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Du M, Wang T, Li C, Chen T. Discovery and Characterization of Epichloë Fungal Endophytes from Elymus spp. in Northwest China. Microorganisms 2024; 12:1497. [PMID: 39065265 PMCID: PMC11278780 DOI: 10.3390/microorganisms12071497] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/17/2024] [Revised: 07/09/2024] [Accepted: 07/20/2024] [Indexed: 07/28/2024] Open
Abstract
Epichloë fungal endophytes hold promise in sustainable agriculture by fortifying cool-season grasses such as Elymus spp. against various stresses. Elymus spp. are widely distributed in Northwest China with a high incidence of endophyte infections. In this study, we identified 20 Epichloë endophytic fungal strains carried by five Elymus spp. from five areas of Northwest China and systematically characterized their morphology, molecular phylogeny, mating type, and alkaloid diversity for the first time. The morphological characterization underscores strain diversity, with variable colony textures and growth rates. A phylogenetic analysis confirms all strains are E. bromicola, emphasizing their taxonomic status. Alkaloid-encoding gene profiling delineates distinct alkaloid synthesis capabilities among the strains, which are crucial for host adaptability and resistance. A mating-type analysis reveals uniformity (mtAC) across the Epichloë strains, simplifying breeding strategies. Notably, the Epichloë strains exhibit diverse alkaloid synthesis gene profiles, impacting host interactions. This research emphasizes the ecological significance of Epichloë endophytes in Elymus spp. ecosystems, offering insights into their genetic diversity and potential applications in sustainable agriculture.
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Affiliation(s)
- Mingxiang Du
- State Key Laboratory of Herbage Improvement and Grassland Agro-Ecosystems, Gansu Tech Innovation Centre of Western China Grassland Industry, College of Pastoral Agriculture Science and Technology, Lanzhou University, Lanzhou 730000, China; (M.D.); (T.W.); (C.L.)
| | - Tian Wang
- State Key Laboratory of Herbage Improvement and Grassland Agro-Ecosystems, Gansu Tech Innovation Centre of Western China Grassland Industry, College of Pastoral Agriculture Science and Technology, Lanzhou University, Lanzhou 730000, China; (M.D.); (T.W.); (C.L.)
| | - Chunjie Li
- State Key Laboratory of Herbage Improvement and Grassland Agro-Ecosystems, Gansu Tech Innovation Centre of Western China Grassland Industry, College of Pastoral Agriculture Science and Technology, Lanzhou University, Lanzhou 730000, China; (M.D.); (T.W.); (C.L.)
- Grassland Research Center of National Forestry and Grassland Administration, Chinese Academy of Forestry, Beijing 100091, China
| | - Taixiang Chen
- State Key Laboratory of Herbage Improvement and Grassland Agro-Ecosystems, Gansu Tech Innovation Centre of Western China Grassland Industry, College of Pastoral Agriculture Science and Technology, Lanzhou University, Lanzhou 730000, China; (M.D.); (T.W.); (C.L.)
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2
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Identification of Three Epichloë Endophytes from Hordeum bogdanii Wilensky in China. J Fungi (Basel) 2022; 8:jof8090928. [PMID: 36135653 PMCID: PMC9502125 DOI: 10.3390/jof8090928] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/11/2022] [Revised: 08/19/2022] [Accepted: 08/27/2022] [Indexed: 11/24/2022] Open
Abstract
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.
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3
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Miller TA, Hudson DA, Johnson RD, Singh JS, Mace WJ, Forester NT, Maclean PH, Voisey CR, Johnson LJ. Dissection of the epoxyjanthitrem pathway in Epichloë sp. LpTG-3 strain AR37 by CRISPR gene editing. FRONTIERS IN FUNGAL BIOLOGY 2022; 3:944234. [PMID: 37746172 PMCID: PMC10512260 DOI: 10.3389/ffunb.2022.944234] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 05/14/2022] [Accepted: 07/18/2022] [Indexed: 09/26/2023]
Abstract
Epichloë festucae var. lolii and Epichloë sp. LpTG-3 are filamentous fungal endophytes of perennial ryegrass (Lolium perenne) that have a substantial impact on New Zealand's agricultural economy by conferring biotic advantages to the host grass. Overall, Epichloë endophytes contribute NZ$200 million to the economy annually, with strain AR37 estimated to contribute NZ$3.6 billion to the New Zealand economy over a 20-year period. This strain produces secondary metabolites, including epoxyjanthitrems, which are a class of indole diterpenes, associated with the observed effects of AR37 on livestock and insect pests. Until very recently, AR37 was intractable to genetic modification but this has changed with the application of CRISPR-Cas9 based gene editing techniques. In this paper, gene inactivation by CRISPR-Cas9 was used to deconvolute the genetic basis for epoxyjanthitrem biosynthesis, including creating an AR37 strain that has been edited to remove the biosynthesis of all indole diterpenes. We show that gene editing of Epichloë can be achieved without off-target events or introduction of foreign DNA (footprint-less) through an AMA1-based plasmid that simultaneously expresses the CRISPR-Cas9 system and selectable marker. Genetic modification events in these transformants were investigated through genome sequencing and in planta chemistry.
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Affiliation(s)
| | | | | | | | | | | | | | | | - Linda J. Johnson
- Grasslands Research Centre, AgResearch, Palmerston North, New Zealand
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4
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Berry D, Lee K, Winter D, Mace W, Becker Y, Nagabhyru P, Treindl AD, Bogantes EV, Young CA, Leuchtmann A, Johnson LJ, Johnson RD, Cox MP, Schardl CL, Scott B. Cross-species transcriptomics identifies core regulatory changes differentiating the asymptomatic asexual and virulent sexual life cycles of grass-symbiotic Epichloë fungi. G3 (BETHESDA, MD.) 2022; 12:jkac043. [PMID: 35191483 PMCID: PMC8982410 DOI: 10.1093/g3journal/jkac043] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 09/21/2021] [Accepted: 02/07/2022] [Indexed: 02/04/2023]
Abstract
Fungi from the genus Epichloë form systemic endobiotic infections of cool season grasses, producing a range of host-protective natural products in return for access to nutrients. These infections are asymptomatic during vegetative host growth, with associations between asexual Epichloë spp. and their hosts considered mutualistic. However, the sexual cycle of Epichloë spp. involves virulent growth, characterized by the envelopment and sterilization of a developing host inflorescence by a dense sheath of mycelia known as a stroma. Microscopic analysis of stromata revealed a dramatic increase in hyphal propagation and host degradation compared with asymptomatic tissues. RNAseq was used to identify differentially expressed genes in asymptomatic vs stromatized tissues from 3 diverse Epichloë-host associations. Comparative analysis identified a core set of 135 differentially expressed genes that exhibited conserved transcriptional changes across all 3 associations. The core differentially expressed genes more strongly expressed during virulent growth encode proteins associated with host suppression, digestion, adaptation to the external environment, a biosynthetic gene cluster, and 5 transcription factors that may regulate Epichloë stroma formation. An additional 5 transcription factor encoding differentially expressed genes were suppressed during virulent growth, suggesting they regulate mutualistic processes. Expression of biosynthetic gene clusters for natural products that suppress herbivory was universally suppressed during virulent growth, and additional biosynthetic gene clusters that may encode production of novel host-protective natural products were identified. A comparative analysis of 26 Epichloë genomes found a general decrease in core differentially expressed gene conservation among asexual species, and a specific decrease in conservation for the biosynthetic gene cluster expressed during virulent growth and an unusual uncharacterized gene.
