In research reported this month in The Plant Cell, scientists highlight a novel role for reactive oxygen species (ROS) in a symbiotic association between a filamentous fungus (Epichloë festucae) and a grass (Lolium perenne). They isolated the fungal gene responsible for the production of ROS and found that disruption of this gene causes the fungus to become pathogenic rather than beneficial. The authors propose that the function of ROS in this association is to control the growth of the fungus within the plant. A surprising result of this work is that the mutation of only one gene was required to switch a symbiotic association from a beneficial to an antagonistic one.
