Role of Epichloë Endophytes in Improving Host Grass Resistance Ability and Soil Properties

Regulation of mineral elements in Hordeum brevisubulatum by Epichloë bromicola under Cd stress

In this study, wild barley (Hordeum brevisubulatum) infected (E+) and uninfected (E-) by Epichloë bromicola were used for hydroponic experiments during the seedling stage. Various attributes, such as the effect of fungal endophyte on the growth and development of wild barley, the absorption of cadmium (Cd) and mineral elements (Ca, Mg, Fe, Mn, Cu, Zn), subcellular distribution, and chemical forms were investigated under CdCl2 stress. The results showed that the fungal endophy significantly reduced the Ca content and percentage of plant roots under Cd stress. The Fe and Mn content of roots, the mineral element content of soluble fractions, and the stems in the pectin acid or protein-chelated state increased significantly in response to fungal endophy. Epichloë endophyte helped Cd2+ to enter into plants; and reduced the positive correlation of Ca-Fe and Ca-Mn in roots. In addition, it also decreased the correlation of soluble components Cd-Cu, Cd-Ca, Cd-Mg in roots, and the negative correlation between pectin acid or protein-chelated Cd in stems and mineral elements, to increase the absorbance of host for mineral elements. In conclusion, fungal endophy regulated the concentration and distribution of mineral elements, while storing more Cd2+ to resist the damage caused by Cd stress. The study could provide a ground for revealing the Cd tolerance mechanism of endophytic fungal symbionts.

Endophytes Alleviate Drought-Derived Oxidative Damage in Achnatherum inebrians Plants Through Increasing Antioxidants and Regulating Host Stress Responses

Endophytes generally increase antioxidant contents of plants subjected to environmental stresses. However, the mechanisms by which endophytes alter the accumulation of antioxidants in plant tissues are not entirely clear. We hypothesized that, in stress situations, endophytes would simultaneously reduce oxidative damage and increase antioxidant contents of plants and that the accumulation of antioxidants would be a consequence of the endophyte ability to regulate the expression of plant antioxidant genes. We investigated the effects of the fungal endophyte Epichloë gansuensis (C.J. Li & Nan) on oxidative damage, antioxidant contents, and expression of representative genes associated with antioxidant pathways in Achnatherum inebrians (Hance) Keng plants subjected to low (15%) and high (60%) soil moisture conditions. Gene expression levels were measured using RNA-seq. As expected, the endophyte reduced the oxidative damage by 17.55% and increased the antioxidant contents by 53.14% (on average) in plants subjected to low soil moisture. In line with the accumulation of antioxidants in plant tissues, the endophyte increased the expression of most plant genes associated with the biosynthesis of antioxidants (e.g., MIOX, crtB, gpx) while it reduced the expression of plant genes related to the metabolization of antioxidants (e.g., GST, PRODH, ALDH). Our findings suggest that endophyte ability of increasing antioxidant contents in plants may reduce the oxidative damage caused by stresses and that the fungal regulation of plant antioxidants would partly explain the accumulation of these compounds in plant tissues.

The Impact of Aboveground Epichloë Endophytic Fungi on the Rhizosphere Microbial Functions of the Host Melica transsilvanica

In nature, the symbiotic relationship between plants and microorganisms is crucial for ecosystem balance and plant growth. This study investigates the impact of Epichloë endophytic fungi, which are exclusively present aboveground, on the rhizosphere microbial functions of the host Melica transsilvanica. Using metagenomic methods, we analyzed the differences in microbial functional groups and functional genes in the rhizosphere soil between symbiotic (EI) and non-symbiotic (EF) plants. The results reveal that the presence of Epichloë altered the community structure of carbon and nitrogen cycling-related microbial populations in the host's rhizosphere, significantly increasing the abundance of the genes (porA, porG, IDH1) involved in the rTCA cycle of the carbon fixation pathway, as well as the abundance of nxrAB genes related to nitrification in the nitrogen-cycling pathway. Furthermore, the presence of Epichloë reduces the enrichment of virulence factors in the host rhizosphere microbiome, while significantly increasing the accumulation of resistance genes against heavy metals such as Zn, Sb, and Pb. This study provides new insights into the interactions among endophytic fungi, host plants, and rhizosphere microorganisms, and offers potential applications for utilizing endophytic fungi resources to improve plant growth and soil health.

