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Li Z, Zhu Z, Qian K, Tang B, Han B, Zhong Z, Fu T, Zhou P, Stukenbrock EH, Martin FM, Yuan Z. Intraspecific diploidization of a halophyte root fungus drives heterosis. Nat Commun 2024; 15:5872. [PMID: 38997287 PMCID: PMC11245560 DOI: 10.1038/s41467-024-49468-7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2023] [Accepted: 06/03/2024] [Indexed: 07/14/2024] Open
Abstract
How organisms respond to environmental stress is a key topic in evolutionary biology. This study focused on the genomic evolution of Laburnicola rhizohalophila, a dark-septate endophytic fungus from roots of a halophyte. Chromosome-level assemblies were generated from five representative isolates from structured subpopulations. The data revealed significant genomic plasticity resulting from chromosomal polymorphisms created by fusion and fission events, known as dysploidy. Analyses of genomic features, phylogenomics, and macrosynteny have provided clear evidence for the origin of intraspecific diploid-like hybrids. Notably, one diploid phenotype stood out as an outlier and exhibited a conditional fitness advantage when exposed to a range of abiotic stresses compared with its parents. By comparing the gene expression patterns in each hybrid parent triad under the four growth conditions, the mechanisms underlying growth vigor were corroborated through an analysis of transgressively upregulated genes enriched in membrane glycerolipid biosynthesis and transmembrane transporter activity. In vitro assays suggested increased membrane integrity and lipid accumulation, as well as decreased malondialdehyde production under optimal salt conditions (0.3 M NaCl) in the hybrid. These attributes have been implicated in salinity tolerance. This study supports the notion that hybridization-induced genome doubling leads to the emergence of phenotypic innovations in an extremophilic endophyte.
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Affiliation(s)
- Zhongfeng Li
- State Key Laboratory of Tree Genetics and Breeding, Chinese Academy of Forestry, 100091, Beijing, China
- Research Institute of Subtropical Forestry, Chinese Academy of Forestry, Hangzhou, 311400, China
| | - Zhiyong Zhu
- State Key Laboratory of Tree Genetics and Breeding, Chinese Academy of Forestry, 100091, Beijing, China
- Research Institute of Subtropical Forestry, Chinese Academy of Forestry, Hangzhou, 311400, China
- Nanjing Forestry University, Nanjing, 100071, China
| | - Kun Qian
- College of Life Science, Zhejiang University, Hangzhou, 310058, Zhejiang, China
- Department of Animal, Plant and Soil Science, School of Agriculture, Biomedical and Environmental Sciences, La Trobe University, Bundoora, VIC, 3086, Australia
| | - Boping Tang
- Jiangsu Key Laboratory for Bioresources of Saline Soils, School of Wetlands, Yancheng Teachers University, Yancheng, 224002, China
| | - Baocai Han
- State Key Laboratory of Systematic and Evolutionary Botany, Institute of Botany, Chinese Academy of Sciences, 100093, Beijing, China
| | - Zhenhui Zhong
- Ministry of Education Key Laboratory for Bio-Resource and Eco-Environment, College of Life Sciences, Sichuan University, Chengdu, 610065, China
| | - Tao Fu
- Shenzhen Zhuoyun Haizhi Medical Research Center Co., Ltd, Shenzhen, 518063, China
| | - Peng Zhou
- National Key Facility for Crop Gene Resources and Genetic Improvement, Institute of Crop Sciences, Chinese Academy of Agricultural Sciences, 100081, Beijing, China.
| | - Eva H Stukenbrock
- Environmental Genomics, Christian-Albrechts University, 24118, Kiel, Germany
- Max Planck Fellow Group Environmental Genomics, Max Planck Institute for Evolutionary Biology, 24306, Plön, Germany
| | - Francis M Martin
- Research Institute of Subtropical Forestry, Chinese Academy of Forestry, Hangzhou, 311400, China.
