Interactive effects of water stress and powdery mildew(Blumeria graminis) on the alkaloid production of Achnatherum inebrians infected by Epichlo? endophyte

正Dear Editor,Achnatherum inebrians,also known as drunken horse grass(DHG),is a toxic perennial bunch grass that can be infected by Epichlo?gansuensis or E.inebrians(Chen et al.,2015).It is well known that Epichlo?fungal endophytes can protect their host plants from herbivores by producing different classes of alkaloids.A recent trial demonstrated that sheep exhibited notable toxicity symptoms by directly feeding with endophyte-infected(E+)A.inebrians(Liang et al.,2017).     

Epichloë endophyte affects the root colonization pattern of belowground symbionts in a wild grass

Plants host multiple symbionts that interact with each other affecting plant performance and regulating their establishment. Here, we analyzed how the association with Epichloë endophytes affects belowground colonization by Dark Septate Endophytes (DSE) and arbuscular mycorrhizal fungi (AMF) in the grass Bromus auleticus. Epichloë-symbiotic (E+) and Epichloë-non symbiotic (E−) plants were sampled from a long-term experimental plot and colonization structures were analyzed in the roots. We also examined the influence of Epichloë exudates on the in vitro growth of DSE Microdochium bolleyi isolated from roots. Epichloë symbiosis increased AMF colonization, although differences were not significant. Despite the lack of differences in total DSE colonization, in concordance with in vitro findings, a higher significant abundance of microsclerotia was observed in E+ plants. A negative correlation between total mycorrhizal and DSE was found. Our findings show a more uniform root colonization pattern in E+ plants, suggesting a root symbiosis modulating role.     

Metabolomics insights into the mechanism by which Epichloë gansuensis endophyte increased Achnatherum inebrians tolerance to low nitrogen stress

Plant and Soil - Epichloë gansuensis increases the tolerance of host plants to abiotic stress. However, little is known about the mechanism by which E. gansuensis improves grass growth under...     

Genetic structure of natural populations of the grass endophyte Epichloë festucae in semiarid grasslands

Plants of red fescue (Festuca rubra), a commercially important turf grass, are infected by the fungal endophyte Epichloë festucae in semiarid natural grasslands, known as dehesas, in western Spain. We used amplified fragment length polymorphism (AFLP) markers to analyse the genetic polymorphism existing in two natural populations of Epichloë festucae. Linkage disequilibrium and the presence of clonal lineages indicated that nonrecombinant asexual reproduction predominates in both populations. However, most genetic variation detected was found to occur within populations, with only a moderate amount of genetic differentiation between populations (F_ST: 0.197). Overall, the study suggests that dehesa grasslands are useful reservoirs of Epichloë festucae endophytes, and provides information on population structure which is relevant to design sampling strategies.     

Effects of Epichloë gansuensis on root-associated fungal communities of Achnatherum inebrians under different growth conditions

This study was conducted to investigate how Epichloë gansuensis endophyte and soil disturbance affect root-associated fungi (RAF) of Achnatherum inebrians (drunken horse grass, DHG), using Illumina sequencing techniques. The rhizosphere soil of wild endophyte-infected (W-EI) DHG had significantly (P < 0.05) higher available phosphorous and potassium, total organic matter, ammonium and nitrate nitrogen than cultivated soil. In addition, the rhizosphere soil of endophyte-infected DHG had significantly (P < 0.05) lower pH and nitrate nitrogen, and higher available phosphorous, than endophyte-free DHG under cultivated conditions. The sequencing provided a total of 54,413 sequences and these were assigned into 190 operational taxonomic units (OTUs) with 97% similarity. Ascomycota was the most dominant phylum in roots of three DHG populations. W-EI DHG had significantly (P < 0.05) higher RAF diversity than cultivated endophyte-infected (C-EI) DHG. The presence of endophyte significantly (P < 0.05) decreased RAF diversity under cultivation. The principal component analysis (PCA) and sample similarity analysis results indicated that both endophyte and soil disturbance could bring changes to RAF community composition. The RDA results demonstrated the RAF of W-EI DHG were positively correlated with soil properties, and the RAF of cultivated DHG roots were negatively correlated with soil properties. This study demonstrated that both endophyte and soil disturbance resulted in changes to the RAF communities.     

