Search Results (15)

A study was conducted to examine the effects of the spray application of nine antifungal products, including microbial-derived fungicides, plant-derived fungicides, and chemical fungicides, on the grass Achnatherum inebrians that was either host to Epichloë gansuensis (E+) or E. gansuensis-free (E−) and that was exposed to Blumeria graminis, the fungal pathogen causing powdery mildew. The Epichloë endophyte is a seed-borne mutualistic biotrophic fungus whose growth is fully synchronized with the host grass. Bl. graminis is a biotrophic pathogen that continually infects leaves and stems via conidia, the formation of appressoria, leading to the presence of haustoria in epidermal cells. Prior to fungicide application, the presence of endophytes significantly increased the resistance of A. inebrians to powdery mildew and was able to increase the chlorophyll content. However, the positive effects of the Epichloë endophyte on the plant were suppressed with the use of some fungicides and the increase in the number of sprays, but the reciprocal relationship between the Epichloë endophyte and the plant was not significantly disrupted. Full article

Despite chemical exchange often serving as the first step in plant–microbe interactions, the specialized chemical metabolites produced by grass–Epichloë endophyte symbiosis as mediators of host growth, nutrient acquisition, and modulators of the rhizosphere community under low-nitrogen conditions are areas lacking in knowledge. In this study, we investigated the plant growth-promoting effects of the Epichloë endophyte strain and identified the growth of the Epichloë strain under different types of nitrogen source treatments. In addition to the in vitro test, we evaluated growth performance for Epichloë endophyte–infected plants (E+) and Epichloë endophyte–free plants (E−) in a pot trial under 0.01 mol/L urea treatment. Seedlings from E+ and E− groups were collected to analyze the plant bacterial microbiome and root metabolites. The E. gansuensis endophyte strain was found not to produce indoleacetic acid (IAA), pectinase, or contain ferritin. The nitrogenase gene, essential for nitrogen fixation, was also absent. These results suggest that E. gansuensis endophyte strains themselves do not contain attributes to promote plant growth. Concerning N fertilization, it was observed an increase in the colony diameter of E. gansuensis strain was observed only in the NO₃⁻-N (NN) treatment, while inhibition was observed in the urea-N (UN) treatment. E. gansuensis endophyte symbiosis significantly increased tiller number and plant dry weight. Overall, our results suggest that the E+ plants had more root forks and greater average root diameter compared to E− plants under the UN treatment. In a pot experiment using UN, data from 16S rRNA amplicon sequencing revealed that E. gansuensis endophyte infection significantly altered the bacterial community composition in shoot and root, and significantly increased Shannon (p < 0.001) and Chao 1 (p < 0.01) indexes. The relative abundance of Acidobacteriota, Actinomycetota, Cyanobacteriota, Fibrobacterota, Myxococcota, and Patescibacteria in the shoot, and Cyanobacteriota, Pseudomonadota, and Verrucomicrobiota in the root were significantly increased by E. gansuensis endophyte infection. Similarly, E. gansuensis endophyte symbiosis shifted the metabolite composition of the host plants, with the E+ plants showing a higher number of metabolites than the E− plants. In addition, co-metabolism network analysis revealed that the positive relevance between exudates and microorganisms in the root of the E+ plants is higher than that of the E− plants. These findings provide valuable insights into the knowledge of the effects of the symbiotic relationship between host plants and Epichloë endophyte on interspecific interactions of plant microbiome, beneficial for harnessing endophytic symbiosis, promoting plant growth. Full article

Strong UV-B radiation is one of the main climatic characteristics of the Qinghai–Tibet Plateau. Plants grown on the Tibetan Plateau are exposed to high-intensity UV radiation and therefore require effective mechanisms to adapt to these stresses. However, little attention has been paid to the response of grass–endophytic fungi symbiosis to UV-B radiation in this area. In this study, we investigated the relationship between Epichloë gansuensis and the growth and antioxidant responses of Achnatherum inebrians seedlings exposed to different UV-B doses, aiming to evaluate the growth and antioxidant capacity of A. inebrians seedlings under UV-B stress. The plant height, tillers, biomass, electrical conductivity, soluble sugars, malondialdehyde (MDA), proline, hydrogen peroxide (H₂O₂), superoxide dismutase (SOD), polyphenol oxidase (POD), and catalase (CAT) of A. inebrians seedlings were determined under different intensities of UV-B radiation treatments. The results showed that, with the increase in UV-B radiation intensity, the plant height, tiller and biomass of A. inebrians seedlings showed a decreasing trend, the electrical conductivity increased, malondialdehyde content increased, soluble sugar and proline content decreased, SOD, POD, and CAT activities showed a decreasing trend, and the content of H₂O₂ increased, which means that the UV-B radiation was able to inhibit the morphogenesis and aggravate the membrane lipid peroxidation of A. inebrians seedlings. The tolerance of the A. inebrians–E. gansuensis symbiont to UV-B may enable it to have a high infection rate on the Qinghai–Tibet Plateau. Full article