- Université de Lorraine, INRAE, UMR Interactions Arbres/Microorganisms, Centre INRAE Grand Est-Nancy, 54280, Champenoux, France.
| | - Zhilin Yuan
- State Key Laboratory of Tree Genetics and Breeding, Chinese Academy of Forestry, 100091, Beijing, China.
- Research Institute of Subtropical Forestry, Chinese Academy of Forestry, Hangzhou, 311400, China.
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Ait-Barka E, Mauch-Mani B. Editorial: Unraveling plant-microbe interactions: from ecology to mechanisms, volume II. FRONTIERS IN PLANT SCIENCE 2023; 14:1234372. [PMID: 37521917 PMCID: PMC10381934 DOI: 10.3389/fpls.2023.1234372] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/04/2023] [Accepted: 06/30/2023] [Indexed: 08/01/2023]
Affiliation(s)
- Essaid Ait-Barka
- Unité de Recherche Résistance Induite et BioProtection des Plantes- EA4707 - USC INRAe1488 UFR Sciences Exactes et Naturelles, Université de Reims Champagne-Ardenne, Reims, France
| | - Brigitte Mauch-Mani
- Département de Biologie, Laboratoire de Biologie Moléculaire et Cellulaire, Université de Neuchâtel, Neuchâtel, Switzerland
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Bubica Bustos LM, Ueno AC, Biganzoli F, Card SD, Mace WJ, Martínez-Ghersa MA, Gundel PE. Can Aphid Herbivory Induce Intergenerational Effects of Endophyte-conferred Resistance in Grasses? J Chem Ecol 2022; 48:867-881. [PMID: 36372818 DOI: 10.1007/s10886-022-01390-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/12/2022] [Revised: 10/20/2022] [Accepted: 10/23/2022] [Indexed: 11/15/2022]
Abstract
Plants have evolved mechanisms to survive herbivory. One such mechanism is the induction of defences upon attack that can operate intergenerationally. Cool-season grasses (sub-family Pooideae) obtain defences via symbiosis with vertically transmitted fungal endophytes (genus Epichloë) and can also show inducible responses. However, it is unknown whether these herbivore-induced responses can have intergenerational effects. We hypothesized that herbivory by aphids on maternal plants induces the intergenerational accumulation of endophyte-derived defensive alkaloids and resistance intensification in the progeny. We subjected mother plants symbiotic or not with Epichloë occultans, a species known for its production of anti-insect alkaloids known as lolines, to the aphid Rhopalosiphum padi. Then, we evaluated the progeny of these plants in terms of loline alkaloid concentration, resistance level (through herbivore performance), and shoot biomass. Herbivory on mother plants did not increase the concentration of lolines in seeds but it tended to affect loline concentration in progeny plants. There was an overall herbivore-induced intergenerational effect increasing the endophyte-conferred defence and resistance. Symbiotic plants were more resistant to aphids and had higher shoot biomass than their non-symbiotic counterparts. Since maternal herbivory did not affect the loline concentrations in seeds, the greater resistance of the progeny could have resulted from an inherited mechanism of epigenetic regulation. It would be interesting to elucidate the origin of this regulation since it could come from the host or the fungal symbiont. Thus, endophyte-driven differential fitness between symbiotic and non-symbiotic plants might be higher as generations pass on in presence of herbivores.
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Affiliation(s)
| | - Andrea C Ueno
- IFEVA, Facultad de Agronomía, Universidad de Buenos Aires, CONICET, Buenos Aires, Argentina
- Centro de Ecología Integrativa, Instituto de Ciencias Biológicas, Universidad de Talca, Campus Lircay, Talca, Chile
| | - Fernando Biganzoli
- Departamento de Métodos Cuantitativos y Sistemas de Información, Facultad de Agronomía, Universidad de Buenos Aires, Buenos Aires, Argentina
| | - Stuart D Card
- Resilient Agriculture, Grasslands Research Centre, AgResearch Limited, Palmerston North, New Zealand
| | - Wade J Mace
- Resilient Agriculture, Grasslands Research Centre, AgResearch Limited, Palmerston North, New Zealand
| | | | - Pedro E Gundel
- IFEVA, Facultad de Agronomía, Universidad de Buenos Aires, CONICET, Buenos Aires, Argentina.