Variation in horizontal and vertical transmission of the endophyte Epichloë elymi infecting the grass Elymus hystrix

Systemic fungal endophytes (Clavicipitaceae) of grasses reproduce sexually when the fungus forms stromata and contagious ascospores, or asexually by vertical transmission of hyphae into seeds and seedlings. Vertical transmission is predicted to favor reduced virulence compared with horizontal transmission in systems with both types of transmission. Here, variation in vertical and horizontal transmission and its potential heritability in a host grass-endophyte interaction, Elymus hystrix infected with Epichlo? elymi, were examined in natural populations and two common garden experiments using field-collected host tillers and seed progeny of maternal plants with known infection phenotypes. Transmission mode exhibited year-to-year variation in field and common garden environments. In the common garden there were consistent differences among maternal plant families in stroma production and significant correlations between stroma production in the common garden and in natural populations. Transmission mode differed among maternal families, spanning a continuum from pure vertical transmission to a high proportion of stroma production and horizontal transmission potential. Vertical transmission to seeds occurred at high rates in all maternal families regardless of their stroma production. Observed patterns of variation indicate that endophyte transmission mode and correlated changes in virulence can respond to selection by biotic and abiotic factors.     

Erratum to: The fungal endophyte Epichloë gansuensis increases NaCl-tolerance in Achnatherum inebrians through enhancing the activity of plasma membrane H+-ATPase and glucose-6-phosphate dehydrogenase

Science China Life Sciences - 1. In the results, we mistakenly described the information of Figure 9B. The correct sentence should be “The factor 1 and factor 2 explained 71.30% and 16.68% of...     

Effect of Epichloë gansuensis endophyte and transgenerational effects on the water use efficiency,nutrient and biomass accumulation of Achnatherum inebrians under soil water deficit

Plant and Soil - This study explored the effects of Epichloë gansuensis endophyte on water use efficiency (WUE), nutrient content and biomass accumulation of Achnatherum inebrians (drunken...     

The fungal endophyte Epichloë gansuensis increases NaCl-tolerance in Achnatherum inebrians through enhancing the activity of plasma membrane H+-ATPase and glucose-6-phosphate dehydrogenase

Salt stress negatively affects plant growth, and the fungal endophyte Epichlo?gansuensis increases the tolerance of its host grass species, Achnatherum inebrians, to abiotic stresses. In this work, we first evaluated the effects of E. gansuensis on glucose-6-phosphate dehydrogenase(G6PDH) and plasma membrane(PM) H~+-ATPase activity of Achnatherum inebrians plants under varying NaCl concentrations. Our results showed that the presence of E. gansuensis increased G6 PDH, PM H~+-ATPase,superoxide dismutase and catalase activity to decrease O_2~(·–), H_2O_2 and Na+contents in A. inebrians under NaCl stress, resulting in enhanced salt tolerance. In addition, the PM NADPH oxidase activity and NADPH/NADP+ratios were all lower in A. inebrians with E. ganusensis plants than A. inebrians plants without this endophyte under NaCl stress. In conclusion, E. gansuensis has a positive role in improving host grass yield under NaCl stress by enhancing the activity of G6PDH and PM H~+-ATPase to decrease ROS content. This provides a new way for the selection of stress-resistant and high-quality forage varieties by the use of systemic fungal endophytes.     

Mixed inoculation alters infection success of strains of the endophyte Epichloë bromicola on its grass host Bromus erectus

Within-host competition in multiply infected hosts is considered an important component of host-parasite interactions, but experimental studies on the dynamics of multiple infections are still rare. We measured the infection frequencies of four strains of the fungal endophyte Epichloë bromicola on two genotypes of its host plant Bromus erectus after single- and double-strain inoculation. Double-strain inoculations resulted in fewer double, but more single, infections than expected on the basis of infection frequencies in single-strain inoculations. In most cases, only one of the two strains established an infection, and strains differed in their overall competitive ability. This pattern resembles the mutual exclusion scenarios in some theoretical models of parasite evolution. In addition, competitive ability varied with host genotype, which may represent a mechanism for the coexistence of strains in a population. Hence, considering the genetic variation in both host and parasite may be important for a better understanding of within-host dynamics and their role in epidemiology or (co)evolution.     

