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Scientists attack maize’s fungal invader to save lost crops

ByGeorgina Hill

Mar 25, 2017

Global health and food security is being threatened by fungus, as the fungus Aspergillus has been invading maize crops across the world. This is a problem because the fungus produces a protein called aflatoxin, which is toxic to humans and other animals, making the corn inedible. The toxic protein can cause liver cancer, as the liver metabolises it into harmful reactive chemicals.

Maize, commonly known as corn, is not only a dietary staple for humans but is used in animal feed and biofuel production. This fungal destruction of maize is happening at a time when worldwide demand for maize is increasing. The fungus thrives in warm, humid conditions where maize is grown and stored.

But genetic modification (GM) can help fight the fungus. GM maize can battle fungal takeover, stopping it from producing the toxic protein. This is great news as this new type of maize can protect itself without the use of fungicides, which can be expensive and damaging to the environment. The GM maize protects itself by RNA interference. But what is RNA interference?

Well, RNA interference works just like your flatmate… stay with me. To be produce a protein, like aflatoxin, RNA, a type of genetic material, must be read by your cell. Working like recipe instructions, RNA dictates which ‘ingredients’ are brought together to make a specific protein.

But this GM maize produces a gene-silencing RNA molecule. This is your flatmate. Whilst you’re trying to read, they interfere, blasting obnoxious tunes from the 90s. Your reading process is blocked.  Gene-silencing RNA molecules interfere with cellular activity, therefore the RNA ‘recipe’ can no longer be read. This stops the toxic protein being produced.

However, fungus is persistent. Growth must be fought at multiple stages. It is important that harvested maize is stored correctly. Unless stored in dry conditions with limited oxygen, fungus can still grow. Even GM maize is at risks. The process of RNA interference can only happen when maize is growing. It cannot happen after harvesting maize. If we are to protect this valuable crop and keep it safe for consumption, steps to protect it from fungal attack need to be put in place throughout the supply chain.

Co-author, Monica Schmidt acknowledges that GM maize might fight fungal production of toxins in a lab setting. However, tackling the toxin in a field setting may present new challenges. In the real-world, Aspergillus fungus is genetically diverse. Therefore, the interfering RNA may not always stop the toxin from being produced. She suggests that the next step is creating GM maize that stops the fungus from growing at all.

Image: PixaBay

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