- Centro de Ecología Integrativa, Instituto de Ciencias Biológicas, Universidad de Talca, Campus Lircay, Talca, Chile.
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Zhang W, Forester NT, Moon CD, Maclean PH, Gagic M, Arojju SK, Card SD, Matthew C, Johnson RD, Johnson LJ, Faville MJ, Voisey CR. Epichloë seed transmission efficiency is influenced by plant defense response mechanisms. FRONTIERS IN PLANT SCIENCE 2022; 13:1025698. [PMID: 36340377 PMCID: PMC9635450 DOI: 10.3389/fpls.2022.1025698] [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: 08/23/2022] [Accepted: 09/30/2022] [Indexed: 06/16/2023]
Abstract
Asexual Epichloë are endophytic fungi that form mutualistic symbioses with cool-season grasses, conferring to their hosts protection against biotic and abiotic stresses. Symbioses are maintained between grass generations as hyphae are vertically transmitted from parent to progeny plants through seed. However, endophyte transmission to the seed is an imperfect process where not all seeds become infected. The mechanisms underpinning the varying efficiencies of seed transmission are poorly understood. Host gene expression in response to Epichloë sp. LpTG-3 strain AR37 was examined within inflorescence primordia and ovaries of high and low endophyte transmission genotypes within a single population of perennial ryegrass. A genome-wide association study was conducted to identify population-level single nucleotide polymorphisms (SNPs) and associated genes correlated with vertical transmission efficiency. For low transmitters of AR37, upregulation of perennial ryegrass receptor-like kinases and resistance genes, typically associated with phytopathogen detection, comprised the largest group of differentially expressed genes (DEGs) in both inflorescence primordia and ovaries. DEGs involved in signaling and plant defense responses, such as cell wall modification, secondary metabolism, and reactive oxygen activities were also abundant. Transmission-associated SNPs were associated with genes for which gene ontology analysis identified "response to fungus" as the most significantly enriched term. Moreover, endophyte biomass as measured by quantitative PCR of Epichloë non-ribosomal peptide synthetase genes, was significantly lower in reproductive tissues of low-transmission hosts compared to high-transmission hosts. Endophyte seed-transmission efficiency appears to be influenced primarily by plant defense responses which reduce endophyte colonization of host reproductive tissues.
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Affiliation(s)
- Wei Zhang
- Grasslands Research Centre, AgResearch Limited, Palmerston North, New Zealand
- School of Agriculture and Environment, Massey University, Palmerston North, New Zealand
| | - Natasha T. Forester
- Grasslands Research Centre, AgResearch Limited, Palmerston North, New Zealand
| | - Christina D. Moon
- Grasslands Research Centre, AgResearch Limited, Palmerston North, New Zealand
| | - Paul H. Maclean
- Grasslands Research Centre, AgResearch Limited, Palmerston North, New Zealand
| | - Milan Gagic
- Grasslands Research Centre, AgResearch Limited, Palmerston North, New Zealand
| | - Sai Krishna Arojju
- Grasslands Research Centre, AgResearch Limited, Palmerston North, New Zealand
| | - Stuart D. Card
- Grasslands Research Centre, AgResearch Limited, Palmerston North, New Zealand
| | - Cory Matthew
- School of Agriculture and Environment, Massey University, Palmerston North, New Zealand
| | - Richard D. Johnson
- Grasslands Research Centre, AgResearch Limited, Palmerston North, New Zealand
| | - Linda J. Johnson
- Grasslands Research Centre, AgResearch Limited, Palmerston North, New Zealand
| | - Marty J. Faville
- Grasslands Research Centre, AgResearch Limited, Palmerston North, New Zealand
| | - Christine R. Voisey
- Grasslands Research Centre, AgResearch Limited, Palmerston North, New Zealand
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Caradus JR, Johnson LJ. Epichloë Fungal Endophytes-From a Biological Curiosity in Wild Grasses to an Essential Component of Resilient High Performing Ryegrass and Fescue Pastures. J Fungi (Basel) 2020; 6:E322. [PMID: 33261217 PMCID: PMC7720123 DOI: 10.3390/jof6040322] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2020] [Revised: 11/13/2020] [Accepted: 11/18/2020] [Indexed: 12/15/2022] Open
Abstract