Although drunken horse grass (Achnatherum inebrians) can be simultaneously infected by the foliar endophyte Epichloë gansuensis and colonized by Bacillus subtilis, it remains unclear whether Epichloë endophyte symbiosis influences B. subtilis colonization, as well as how their interaction affects nitrogen fixation and assimilation. The purpose of the present study was to investigate whether E. gansuensis endophyte infection facilitates the colonization of B. subtilis in the roots of host plants, with a focus on understanding the interaction effects of the E. gansuensis endophyte and B. subtilis on plant growth and nutrient absorption. In this study, we measured the colony growth rate of B. subtilis LZU7 when co-cultured with E. gansuensis strains. In addition to an in vitro test, we investigated the root colonization of Epichloë endophyte-infected plants (E+) and Epichloë endophyte-free plants (E−) with the GFP-tagged B. subtilis LZU7 in an inoculation test. Furthermore, we evaluated the interactions between E. gansuensis endophyte symbiosis and B. subtilis LZU7 colonization on the dry weight, nitrogen fixation, nitrogen converting-enzyme activity, and nutrients for E+ and E− plants by labeling with ¹⁵N₂. The results showed that the growth rates of B. subtilis LZU7 were altered and increased in a co-culture with the E. gansuensis endophyte. A significantly greater colonization of GFP-tagged B. subtilis LZU7 was detected in the roots of E+ plants compared with the roots of E− plants, suggesting that E. gansuensis endophyte symbiosis enhances the colonization of beneficial microorganisms. The combination of E. gansuensis endophyte symbiosis and B. subtilis LZU7 inoculation significantly altered the expression of the nitrogenase (nifH) gene, thereby promoting increased biological nitrogen fixation (BNF). The E. gansuensis endophyte infection and inoculation with B. subtilis LZU7 significantly increased δ15NAir in plants. Co-inoculation with the E. gansuensis endophyte and B. subtilis LZU7 significantly elevated NH₄⁺ accumulation in the roots, depleted the NH₄⁺ availability in the surrounding soil, and showed no measurable impact on the foliar NH₄⁺ content. The observed alterations in the NH₄⁺ content were linked to nitrogen-fixing microorganisms that promoted nitrogen fixation, thereby enhancing nitrogen uptake and contributing to greater biomass production in A. inebrians. Our findings highlighted the fact that a foliar symbiosis with the E. gansuensis endophyte enhances the recruitment of beneficial bacteria, and that the resulting interaction significantly impacts nitrogen fixation, assimilation, and allocation in host plants. Full article

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. Full article

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. Full article

Endophytic fungal infection is the major reason for intoxication of animals caused by drunken horse grass. Fortunately, it has been established that seed detoxification techniques and isolation of endophytic fungi infect non-endophytic fungi populations with the same genetic background as endophyte-infected Achnatherum inebrians. Moreover, sheep can use endophyte-free Achnatherum inebriants (EF) without obvious toxicity symptoms. The present study selected EF as a representative grass, consisting of five different replacement levels, EF0, EF25, EF50, EF75, and EF100, corresponding to 0%, 25%, 50%, 75%, and 100% of the fermentation substrate, respectively. Simultaneously, in vitro fermentation and the 16S rRNA amplicon sequencing method was used to explore the effect of EF on sheep ruminal fermentation and microbial diversity. The results revealed that EF100 had the highest values for pH, acetate: propionate, the Patescibacteria, Kiritimatiellaeota, and Synergistetes phylum levels, Ruminococcaceae, Prevotellaceae, and Saccharofermentans genus levels than the other treatments (p < 0.05). In contrast, EF25 was associated with higher levels of abundance-based coverage estimator (ACE), Chaol index of the phyla Synergistetes and Bacteroidetes, and of the genus Erysipelotrichaceae, Rikenellaceae, and Prevotella as compared with other treatments (p < 0.05). EF50 resulted in the greatest values for the genus Christensenellaceae and Lachnospiraceae as compared with other treatments (p < 0.05). EF75 resulted in the greatest values for the Shannon index as compared with other treatments (p < 0.05). EF0 resulted in the greatest values for gas production (GP), ammonia nitrogen (NH₃-N), total volatile fatty acid (TVFA), acetate, propionate, butyrate, valerate, isobutyrate, isovalerate, and the phyla Firmicutes, Proteobacteria, and Spirochaetes, and the genus Succiniclasticum, Ruminobacter, Family_XIII and Treponema as compared with other treatments (p < 0.05). PICRUSt2 analysis indicated that most of the functional prediction pathways were involved in Carbohydrate metabolism and, Amino acid metabolism. Therefore, the recommended ratio of EF in sheep diet should range from 25% to 50%, and the maximum proportion should not exceed 75%. Full article

