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Christopher L Schardl - One of the best experts on this subject based on the ideXlab platform.
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transcriptomics of Epichloe grass symbioses in host vegetative and reproductive stages
Molecular Plant-microbe Interactions, 2019Co-Authors: Padmaja Nagabhyru, Randy D Dinkins, Christopher L SchardlAbstract:: Epichloe species are fungal symbionts (endophytes) of cool-season grasses that transmit vertically via inflorescence primordia (IP), ovaries (OV), and ultimately, embryos. Epichloe coenophiala, an endophyte of tall fescue (Schedonorus arundinaceus), provides multiple protective benefits to the grass. We conducted transcriptome analysis of the tall fescue-E. coenophiala symbiosis, comparing IP, OV, vegetative pseudostems (PS), and the lemma and palea (LP) (bracts) of the young floret. Transcriptomes of host OV and PS exhibited almost no significant differences attributable to endophyte presence or absence. Comparison of endophyte gene expression in different plant parts revealed numerous differentially expressed genes (DEGs). The 150 endophyte DEGs significantly higher in PS over OV included genes for alkaloid biosynthesis and sugar or amino acid transport. The 277 endophyte DEGs significantly higher in OV over PS included genes for protein chaperones (including most heat-shock proteins), trehalose synthesis complex, a bax inhibitor-1 protein homolog, the CLC chloride ion channel, catalase, and superoxide dismutase. Similar trends were apparent in the Brachypodium sylvaticum-Epichloe sylvatica symbiosis. Gene expression profiles in tall fescue IP and LP indicated that the endophyte transcriptome shift began early in host floral development. We discuss possible roles of the endophyte DEGs in colonization of reproductive grass tissues.
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MOLECULAR SYSTEMATICS OF CLAVICIPITACEAE SUPPORTING MONOPHYLY OF GENUS Epichloe AND FORM GENUS EPHELIS
Mycologia, 2018Co-Authors: Gretchen Anna Kuldau, James F. White, Malcolm R. Siegel, Christopher L SchardlAbstract:The family Clavicipitaceae (Ascomycota) is comprised of fungi with perithecia borne on stro- mata, unitunicate asci, and filamentous, multiseptate ascospores. All are biotrophic symbionts, either mu- tualistic with plant hosts or pathogenic to plants, in- vertebrate animals or other fungi. Genera of plant- associated Clavicipitaceae (tribes Balansieae and Clavicipieae) are distinguished, in part, by stromal and ascus morphology, ascospore germination pat- terns, whether sclerotia are formed, and host inter- actions. Their anamorphs include enteroblastic mi- croconidial states, classified in anamorphic genera Neotyphodium and Sphacelia (for teleomorphs Atkin- sonella, Claviceps, Echinodothis, and Epichloe), and ho- loblastic macroconidia, classified in the anamorphic genus Ephelis (teleomorphs Atkinsonella, Balansia, and Myriogenospora). Epichloe' species often are mu- tualistic with grass hosts, and are ancestral to asexual, seed transmitted endophytes symbiotic with many cool-season grasses. Partial 28S nuclear rDNA se- quences were determined from isolates of five species and two undescribed mating populations of Epichloe, one asexual Epichloe hybrid (Neotyphodium coeno- phialum), and representatives of six other genera in the family. Results from phylogenetic analysis of the sequences supported monophyly of plant-associated Clavicipitaceae, with insect-pathogenic Cordyceps spe- cies more deeply rooted. Four clades were distin-
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Toxin-producing Epichloë bromicola strains symbiotic with the forage grass Elymus dahuricus in China
Mycologia, 2017Co-Authors: Shazhou An, Christopher L Schardl, Carolyn A Young, Daniel G. Panaccione, Chunjie LiAbstract:ABSTRACTCool-season grasses (Poaceae subfamily Pooideae) are an important forage component for livestock in western China, and many have seed-transmitted symbionts of the genus Epichloe, fungal end...