The relationship between Epichloë endophytes found in a wide range of temperate grasses spans the continuum from antagonistic to mutualistic. The diversity of asexual mutualistic types can be characterised by the types of alkaloids they produce in planta. Some of these are responsible for detrimental health and welfare issues of ruminants when consumed, while others protect the host plant from insect pests and pathogens. In many temperate regions they are an essential component of high producing resilient tall fescue and ryegrass swards. This obligate mutualism between fungus and host is a seed-borne technology that has resulted in several commercial products being used with high uptake rates by end-user farmers, particularly in New Zealand and to a lesser extent Australia and USA. However, this has not happened by chance. It has been reliant on multi-disciplinary research teams undertaking excellent science to understand the taxonomic relationships of these endophytes, their life cycle, symbiosis regulation at both the cellular and molecular level, and the impact of secondary metabolites, including an understanding of their mammalian toxicity and bioactivity against insects and pathogens. Additionally, agronomic trials and seed biology studies of these microbes have all contributed to the delivery of robust and efficacious products. The supply chain from science, through seed companies and retailers to the end-user farmer needs to be well resourced providing convincing information on the efficacy and ensuring effective quality control to result in a strong uptake of these Epichloë endophyte technologies in pastoral agriculture.
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Affiliation(s)
- John R. Caradus
- Grasslanz Technology Ltd., Palmerston North PB11008, New Zealand
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Pérez LI, Gundel PE, Zabalgogeazcoa I, Omacini M. An ecological framework for understanding the roles of Epichloë endophytes on plant defenses against fungal diseases. FUNGAL BIOL REV 2020. [DOI: 10.1016/j.fbr.2020.06.001] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
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Cagnano G, Lenk I, Roulund N, Jensen CS, Cox MP, Asp T. Mycelial biomass and concentration of loline alkaloids driven by complex population structure in Epichloë uncinata and meadow fescue ( Schedonorus pratensis). Mycologia 2020; 112:474-490. [PMID: 32412888 DOI: 10.1080/00275514.2020.1746607] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
Many efforts have been made to select and isolate naturally occurring animal-friendly Epichloë strains for later reinfection into elite cultivars. Often this process involves large-scale screening of Epichloë-infected wild grass populations where strains are characterized and alkaloids measured. Here, we describe for the first time the use of genotyping-by-sequencing (GBS) on a collection of 217 Epichloë-infected grasses (7 S. arundinaceum, 4 L. perenne, and 206 S. pratensis). This genotyping strategy is cheaper than complete genome sequencing, is suitable for a large number of individuals, and, when applied to endophyte-infected grasses, conveniently genotypes both organisms. In total, 6273 single nucleotide polymorphisms (SNPs) in the endophyte data set and 38 323 SNPs in the host data set were obtained. Our findings reveal a composite structure with three distinct endophyte clusters unrelated to the three main S. pratensis gene pools that have most likely spread from different glacial refugia in Eurasia. All three gene pools can establish symbiosis with E. uncinata. A comparison of the endophyte clusters with microsatellite-based fingerprinting of the same samples allows a quick test to discriminate between these clusters using two simple sequence repeats (SSRs). Concentrations of loline alkaloids and mycelial biomass are correlated and differ significantly among the plant and endophyte subpopulations; one endophyte strain has higher levels of lolines than others, and one specific host genotype is particularly suitable to host E. uncinata. These findings pave the way for targeted artificial inoculations of specific host-endophyte combinations to boost loline production in the symbiota and for genome association studies with the aim of isolating genes involved in the compatibility between meadow fescue and E. uncinata.