Cuticular wax plays a critical role as a plant protectant against various environmental stresses. We predicted that the presence of the mutualistic fungal endophyte Epichloë gansuensis in Achnatherum inebrians would change both the composition of leaf cuticular wax as plants aged during the growing season and the gene expression levels associated with the wax biosynthesis pathway. Endophyte-infected (EI) and endophyte-free (EF) A. inebrians plants were established for a four-month pot experiment. In agreement with our prediction, the presence of E. gansuensis can change the composition of leaf cuticular wax at different growing periods, particularly the proportion of esters, fatty acids and hydrocarbons. The proportion of fatty acids in EI plants was lower than that in EF plants. The proportion of hydrocarbons increased and esters decreased as plants grew. Furthermore, we found 11 DEGs coding for proteins involved in cuticular wax biosynthesis, including FabF, FAB2, ECR, FAR, CER1, ABCB1 and SEC61A. The present study highlights the significant contribution of E. gansuensis to leaf cuticular wax composition and biosynthesis in A. inebrians plants. Full article

The cuticular wax serves as the outermost hydrophobic barrier of plants against nonstomatal water loss and various environmental stresses. An objective of this study was to investigate the contribution of the mutualistic fungal endophyte Epichloë gansuensis to leaf cuticular wax of Achnatherum inebrians under different soil moisture availability. Through a pot experiment and gas chromatography−mass spectrometry (GC−MS) analysis, our results indicated that the hydrocarbons were the dominant components of leaf cuticular wax, and the proportion of alcohols, aldehydes, amines, and ethers varied with the presence or absence of E. gansuensis and different soil moisture availability. Amines and ethers are unique in endophyte-free (EF) A. inebrians plants and endophyte-infected (EI) A. inebrians plants, respectively. By transcriptome analysis, we found a total of 13 differentially expressed genes (DEGs) related to cuticular biosynthesis, including FabG, desB, SSI2, fadD, BiP, KCS, KAR, FAR, and ABCB1. A model is proposed which provides insights for understanding cuticular wax biosynthesis in the association of A. inebrians plants with E. gansuensis. These results may help guide the functional analyses of candidate genes important for improving the protective layer of cuticular wax of endophyte-symbiotic plants. Full article

Achnatherum sibiricum can be infected by two species of fungal endophytes, Epichloë gansuensis (Eg) and Epichloë sibirica (Es). In this study, the metabolites of Eg, Es, and their infected plants were studied by GC–MS analysis. The results showed that the metabolic profiles of Eg and Es were similar in general, and only six differential metabolites were detected. The direct effect of endophyte infection on the metabolites in A. sibiricum was that endophyte-infected plants could produce mannitol, which was not present in uninfected plants. Epichloë infection indirectly caused an increase in the soluble sugars in A. sibiricum related to growth and metabolites related to the defense against pathogens and herbivores, such as α-tocopherol, α-linolenic acid and aromatic amino acids. Epichloë infection could regulate galactose metabolism, starch and sucrose metabolism, tyrosine metabolism and phenylalanine metabolism of host grass. In addition, there was a significant positive correlation in the metabolite contents between the endophyte and the host. Full article