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endophytic Epichloe species and their grass hosts from evolution to applications
Plant Molecular Biology, 2016Co-Authors: Kari Saikkonen, Marjo Helander, Carolyn A Young, Christopher L SchardlAbstract:The closely linked fitness of the Epichloe symbiont and the host grass is presumed to align the coevolution of the species towards specialization and mutually beneficial cooperation. Ecological observations demonstrating that Epichloe-grass symbioses can modulate grassland ecosystems via both above- and belowground ecosystem processes support this. In many cases the detected ecological importance of Epichloe species is directly or indirectly linked to defensive mutualism attributable to alkaloids of fungal-origin. Now, modern genetic and molecular techniques enable the precise studies on evolutionary origin of endophytic Epichloe species, their coevolution with host grasses and identification the genetic variation that explains phenotypic diversity in ecologically relevant characteristics of Epichloe-grass associations. Here we briefly review the most recent findings in these areas of research using the present knowledge of the genetic variation that explains the biosynthetic pathways driving the diversity of alkaloids produced by the endophyte. These findings underscore the importance of genetic interplay between the fungus and the host in shaping their coevolution and ecological role in both natural grass ecosystems, and in the agricultural arena.
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detection and isolation of Epichloe species fungal endophytes of grasses
Current protocols in microbiology, 2015Co-Authors: Simona Florea, Christopher L Schardl, Walter HollinAbstract:Epichloe species (including former Neotyphodium species) are endophytic fungi that significantly affect fitness of cool-season grass hosts, potentially by increasing nutrient uptake and resistance to drought, parasitism and herbivory. Epichloe species are obligately biotrophic, living in the intercellular spaces of their plant hosts, and spreading systemically throughout host aerial tissues. The reproduction of Epichloe species is versatile; some strains have both sexual and asexual modes of reproduction, but others are restricted to one or the other mode. The reproduction mode determines the dissemination mechanism, and the asexual species most important to agriculture are strictly seed-borne, cause no signs or symptoms, and are undetectable except by specialized microscopic, molecular or antigenic procedures. These procedures can be used to identify endophytes in a variety of plant tissues. Similar protocols can be modified to detect less common symbionts, such as the penicillate “p-endophytes,” when they occur by themselves or together with Epichloe species. © 2015 by John Wiley & Sons, Inc. Keywords: symbiosis; isolation; detection; aniline-blue; tissue staining; serology; multiplex PCR
Adrian Leuchtmann - One of the best experts on this subject based on the ideXlab platform.
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Taxonomy and diversity of Epichloë endophytes.
2020Co-Authors: Adrian Leuchtmann, James F. White, Charles W Bacon, Nigel L. Hywel-jones, J. W. SpataforaAbstract:Epichloe is one of seven genera recognized within the tribe Balansieae of the Clavicipitaceae, which represent exclusively systemic biotrophs of graminoid hosts (Diehl, 1950; White, 1994b; White and Reddy, 1998; White et al., 2000). Other members of the family are either not systemic and perennial (tribes Clavicipeae, Ustilaginoideae) or are pathogens of invertebrates or other fungi (tribe Cordycipeae). A key feature of Epichloe is the endophytic lifestyle, which includes intercellular colonization of host tissues and frequent seed transmission. Most species of other balansiean genera (e.g., Atkinsonella, Balansia, Myriogenospora, ParEpichloe) live epibiotically on host meristems and surfaces of leafs or culms. Epichloe species form light-colored, external reproductive structures, the stromata, which envelope inflorescences and the upper leaf sheaths of flowering culms (choke disease). The anamorphic state which is formed on the surface of the young stromata is classified in Neotyphodium (Glenn et al., 1996). Its one-celled conidia, typically ovoid to navicular in shape, are borne from simple phialids.
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botanophila flies vectors of Epichloe fungal spores are infected by wolbachia
Mycology, 2019Co-Authors: Lydia Pagel, Adrian Leuchtmann, Marlena Lembicz, Thomas L Bultman, Karolina Gorzynska, Anne Sangliana, Nicola RichardsAbstract:Epichloe fungi are endophytes within grasses that can form stromata on culms of their hosts. Botanophila flies visit the stromata for egg laying and in the process can vector spermatial spo...