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Affiliation(s)
- G Cagnano
- DLF Seeds A/S, Højerupvej 31, 4660 Store Heddinge , Denmark
| | - I Lenk
- DLF Seeds A/S, Højerupvej 31, 4660 Store Heddinge , Denmark
| | - N Roulund
- DLF Seeds A/S, Højerupvej 31, 4660 Store Heddinge , Denmark
| | - C S Jensen
- DLF Seeds A/S, Højerupvej 31, 4660 Store Heddinge , Denmark
| | - M P Cox
- Statistics and Bioinformatics Group, School of Fundamental Sciences, Massey University , Palmerston North 4442, New Zealand
| | - T Asp
- Department of Molecular Biology and Genetics, Faculty of Science and Technology, Aarhus University , Aarhus, Denmark
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Cagnano G, Roulund N, Jensen CS, Forte FP, Asp T, Leuchtmann A. Large Scale Screening of Epichloë Endophytes Infecting Schedonorus pratensis and Other Forage Grasses Reveals a Relation Between Microsatellite-Based Haplotypes and Loline Alkaloid Levels. FRONTIERS IN PLANT SCIENCE 2019; 10:765. [PMID: 31249582 PMCID: PMC6582706 DOI: 10.3389/fpls.2019.00765] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 04/17/2019] [Accepted: 05/24/2019] [Indexed: 06/09/2023]
Abstract
Species belonging to the Festuca-Lolium complex are often naturally infected with endophytic fungi of genus Epichloë. Recent studies on endophytes have shown the beneficial roles of host-endophyte associations as protection against insect herbivores in agriculturally important grasses. However, large-scale screenings are crucial to identify animal friendly strains suitable for agricultural use. In this study we analyzed collected populations of meadow fescue (Schedonorus pratensis) from 135 different locations across Europe, 255 accessions from the United States Department of Agriculture and 96 accessions from The Nordic Genetic Resource Centre. The analysis also included representatives of S. arundinaceus, S. giganteus, and Lolium perenne. All plants were screened for the presence of Epichloë endophytes, resulting in a nursery of about 2500 infected plants from 176 different locations. Genetic diversity was investigated on 250 isolates using a microsatellite-based PCR fingerprinting assay at 7 loci, 5 of which were uncharacterized for these species. Phylogenetic and principal components analysis showed a strong interspecific genetic differentiation among isolates, and, with E. uncinata isolates, a small but significant correlation between genetic diversity and geographical effect (r = 0.227) was detected. Concentrations of loline alkaloids were measured in 218 infected meadow fescue plants. Average amount of total loline and the proportions of the single loline alkaloids differed significantly among endophyte haplotypes (P < 0.005). This study provides insight into endophyte genetic diversity and geographic variation in Europe and a reference database of allele sizes for fast discrimination of isolates. We also discuss the possibility of multiple hybridization events as a source of genetic and alkaloid variation observed in E. uncinata.