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Affiliation(s)
- Daniel Berry
- Institute of Fundamental Sciences, Massey University, Palmerston North 4442, New Zealand
| | - Kate Lee
- Institute of Fundamental Sciences, Massey University, Palmerston North 4442, New Zealand
| | - David Winter
- Institute of Fundamental Sciences, Massey University, Palmerston North 4442, New Zealand
| | - Wade Mace
- AgResearch Ltd, Grasslands Research Centre, Palmerston North 4442, New Zealand
| | - Yvonne Becker
- Institute for Epidemiology and Pathogen Diagnostics, Julius Kühn Institute, Federal Research Centre for Cultivated Plants, 38104 Braunschweig, Germany
| | - Padmaja Nagabhyru
- Department of Plant Pathology, University of Kentucky, Lexington, KY 40546, USA
| | - Artemis D Treindl
- Institute of Integrative Biology, ETH Zurich, 8092 Zürich, Switzerland
| | | | | | - Adrian Leuchtmann
- Institute of Integrative Biology, ETH Zurich, 8092 Zürich, Switzerland
| | | | | | - Murray P Cox
- Institute of Fundamental Sciences, Massey University, Palmerston North 4442, New Zealand
| | | | - Barry Scott
- Institute of Fundamental Sciences, Massey University, Palmerston North 4442, New Zealand
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5
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von Cräutlein M, Helander M, Korpelainen H, Leinonen PH, Vázquez de Aldana BR, Young CA, Zabalgogeazcoa I, Saikkonen K. Genetic Diversity of the Symbiotic Fungus Epichloë festucae in Naturally Occurring Host Grass Populations. Front Microbiol 2021; 12:756991. [PMID: 34925265 PMCID: PMC8678516 DOI: 10.3389/fmicb.2021.756991] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2021] [Accepted: 10/29/2021] [Indexed: 11/20/2022] Open
Abstract
Epichloë festucae is a common symbiont of the perennial and widely distributed cool season grass, Festuca rubra. The symbiosis is highly integrated involving systemic growth of the fungus throughout above-ground host parts and vertical transmission from plant to its offspring via host seeds. However, the nature of symbiosis is labile ranging from antagonistic to mutualistic depending on prevailing selection pressures. Both the loss of fungus in the maternal host lineage and horizontal transmission through sexual spores within the host population may partly explain the detected variation in symbiosis in wild grass populations. Epichloë species are commonly considered as pathogens when they produce sexual spores and partly castrate their host plant. This is the pathogenic end of the continuum from antagonistic to mutualistic interactions. Here we examined the population genetic structure of E. festucae to reveal the gene flow, importance of reproduction modes, and alkaloid potential of the symbiotic fungus in Europe. Epichloë-species are highly dependent on the host in survival and reproduction whilst benefits to the host are largely linked to defensive mutualism attributable to fungal-origin bioactive alkaloids that negatively affect vertebrate and/or invertebrate herbivores. We detected decreased genetic diversity in previously glaciated areas compared to non-glaciated regions during the last glacial maximum period and found three major genetic clusters in E. festucae populations: southern, northeastern and northwestern Europe. Sexual reproduction may have a higher role than expected in Spanish E. festucae populations due to the predominance of unique genotypes and presence of both mating types in the region. In contrast, asexual reproduction via host seeds predominates in the Faroe Island and Finland in northern Europe due to the presence of biased mating-type ratios and large dominant genotypes in the E. festucae populations within the region. A substantially larger variation of alkaloid genotypes was observed in the fungal populations than expected, although the variability of the alkaloid genotypes within populations is considerably lower in northern than Spanish populations in southern Europe. E. festucae populations consist of different combinations of alkaloid classes from the gene clusters of ergot alkaloid and indole-terpenes, and from pyrrolopyrazine alkaloid gene. We suggest that the postglacial distribution history of the host grass, prevailing reproduction strategies of E. festucae, and local selection pressures likely explain a large part of the genetic variation observed in fungal populations among geographic regions. The identified alkaloid genotypes can be used by turfgrass breeders to improve resistance against herbivores in red fescue varieties and to develop new sustainable cultivars in Europe.
