS technology enables a more nuanced approach to tackling threats to plants such as bananas. “With a gene knockout approach, you are basically switching a gene on or off. With GEiGS, you can say, I want that gene to be reduced by 50% [in order to get certain benefits without the downsides].”

It also allows for greater tissue specificity, he claimed. “With gene knockouts, in every single cell of the plant, that gene will not function. But with GEiGS, because we are repurposing existing regulators [non-coding genes that regulate gene activity] with different gene expression patterns within the plant, we can say we only want to change the root, the stem, or the fruit, for example, so it is a far more flexible approach than just a gene knock out.”

He added: “If you over-silence some genes and stop them from working altogether, there can be a deleterious effect on the plant. But we are able to reduce the activity to varying degrees in specific parts of the plant.”

Field trials for TR4 resistant bananas

Gershon would not name names, but said Tropic is now “working with many of the biggest banana companies the world” on its TR4 technology, adding, “Honestly, I don’t think that they have too many other viable options beside Tropic right now.”

Tropic started seeing very promising results of clear resistance [to TR4] more than three years ago, he said. “Last year, we started testing candidates in the field and this year we will be doing more field trials in multiple locations. So far we feel incredibly strong about the resistance that we’re seeing.”

He added: “Maybe one of the main benefits of this RNAi approach is that first of all, it’s inherent in the plants, and second, it’s not GMO, which makes things far easier from a regulatory perspective.”

The business model

Given the broad potential of the patented GEiGS technology, Tropic has also licensed it to other players such as Corteva (to develop disease resistance traits in corn and soybean), British Sugar (disease resistant sugar beet), and Genus (to address critical livestock diseases), he said.

Asked where Tropic—which has raised about $80 million to date—fits into the emerging plant gene editing space, he said: “Each player brings something unique to the table. Many of these leading companies have very valuable tools, different types of CRISPR, genetic scissors, whereas GEiGS is unique to Tropic, so we’re happy to work with them and we’re generating revenue from those partnerships.”