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biology and evolution of the Epichloe associated botanophila species found in europe diptera anthomyiidae
Insect Systematics & Evolution, 2016Co-Authors: Adrian Leuchtmann, Verner MichelsenAbstract:The anthomyiid genus Botanophila consists of over 200, mostly phytophagous, species. One species group maintains a mutualistic relationship with Epichloe fungi, thereby acting as vector of fungal spermatia required for fertilization, similar to pollinating parasites. The phylogenetic relationship of these flies with other Botanophila and the related Chiastocheta species (obligatory associated with globeflowers) remains largely unresolved. In this study, we obtained new sequences of the mitochondrial genes COI and COII from a representative sample of 17 European Botanophila and Chiastocheta species including all six Epichloe-associated species, as well as from four outgroup taxa. Phylogenetic analyses indicated that Epichloe-associated Botanophila form a distinct clade suggesting that ancestral Botanophila may have expanded its niche to European fungal hosts once and then successfully radiated while exploiting fungal tissue as additional food source. Furthermore, the three included Chiastocheta species formed a distinct clade nested within Botanophila, leaving the genus paraphyletic as currently circumscribed.
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The role of host-specificity in the reproductive isolation of Epichloë endophytes revealed by reciprocal infections
Fungal Ecology, 2015Co-Authors: Melanie K. Schirrmann, Adrian LeuchtmannAbstract:Abstract Speciation in sexually reproducing organisms hinges on reproductive barriers that reduce gene flow between species or preclude the formation of hybrids. Here, we studied potential reproductive barriers in four members of the Epichloe typhina (Ascomycota, Clavicipitaceae) complex, i.e. Epichloe typhina infecting Dactylis glomerata, E. typhina subsp. clarkii infecting Holcus lanatus, E. typhina subsp. poae infecting Poa nemoralis and E. typhina infecting P. trivialis. Reciprocal inoculation tests showed that these endophytes are host-specific. This suggests that reproductive isolation among Epichloe strains may be the result of specialization to one host, on which mating between different individuals occurs. Furthermore, significantly lower infection frequencies of F1 progeny from crosses between host-strains compared to parental strains and within host-strain progeny suggest that host-dependent effects upon hybrid fitness exist, which would conform to an extrinsic postzygotic isolation barrier. Our results may explain, why members of the E. typhina complex remain genetically differentiated in natural populations.
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Genetic evidence for reproductive isolation among sympatric Epichloë endophytes as inferred from newly developed microsatellite markers.
Microbial Ecology, 2014Co-Authors: Melanie K. Schirrmann, Stefan Zoller, Simone Fior, Adrian LeuchtmannAbstract:Reproductive isolation is central to the maintenance of species, and especially in sympatry, effective barriers to prevent interspecific crosses are expected. Host specificity is thought to constitute an effective mechanism for the formation of barriers in different genera of Fungi, but evidence for endophytes is so far lacking. Sexual Epichloe species (Ascomycota, Clavicipitaceae) represent an ideal study system to investigate the mechanisms underlying speciation as mediated by host specificity because they include species complexes with several host-specific taxa. Here, we studied genetic differentiation of three host-specific Epichloe species using microsatellite markers that were newly in silico identified on the genome of Epichloe poae. Among these, 15 were experimentally tested and applied to study an extensive sampling of isolates representing Epichloe typhina infecting Dactylis glomerata and Epichloe clarkii infecting Holcus lanatus from a site with sympatric populations in Switzerland, as well as a reduced sampling of E. poae infecting Poa nemoralis to create a three-taxon dataset. Both principal coordinate analysis and Bayesian clustering algorithm showed three genetically distinct groups representing the three host-specific species. High pairwise FST values among the three species, as well as sequencing data of the tefA gene revealing diagnostic single nucleotide polymorphisms (SNPs), further support the hypothesis of genetic discontinuities among the taxa. These results provide genotypic evidence of the maintenance of reproductive isolation of the species in a context of sympatry. In silico testing of 885 discovered microsatellites on the genome of Epichloe festucae extend their applicability to a wider taxonomic range of Epichloe.
Carolyn A Young - One of the best experts on this subject based on the ideXlab platform.
