Project description:Perennial ryegrass (Lolium perenne L.) is the most cultivated cool-season grass worldwide with crucial roles in carbon fixation and fodder for livestock. Protection of these grasses from biotic and abiotic factors are dictated through a mutually-beneficial relationship with endophytes that confer bioprotective properties. Common endophytes of the genus Epichloë promote the health and survival of cool-season forages greases and protect the plants from fluctuating environmental conditions. Climate change, and specifically, a steady increase in atmospheric CO2 levels, presents a dramatic and imminent threat faced by our ecosystem, which poses substantial pressures on plant health and survival. Defining the relationships between endophytes and the host plant may uncover mechanisms of bioprotection, which can be exploited to promote adaptable plant systems in rising CO2 conditions. In this study, we quantify changes in biomass and seed production of L. perenne L. at 400 and 800 ppm CO2 and identify endophyte-specific changes in metabolite production. Additionally, we discover protein-level changes from both the endophyte and plant perspectives, which underscore the compatible relationship between a common, natural endophyte and L. perenne L., compared to an incompatible and detrimental relationship the epichloid strain, AR1. Taken together, our data set provides new understanding into the intricacy of compatibility between endophyte and host from multiple molecular levels and suggests opportunity to promote plant robustness and survivability in rising CO2 environmental conditions through application of bioprotective epichloid strains.