Effect of Epichloë Endophyte on the Growth and Carbon Allocation of Its Host Plant Stipa purpurea under Hemiparasitic Root Stress

Epichloë endophytes not only affect the growth and resistance of their host plants but also confer nutrient benefits to parasitized hosts. In this study, we used Pedicularis kansuensis to parasitize Stipa purpurea, both with and without endophytic fungi, and to establish a parasitic system. In this study, endophytic fungal infection was found to increase the dry weight of the leaf, stem, and leaf sheath, as well as the plant height, root length, tiller number, aboveground biomass, and underground biomass of S. purpurea under root hemiparasitic stress. Meanwhile, the 13C allocation of the leaf sheaths and roots of S. purpurea increased as the density of P. kansuensis increased, while the 13C allocation of the leaf sheaths and roots of E+ S. purpurea was lower than that of E- S. purpurea. The 13C allocation of the stem, leaf sheath, and root of E+ S. purpurea was higher than that of its E- counterpart. Furthermore, the content of photosynthetic 13C and the 13C partition rate of the stems, leaves, roots, and entire plant of S. purpurea and P. kansuensis transferred from S. purpurea increased as the density of P. kansuensis increased. These results will generate new insights into the potential role of symbiotic microorganisms in regulating the interaction between root hemiparasites and their hosts.

Cultivable Endophyte Resources in Medicinal Plants and Effects on Hosts

With the increasing demand for medicinal plants and the increasing shortage of resources, improving the quality and yield of medicinal plants and making more effective use of medicinal plants has become an urgent problem to be solved. During the growth of medicinal plants, various adversities can lead to nutrient loss and yield decline. Using traditional chemical pesticides to control the stress resistance of plants will cause serious pollution to the environment and even endanger human health. Therefore, it is necessary to find suitable pesticide substitutes from natural ingredients. As an important part of the microecology of medicinal plants, endophytes can promote the growth of medicinal plants, improve the stress tolerance of hosts, and promote the accumulation of active components of hosts. Endophytes have a more positive and direct impact on the host and can metabolize rich medicinal ingredients, so researchers pay attention to them. This paper reviews the research in the past five years, aiming to provide ideas for improving the quality of medicinal plants, developing more microbial resources, exploring more medicinal natural products, and providing help for the development of research on medicinal plants and endophytes.

Comparative Transcriptomics Profiling of Perennial Ryegrass Infected with Wild Type or a ΔvelA Epichloë festucae Mutant Reveals Host Processes Underlying Mutualistic versus Antagonistic Interactions

Epichloë species form bioprotective endophytic symbioses with many cool-season grasses, including agriculturally important forage grasses. Despite its importance, relatively little is known about the molecular details of the interaction and the regulatory genes involved. VelA is a key global regulator in fungal secondary metabolism and development. In previous studies, we showed the requirement of velA for E. festucae to form a mutualistic interaction with Lolium perenne. We showed that VelA regulates the expression of genes encoding proteins involved in membrane transport, fungal cell wall biosynthesis, host cell wall degradation, and secondary metabolism, along with several small-secreted proteins in Epichloë festucae. Here, by a comparative transcriptomics analysis on perennial ryegrass seedlings and mature plants, which are endophyte free or infected with wild type (mutualistic interaction) or mutant ΔvelA E. festucae (antagonistic or incompatible interaction), regulatory effects of the endophytic interaction on perennial ryegrass development was studied. We show that ΔvelA mutant associations influence the expression of genes involved in primary metabolism, secondary metabolism, and response to biotic and abiotic stresses compared with wild type associations, providing an insight into processes defining mutualistic versus antagonistic interactions.