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Epichloë Endophyte Infection Rates and Alkaloid Content in Commercially Available Grass Seed Mixtures in Europe
Microorganisms, 2020Co-Authors: Jochen Krauss, Carolyn A Young, Veronika Vikuk, Markus Krischke, Martin J. Mueller, Katja BaerenfallerAbstract:Fungal endophytes of the genus Epichloe live symbiotically in cool season grass species and can produce alkaloids toxic to insects and vertebrates, yet reports of intoxication of grazing animals have been rare in Europe in contrast to overseas. However, due to the beneficial resistance traits observed in Epichloe infected grasses, the inclusion of Epichloe in seed mixtures might become increasingly advantageous. Despite the toxicity of fungal alkaloids, European seed mixtures are rarely tested for Epichloe infection and their infection status is unknown for consumers. In this study, we tested 24 commercially available seed mixtures for their infection rates with Epichloe endophytes and measured the concentrations of the alkaloids ergovaline, lolitrem B, paxilline, and peramine. We detected Epichloe infections in six seed mixtures, and four contained vertebrate and insect toxic alkaloids typical for Epichloe festucae var. lolii infecting Lolium perenne. As Epichloe infected seed mixtures can harm livestock, when infected grasses become dominant in the seeded grasslands, we recommend seed producers to test and communicate Epichloe infection status or avoiding Epichloe infected seed mixtures.
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infection rates and alkaloid patterns of different grass species with systemic Epichloe endophytes
Applied and Environmental Microbiology, 2019Co-Authors: Veronika Vikuk, Carolyn A Young, Markus Krischke, Martin J. Mueller, Padmaja Nagabhyru, Jochen KraussAbstract:ABSTRACT Symbiotic Epichloe species are fungal endophytes of cool-season grasses that can produce alkaloids with toxicity to vertebrates and/or invertebrates. Monitoring infections and presence of alkaloids in grasses infected with Epichloe species can provide an estimate of possible intoxication risks for livestock. We sampled 3,046 individuals of 13 different grass species in three regions on 150 study sites in Germany. We determined infection rates and used PCR to identify Epichloe species diversity based on the presence of different alkaloid biosynthesis genes, then confirmed the possible chemotypes with high-performance liquid chromatography (HPLC)/ultraperformance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) and gas chromatography-mass spectrometry (GC-MS) measurements. Infections of Epichloe spp. were found in Festuca pratensis Huds. (81%), Festuca ovina L. aggregate (agg.) (73%), Lolium perenne L. (15%), Festuca rubra L. (15%) and Dactylis glomerata L. (8%). The other eight grass species did not appear to be infected. For the majority of Epichloe-infected L. perenne samples (98%), the alkaloids lolitrem B and peramine were present, but ergovaline was not detected, which was consistent with the genetic evaluation, as dmaW, the gene encoding the first step of the ergot alkaloid biosynthesis pathway, was absent. Epichloe uncinata in F. pratensis produced anti-insect loline compounds. The Epichloe spp. observed in the F. ovina agg. samples showed the greatest level of diversity, and different intermediates of the indole-diterpene pathway could be detected. Epichloe infection rates alone are insufficient to estimate intoxication risks for livestock, as other factors, like the ability of the endophyte to produce the alkaloids, also need to be assessed. IMPORTANCE Severe problems of livestock intoxication from Epichloe-infected forage grasses have been reported from New Zealand, Australia, and the United States, but much less frequently from Europe, and particularly not from Germany. Nevertheless, it is important to monitor infection rates and alkaloids of grasses with Epichloe fungi to estimate possible intoxication risks. Most studies focus on agricultural grass species like Lolium perenne and Festuca arundinacea, but other cool-season grass species can also be infected. We show that in Germany, infection rates and alkaloids differ between grass species and that some of the alkaloids can be toxic to livestock. Changes in grassland management due to changing climate, especially with a shift toward grasslands dominated with Epichloe-infected species such as Lolium perenne, may result in greater numbers of intoxicated livestock in the near future. We therefore suggest regular monitoring of grass species for infections and alkaloids and call for maintaining heterogenous grasslands for livestock.
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Toxin-producing Epichloë bromicola strains symbiotic with the forage grass Elymus dahuricus in China
Mycologia, 2017Co-Authors: Shazhou An, Christopher L Schardl, Carolyn A Young, Daniel G. Panaccione, Chunjie LiAbstract:ABSTRACTCool-season grasses (Poaceae subfamily Pooideae) are an important forage component for livestock in western China, and many have seed-transmitted symbionts of the genus Epichloe, fungal end...
