Discovery of a common ‘weapon’ used by disease-causing fungi could help engineer more resilient food crops

The discovery of a powerful “weapon” used by many disease-causing fungi to infect and destroy major food crop staples, such as rice and corn, could offer new strategies to bolster global food security, according to researchers from The Australian National University (ANU) in collaboration with scientists in Germany and the United States. 

Like humans, many fungi rely on plants as a food source. This impacts the yield of food crops. It’s estimated farmers lose between 10 to 23 per cent of their crops to fungal disease every year. 

The global research team discovered that an enzyme known as a ‘NUDIX hydrolase’ is used by many fungal pathogens as a weapon to cause disease in plants. The findings are published in Science. 

Resilient rice

By uncovering the role this enzyme plays in infecting plants, the researchers believe they can engineer more resilient rice crops, as well as other fruit and vegetable crops, capable of safeguarding themselves against disease. 

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The findings could help bolster food security in nations where rice and corn are major commodities. According to the US Department of Agriculture, rice is the primary staple food for more than half of the world’s population. 

Lead author Dr Carl McCombe, who completed this work as part of his PhD at ANU, said the disease-causing enzyme can infiltrate plant cells and attack a key signalling molecule involved in the sensing of phosphate – a vital nutrient necessary for plant survival. 

Starvation response

He said the enzyme “hijacks” key molecular pathways and tricks the plant into thinking it has a shortage of phosphate, activating a starvation-like response in the plant. This allows the pathogen to evade the immune system’s natural defence mechanisms and cause disease in the crop. 

“In collaboration with colleagues at the Australian Nuclear Science and Technology Organisation, we were able to reveal the structure of the enzyme in detail using a technique called X-ray crystallography,” Dr McCombe, who is now a postdoctoral researcher at the California Institute of Technology (Caltech), said. 

“Understanding what the enzyme looks like gave us critical insights into how it is used by pathogens to attack plants.”

Hijacking effect 

Associate Professor Simon Williams, who led the ANU research team’s contribution to this work, said in addition to engineering new crops with a turbocharged immune system, the research findings could also help scientists uncover new ways to deactivate the “hijacking effect” of the enzyme, similar to turning it on and off like a light switch. 

“Much of our work focused on the pathogenic fungus Magnaporthe oryzae, which causes rice blast disease. Rice is a critically important food staple, and losses from rice blast could feed 60 million people each year,” Associate Professor Williams said. 

“Our research also reveals that the NUDIX hydrolase is used as a ‘weapon’ by many different fungi, including ones that are responsible for causing anthracnose disease in fruit, vegetable and seed crops. These diseases impact crop production in foods such as mangoes, melons, corn and chickpeas – produce that Australians enjoy daily. 

“This suggests our work also has implications to safeguard other important fruit and vegetable staples.” 

Roadmap to disease management

Associate Professor Williams said the findings offer a roadmap to develop new disease management strategies. 

“This could involve engineering the plant’s immune system to detect the enzyme or block its function. This could help farmers protect their crops and secure global food supplies,” he said. 

This work involved scientists from ANU, RWTH Aachen University and Louisiana State University.