Improving rice's resistance to leaf blight

Rice is central to the food security of more than half the world’s population in many of the poorest countries. But the early development of bacterial leaf blight can destroy up to 80% of a crop in some countries.

In a discovery that could boost rice crop yields and lead to more disease-resistant types of rice, biologists studying bacterial leaf blight have discovered how the rice plant’s immune system is triggered by the disease.

“We’ve discovered a new molecule that’s never been seen before,” said Dr Benjamin Schwessinger, from The Australian National University (ANU).

“We’ve realised that this type of molecule plays an important role in the immune response of rice plants. It will now be much easier to develop containment strategies against the disease and breed more robust rice plants.”

The team discovered that the rice plant’s XA21 immune system is triggered when a molecule called RaxX is secreted by the leaf blight bacterium Xanthomonas oryzae pv. oryzae (Xoo).

The team generated mutants of Xoo that did not produce RaxX and tested whether they triggered the rice immune response, which allowed them to isolate the Xoo gene that was creating the RaxX molecule.

The research could help the fight against similar diseases in other crops, Dr Schwessinger said, and could also have a wider significance.

“Several major human diseases, for example HIV, involve tyrosine sulfated proteins. The new understanding could lead to the development of novel methods to block such diseases,” he said.

The research, published in Science Advances, marks a new chapter for Dr Schwessinger, who was part of the team that had to retract a 2009 paper on the subject, after they found problems with their results.