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endophytic Epichloe species and their grass hosts from evolution to applications
Plant Molecular Biology, 2016Co-Authors: Kari Saikkonen, Marjo Helander, Carolyn A Young, Christopher L SchardlAbstract:The closely linked fitness of the Epichloe symbiont and the host grass is presumed to align the coevolution of the species towards specialization and mutually beneficial cooperation. Ecological observations demonstrating that Epichloe-grass symbioses can modulate grassland ecosystems via both above- and belowground ecosystem processes support this. In many cases the detected ecological importance of Epichloe species is directly or indirectly linked to defensive mutualism attributable to alkaloids of fungal-origin. Now, modern genetic and molecular techniques enable the precise studies on evolutionary origin of endophytic Epichloe species, their coevolution with host grasses and identification the genetic variation that explains phenotypic diversity in ecologically relevant characteristics of Epichloe-grass associations. Here we briefly review the most recent findings in these areas of research using the present knowledge of the genetic variation that explains the biosynthetic pathways driving the diversity of alkaloids produced by the endophyte. These findings underscore the importance of genetic interplay between the fungus and the host in shaping their coevolution and ecological role in both natural grass ecosystems, and in the agricultural arena.
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disparate independent genetic events disrupt the secondary metabolism gene pera in certain symbiotic Epichloe species
Applied and Environmental Microbiology, 2015Co-Authors: Daniel Berry, Christopher L Schardl, Barry Scott, Nikki D Charlton, Johanna E Takach, Carolyn A YoungAbstract:ABSTRACT Peramine is an insect-feeding deterrent produced by Epichloe species in symbiotic association with C 3 grasses. The perA gene responsible for peramine synthesis encodes a two-module nonribosomal peptide synthetase. Alleles of perA are found in most Epichloe species; however, peramine is not produced by many perA -containing Epichloe isolates. The genetic basis of these peramine-negative chemotypes is often unknown. Using PCR and DNA sequencing, we analyzed the perA genes from 72 Epichloe isolates and identified causative mutations of perA null alleles. We found nonfunctional perA -ΔR* alleles, which contain a transposon-associated deletion of the perA region encoding the C-terminal reductase domain, are widespread within the Epichloe genus and represent a prevalent mutation found in nonhybrid species. Disparate phylogenies of adjacent A2 and T2 domains indicated that the deletion of the reductase domain (R*) likely occurred once and early in the evolution of the genus, and subsequently there have been several recombinations between those domains. A number of novel point, deletion, and insertion mutations responsible for abolishing peramine production in full-length perA alleles were also identified. The regions encoding the first and second adenylation domains (A1 and A2, respectively) were common sites for such mutations. Using this information, a method was developed to predict peramine chemotypes by combining PCR product size polymorphism analysis with sequencing of the perA adenylation domains.
Kari Saikkonen - One of the best experts on this subject based on the ideXlab platform.
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variation and plasticity in Epichloe alkaloid content of festuca rubra across europe
Fungal Ecology, 2020Co-Authors: Beatriz Vazquez R De Aldana, Marjo Helander, Iñigo Zabalgogeazcoa, Paivi H Leinonen, Kari SaikkonenAbstract:Abstract Many symbiotic microbes can aid their host plant's defense against herbivores and pathogens either directly or indirectly through plant-mediated mechanisms. Thus, microbes are of interest to agricultural research. In this study, we used vertically transmitted Epichloe species because these fungal endophytes of grasses produce alkaloids that have been shown to protect the host from herbivory. Depending on the amount, type, and profile of alkaloids, Epichloe species can promote the host's defense against invertebrate or vertebrate herbivores. Here, we used Festuca rubra colonized by Epichloe festucae from wild populations of different geographic origins in a reciprocal transplant experiment at three locations across Europe. We sought to determine whether genetic differences among Epichloe-colonized plants from different origins or phenotypic plasticity explained variations in alkaloid content and whether the alkaloid content was correlated with the growth and reproduction of the plants colonized by Epichloe. We found that the geographic origin of the Epichloe-colonized genotypes explained differences in ergovaline and peramine production. The ergovaline content also indicated chemotypic plasticity, as profiles changed when transplanted to a new environment, while the concentration of peramine was constant among the transplantation sites. The lack of a strong correlation between alkaloid content and plant performance (number of reproductive stems and total biomass) indicated that the costs of alkaloid production were too low to have consequences for fitness in terms of those parameters. Our findings emphasize the importance of estimating the fungal alkaloid content in multiple field environments in order to determine its potential toxicity and value for breeding programs that are aimed at the improvement of turfgrass and forage cultivars.
