Comparison of Plant Metabolites in Root Exudates of Lolium perenne Infected with Different Strains of the Fungal Endophyte Epichloë festucae var. lolii

Abstract

Lolium perenne infected with the fungal endophyte Epichloë festucae var. lolii have specific, endophyte strain-dependent, chemical phenotypes in their above-ground tissues. Differences in these chemical phenotypes have been largely associated with classes of fungal-derived alkaloids which protect the plant against many insect pests. However, the use of new methodologies, such as various omic techniques, has demonstrated that many other chemical changes occur in both primary and secondary metabolites. Few studies have investigated changes in plant metabolites exiting the plant in the form of root exudates. As root exudates play an essential role in the acquisition of nutrients, microbial associations, and defense in the below-ground environment, it is of interest to understand how plant root exudate chemistry is influenced by the presence of strains of a fungal endophyte. In this study, we tested the influence of four strains of E. festucae var. lolii (E+ (also known as Lp19), AR1, AR37, NEA2), and uninfected controls (E−), on L. perenne growth and the composition of root exudate metabolites. Root exudates present in the hydroponic water were assessed by untargeted metabolomics using Accurate-Mass Quadrupole Time-of-Flight (Q–TOF) liquid chromatography–mass spectrometry (LC–MS). The NEA2 endophyte strain resulted in the greatest plant biomass and the lowest endophyte concentration. We found 84 metabolites that were differentially expressed in at least one of the endophyte treatments compared to E− plants. Two compounds were strongly associated with one endophyte treatment, one in AR37 (m/z 135.0546 RT 1.17), and one in E+ (m/z 517.1987 RT 9.26). These results provide evidence for important changes in L. perenne physiology in the presence of different fungal endophyte strains. Further research should aim to connect changes in root exudate chemical composition with soil ecosystem processes.

Epichloë Fungal Endophytes Have More Host-Dependent Effects on the Soil Microenvironment than on the Initial Litter Quality

“…It is though difficult to identify direct or indirect relationships between them based on our current data set, such a correlation may suggest some potential processes. For instance, studies have shown that the quality and the quantity of root exudates of plants can experience great changes when they are infected by fungal endophytes [ 72 , 73 ], which can consequently lead to a shift in microbe-mediated soil nutrient pools. Alternatively, this linkage possibly resulted from interactions between the plant–soil microbiome for nutrient competence and transmissions [ 74 ].…”

Costs, Benefits, Parasites and Mutualists: The Use and Abuse of the Mutualism–Parasitism Continuum Concept for “Epichloë” Fungi

“…We know from metabolomic and proteomic studies that these endophytes have profound effects on the plant's metabolism, biochemistry (see, e.g., Rasmussen, Parsons, Fraser, et al 2008;Rasmussen et al 2007;Patchett and Newman 2021;Geddes-McAlister et al 2020) and nutrient uptake (see, e.g., Soto-Barajas et al 2016, and references therein). Another empirically well-supported advantage conferred by the endophyte is drought resistance (see, e.g., Hosseini et al 2016, and references therein).…”

Endophytic Fungi: An Effective Alternative Source of Plant-Derived Bioactive Compounds for Pharmacological Studies

“…The term "endophytic fungi" refers to fungi that live in plant tissues throughout the entire or partial life cycle by establishing a mutually beneficial symbiotic relationship with its host plant without causing any adverse effect or disease [1,2]. They are natural components of the plant micro-ecosystem that positively affect the physiological activities of the host plant in several ways, including producing hormones such as indoleacetic acid, biosynthesizing and acquiring nutrients for plant growth and development, secreting stress-adaptor metabolites to protect the host plant from the invasion of herbivores, pathogens, and improving the host's adaptability to abiotic stressors.…”