Plant stress responses compromise mutualisms with Epichloë endophytes.

Plants commonly form mutualistic associations with fungal endophytes. We put forward the hypothesis, with supporting evidence, that certain plant physiological responses to stress (i.e., phytohormones and ROS) change the symbiosis between plants and Epichloë endophytes from mutualistic to parasitic. The negative effects of the plant physiological responses on the endophyte performance would explain the change in the symbiosis outcome. Furthermore, we posit that endophytes may protect the mutualism by the induction of plant defence hormone responses and antioxidants.