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. Full article

The present study was designed to explore the effects of the endophyte Epichloë gansuensis on gene expression related to plant hormone biosynthesis and response pathways and the content of salicylic acid (SA) and jasmonic acid (JA) hormones of Achnatherum inebrians, under different moisture conditions. Through a pot experiment and transcriptome analysis, we found a total of 51 differentially expressed genes (DEGs) related to hormone biosynthesis and response pathways, including 12 auxin related genes, 8 cytokinin (CTK) related genes, 3 gibberellin (GA) related genes, 7 abscisic acid (ABA) related genes, 7 ethylene (ET) related genes, 12 JA related genes and 4 SA related genes. Furthermore, key genes of JA and SA biosynthesis and response pathways, such as LOX2S, AOS, OPR, ACX, JMT, JAZ, PAL, NPR1, TGA and PR-1, showed different degrees of upregulation or downregulation. Under 60% soil moisture content, the JA content of endophyte-free (EF) A. inebrians was significantly (p < 0.05) higher than that of endophyte-infected (EI) A. inebrians. Under 30% and 60% soil moisture content, the SA content of EF A. inebrians was significantly (p < 0.05) higher than that of EI A. inebrians. SA content of EI A. inebrians under 30% and 60% soil moisture content was significantly (p < 0.05) higher than that under 15% soil moisture content. With both EI and EF plants, the SA and JA levels, respectively, are very similar at 15% soil moisture content. This study has revealed that E. gansuensis differentially activated plant hormone synthesis and signal transduction pathways of A. inebrians plants under different soil moisture availability. Full article

The study of the contribution of the plant defence hormones, salicylic acid (SA) and jasmonic acid (JA), in the resistance against pathogens of plants associated with Epichloë fungal endophytes has been scanty. We hypothesised that Epichloë spp., capable of inducing host plant SA-dependent defences, would increase the levels of plant resistance against biotrophic pathogens. Plants of Achnatherum inebrians, with and without the fungal endophyte Epichloë gansuensis, were inoculated with the biotrophic fungal pathogen Blumeria graminis. We measured the status of plant defences (associated with SA and JA signalling pathways) and the levels of resistance to the pathogen. Plants associated with the endophyte showed less disease symptoms caused by the biotrophic pathogen than plants without the endophyte. In agreement with our hypothesis, the Epichloë endophyte increased the plant production of SA and enhanced the expression levels of plant genes of synthesis and response to the SA hormone. The elevated expression of SA-related genes coding for putative plant enzymes with anti-fungal activities promoted by the endophyte may explain the enhanced resistance to the pathogen. The present study highlights that interaction between the plant immune system and Epichloë fungal endophytes can contribute significantly to the resistance of endophyte-symbiotic plants against pathogens. Full article

In the long-term evolutionary process, Achnatherum inebrians and seed-borne endophytic fungi, Epichloë gansuensis, formed a mutually beneficial symbiosis relationship, and Epichloë gansuensis has an important biological role in improving the tolerance of host grasses to abiotic stress. In this work, we first assessed the effects of Epichloë gansuensis on dry weight, the content of C, N, P and metal ions, and metabolic pathway of amino acids, and phosphorus utilization efficiency (PUE) of Achnatherum inebrians at low P stress. Our results showed that the dry weights, the content of alanine, arginine, aspartic acid, glycine, glutamine, glutamic acid, L-asparagine, lysine, phenylalanine, proline, serine, threonine, and tryptophan were higher in leaves of Epichloë gansuensis-infected (E+) Achnatherum inebrians than Epichloë gansuensis-uninfected (E−) Achnatherum inebrians at low P stress. Further, low P stress increased C content of leaves of E+ Achnatherum inebrians compared to 0.5 mM P; Epichloë gansuensis increased K content of leaves compared to the leaf of E− plant at 0.01 mM P and 0.5 mM P. Epichloë gansuensis reduced Ca content of roots compared to the root of E− plant at 0.01 mM P and 0.5 mM P; Epichloë gansuensis reduced the content of Mg and Fe in leaves compared to the leaf of E− plant at 0.01 mM P and 0.5 mM P. In addition, at low P stress, Epichloë gansuensis most probably influenced aspartate and glutamate metabolism; valine, leucine, and isoleucine biosynthesis in leaves; and arginine and proline metabolism; alanine, aspartate, and glutamate metabolism in roots. Epichloë gansuensis also affected the content of organic acid and stress-related metabolites at low P stress. In conclusion, Epichloë gansuensis improves Achnatherum inebrians growth at low P stress by regulating the metabolic pathway of amino acids, amino acids content, organic acid content, and increasing PUE. Full article