Epichloë gansuensis endophyte-infection alters soil enzymes activity and soil nutrients at different growth stages of Achnatherum inebrians

Plant and Soil - Epichloë endophytes are a unique model system for the study of the linkages between organisms above and belowground in ecosystems. However, the impact of Epichloë...     

An important role for secreted esterase in disease establishment of the wheat powdery mildew fungus Blumeria graminis f. sp. tritici

The activity of esterase secreted by conidia of wheat powdery mildew fungus, Blumeria graminis f.?sp. tritici, was assayed using indoxyl acetate hydrolysis, which generates indigo blue crystals. Mature, ungerminated, and germinating conidia secrete esterase(s) on artificial media and on plant leaf surfaces. The activity of these esterases was inhibited by diisopropyl fluorophosphate, which is selective for serine esterases. When conidia were inoculated on wheat leaves pretreated with diisopropyl fluorophosphate, both appressorial germ tube differentiation and symptom development were significantly impaired, indicating an important role of secreted serine esterases in wheat powdery mildew disease establishment.     

Soil microbial and chemical responses to foliar Epichloë fungal infection in Lolium perenne,Hordeum brevisubulatum and Achnatherum inebrians

We tested whether the host species identity in grass-Epichloë symbioses affected soil chemical and microbial properties. We grew endophyte infected (E+) and endophyte free (E−) Lolium perenne, Hordeum brevisubulatum and Achnatherum inebrians for 18 months in field plots. In E+ soil of all three grasses, available phosphorus was lower whereas total soil nitrogen was higher. Endophyte effects on soil pH, microbial biomass nitrogen, total carbon and organic carbon as well as bacteria and fungi abundance were host species dependent. Ammonia oxidizing bacteria abundance was higher in E+ soils for all species. Bacterial community composition of E+ and E− soils were different only for Lolium perenne with soil pH being the key factor. Fungal community composition of E+ and E− soils was not different for the three grasses. This study confirmed that the effects of foliar Epichloë infection on belowground properties depended on host species identity.     

Effect of the fungal endophyte Epichloë bromicola on polyamines in wild barley (Hordeum brevisubulatum) under salt stress

Plant and Soil - The endophytic fungus Epichloë bromicola forms mutualistic symbiotic associations with wild barley (Hordeum brevisubulatum) in the saline-alkali areas of northwestern China....     

Epichloë endophyte effects on leaf blotch pathogen (Rhynchosporium sp.) of tall fescue (Schedonorus phoenix) vary among grass origin and environmental conditions

ABSTRACT

Background

Systemic Epichloë endophytes are common fungal symbionts of many cool-season grasses. They are known for their capability of increasing host plant tolerance against biotic and abiotic stressors, including grass pathogens. However, results on endophyte-mediated disease resistance have been ambiguous, and the underlying mechanisms of disease resistance remain unknown.     

Functional analysis of a beta-1,6-glucanase gene from the grass endophytic fungus Epichloë festucae

β-1,6-glucanases degrade the polysaccharide β-1,6-glucan, a cell wall component in some filamentous fungi. A single copy of a β-1,6-glucanase gene, designated gcnA, was identified in each of the grass endophytic fungi Neotyphodium lolii and Epichloë festucae. Phylogenetic analysis indicates that the GcnA protein is a member of glycosyl hydrolase family 5, and is closely related to fungal β-1,6-glucanases implicated in mycoparasitism. The E. festucae gcnA gene was expressed in mycelium grown in culture and in both vegetative and reproductive tissues of perennial ryegrass. A gcnA replacement mutant had reduced β-1,6-glucanase activity when grown in media containing pustulan as the major carbon source. β-1,6-glucanase activity was restored in the replacement mutant by introducing multiple copies of the gcnA gene. Growth of ΔgcnA and gcnA-overexpressing strains in vegetative grass tissues was indistinguishable from wild type strains.