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Affiliation(s)
- Maria von Cräutlein
- Department of Agricultural Sciences, Viikki Plant Science Centre, University of Helsinki, Helsinki, Finland.,Management and Production of Renewable Resources, Natural Resources Institute Finland (Luke), Helsinki, Finland.,Biodiversity Unit, University of Turku, Turku, Finland
| | - Marjo Helander
- Department of Biology, University of Turku, Turku, Finland
| | - Helena Korpelainen
- Department of Agricultural Sciences, Viikki Plant Science Centre, University of Helsinki, Helsinki, Finland
| | - Päivi Helena Leinonen
- Management and Production of Renewable Resources, Natural Resources Institute Finland (Luke), Helsinki, Finland.,Biodiversity Unit, University of Turku, Turku, Finland
| | - Beatriz R Vázquez de Aldana
- Institute of Natural Resources and Agrobiology of Salamanca, Spanish National Research Council (CSIC), Salamanca, Spain
| | | | - Iñigo Zabalgogeazcoa
- Institute of Natural Resources and Agrobiology of Salamanca, Spanish National Research Council (CSIC), Salamanca, Spain
| | - Kari Saikkonen
- Biodiversity Unit, University of Turku, Turku, Finland.,Management and Production of Renewable Resources, Natural Resources Institute Finland (Luke), Turku, Finland
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7
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Green KA, Berry D, Feussner K, Eaton CJ, Ram A, Mesarich CH, Solomon P, Feussner I, Scott B. Lolium perenne apoplast metabolomics for identification of novel metabolites produced by the symbiotic fungus Epichloë festucae. THE NEW PHYTOLOGIST 2020; 227:559-571. [PMID: 32155669 PMCID: PMC7317419 DOI: 10.1111/nph.16528] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/08/2019] [Accepted: 02/28/2020] [Indexed: 05/05/2023]
Abstract
Epichloë 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 Epichloë metabolite database. We were able to identify the known endophyte-specific metabolites, peramine and epichloëcyclins, as well as a large number of unknown markers. To determine whether these methods can be applied to the identification of novel Epichloë-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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Affiliation(s)
- Kimberly A. Green
- School of Fundamental SciencesMassey UniversityPalmerston North4442New Zealand
- Bioprotection Research CentreMassey UniversityPalmerston North4442New Zealand
| | - Daniel Berry
- School of Fundamental SciencesMassey UniversityPalmerston North4442New Zealand
- Bioprotection Research CentreMassey UniversityPalmerston North4442New Zealand
| | - Kirstin Feussner
- Department of Plant BiochemistryAlbrecht von Haller Institute for Plant SciencesUniversity of GoettingenD‐37077GoettingenGermany
- Service Unit for Metabolomics and LipidomicsGoettingen Center for Molecular Biosciences (GZMB)University of GoettingenD‐37077GoettingenGermany
| | - Carla J. Eaton
- School of Fundamental SciencesMassey UniversityPalmerston North4442New Zealand
- Bioprotection Research CentreMassey UniversityPalmerston North4442New Zealand
| | - Arvina Ram
- School of Fundamental SciencesMassey UniversityPalmerston North4442New Zealand
| | - Carl H. Mesarich
- Bioprotection Research CentreMassey UniversityPalmerston North4442New Zealand
- School of Agriculture and EnvironmentMassey UniversityPalmerston North4442New Zealand
| | - Peter Solomon
- Research School of BiologyAustralian National UniversityCanberraACT0200Australia
| | - Ivo Feussner
- Department of Plant BiochemistryAlbrecht von Haller Institute for Plant SciencesUniversity of GoettingenD‐37077GoettingenGermany
- Service Unit for Metabolomics and LipidomicsGoettingen Center for Molecular Biosciences (GZMB)University of GoettingenD‐37077GoettingenGermany
- Department of Plant BiochemistryGoettingen Center for Molecular Biosciences (GZMB)University of GoettingenD‐37077GoettingenGermany
| | - Barry Scott
- School of Fundamental SciencesMassey UniversityPalmerston North4442New Zealand
- Bioprotection Research CentreMassey UniversityPalmerston North4442New Zealand
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8
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Fernando K, Reddy P, Hettiarachchige IK, Spangenberg GC, Rochfort SJ, Guthridge KM. Novel Antifungal Activity of Lolium-Associated Epichloë Endophytes. Microorganisms 2020; 8:microorganisms8060955. [PMID: 32599897 PMCID: PMC7355949 DOI: 10.3390/microorganisms8060955] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/27/2020] [Revised: 06/19/2020] [Accepted: 06/19/2020] [Indexed: 01/22/2023] Open
Abstract
Asexual Epichloë spp. fungal endophytes have been extensively studied for their functional secondary metabolite production. Historically, research mostly focused on understanding toxicity of endophyte-derived compounds on grazing livestock. However, endophyte-derived compounds also provide protection against invertebrate pests, disease, and other environmental stresses, which is important for ensuring yield and persistence of pastures. A preliminary screen of 30 strains using an in vitro dual culture bioassay identified 18 endophyte strains with antifungal activity. The novel strains NEA12, NEA21, and NEA23 were selected for further investigation as they are also known to produce alkaloids associated with protection against insect pests. Antifungal activity of selected endophyte strains was confirmed against three grass pathogens, Ceratobasidium sp., Dreschlera sp., and Fusarium sp., using independent isolates in an in vitro bioassay. NEA21 and NEA23 showed potent activity against Ceratobasidium sp. and NEA12 showed moderate inhibition against all three pathogens. Crude extracts from liquid cultures of NEA12 and NEA23 also inhibited growth of the phytopathogens Ceratobasidium sp. and Fusarium sp. and provided evidence that the compounds of interest are stable, constitutively expressed, and secreted. Comparative analysis of the in vitro and in planta metabolome of NEA12 and NEA23 using LCMS profile data revealed individual metabolites unique to each strain that are present in vitro and in planta. These compounds are the best candidates for the differential bioactivity observed for each strain. Novel endophyte strains show promise for endophyte-mediated control of phytopathogens impacting Lolium spp. pasture production and animal welfare.
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Affiliation(s)
- Krishni Fernando
- Agriculture Victoria, AgriBio, Centre for AgriBioscience, Bundoora, 3083 Victoria, Australia; (K.F.); (P.R.); (I.K.H.); (G.C.S.); (S.J.R.)
- School of Applied Systems Biology, La Trobe University, Bundoora, 3083 Victoria, Australia
| | - Priyanka Reddy
- Agriculture Victoria, AgriBio, Centre for AgriBioscience, Bundoora, 3083 Victoria, Australia; (K.F.); (P.R.); (I.K.H.); (G.C.S.); (S.J.R.)
| | - Inoka K. Hettiarachchige
- Agriculture Victoria, AgriBio, Centre for AgriBioscience, Bundoora, 3083 Victoria, Australia; (K.F.); (P.R.); (I.K.H.); (G.C.S.); (S.J.R.)
| | - German C. Spangenberg
- Agriculture Victoria, AgriBio, Centre for AgriBioscience, Bundoora, 3083 Victoria, Australia; (K.F.); (P.R.); (I.K.H.); (G.C.S.); (S.J.R.)
- School of Applied Systems Biology, La Trobe University, Bundoora, 3083 Victoria, Australia
| | - Simone J. Rochfort
- Agriculture Victoria, AgriBio, Centre for AgriBioscience, Bundoora, 3083 Victoria, Australia; (K.F.); (P.R.); (I.K.H.); (G.C.S.); (S.J.R.)
- School of Applied Systems Biology, La Trobe University, Bundoora, 3083 Victoria, Australia
| | - Kathryn M. Guthridge
- Agriculture Victoria, AgriBio, Centre for AgriBioscience, Bundoora, 3083 Victoria, Australia; (K.F.); (P.R.); (I.K.H.); (G.C.S.); (S.J.R.)