Parthenium hysterophorus's Endophytes: The Second Layer of Defense against Biotic and Abiotic Stresses

Parthenium hysterophorus L. is considered an obnoxious weed due to its rapid dispersal, fast multiplications, and agricultural and health hazards. In addition to its physio-molecular and phytotoxic allelochemical usage, this weed most probably uses endophytic flora as an additional line of defense to deal with stressful conditions and tolerate both biotic and abiotic stresses. The aim of this article is to report the diversity of endophytic flora (fungi and bacteria) in P. hysterophorus and their role in the stress mitigation (biotic and abiotic) of other important crops. Various endophytes were reported from P. hysterophorus and their roles in crops evaluated under biotic and abiotic stressed conditions. These endophytes have the potential to alleviate different stresses by improving crops/plants growth, development, biomass, and photosynthetic and other physiological traits. The beneficial role of the endophytes may be attributed to stress-modulating enzymes such as the antioxidants SOD, POD and APX and ACC deaminases. Additionally, the higher production of different classes of bioactive secondary metabolites, i.e., flavonoids, proline, and glutathione may also overcome tissue damage to plants under stressed conditions. Interestingly, a number of medicinally important phytochemicals such as anhydropseudo-phlegmcin-9, 10-quinone-3-amino-8-O methyl ether 'anhydropseudophlegmacin-9, 10-quinone-3-amino-8-Omethyl ether were reported from the endophytic flora of P. hysterophorus. Moreover, various reports revealed that fungal and bacterial endophytes of P. hysterophorus enhance plant growth-promoting attributes and could be added to the consortium of biofertilizers.

Abscisic Acid May Play a Critical Role in the Moderating Effect of Epichloë Endophyte on Achnatherum inebrians under Drought Stress

Water scarcity is a major constraint that adversely affects plant development and growth. Abscisic acid (ABA) is a plant stress hormone that is rapidly synthesized and can induce stomatal closure to conserve water, thereby alleviating the drought stress of plants. The Epichloë endophyte enhances the drought tolerance of Achnatherum inebrians (drunken horse grass, DHG). To better understand how the Epichloë endophyte enhances drought tolerance, DHG plants without (EF) and with (EI), an Epichloë endophyte, were grown under 20% and 60% soil water conditions (SWC), and the leaves of the three treatments of EF and EI plants were sprayed with ABA solution (1 mg/L); fluridone (FLU), the ABA biosynthesis inhibitor solution (1 mg/L); and distilled water, respectively. Four-weeks later, the results indicated that the exogenous ABA application promoted plant growth, stomatal conductance, and photosynthetic rate, while the opposite effect occurred with plants sprayed with FLU. The differences between EI and EF plants in tiller number, height, chlorophyll content, stomata conductance, and photosynthetic rate were highest when sprayed with ABA. Thus, it is concluded that ABA might be involved in the moderating effect of Epichloë endophytes on DHG plants exposed to drought by maintaining growth and improving photosynthetic efficiency.

Epichloë Increases Root Fungal Endophyte Richness and Alters Root Fungal Endophyte Composition in a Changing World

Plants harbor a variety of fungal symbionts both above- and belowground, yet little is known about how these fungi interact within hosts, especially in a world where resource availability is changing due to human activities. Systemic vertically transmitted endophytes such as Epichloë spp. may have particularly strong effects on the diversity and composition of later-colonizing symbionts such as root fungal endophytes, especially in primary successional systems. We made use of a long-term field experiment in Great Lakes sand dunes to test whether Epichloë colonization of the dune-building grass, Ammophila breviligulata, could alter fungal root endophyte species richness or community composition in host plants. We also tested whether nitrogen addition intensified the effects of Epichlöe on the root endophyte community. We found that Epichloë increased richness of root endophytes in Ammophila by 17% overall, but only shifted community composition of root endophytes under nitrogen-enriched conditions. These results indicate that Epichlöe acts as a key species within Ammophila, changing richness and composition of the root mycobiome and integrating above- and belowground mycobiome interactions. Further, effects of Epichloë on root endophyte communities were enhanced by N addition, indicating that this fungal species may become even more important in future environments.