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Interactive effects of Epichloë fungal and host origins on the seed germination of Achnatherum inebrians
Symbiosis, 2019Co-Authors: Meiling Song, Kari Saikkonen, Yuqin Wang, Hongsheng WangAbstract:Cool-season grasses have developed a symbiotic relationship with Epichloe endophytes. In many environments, Epichloe endophytes have been shown to be mutualistic symbionts of plants by increasing the fitness of their host against abiotic or biotic stresses. The effects of Epichloe endophytes on other fitness-correlated plant characteristics are less intensively studied, and the results are usually variable and contradictory. In this study, we evaluated the effects of endophyte infection on seed germination in Achnatherum inebrians from four origins. Our results indicate that the germination rate of the seeds collected from alpine regions was higher at low temperatures than that of seeds with desert and arid grassland origins. By contrast, a higher germination percentage was detected in seeds with desert and arid grassland origins than in those with alpine origins in higher temperatures. Epichloe endophyte infection affects the cardinal temperatures of seeds from different origins. Endophyte-infected seeds have a lower base temperature and a higher ceiling temperature than their endophyte-free counterparts. The value of the base temperature was higher in seeds with alpine grassland origins than in those with desert and arid grassland origins. However, the ceiling temperature was higher in seeds with desert and arid grassland origins than in those with alpine grassland origins. Consequently, future experiments should consider the effects of endophytes on seed germination and seedling recruitment in suboptimal climatic conditions.
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direct and indirect effects of the fungal endophyte Epichloe uncinatum on litter decomposition of the host grass schedonorus pratensis
Plant Ecology, 2017Co-Authors: Pedro E. Gundel, Marjo Helander, Iñigo Zabalgogeazcoa, Beatriz R Vazquezdealdana, Lucas A Garibaldi, Kari SaikkonenAbstract:Microbial plant symbionts have been suggested to mediate plant-soil feedback and affect ecosystem functions. Systemic Epichloe fungal endophytes of grasses are found to mediate litter decomposition. These effects are often linked to alkaloids produced by Epichloe species, which are hypothesized to negatively affect decomposers. Although endophytes have been found to affect plant community and soil biota, direct (through litter quality) and indirect (through the environment) effects of fungal endophytes on litter decomposition have been scarcely scrutinized. We placed litterbags with endophyte-symbiotic (E+) and non-symbiotic (E−) Schedonorus pratensis plant litter in plots dominated by E+ or E− plants of the same species, and followed the dynamics of mass losses over time. We predicted the endophyte would hinder decomposition through changes in litter quality and that both types of litter would decompose faster in home environments. E+ litter decomposed faster in both environments. The mean difference between decomposition rate of E+ and E− litter tended to be higher in E− plots. Nitrogen and phosphorus, two elements usually associated with high decomposition rates, were significantly lower in E+ litter. We also detected a higher proportion of C in the cellulose form in E+ litter. Contrary to the general assumption, we found that symbiosis with Epichloe fungal endophytes can be associated with higher decomposition of plant litter. Since direct effects of Epichloe fungi were still stronger than indirect effects, it is suggested that besides the alkaloids, other changes in plant biomass would explain in a context-dependent manner, the endophyte effects on the litter decomposition.
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no effects of Epichloe endophyte infection on nitrogen cycling in meadow fescue schedonorus pratensis grassland
Plant and Soil, 2016Co-Authors: Juha Mikola, Marjo Helander, Kari SaikkonenAbstract:Background and aims Systemic Epichloe endophytes produce alkaloids that protect their grass hosts against pathogens and herbivores. These alkaloids, together with other endophyte induced changes in litter quality, may decelerate the decomposition of infected grass litter, but so far no study has tested whether the effects on decomposition rate translate into changes in N cycling in infected grasslands. Here we test if the Epichloe uncinata infection of meadow fescue, Schedonorus pratensis decelerates litter decomposition and N release, increases soil C and N accumulation and lowers the availability of mineral N in the soil under infected grass.