- Correspondence: ; Tel.: +61390327062
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Bharadwaj R, Jagadeesan H, Kumar SR, Ramalingam S. Molecular mechanisms in grass-Epichloë interactions: towards endophyte driven farming to improve plant fitness and immunity. World J Microbiol Biotechnol 2020; 36:92. [PMID: 32562008 DOI: 10.1007/s11274-020-02868-5] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2020] [Accepted: 06/10/2020] [Indexed: 11/26/2022]
Abstract
All plants harbor many microbial species including bacteria and fungi in their tissues. The interactions between the plant and these microbes could be symbiotic, mutualistic, parasitic or commensalistic. Mutualistic microorganisms are endophytic in nature and are known to play a role in plant growth, development and fitness. Endophytes display complex diversity depending upon the agro-climatic conditions and this diversity could be exploited for crop improvement and sustainable agriculture. Plant-endophyte partnerships are highly specific, several genetic and molecular cascades play a key role in colonization of endophytes in host plants leading to rapid changes in host and endophyte metabolism. This results in the accumulation of secondary metabolites, which play an important role in plant defense against biotic and abiotic stress conditions. Alkaloids are one of the important class of metabolites produced by Epichloë genus and other related classes of endophytes and confer protection against insect and mammalian herbivory. In this context, this review discusses the evolutionary aspects of the Epichloë genus along with key molecular mechanisms determining the lifestyle of Epichloë endophytes in host system. Novel hypothesis is proposed to outline the initial cellular signaling events during colonization of Epichloë in cool season grasses. Complex clustering of alkaloid biosynthetic genes and molecular mechanisms involved in the production of alkaloids have been elaborated in detail. The natural defense and advantages of the endophyte derived metabolites have also been extensively discussed. Finally, this review highlights the importance of endophyte-arbitrated plant immunity to develop novel approaches for eco-friendly agriculture.
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Affiliation(s)
- R Bharadwaj
- Plant Genetic Engineering Laboratory, Department of Biotechnology, Bharathiar University, Coimbatore, Tamil Nadu, 641046, India
| | - H Jagadeesan
- Department of Biotechnology, PSG College of Technology, Coimbatore, Tamil Nadu, India
| | - S R Kumar
- Plant Genetic Engineering Laboratory, Department of Biotechnology, Bharathiar University, Coimbatore, Tamil Nadu, 641046, India
| | - S Ramalingam
- Plant Genetic Engineering Laboratory, Department of Biotechnology, Bharathiar University, Coimbatore, Tamil Nadu, 641046, India.
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10
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Berry D, Mace W, Grage K, Wesche F, Gore S, Schardl CL, Young CA, Dijkwel PP, Leuchtmann A, Bode HB, Scott B. Efficient nonenzymatic cyclization and domain shuffling drive pyrrolopyrazine diversity from truncated variants of a fungal NRPS. Proc Natl Acad Sci U S A 2019; 116:25614-25623. [PMID: 31801877 PMCID: PMC6926027 DOI: 10.1073/pnas.1913080116] [Citation(s) in RCA: 22] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
Nonribosomal peptide synthetases (NRPSs) generate the core peptide scaffolds of many natural products. These include small cyclic dipeptides such as the insect feeding deterrent peramine, which is a pyrrolopyrazine (PPZ) produced by grass-endophytic Epichloë fungi. Biosynthesis of peramine is catalyzed by the 2-module NRPS, PpzA-1, which has a C-terminal reductase (R) domain that is required for reductive release and cyclization of the NRPS-tethered dipeptidyl-thioester intermediate. However, some PpzA variants lack this R domain due to insertion of a transposable element into the 3' end of ppzA We demonstrate here that these truncated PpzA variants utilize nonenzymatic cyclization of the dipeptidyl thioester to a 2,5-diketopiperazine (DKP) to synthesize a range of novel PPZ products. Truncation of the R domain is sufficient to subfunctionalize PpzA-1 into a dedicated DKP synthetase, exemplified by the truncated variant, PpzA-2, which has also evolved altered substrate specificity and reduced N-methyltransferase activity relative to PpzA-1. Further allelic diversity has been generated by recombination-mediated domain shuffling between ppzA-1 and ppzA-2, resulting in the ppzA-3 and ppzA-4 alleles, each of which encodes synthesis of a unique PPZ metabolite. This research establishes that efficient NRPS-catalyzed DKP biosynthesis can occur in vivo through nonenzymatic dipeptidyl cyclization and presents a remarkably clean example of NRPS evolution through recombinant exchange of functionally divergent domains. This work highlights that allelic variants of a single NRPS can result in a surprising level of secondary metabolite diversity comparable to that observed for some gene clusters.
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Affiliation(s)
- Daniel Berry
- School of Fundamental Sciences, Massey University, Palmerston North 4442, New Zealand
- Bioprotection Research Centre, Massey University, Palmerston North 4442, New Zealand
| | - Wade Mace
- Grasslands Research Centre, AgResearch Ltd., Palmerston North 4442, New Zealand
| | - Katrin Grage
- School of Fundamental Sciences, Massey University, Palmerston North 4442, New Zealand
| | - Frank Wesche
- Fachbereich Biowissenschaften, Molekulare Biotechnologie, Goethe Universität Frankfurt, 60438 Frankfurt am Main, Germany
| | - Sagar Gore
- Leibniz Institute for Natural Product Research and Infection Biology, Hans Knöll Institute, 07745 Jena, Germany
| | | | | | - Paul P Dijkwel
- School of Fundamental Sciences, Massey University, Palmerston North 4442, New Zealand
- Bioprotection Research Centre, Massey University, Palmerston North 4442, New Zealand
| | - Adrian Leuchtmann
- Institute of Integrative Biology, ETH Zürich, CH-8092 Zürich, Switzerland
| | - Helge B Bode
- Fachbereich Biowissenschaften, Molekulare Biotechnologie, Goethe Universität Frankfurt, 60438 Frankfurt am Main, Germany;
- Buchmann Institute for Molecular Life Sciences, Goethe-Universität, 60438 Frankfurt am Main, Germany
- Landes-Offensive zur Entwicklung Wissenschaftlich-Ökonomischer Exzellenz (LOEWE) Centre for Translational Biodiversity Genomics, 60325 Frankfurt am Main, Germany
| | - Barry Scott
- School of Fundamental Sciences, Massey University, Palmerston North 4442, New Zealand;
- Bioprotection Research Centre, Massey University, Palmerston North 4442, New Zealand
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11
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Wang R, Clarke BB, Belanger FC. Transcriptome Analysis of Choke Stroma and Asymptomatic Inflorescence Tissues Reveals Changes in Gene Expression in Both Epichloë festucae and Its Host Plant Festuca rubra subsp. rubra. Microorganisms 2019; 7:E567. [PMID: 31744076 PMCID: PMC6921078 DOI: 10.3390/microorganisms7110567] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/07/2019] [Revised: 11/13/2019] [Accepted: 11/14/2019] [Indexed: 02/07/2023] Open
Abstract
Many cool-season grasses have symbiotic relationships with Epichloë (Ascomycota, Clavicipitaceae) fungal endophytes that inhabit the intercellular spaces of the above-ground parts of the host plants. The presence of the Epichloë endophytes is generally beneficial to the hosts due to enhanced tolerance to biotic and abiotic stresses conferred by the endophytes. Many Epichloë spp. are asexual, and those infections always remain asymptomatic. However, some Epichloë spp. have a sexual stage and produce a macroscopic fruiting body, a stroma, that envelops the developing inflorescence causing a syndrome termed "choke disease". Here, we report a fungal and plant gene expression analysis of choke stroma tissue and asymptomatic inflorescence tissue of Epichloë festucae-infected strong creeping red fescue (Festuca rubra subsp. rubra). Hundreds of fungal genes and over 10% of the plant genes were differentially expressed when comparing the two tissue types. The differentially expressed fungal genes in the choke stroma tissue indicated a change in carbohydrate and lipid metabolism, as well as a change in expression of numerous genes for candidate effector proteins. Plant stress-related genes were up-regulated in the stroma tissue, suggesting the plant host was responding to the epiphytic stage of E. festucae as a pathogen.