Increase in Cd Tolerance through Seed-Borne Endophytic Fungus Epichloë gansuensis Affected Root Exudates and Rhizosphere Bacterial Community of Achnatherum inebrians

Soil cadmium (Cd) pollution is a serious environmental problem imperiling food safety and human health. The endophyte Epichloë gansuensis can improve the tolerance of Achnatherum inebrians to Cd stress. However, it is still unknown whether and how the endophyte helps host plants build up a specific bacterial community when challenged by CdCl2. In this study, the responses of the structure and function of bacterial community and root exudates of E+ (E. gansuensis infected) and E- (E. gansuensis uninfected) plants to Cd stress were investigated. Analysis of bacterial community structure indicated that the rhizosphere bacterial community predominated over the root endosphere bacterial community in enhancing the resistance of CdCl2 in a host mediated by E. gansuensis. E+ plant strengthened the interspecific cooperation of rhizosphere bacterial species. Moreover, the analysis of root exudates demonstrated E. gansuensis and increased the contents of organic acids and amino acids under Cd stress, and most root exudates were significantly correlated with rhizosphere bacteria. These results suggested that E. gansuensis employed a specific strategy to recruit distinct rhizosphere bacterial species and relevant functions by affecting root exudates to improve the tolerance of the host to Cd stress. This study provides a firm foundation for the potential application of symbionts in improving phytostabilization efficiency.

Comprehensive Analysis of Transcriptome and Metabolome Elucidates the Molecular Regulatory Mechanism of Salt Resistance in Roots of Achnatherum inebrians Mediated by Epichloë gansuensis

Salinization of soil is a major environmental risk factor to plant functions, leading to a reduction of productivity of crops and forage. Epichloë gansuensis, seed-borne endophytic fungi, establishes a mutualistic symbiotic relationship with Achnatherum inebrians and confers salt tolerance in the host plants. In this study, analysis of transcriptome and metabolome was used to explore the potential molecular mechanism underlying the salt-adaptation of A. inebrians roots mediated by E. gansuensis. We found that E. gansuensis played an important role in the gene expression of the host’s roots and regulated multiple pathways involved in amino acid metabolism, carbohydrate metabolism, TCA cycle, secondary metabolism, and lipid metabolism in the roots of A. inebrians. Importantly, E. gansuensis significantly induced the biological processes, including exocytosis, glycolytic process, fructose metabolic process, and potassium ion transport in roots of host plants at transcriptional levels, and altered the pathways, including inositol phosphate metabolism, galactose metabolism, starch, and sucrose metabolism at metabolite levels under NaCl stress. These findings provided insight into the molecular mechanism of salt resistance in roots of A. inebrians mediated by E. gansuensis and could drive progress in the cultivation of new salt-resistance breeds with endophytes.

Identification of Three Epichloë Endophytes from Hordeum bogdanii Wilensky in China

Cool season grasses often form reciprocal symbiotic relationships with endophytic fungal species in genus Epichloë. In this study, we characterized three fungal endophytes isolated from the grass Hordeum bogdanii native to northwest China. Based on morphological characteristics and phylogenetic analyses of tefA, tubB, and actG sequences, we identified them as Epichloë sp. HboTG-2 (H. bogdanii Taxonomic Group 2: E. bromicola × E. typhina). Alkaloid synthesis related genes analysis showed that Epichloë sp. HboTG-2 may have the ability only to produce peramine which is toxic to insects but not to animals. In the process of this study, we did not observe sexual structures or epiphyllous growth on leaves of infected plants.