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endophytic Epichloe species and their grass hosts from evolution to applications
Plant Molecular Biology, 2016Co-Authors: Kari Saikkonen, Marjo Helander, Carolyn A Young, Christopher L SchardlAbstract:The closely linked fitness of the Epichloe symbiont and the host grass is presumed to align the coevolution of the species towards specialization and mutually beneficial cooperation. Ecological observations demonstrating that Epichloe-grass symbioses can modulate grassland ecosystems via both above- and belowground ecosystem processes support this. In many cases the detected ecological importance of Epichloe species is directly or indirectly linked to defensive mutualism attributable to alkaloids of fungal-origin. Now, modern genetic and molecular techniques enable the precise studies on evolutionary origin of endophytic Epichloe species, their coevolution with host grasses and identification the genetic variation that explains phenotypic diversity in ecologically relevant characteristics of Epichloe-grass associations. Here we briefly review the most recent findings in these areas of research using the present knowledge of the genetic variation that explains the biosynthetic pathways driving the diversity of alkaloids produced by the endophyte. These findings underscore the importance of genetic interplay between the fungus and the host in shaping their coevolution and ecological role in both natural grass ecosystems, and in the agricultural arena.
Barry Scott - One of the best experts on this subject based on the ideXlab platform.
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lolium perenne apoplast metabolomics for identification of novel metabolites produced by the symbiotic fungus Epichloe festucae
New Phytologist, 2020Co-Authors: Kimberly A Green, Daniel Berry, Kirstin Feussner, Carla J Eaton, Carl H Mesarich, Peter S Solomon, Ivo Feussner, Barry ScottAbstract:Epichloe festucae is an endophytic fungus that forms a symbiotic association with Lolium perenne. Here we analysed how the metabolome of the ryegrass apoplast changed upon infection of this host with sexual and asexual isolates of E. festucae. A metabolite fingerprinting approach was used to analyse the metabolite composition of apoplastic wash fluid from non-infected and infected L. perenne. Metabolites enriched or depleted in one or both of these treatments were identified using a set of interactive tools. A genetic approach in combination with tandem mass spectrometry was used to identify a novel product of a secondary metabolite gene cluster. Metabolites likely to be present in the apoplast were identified using MarVis in combination with the BioCyc and KEGG databases, and an in-house Epichloe metabolite database. We were able to identify the known endophyte-specific metabolites, peramine and Epichloecyclins, as well as a large number of unknown markers. To determine whether these methods can be applied to the identification of novel Epichloe-derived metabolites, we deleted a gene encoding a NRPS (lgsA) that is highly expressed in planta. Comparative mass spectrometric analysis of apoplastic wash fluid from wild-type- versus mutant-infected plants identified a novel Leu/Ile glycoside metabolite present in the former.
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lolium perenne apoplast metabolomics for identification of novel metabolites produced by the symbiotic fungus Epichloe festucae
New Phytologist, 2020Co-Authors: Kimberly A Green, Daniel Berry, Kirstin Feussner, Carla J Eaton, Carl H Mesarich, Peter S Solomon, Ivo Feussner, Barry ScottAbstract:: Epichloe festucae is an endophytic fungus that forms a symbiotic association with Lolium perenne. Here we analysed how the metabolome of the ryegrass apoplast changed upon infection of this host with sexual and asexual isolates of E. festucae. A metabolite fingerprinting approach was used to analyse the metabolite composition of apoplastic wash fluid from uninfected and infected L. perenne. Metabolites enriched or depleted in one or both of these treatments were identified using a set of interactive tools. A genetic approach in combination with tandem MS was used to identify a novel product of a secondary metabolite gene cluster. Metabolites likely to be present in the apoplast were identified using MarVis in combination with the BioCyc and KEGG databases, and an in-house Epichloe metabolite database. We were able to identify the known endophyte-specific metabolites, peramine and Epichloecyclins, as well as a large number of unknown markers. To determine whether these methods can be applied to the identification of novel Epichloe-derived metabolites, we deleted a gene encoding a NRPS (lgsA) that is highly expressed in planta. Comparative MS analysis of apoplastic wash fluid from wild-type- vs mutant-infected plants identified a novel Leu/Ile glycoside metabolite present in the former.