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Affiliation(s)
| | | | - Faith C. Belanger
- Department of Plant Biology, Rutgers University, New Brunswick, NJ 08901, USA; (R.W.); (B.B.C.)
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Infection Rates and Alkaloid Patterns of Different Grass Species with Systemic Epichloë Endophytes. Appl Environ Microbiol 2019; 85:AEM.00465-19. [PMID: 31227553 DOI: 10.1128/aem.00465-19] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/25/2019] [Accepted: 06/14/2019] [Indexed: 01/05/2023] Open
Abstract
Symbiotic Epichloë 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 Epichloë 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 Epichloë 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 Epichloë 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 Epichloë-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. Epichloë uncinata in F. pratensis produced anti-insect loline compounds. The Epichloë 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. Epichloë 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 Epichloë-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 Epichloë 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 Epichloë-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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Olarte RA, Menke J, Zhang Y, Sullivan S, Slot JC, Huang Y, Badalamenti JP, Quandt AC, Spatafora JW, Bushley KE. Chromosome rearrangements shape the diversification of secondary metabolism in the cyclosporin producing fungus Tolypocladium inflatum. BMC Genomics 2019; 20:120. [PMID: 30732559 PMCID: PMC6367777 DOI: 10.1186/s12864-018-5399-x] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/21/2018] [Accepted: 12/19/2018] [Indexed: 01/07/2023] Open
Abstract
BACKGROUND Genes involved in production of secondary metabolites (SMs) in fungi are exceptionally diverse. Even strains of the same species may exhibit differences in metabolite production, a finding that has important implications for drug discovery. Unlike in other eukaryotes, genes producing SMs are often clustered and co-expressed in fungal genomes, but the genetic mechanisms involved in the creation and maintenance of these secondary metabolite biosynthetic gene clusters (SMBGCs) remains poorly understood. RESULTS In order to address the role of genome architecture and chromosome scale structural variation in generating diversity of SMBGCs, we generated chromosome scale assemblies of six geographically diverse isolates of the insect pathogenic fungus Tolypocladium inflatum, producer of the multi-billion dollar lifesaving immunosuppressant drug cyclosporin, and utilized a Hi-C chromosome conformation capture approach to address the role of genome architecture and structural variation in generating intraspecific diversity in SMBGCs. Our results demonstrate that the exchange of DNA between heterologous chromosomes plays an important role in generating novelty in SMBGCs in fungi. In particular, we demonstrate movement of a polyketide synthase (PKS) and several adjacent genes by translocation to a new chromosome and genomic context, potentially generating a novel PKS cluster. We also provide evidence for inter-chromosomal recombination between nonribosomal peptide synthetases located within subtelomeres and uncover a polymorphic cluster present in only two strains that is closely related to the cluster responsible for biosynthesis of the mycotoxin aflatoxin (AF), a highly carcinogenic compound that is a major public health concern worldwide. In contrast, the cyclosporin cluster, located internally on chromosomes, was conserved across strains, suggesting selective maintenance of this important virulence factor for infection of insects. CONCLUSIONS This research places the evolution of SMBGCs within the context of whole genome evolution and suggests a role for recombination between chromosomes in generating novel SMBGCs in the medicinal fungus Tolypocladium inflatum.
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Affiliation(s)
- Rodrigo A. Olarte
- 0000000419368657grid.17635.36Department of Plant and Microbial Biology, University of Minnesota, St. Paul, MN USA
| | - Jon Menke
- 0000 0001 0703 5300grid.450240.7Cargill Inc., Wayzata, MN USA
| | - Ying Zhang
- 0000000419368657grid.17635.36Minnesota Supercomputing Institute, Minneapolis, MN USA
| | | | - Jason C. Slot
- 0000 0001 2285 7943grid.261331.4Department of Plant Pathology, Ohio State University, Columbus, OH USA
| | - Yinyin Huang
- 0000000419368657grid.17635.36Department of Plant and Microbial Biology, University of Minnesota, St. Paul, MN USA
| | - Jonathan P. Badalamenti
- 0000000419368657grid.17635.36University of Minnesota Genomics Center, University of Minnesota, Minneapolis, MN USA
| | - Alisha C. Quandt
- 0000000096214564grid.266190.aDepartment of Ecology and Evolutionary Biology, University of Colorado, Boulder, CO USA
| | - Joseph W. Spatafora
- 0000 0001 2112 1969grid.4391.fDepartment of Botany and Plant Pathology, Oregon State University, Corvallis, OR USA
| | - Kathryn E. Bushley
- 0000000419368657grid.17635.36Department of Plant and Microbial Biology, University of Minnesota, St. Paul, MN USA
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Bushman BS, Singh D, Lamp R, Young CA, Charlton ND, Robins JG, Anderson N. Variation Among Orchardgrass (Dactylis glomerata) Germplasm for Choke Prevalence Caused by Epichloë typhina. PLANT DISEASE 2019; 103:324-330. [PMID: 30522401 DOI: 10.1094/pdis-05-18-0867-re] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
Orchardgrass, or cocksfoot (Dactylis glomerata L.), is a cool-season forage grass susceptible to the choke disease caused by Epichloë typhina. Choke has been reported in orchardgrass seed production fields across the temperate regions of the world, but fungicides have not been efficacious in reducing choke incidence or prevalence. To assess the potential for genetic resistance or tolerance of orchardgrass to choke, we evaluated the variation in orchardgrass cultivars and accessions for choke prevalence and characterized infected plants for endophyte secondary metabolite and mating type gene presence. Significant variation was detected across years and locations. Choke prevalence did not always increase with the age of the stand, nor did choke prevalence correlate with flowering time or swathing time of the entries. Both mating types of E. typhina were detected in approximately equal proportions, and no evidence for loline, ergot alkaloid, or indole-diterpene biosynthesis was found. Plants with multiple infected tillers often showed more than one mating type present in the plant, indicating multiple infection events rather than a single infection event that spread to multiple tillers. Both accessions and cultivars with significant choke, and no choke, were detected, which constitute sources of germplasm for further testing and breeding.