Transcriptome analysis of Epichloë strains in tall fescue in response to drought stress

Epichloë coenophiala, a systemic fungal symbiont (endophyte) of tall fescue (Lolium arundinaceum), has been documented to confer to this grass better persistence than plants lacking the endophyte, especially under stress conditions such as drought. The response, if any, of the endophyte to imposition of stress on the host plant has not been characterized previously. Therefore, we investigated effects on gene expression by E. coenophiala and a related endophyte when plant-endophyte symbiota were subjected to acute water-deficit stress. Plants harboring different endophyte strains were grown in sand in the greenhouse, then half were deprived of water for 48 h and the other half were watered controls. RNA was isolated from different plant tissues, and mRNA sequencing (RNA-seq) was conducted to identify genes that were differentially expressed comparing stress treatment with control. We compared two different plants harboring the common toxic E. coenophiala strain (CTE) and two non-ergot-alkaloid-producing Epichloë strains in tall fescue pseudostems, and in a second experiment we compared responses of E. coenophiala CTE in plant pseudostem and crown tissues. The endophytes responded to the stress with increased expression of genes involved in oxidative stress response, oxygen radical detoxification, C-compound carbohydrate metabolism, heat shock, and cellular transport pathways. The magnitude of fungal gene responses during stress varied among plant-endophyte symbiota. Responses in pseudostems and crowns involved some common pathways as well as some tissue-specific pathways. The fungal response to water-deficit stress involved gene expression changes in similar pathways that have been documented for plant stress responses, indicating that Epichloë spp. and their host plants either coordinate stress responses or separately activate similar stress response mechanisms that work together for mutual protection.

Interactive Effects of Epichloë Endophytes and Arbuscular Mycorrhizal Fungi on Saline-Alkali Stress Tolerance in Tall Fescue

Epichloë endophytes and arbuscular mycorrhizal fungi (AMFs) are two important symbiotic microorganisms of tall fescue (Lolium arundinaceum). Our research explores the combined effects of endophytes and AMF on saline-alkali stress. The finding revealed that a significant interaction between Epichloë endophytes and AMF, and saline-alkali stress occurred in the growth and physiological parameters of tall fescue. Endophyte infection significantly enhanced tall fescue resistance to saline-alkali stress by increasing shoot and root biomass and nutrient uptake (organic carbon, total nitrogen, and total phosphorus concentration), and accumulating K⁺ while decreasing Na⁺ concentration. Furthermore, the beneficial effect of endophytes was enhanced by the beneficial AMF, Claroideoglomus etunicatum (CE) but was reduced by the detrimental AMF, Funneliformis mosseae (FM). Our findings highlight the importance of interactions among multiple microorganisms for plant performance under saline-alkali stress.

Effect of Fungal Endophyte Epichloë bromicola Infection on Cd Tolerance in Wild Barley (Hordeum brevisubulatum)

Hydroponic Hordeum brevisubulatum (wild barley) was used as material in the greenhouse to study the effects of endophyte infection on plant growth, Cd absorption and transport, subcellular distribution, and Cd chemical forms under CdCl2 stress. Endophytic fungi respond positively to chlorophyll content and photosynthetic efficiency under Cd stress. The order of Cd absorption in different parts of the plant was: roots > stems > leaves. Endophyte infection increased the plant’s absorption and transport of Cd while causing a significant difference in the stem, which was associated with the distribution density of endophyte hyphae. The proportion of organelle Cd in endophyte-infected wild barley was significantly higher, which facilitated more Cd transport to aboveground. Cd stress showed a slight effect on the chemical forms of Cd in leaves. The proportion of phosphate, oxalate, and residual Cd increased in the stem. Cd existed in the form of inorganic salt, organic acid, pectin, and protein in roots. Endophyte infection reduced the Cd content of the more toxic chemical forms to protect the normal progress of plant physiological functions. Therefore, the isolation of cell walls and vacuoles is a key mechanism for plant Cd tolerance and detoxification. As endophyte infections have more ability to absorb Cd in plants, H. brevisubulatum−Epichloë bromicola symbionts can improve heavy metal contaminated soil and water.