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reprogramming of the apoplast metabolome of lolium perenne upon infection with the mutualistic symbiont Epichloe festucae
bioRxiv, 2019Co-Authors: Kimberly A Green, Daniel Berry, Kirstin Feussner, Carla J Eaton, Carl H Mesarich, Peter S Solomon, Ivo Feussner, Barry ScottAbstract:Summary Epichloe festucae is an endophytic fungus that forms a mutualistic symbiotic association with Lolium perenne. Here we analysed how the metabolome of the ryegrass apoplast changed upon infection of this host with sexual and asexual isolates of E. festucae. A metabolite fingerprinting approach was used to analyse the metabolite composition of apoplastic wash fluid from non-infected and infected L. perenne. Metabolites enriched or depleted in one or both of these treatments were identified using a set of interactive tools. A genetic approach in combination with tandem mass spectrometry was used to identify a novel product of a secondary metabolite gene cluster. Metabolites likely to be present in the apoplast were identified using the MarVis Pathway in combination with the BioCyc and KEGG databases, and an in-house Epichloe metabolite database. We were able to identify the known endophyte-specific metabolites, peramine and Epichloecyclins, as well as a large number of unknown markers. To determine whether these methods can be applied to the identification of novel Epichloe-derived metabolites, we deleted a gene encoding a NRPS (lgsA) that is highly expressed in planta. Comparative mass spectrometric analysis of apoplastic wash fluid from wild-type- versus mutant- infected plants identified a novel Leu/Ile glycoside metabolite present in the former.
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analysis of simple sequence repeat ssr structure and sequence within Epichloe endophyte genomes reveals impacts on gene structure and insights into ancestral hybridization events
PLOS ONE, 2017Co-Authors: William Clayton, Pierre-yves Dupont, Carla J Eaton, Tim Gillanders, Nick Cameron, Sanjay Saikia, Barry ScottAbstract:Epichloe grass endophytes comprise a group of filamentous fungi of both sexual and asexual species. Known for the beneficial characteristics they endow upon their grass hosts, the identification of these endophyte species has been of great interest agronomically and scientifically. The use of simple sequence repeat loci and the variation in repeat elements has been used to rapidly identify endophyte species and strains, however, little is known of how the structure of repeat elements changes between species and strains, and where these repeat elements are located in the fungal genome. We report on an in-depth analysis of the structure and genomic location of the simple sequence repeat locus B10, commonly used for Epichloe endophyte species identification. The B10 repeat was found to be located within an exon of a putative bZIP transcription factor, suggesting possible impacts on polypeptide sequence and thus protein function. Analysis of this repeat in the asexual endophyte hybrid Epichloe uncinata revealed that the structure of B10 alleles reflects the ancestral species that hybridized to give rise to this species. Understanding the structure and sequence of these simple sequence repeats provides a useful set of tools for readily distinguishing strains and for gaining insights into the ancestral species that have undergone hybridization events.
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disparate independent genetic events disrupt the secondary metabolism gene pera in certain symbiotic Epichloe species
Applied and Environmental Microbiology, 2015Co-Authors: Daniel Berry, Christopher L Schardl, Barry Scott, Nikki D Charlton, Johanna E Takach, Carolyn A YoungAbstract:ABSTRACT Peramine is an insect-feeding deterrent produced by Epichloe species in symbiotic association with C 3 grasses. The perA gene responsible for peramine synthesis encodes a two-module nonribosomal peptide synthetase. Alleles of perA are found in most Epichloe species; however, peramine is not produced by many perA -containing Epichloe isolates. The genetic basis of these peramine-negative chemotypes is often unknown. Using PCR and DNA sequencing, we analyzed the perA genes from 72 Epichloe isolates and identified causative mutations of perA null alleles. We found nonfunctional perA -ΔR* alleles, which contain a transposon-associated deletion of the perA region encoding the C-terminal reductase domain, are widespread within the Epichloe genus and represent a prevalent mutation found in nonhybrid species. Disparate phylogenies of adjacent A2 and T2 domains indicated that the deletion of the reductase domain (R*) likely occurred once and early in the evolution of the genus, and subsequently there have been several recombinations between those domains. A number of novel point, deletion, and insertion mutations responsible for abolishing peramine production in full-length perA alleles were also identified. The regions encoding the first and second adenylation domains (A1 and A2, respectively) were common sites for such mutations. Using this information, a method was developed to predict peramine chemotypes by combining PCR product size polymorphism analysis with sequencing of the perA adenylation domains.