Fungal diseases can protect themselves from their toxins

In Canada, fusarium is a particular concern. It produces fumonisin mycotoxins, a common contaminant of corn and wheat. Total losses due to mycotoxins in Canada can be $1 billion in a bad year. | File photo

Canadian farmers are aware of the harm fungi can cause during crop growth, processing or crop storage.

Fungi secrete mycotoxins that weaken plants and can cause huge damage and economic loss. As well, some strains can cause serious human and animal health consequences, if ingested.

In Canada, fusarium is a particular concern. It produces fumonisin mycotoxins, a common contaminant of corn and wheat. Total losses due to mycotoxins in Canada can be $1 billion in a bad year.

Now, scientists at Agriculture Canada’s London Research and Development Centre have made an important discovery.

Mark Sumarah, a mycotoxin and fungal expert at the centre, was analyzing fumonisin and began wondering how the fungus could produce so much toxin but not have the toxin kill itself. His colleague Justin Renaud, a chemist specializing in metabolomics and analytical chemistry, suggested they analyze the fumonisin mycotoxin using the centre’s high resolution mass spectrometer.

“Fumonisin is a toxin produced by a number of fungi on corn and other crops,” said Renaud. “Fungi use an arsenal of chemical weapons to attack plants and suck out their nutrients.”

The researchers focused on the common fungus Aspergillus niger. The equipment allowed them to see not only everything being made by the fungi but, more importantly, they discovered how it produced an enzyme to remove a single nitrogen atom and replace it with an oxygen molecule.

“What was interesting about that is that we did a study to grow the fungus over a week’s period and we could see that this fungus was making normal toxic fumonisins,” said Sumarah. “Then, as time went on, these were going down and new fumonisins were being made. What we thought was that Aaspergillus niger was making normal fumonisins but then was using what we believed was an enzyme to convert them to these new (non-toxic) ones as a self-protection mechanism by swapping the nitrogen molecule for an oxygen molecule to eliminate all the toxicity.”

Chris Garnham, a biochemist and structural biologist who had started up his own lab at the centre, was also involved with the research.

Garnham isolated and analyzed protein from the fungus and, after some trial and error, identified the enzyme responsible for decreasing the toxicity. In further studies, the enzyme was cloned and tested to see how it would react in yeast systems similar to those used in bioethanol productions.

“This enzyme fully converted the fumonisin toxin into a non-toxic form,” said Garnham. “We were very excited when we saw the data indicating the enzyme was active and capable of targeting fumonisins.”

Renaud said the fungus that’s causing impacts to human health has learned to detoxify itself.

“It removes just one single atom. There is a nitrogen atom that is key for toxicity and the enzyme just goes in there, pumps it away and puts oxygen in. The toxicity disappears. We were so surprised at how stable this was and, so far, it has been very promising.”

He said that further research is needed to learn how this enzyme functions at the molecular level and identify the best ways to use it to detoxify potentially contaminated food and feed.

The enzyme is pending a patent and shows potential to be used as an effective tool to remediate fumonisin-contaminated food and feed.

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