Rice Pathogen’s Trick Revealed

About 30% of the worldwide rice crop— enough food for 60 million people—is lost annually to a fungus called Magnaporthe oryzae. Now, researchers have figured out how the pathogen, known as the rice blast fungus, infects its prey (Science, DOI: 10.1126/science.1222934). When it’s time to infect, the fungus begins to grow an enormous batlike appendage called an appressorium, which it rams through a rice plant’s cell wall to gain entry. Yasin F. Dagdas and Nicholas J. Talbot of the University of Exeter, in England, led the work to find out which protein structures within the appressorium supply the right shape and rigidity to allow the fungal peg to blast into a rice cell. They found that cytoskeleton proteins called septins polymerize into a toroidal ring to channel the pressure for the penetration peg. “We’ve never seen rings like that in other organisms,” Dagdas says. Because septins are not found in plants, a pesticide that targets these proteins or their polymerization might be an effective treatment and unlikely to hurt the rice. However, septins are found in other organisms, including humans, so any treatments would have to be made specific to the fungus’s septins.