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

Fungal endophytes have been extensively found in most terrestrial plants. This type of plant–microorganism symbiosis generates many benefits for plant growth by promoting nutrient availability, uptake, and resistance to environmental disease or stress. Recent studies have reported that fungal endophytes have a potential impact on plant litter decomposition, but the mechanisms behind its effect are not well understood. We proposed a hypothesis that the impacts of fungal endophytes on litter decomposition are not only due to a shift in the symbiont-induced litter quality but a shift in soil microenvironment. To test this hypothesis, we set-up a field trial by planting three locally dominant grass species (wild barley, drunken horse grass, and perennial ryegrass) with Epichloë endophyte-infected (E+) and -free (E-) status, respectively. The aboveground litter and bulk soil from each plant species were collected. The litter quality and the soil biotic and abiotic parameters were analyzed to identify their changes across E+ and E- status and plant species. While Epichloë endophyte status mainly caused a significant shift in soil microenvironment, plant species had a dominant effect on litter quality. Available nitrogen (N) and phosphorus (P) as well as soil organic carbon and microbial biomass in most soils with planting E+ plants increased by 17.19%, 14.28%, 23.82%, and 11.54%, respectively, in comparison to soils with planting E- plants. Our results confirm that fungal endophytes have more of an influence on the soil microenvironment than the aboveground litter quality, providing a partial explanation of the home-field advantage of litter decomposition.

Elucidating the Molecular Mechanisms by which Seed-Borne Endophytic Fungi, Epichloë gansuensis, Increases the Tolerance of Achnatherum inebrians to NaCl Stress

Seed-borne endophyte Epichloë gansuensis enhance NaCl tolerance in Achnatherum inebrians and increase its biomass. However, the molecular mechanism by which E. gansuensis increases the tolerance of host grasses to NaCl stress is unclear. Hence, we firstly explored the full-length transcriptome information of A. inebrians by PacBio RS II. In this work, we obtained 738,588 full-length non-chimeric reads, 36,105 transcript sequences and 27,202 complete CDSs from A. inebrians. We identified 3558 transcription factors (TFs), 15,945 simple sequence repeats and 963 long non-coding RNAs of A. inebrians. The present results show that 2464 and 1817 genes were differentially expressed by E. gansuensis in the leaves of E+ and E− plants at 0 mM and 200 mM NaCl concentrations, respectively. In addition, NaCl stress significantly regulated 4919 DEGs and 502 DEGs in the leaves of E+ and E− plants, respectively. Transcripts associated with photosynthesis, plant hormone signal transduction, amino acids metabolism, flavonoid biosynthetic process and WRKY TFs were differentially expressed by E. gansuensis; importantly, E. gansuensis up-regulated biology processes (brassinosteroid biosynthesis, oxidation–reduction, cellular calcium ion homeostasis, carotene biosynthesis, positive regulation of proteasomal ubiquitin-dependent protein catabolism and proanthocyanidin biosynthesis) of host grass under NaCl stress, which indicated an increase in the ability of host grasses’ adaptation to NaCl stress. In conclusion, our study demonstrates the molecular mechanism for E. gansuensis to increase the tolerance to salt stress in the host, which provides a theoretical basis for the molecular breed to create salt-tolerant forage with endophytes.

Influence of Tall Fescue Epichloë Endophytes on Rhizosphere Soil Microbiome

Tall fescue (Lolium arundinaceum (Schreb.) S.J. Darbyshire) often forms a symbiotic relationship with fungal endophytes (Epichloë coenophiala), which provides increased plant performance and greater tolerance to environmental stress compared to endophyte-free tall fescue. Whether this enhanced performance of tall fescue exclusively results from the grass–fungus symbiosis, or this symbiosis additionally results in the recruitment of soil microbes in the rhizosphere that in turn promote plant growth, remain a question. We investigated the soil bacterial and fungal community composition in iron-rich soil in the southeastern USA, and possible community shifts in soil microbial populations based on endophyte infection in tall fescue by analyzing the 16s rRNA gene and ITS specific region. Our data revealed that plant-available phosphorus (P) was significantly (p < 0.05) influenced by endophyte infection in tall fescue. While the prominent soil bacterial phyla were similar, a clear fungal community shift was observed between endophyte-infected (E+) and endophyte-free (E−) tall fescue soil at the phylum level. Moreover, compared to E− soil, E+ soil showed a greater fungal diversity at the genus level. Our results, thus, indicate a possible three-way interaction between tall fescue, fungal endophyte, and soil fungal communities resulting in improved tall fescue performance.