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Affiliation(s)
- B Shaun Bushman
- USDA-ARS Forage and Range Research Laboratory, Logan, UT 84322
| | | | | | | | | | - Joseph G Robins
- USDA-ARS Forage and Range Research Laboratory, Logan, UT 84322
| | - Nicole Anderson
- Department of Crop and Soil Science, Oregon State University, Corvallis, OR 97331
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15
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Hettiarachchige IK, Elkins AC, Reddy P, Mann RC, Guthridge KM, Sawbridge TI, Forster JW, Spangenberg GC. Genetic modification of asexual Epichloë endophytes with the perA gene for peramine biosynthesis. Mol Genet Genomics 2018; 294:315-328. [PMID: 30443676 DOI: 10.1007/s00438-018-1510-x] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/05/2017] [Accepted: 11/08/2018] [Indexed: 10/27/2022]
Abstract
Development of grass-endophyte associations with minimal or no detrimental effects in combination with beneficial characteristics is important for pastoral agriculture. The feasibility of enhancing production of an endophyte-derived beneficial alkaloid through introduction of an additional gene copy was assessed in a proof-of-concept study. Sexual and asexual Epichloë species that form symbiotic associations with cool-season grasses of the Poaceae sub-family Pooideae produce bioactive alkaloids that confer resistance to herbivory by a number of organisms. Of these, peramine is thought to be crucial for protection of perennial ryegrass (Lolium perenne L.) from the Argentinian stem weevil, an economically important exotic pest in New Zealand, contributing significantly to pasture persistence. A single gene (perA) has been identified as solely responsible for peramine biosynthesis and is distributed widely across Epichloë taxa. In the present study, a functional copy of the perA gene was introduced into three recipient endophyte genomes by Agrobacterium tumefaciens-mediated transformation. The target strains included some that do not produce peramine, and others containing different perA gene copies. Mitotically stable transformants generated from all three endophyte strains were able to produce peramine in culture and in planta at variable levels. In summary, this study provides an insight into the potential for artificial combinations of alkaloid biosynthesis in a single endophyte strain through transgenesis, as well as the possibility of using novel genome editing techniques to edit the perA gene of non-peramine producing strains.
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Affiliation(s)
| | - Aaron C Elkins
- Agriculture Victoria, AgriBio, Centre for AgriBioscience, 3083, Bundoora, VIC, Australia
| | - Priyanka Reddy
- Agriculture Victoria, AgriBio, Centre for AgriBioscience, 3083, Bundoora, VIC, Australia
| | - Ross C Mann
- Agriculture Victoria, AgriBio, Centre for AgriBioscience, 3083, Bundoora, VIC, Australia
| | - Kathryn M Guthridge
- Agriculture Victoria, AgriBio, Centre for AgriBioscience, 3083, Bundoora, VIC, Australia
| | - Timothy I Sawbridge
- Agriculture Victoria, AgriBio, Centre for AgriBioscience, 3083, Bundoora, VIC, Australia.,School of Applied Systems Biology, La Trobe University, 3086, Bundoora, VIC, Australia
| | - John W Forster
- Agriculture Victoria, AgriBio, Centre for AgriBioscience, 3083, Bundoora, VIC, Australia.,School of Applied Systems Biology, La Trobe University, 3086, Bundoora, VIC, Australia
| | - German C Spangenberg
- Agriculture Victoria, AgriBio, Centre for AgriBioscience, 3083, Bundoora, VIC, Australia. .,School of Applied Systems Biology, La Trobe University, 3086, Bundoora, VIC, Australia.
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16
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Yi M, Hendricks WQ, Kaste J, Charlton ND, Nagabhyru P, Panaccione DG, Young CA. Molecular identification and characterization of endophytes from uncultivated barley. Mycologia 2018; 110:453-472. [PMID: 29923795 DOI: 10.1080/00275514.2018.1464818] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/17/2022]
Abstract
Epichloë species (Clavicipitaceae, Ascomycota) are endophytic symbionts of many cool-season grasses. Many interactions between Epichloë and their host grasses contribute to plant growth promotion, protection from many pathogens and insect pests, and tolerance to drought stress. Resistance to insect herbivores by endophytes associated with Hordeum species has been previously shown to vary depending on the endophyte-grass-insect combination. We explored the genetic and chemotypic diversity of endophytes present in wild Hordeum species. We analyzed seeds of Hordeum bogdanii, H. brevisubulatum, and H. comosum obtained from the US Department of Agriculture's (USDA) National Plant Germplasm System (NPGS), of which some have been reported as endophyte-infected. Using polymerase chain reaction (PCR) with primers specific to Epichloë species, we were able to identify endophytes in seeds from 17 of the 56 Plant Introduction (PI) lines, of which only 9 lines yielded viable seed. Phylogenetic analyses of housekeeping, alkaloid biosynthesis, and mating type genes suggest that the endophytes of the infected PI lines separate into five taxa: Epichloë bromicola, Epichloë tembladerae, and three unnamed interspecific hybrid species. One PI line contained an endophyte that is considered a new taxonomic group, Epichloë sp. HboTG-3 (H. bogdanii Taxonomic Group 3). Phylogenetic analyses of the interspecific hybrid endophytes from H. bogdanii and H. brevisubulatum indicate that these taxa all have an E. bromicola allele but the second allele varies. We verified in planta alkaloid production from the five genotypes yielding viable seed. Morphological characteristics of the isolates from the viable Hordeum species were analyzed for their features in culture and in planta. In the latter, we observed epiphyllous growth and in some cases sporulation on leaves of infected plants.
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Affiliation(s)
- Mihwa Yi
- a Noble Research Institute, LLC , Ardmore , Oklahoma 73401
| | | | - Joshua Kaste
- a Noble Research Institute, LLC , Ardmore , Oklahoma 73401
| | | | - Padmaja Nagabhyru
- b Department of Plant Pathology , University of Kentucky , Lexington , Kentucky 40546
| | - Daniel G Panaccione
- c Division of Plant and Soil Sciences , West Virginia University , Morgantown , West Virginia 26506
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Shi C, An S, Yao Z, Young CA, Panaccione DG, Lee ST, Schardl CL, Li C. Toxin-producing Epichloë bromicola strains symbiotic with the forage grass Elymus dahuricus in China. Mycologia 2018. [PMID: 29528270 DOI: 10.1080/00275514.2018.1426941] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
Cool-season grasses (Poaceae subfamily Poöideae) are an important forage component for livestock in western China, and many have seed-transmitted symbionts of the genus Epichloë, fungal endophytes that are broadly distributed geographically and in many tribes of the Poöideae. Epichloë strains can produce any of several classes of alkaloids, of which ergot alkaloids and indole-diterpenes can be toxic to mammalian and invertebrate herbivores, whereas lolines and peramine are more selective against invertebrates. The authors characterized genotypes and alkaloid profiles of Epichloë bromicola isolates symbiotic with Elymus dahuricus, an important forage grass in rangelands of China. The endophyte was seed-transmitted and occasionally produced fruiting bodies (stromata), but its sexual state was not observed on this host. The genome sequence of E. bromicola isolate E7626 from El. dahuricus in Xinjiang Province revealed gene sets for peramine, ergot alkaloids, and indole-diterpenes. In multiplex polymerase chain reaction (PCR) screens of El. dahuricus-endophyte isolates from Beijing and two locations in Shanxi Province, most were also positive for these genes. Ergovaline and other ergot alkaloids, terpendoles and other indole-diterpenes, and peramine were confirmed in El. dahuricus plants with E. bromicola. The presence of ergot alkaloids and indole-diterpenes in this grass is a potential concern for managers of grazing livestock.
