Michigan State University researchers make big strides towards reducing cold-induced sweetening.
In a landmark discovery that could revolutionize the snack food industry, a team of Michigan State University (MSU) scientists have uncovered a crucial genetic mechanism behind the darkening and potential health risks associated with cold-stored potatoes. Their research could pave the way for developing potato varieties that retain their quality under cold storage, resulting in healthier and tastier chips and fries.
“This discovery represents a significant advancement in our understanding of potato development and its implications for food quality and health,” says Jiming Jiang, a lead researcher on the team.
“This research has the potential to affect every single bag of potato chips around the world.”
The Problem with Cold Storage
The Canadian snack market relies heavily on a consistent supply of high-quality potatoes. In Alberta, the nation’s leading producer of potatoes for chips, the industry is valued at $2.87 billion annually. However, the challenge for Canadian farmers lies in the necessary use of cold storage – a method that can lead to cold-induced sweetening (CIS).
CIS is a natural process where potatoes convert starches to sugars. When fried, baked or otherwise cooked at high temperatures, these sugars react with amino acids to cause characteristic darkening of potato chips and fries. This not only impacts flavour, it also produces a compound called acrylamide.
Acrylamide, which forms in many plant-based foods that are cooked at high temperature, may be linked to cancer (though research trials on humans haven’t found clear evidence of cancer risk from consuming acrylamide, the National Toxicology Program lists it as “reasonably anticipated to be a human carcinogen”.)
While various techniques exist to mitigate the effects of starch to sugar conversion in cold-stored tubers — sprout inhibitors, curing, modified atmosphere storage, and chemical treatments — these methods incur additional costs and can compromise taste.
Jiang and his colleague David Douches are getting to the root of the problem by studying potato genetics. Their team has identified a specific gene responsible for CIS — the potato vacuolar invertase gene (VInv).
“The VInv gene plays a crucial role in the accumulation of sugars, which are the precursors to acrylamide formation during frying,” Jiang explains.
Control the Gene, Reduce CIS
In studying the VInv gene, Jiang and Douches have discovered an enhancer that controls its activity during cold storage. An enhancer is a tiny piece of DNA that regulates the action of a gene at a specific stage of plant development or during a specific environmental condition.
Unlike promoters, which put a gene into action, enhancers control when, where, and how much.
“The promoter of a gene can be compared to a country’s leader,” explains Jiang. “They make the final decision on an action, but their choice is influenced by members of government — the enhancers.”
The enhancer discovered by Jiang and Douches governs the VInv gene’s actions during cold storage, triggering the potato to produce more sugar. This ultimately leads to darkening and the formation of acrylamide.
“By understanding how the gene is influenced, we can use gene-editing techniques to turn off the enhancer and produce CIS-resistant potatoes,” Jiang says.
A New Approach to Gene Editing
Jiang and Douches are manipulating the enhancer using CRISPR, an advanced gene-editing technology derived from a natural defense mechanism in bacteria. Unlike traditional genetically modified organisms (GMOs) that add foreign genes to crops, the CRISPR technology controls existing genes instead of adding new ones. While promising, this method comes with hurdles.
“It’s a long process,” Jiang says.
Editing genes in potatoes is particularly challenging because they are propagated through tubers, without natural seeds or generations. They maintain the same genetic make up from generation to generation, hindering the introduction of changes.
In addition, unlike many seed-propagated crops which have two copies of each gene, most commercial potato varieties have four copies of each gene. This makes it harder to manipulate them.
“Most success stories right now are coming from seed-propagated crops like rice and tomatoes, with better nutrients and yields,” remarks Jiang. “It may take longer for asexually propagated crops like potatoes, bananas and citrus to see these kinds of advancements.”
Another challenge lies in making sure not to disturb a gene’s ability to perform its actions.
“In humans, we have 20,000 genes, and we need every single one,” Jiang explains. “Turning off a gene can cause defects, so it’s important to make sure that turning off a plant gene does not negatively effect growth and development.”
With an extensive background in gene-editing, Jiang isn’t letting these roadblocks stop him. He is planning to target the enhancer without disrupting the gene’s overall function.
“We can use CRISPR to target and delete specific sequences,” he says. “This allows us to address genetic issues without completely shutting down the genes, ensuring the plant remains healthy and productive.”
The Future of CIS-Free Potatoes
Jiang and Douches conduct their research as part of the MSU potato breeding and genetics project, which has been led by Douches since 1988.
“I am humbly impressed by Dr. Jiang’s ability to conduct fundamental research that can have applied outcomes,” says Douches. “Partnerships like this one propels the potato improvement forward.”
The implication of their work extends beyond just improving snack quality. By abolishing CIS in potatoes, they hope to drastically improve processes for farmers across North America, decreasing waste and reducing costs.
“Right now, the industry loses a significant portion of their crop each year due to long storage times,” Jiang remarks. “Imagine if we solve this problem and every potato variety can store as long as you want. That’s going to save a lot of time, money and stress.”
The next steps for Jiang and Douches’ research are to refine the gene-editing techniques and conduct further tests to ensure the stability and effectiveness of the CIS-resistant potatoes.
While the current research is primarily executed in greenhouses on MSU’s campus, the ultimate goal is to test these CRISPR-edited potatoes in the field and eventually make them available to growers.
“The opportunity to apply gene editing to achieve resistance to cold-induced sweetening will undoubtedly increase our ability to create better potatoes for chip-processing,” says Douches.
And with research progressing rapidly, CIS-resistant potatoes could be ready soon.
“Our dream is that one day, the industry can use CIS-Ready potatoes just like they use Roundup Ready soybeans,” Jiang says.
“It’s an exciting time for potato research, and we’re just beginning to see the potential applications of our work.”