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Affiliation(s)
- Giovanni Cagnano
- DLF Trifolium A/S, Roskilde, Denmark
- Department of Molecular Biology and Genetics, Faculty of Science and Technology, Research Centre Flakkebjerg, Aarhus University, Slagelse, Denmark
| | | | | | - Flavia Pilar Forte
- Department of Molecular Biology and Genetics, Faculty of Science and Technology, Research Centre Flakkebjerg, Aarhus University, Slagelse, Denmark
| | - Torben Asp
- Department of Molecular Biology and Genetics, Faculty of Science and Technology, Research Centre Flakkebjerg, Aarhus University, Slagelse, Denmark
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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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10
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Selosse MA, Schneider-Maunoury L, Martos F. Time to re-think fungal ecology? Fungal ecological niches are often prejudged. THE NEW PHYTOLOGIST 2018; 217:968-972. [PMID: 29334598 DOI: 10.1111/nph.14983] [Citation(s) in RCA: 80] [Impact Index Per Article: 13.3] [Reference Citation Analysis] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/20/2023]
Affiliation(s)
- Marc-André Selosse
- Institut de Systématique, Évolution, Biodiversité (UMR 7205 - CNRS, MNHN, UPMC, EPHE), Muséum national d'Histoire naturelle, Sorbonne Universités, 57 rue Cuvier, 75005 Paris, France
- Department of Plant Taxonomy and Nature Conservation, University of Gdansk, Wita Stwosza 59, 80-308, Gdansk, Poland
| | - Laure Schneider-Maunoury
- Institut de Systématique, Évolution, Biodiversité (UMR 7205 - CNRS, MNHN, UPMC, EPHE), Muséum national d'Histoire naturelle, Sorbonne Universités, 57 rue Cuvier, 75005 Paris, France
| | - Florent Martos
- Institut de Systématique, Évolution, Biodiversité (UMR 7205 - CNRS, MNHN, UPMC, EPHE), Muséum national d'Histoire naturelle, Sorbonne Universités, 57 rue Cuvier, 75005 Paris, France
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11
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Campbell MA, Tapper BA, Simpson WR, Johnson RD, Mace W, Ram A, Lukito Y, Dupont PY, Johnson LJ, Scott DB, Ganley ARD, Cox MP. Epichloë hybrida, sp. nov., an emerging model system for investigating fungal allopolyploidy. Mycologia 2018; 109:715-729. [PMID: 29370579 DOI: 10.1080/00275514.2017.1406174] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023]
Abstract
Endophytes of the genus Epichloë (Clavicipitaceae, Ascomycota) frequently occur within cool-season grasses and form interactions with their hosts that range from mutualistic to antagonistic. Many Epichloë species have arisen via interspecific hybridization, resulting in species with two or three subgenomes that retain all or nearly all of their original parental genomes, a process termed allopolyploidization. Here, we characterize Epichloë hybrida, sp. nov., a mutualistic species that has increasingly become a model system for investigating allopolyploidy in fungi. The Epichloë species so far identified as the closest known relatives of the two progenitors of E. hybrida are E. festucae var. lolii and E. typhina. We confirm that the nuclear genome of E. hybrida contains two homeologs of most protein-coding genes from E. festucae and E. typhina, with genome-wide gene expression analysis indicating a slight bias in overall gene expression from the E. typhina subgenome. Mitochondrial DNA is detectable only from E. festucae, whereas ribosomal DNA is detectable only from E. typhina. Inheriting ribosomal DNA from just one parent might be expected to preferentially favor interactions with ribosomal proteins from the same parent, but we find that ribosomal protein genes from both parental subgenomes are nearly all expressed equally in E. hybrida. Finally, we provide a comprehensive set of resources for this model system that are intended to facilitate further study of fungal hybridization by other researchers.
