Plant stress responses compromise mutualisms with Epichloë endophytes

Abstract

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 reactive oxygen species (ROS)] change the symbiosis between plants and Epichloë endophytes from mutualistic to parasitic. The change in symbiosis outcome would be explained by the negative effects of the plant physiological responses on the endophyte performance. Furthermore, we posit that endophytes may protect the mutualism by the induction of plant defence hormone responses and antioxidants.