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Affiliation(s)
- Chong Shi
- a College of Grassland and Environmental Science, Xinjiang Agricultural University , Urumqi , Xinjiang , China 830052
| | - Shazhou An
- a College of Grassland and Environmental Science, Xinjiang Agricultural University , Urumqi , Xinjiang , China 830052
| | - Zhengpei Yao
- b College of Agriculture, Xinjiang Agricultural University , Urumqi , Xinjiang , China 830052
| | - Carolyn A Young
- c Noble Research Institute , 2510 Sam Noble Parkway, Ardmore , Oklahoma 73401
| | - Daniel G Panaccione
- d Division of Plant and Soil Sciences , West Virginia University , Morgantown , West Virginia 26506-6108
| | - Stephen T Lee
- e Poisonous Plant Research Laboratory, Agricultural Research Service , United States Department of Agriculture , 1150 E. 1400 N., Logan , Utah 84341
| | - Christopher L Schardl
- f Department of Plant Pathology , University of Kentucky , Lexington , Kentucky 40546-0312
| | - Chunjie Li
- g State Key Laboratory of Grassland Agro-ecosystems, College of Pastoral Agriculture Science and Technology, Lanzhou University , Lanzhou , Gansu , China 730000
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18
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Metabolism or behavior: explaining the performance of aphids on alkaloid-producing fungal endophytes in annual ryegrass (Lolium multiflorum). Oecologia 2017; 185:245-256. [DOI: 10.1007/s00442-017-3940-2] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2016] [Accepted: 08/24/2017] [Indexed: 10/18/2022]
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19
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Song H, Liu J, Song Q, Zhang Q, Tian P, Nan Z. Comprehensive Analysis of Codon Usage Bias in Seven Epichloë Species and Their Peramine-Coding Genes. Front Microbiol 2017; 8:1419. [PMID: 28798739 PMCID: PMC5529348 DOI: 10.3389/fmicb.2017.01419] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/12/2016] [Accepted: 07/13/2017] [Indexed: 11/22/2022] Open
Abstract
Codon usage bias plays an important role in shaping genomes and genes in unicellular species and multicellular species. Here, we first analyzed codon usage bias in seven Epichloë species and their peramine-coding genes. Our results showed that both natural selection and mutation pressure played a role in forming codon usage bias in seven Epichloë species. All seven Epichloë species contained a peramine-coding gene cluster. Interestingly, codon usage bias of peramine-coding genes were not affected by natural selection or mutation pressure. There were 13 codons more frequently found in Epichloë genome sequences, peramine-coding gene clusters and orthologous peramine-coding genes, all of which had a bias to end with a C nucleotide. In the seven genomes analyzed, codon usage was biased in highly expressed coding sequences (CDSs) with shorter length and higher GC content. Genes in the peramine-coding gene cluster had higher GC content at the third nucleotide position of the codon, and highly expressed genes had higher GC content at the second position. In orthologous peramine-coding CDSs, high expression level was not significantly correlated with CDS length and GC content. Analysis of selection pressure identified that the genes orthologous to peramine genes were under purifying selection. There were no differences in codon usage bias and selection pressure between peramine product genes and non-functional peramine product genes. Our results provide insights into understanding codon evolution in Epichloë species.
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Affiliation(s)
- Hui Song
- State Key Laboratory of Grassland Agro-ecosystems, College of Pastoral Agriculture Science and Technology, Lanzhou UniversityLanzhou, China
| | - Jing Liu
- State Key Laboratory of Grassland Agro-ecosystems, College of Pastoral Agriculture Science and Technology, Lanzhou UniversityLanzhou, China
| | - Qiuyan Song
- State Key Laboratory of Grassland Agro-ecosystems, College of Pastoral Agriculture Science and Technology, Lanzhou UniversityLanzhou, China
| | - Qingping Zhang
- State Key Laboratory of Grassland Agro-ecosystems, College of Pastoral Agriculture Science and Technology, Lanzhou UniversityLanzhou, China
| | - Pei Tian
- State Key Laboratory of Grassland Agro-ecosystems, College of Pastoral Agriculture Science and Technology, Lanzhou UniversityLanzhou, China
| | - Zhibiao Nan
- State Key Laboratory of Grassland Agro-ecosystems, College of Pastoral Agriculture Science and Technology, Lanzhou UniversityLanzhou, China
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20
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Shymanovich T, Charlton ND, Musso AM, Scheerer J, Cech NB, Faeth SH, Young CA. Interspecific and intraspecific hybrid Epichloë species symbiotic with the North American native grass Poa alsodes. Mycologia 2017; 109:459-474. [PMID: 28723242 DOI: 10.1080/00275514.2017.1340779] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/19/2022]
Abstract
The endophyte presence and diversity in natural populations of Poa alsodes were evaluated along a latitudinal transect from the southern distribution range in North Carolina to New York. Two distinct Epichloë hybrid taxa were identified from 23 populations. Each taxon could easily be distinguished by polymerase chain reaction (PCR) genotyping with primers designed to mating type genes and alkaloid biosynthesis genes that encode key pathway steps for ergot alkaloids, indole-diterpenes, lolines, and peramine. The most commonly found Epichloë taxon, Poa alsodes Taxonomic Group-1 (PalTG-1), was detected in 22 populations at high infection frequencies (72-100%), with the exception of one population at high elevation (26% infection). The second taxon, PalTG-2, was observed only in five populations in Pennsylvania constituting 12% of infected samples. Phylogenetic analyses placed PalTG-1 as an interspecific hybrid of E. amarillans and E. typhina subsp. poae ancestors, and it is considered a new hybrid species, which the authors name Epichloë alsodes. PalTG-2 is an intraspecific hybrid of two E. typhina subsp. poae ancestors, similar to E. schardlii from the host Cinna arundinacea, which the authors propose as a new variety, Epichloë schardlii var. pennsylvanica. Epichloë alsodes isolates were all mating type MTA MTB and tested positive for dmaW, easC, perA, and some LOL genes, but only the alkaloid N-acetylnorloline was detected in E. alsodes-infected plant material. Epichloë schardlii var. pennsylvanica isolates were all mating type MTB MTB and tested positive for perA, but peramine was not produced. Both E. alsodes and E. schardlii var. pennsylvanica appeared to have complete perA genes, but point mutations were identified in E. alsodes that would render the encoded perA gene nonfunctional.