Influence of Interactions between Nitrogen, Phosphorus Supply and Epichloёbromicola on Growth of Wild Barley (Hordeum brevisubulatum)

Epichloë endophytes are biotrophic fungi that establish mutualistic symbiotic relationship with grasses and affect performance of the host under different environments. Wild barley (Hordeum brevisubulatum) is an important forage grass and often infected by Epichloë&nbsp;bromicola, thus showing tolerances to stresses. Since the plant growth correlates with both microbial infection and nutrient stoichiometry, this study was performed to investigate whether the function of Epichloë&nbsp;bromicola endophyte to improve host growth depend upon the nitrogen (N), phosphorus (P) fertilization. Epichloë-infected (E+) and Epichloë-free (E-) wild barley plants were subjected to nine types of mixed N (0.2 mM, 3 mM, 15 mM) and P (0.01 mM, 0.1 mM, 1.5 mM) levels treatments for 90 d to collect plant samples and determine multiple related indexes. We found that E. bromicola and N, P additions positively affected seed germination. Further, E. bromicola significantly enhanced chlorophyll content and root metabolic activity under N-deficiency, and meanwhile, might alter allocation of photosynthate under different conditions. The contents of N, P and stoichiometry of C:N:P of E+ plants were significantly higher than that of E- under nutrient deficiency, but contrary results were observed under adequate nutrients. Therefore, we propose that the growth-promoting ability of E. bromicola is closely correlated with N and P additional levels. Under low N, P additions, positive roles of endophyte are significant as opposed to negative roles under high N, P additions.

Applications of endophytic microbes in agriculture, biotechnology, medicine, and beyond

Endophytes are emerging as integral components of plant microbiomes. Some of them play pivotal roles in plant development and plant responses to pathogens and abiotic stresses, whereas others produce useful and/or interesting secondary metabolites. The appreciation of their abilities to affect plant phenotypes and produce useful compounds via genetic and molecular interactions has paved the way for these abilities to be exploited for health and welfare of plants, humans and ecosystems. Here we comprehensively review current and potential applications of endophytes in the agricultural, pharmaceutical, and industrial sectors. In addition, we briefly discuss the research objectives that should be focused upon in the coming years in order for endophytes and their metabolites to be fully harnessed for potential use in diverse areas.

A Systematic Review on the Effects of Epichloë Fungal Endophytes on Drought Tolerance in Cool-Season Grasses

Symptomless fungal endophytes in the genus Epichloë are repeatedly mentioned to increase tolerance of cool-season grasses to a wide range of environmental stress factors, mainly drought. However, the generality of this idea is challenged because (i) most studies have been conducted on two economically important forage grasses {tall fescue [Festuca arundinacea (Schreb.) Dumort] and perennial ryegrass (Lolium perenne L.)}, (ii) endophyte-mediated mechanisms and effects on plant responses to drought have shown to be highly variable across species, and that (iii) symbiosis incidence in plant populations occurring in extremely arid environments is usually low. We question this idea by reviewing the existing information about Epichloë fungal endophyte effects on drought tolerance in cool-season grasses. We combined standard review, vote counting, and calculation of effect sizes to synthesize the literature, identify information gaps, and guide future research. The total number of studies was higher for domesticated than for wild species, a ratio that was balanced when papers with data quality for effect size calculus were considered. After the drought, endophyte-infected plants accumulated more aboveground and belowground biomass than non-infected counterparts, while no effect on tillering was observed. However, these effects remained significant for wild (even on tillering) but not for domesticated species. Interestingly, despite the continuous effort in determining physiological mechanisms behind the endophyte effects, no studies evaluated plant fecundity as a measure of ecological fitness nor vital rates (such as survival) as to escalate individual-level variables to population. Together with the high variability in results, our work shows that generalizing a positive effect of fungal endophytes in plant tolerance to drought may be misleading. Future studies combining field surveys with manipulative experiments would allow us to unravel the role of fungal endophytes in plant adaptation by considering the evolutionary history of species and populations to the different ecological contexts.