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Affiliation(s)
- Tatsiana Shymanovich
- a Department of Biology , University of North Carolina Greensboro , 312 Eberhart Building, Greensboro , North Carolina 27412
| | - Nikki D Charlton
- b Noble Research Institute, LLC ., 2510 Sam Noble Parkway, Ardmore , Oklahoma 73401
| | - Ashleigh M Musso
- c Department of Chemistry and Biochemistry , University of North Carolina Greensboro , 435 Patricia A. Sullivan Science Building, Greensboro , North Carolina 27402
| | | | - Nadja B Cech
- c Department of Chemistry and Biochemistry , University of North Carolina Greensboro , 435 Patricia A. Sullivan Science Building, Greensboro , North Carolina 27402
| | - Stanley H Faeth
- a Department of Biology , University of North Carolina Greensboro , 312 Eberhart Building, Greensboro , North Carolina 27412
| | - Carolyn A Young
- b Noble Research Institute, LLC ., 2510 Sam Noble Parkway, Ardmore , Oklahoma 73401
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Dupont PY, Cox MP. Genomic Data Quality Impacts Automated Detection of Lateral Gene Transfer in Fungi. G3 (BETHESDA, MD.) 2017; 7:1301-1314. [PMID: 28235827 PMCID: PMC5386878 DOI: 10.1534/g3.116.038448] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 12/13/2016] [Accepted: 02/17/2017] [Indexed: 12/26/2022]
Abstract
Lateral gene transfer (LGT, also known as horizontal gene transfer), an atypical mechanism of transferring genes between species, has almost become the default explanation for genes that display an unexpected composition or phylogeny. Numerous methods of detecting LGT events all rely on two fundamental strategies: primary structure composition or gene tree/species tree comparisons. Discouragingly, the results of these different approaches rarely coincide. With the wealth of genome data now available, detection of laterally transferred genes is increasingly being attempted in large uncurated eukaryotic datasets. However, detection methods depend greatly on the quality of the underlying genomic data, which are typically complex for eukaryotes. Furthermore, given the automated nature of genomic data collection, it is typically impractical to manually verify all protein or gene models, orthology predictions, and multiple sequence alignments, requiring researchers to accept a substantial margin of error in their datasets. Using a test case comprising plant-associated genomes across the fungal kingdom, this study reveals that composition- and phylogeny-based methods have little statistical power to detect laterally transferred genes. In particular, phylogenetic methods reveal extreme levels of topological variation in fungal gene trees, the vast majority of which show departures from the canonical species tree. Therefore, it is inherently challenging to detect LGT events in typical eukaryotic genomes. This finding is in striking contrast to the large number of claims for laterally transferred genes in eukaryotic species that routinely appear in the literature, and questions how many of these proposed examples are statistically well supported.
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Affiliation(s)
- Pierre-Yves Dupont
- Statistics and Bioinformatics Group, Institute of Fundamental Sciences, Massey University, Palmerston North 4442, New Zealand
- the Bio-Protection Research Centre, Massey University, Palmerston North 4442, New Zealand
| | - Murray P Cox
- Statistics and Bioinformatics Group, Institute of Fundamental Sciences, Massey University, Palmerston North 4442, New Zealand
- the Bio-Protection Research Centre, Massey University, Palmerston North 4442, New Zealand
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Saikkonen K, Young CA, Helander M, Schardl CL. Endophytic Epichloë species and their grass hosts: from evolution to applications. PLANT MOLECULAR BIOLOGY 2016; 90:665-75. [PMID: 26542393 PMCID: PMC4819788 DOI: 10.1007/s11103-015-0399-6] [Citation(s) in RCA: 71] [Impact Index Per Article: 8.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/04/2015] [Accepted: 10/26/2015] [Indexed: 05/21/2023]
Abstract
The closely linked fitness of the Epichloë symbiont and the host grass is presumed to align the coevolution of the species towards specialization and mutually beneficial cooperation. Ecological observations demonstrating that Epichloë-grass symbioses can modulate grassland ecosystems via both above- and belowground ecosystem processes support this. In many cases the detected ecological importance of Epichloë 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 Epichloë species, their coevolution with host grasses and identification the genetic variation that explains phenotypic diversity in ecologically relevant characteristics of Epichloë-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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Affiliation(s)
- Kari Saikkonen
- Management and Production of Renewable Resources, Natural Resources Institute Finland (Luke), Itäinen Pitkäkatu 3, 20520, Turku, Finland.
| | - Carolyn A Young
- The Samuel Roberts Noble Foundation, Ardmore, OK, 73401, USA
| | - Marjo Helander
- Management and Production of Renewable Resources, Natural Resources Institute Finland (Luke), Itäinen Pitkäkatu 3, 20520, Turku, Finland
- Section of Ecology, Department of Biology, University of Turku, 20014, Turku, Finland
| | - Christopher L Schardl
- Department of Plant Pathology, University of Kentucky, Lexington, KY, 40546-0312, USA
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Spatafora JW, Bushley KE. Phylogenomics and evolution of secondary metabolism in plant-associated fungi. CURRENT OPINION IN PLANT BIOLOGY 2015; 26:37-44. [PMID: 26116974 DOI: 10.1016/j.pbi.2015.05.030] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/05/2015] [Revised: 05/20/2015] [Accepted: 05/25/2015] [Indexed: 06/04/2023]
Abstract
Fungi produce a myriad of secondary metabolites, compounds that are not required for basic cellular processes, but are thought to be central to ecological functions. Genomic sequencing of fungi has revealed a greater diversity of secondary metabolism than previously realized, including novel taxonomic distributions of known compounds and uncharacterized gene clusters in well-studied organisms. Here we provide an overview of the major groups of metabolites, their ecological functions, the genetic systems that produce them, and the patterns and processes associated with evolutionary diversification of secondary metabolism in plant-associated filamentous ascomycetes.
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Affiliation(s)
- Joseph W Spatafora
- Department of Botany and Plant Pathology, Oregon State University, Corvallis, OR 97331, USA.
| | - Kathryn E Bushley
- Department of Plant Biology, University of Minnesota, St. Paul, MN 55108, USA
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