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Affiliation(s)
- Matthew A Campbell
- a Institute of Fundamental Sciences, Massey University , Private Bag 11 222, Palmerston North 4410 , New Zealand
| | - Brian A Tapper
- b AgResearch Ltd., Grasslands Research Centre , Tennent Drive, Palmerston North 4442 , New Zealand
| | - Wayne R Simpson
- b AgResearch Ltd., Grasslands Research Centre , Tennent Drive, Palmerston North 4442 , New Zealand
| | - Richard D Johnson
- b AgResearch Ltd., Grasslands Research Centre , Tennent Drive, Palmerston North 4442 , New Zealand
| | - Wade Mace
- b AgResearch Ltd., Grasslands Research Centre , Tennent Drive, Palmerston North 4442 , New Zealand
| | - Arvina Ram
- a Institute of Fundamental Sciences, Massey University , Private Bag 11 222, Palmerston North 4410 , New Zealand
| | - Yonathan Lukito
- a Institute of Fundamental Sciences, Massey University , Private Bag 11 222, Palmerston North 4410 , New Zealand
| | - Pierre-Yves Dupont
- a Institute of Fundamental Sciences, Massey University , Private Bag 11 222, Palmerston North 4410 , New Zealand
| | - Linda J Johnson
- b AgResearch Ltd., Grasslands Research Centre , Tennent Drive, Palmerston North 4442 , New Zealand
| | - D Barry Scott
- a Institute of Fundamental Sciences, Massey University , Private Bag 11 222, Palmerston North 4410 , New Zealand
| | - Austen R D Ganley
- c School of Biological Sciences, University of Auckland , Private Bag 92019, Auckland 1142 , New Zealand
| | - Murray P Cox
- a Institute of Fundamental Sciences, Massey University , Private Bag 11 222, Palmerston North 4410 , New Zealand
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12
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Sneck ME, Rudgers JA, Young CA, Miller TEX. Variation in the Prevalence and Transmission of Heritable Symbionts Across Host Populations in Heterogeneous Environments. MICROBIAL ECOLOGY 2017; 74:640-653. [PMID: 28314899 DOI: 10.1007/s00248-017-0964-4] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/11/2016] [Accepted: 03/09/2017] [Indexed: 05/29/2023]
Abstract
Heritable microbes are abundant in nature and influential to their hosts and the communities in which they reside. However, drivers of variability in the prevalence of heritable symbionts and their rates of transmission are poorly resolved, particularly across host populations experiencing variable biotic and abiotic environments. To fill these gaps, we surveyed 25 populations of two native grasses (Elymus virginicus and Elymus canadensis) across the southern Great Plains (USA). Both grass species host heritable endophytic fungi (genus Epichloё) and can hybridize where their ranges overlap. From a subset of hosts, we characterized endophyte genotype using genetic loci that link to bioactive alkaloid production. First, we found mean vertical transmission rates and population-level prevalence were positively correlated, specifically for E. virginicus. However, both endophyte prevalence and transmission varied substantially across populations and did not strongly correlate with abiotic variables, with one exception: endophyte prevalence decreased as drought stress decreased for E. virginicus hosts. Second, we evaluated the potential influence of biotic factors and found that, after accounting for climate, endophyte genotype explained significant variation in symbiont inheritance. We also contrasted populations where host species co-occurred in sympatry vs. allopatry. Sympatry could potentially increase interspecific hybridization, but this variable did not associate with patterns of symbiont prevalence or transmission success. Our results reveal substantial variability in symbiont prevalence and transmission across host populations and identify symbiont genotype, and to a lesser extent, the abiotic environment as sources of this variation.
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Affiliation(s)
- Michelle E Sneck
- Department of BioSciences, Program in Ecology and Evolutionary Biology, Rice University, 6100 Main Street, Houston, TX, 77005, USA.
| | - Jennifer A Rudgers
- Department of Biology, University of New Mexico, Albuquerque, NM, 87131, USA
| | - Carolyn A Young
- Samuel Roberts Noble Foundation, Inc, Ardmore, OK, 73401, USA
| | - Tom E X Miller
- Department of BioSciences, Program in Ecology and Evolutionary Biology, Rice University, 6100 Main Street, Houston, TX, 77005, USA
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Faeth SH, Oberhofer M, Saari S, Haskins KE, Shymanovich T. Does hybridization of endophytic symbionts in a native grass increase fitness in resource-limited environments? Ecology 2017; 98:138-149. [PMID: 28052394 DOI: 10.1002/ecy.1626] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/10/2016] [Revised: 10/03/2016] [Accepted: 10/13/2016] [Indexed: 11/10/2022]
Abstract
Hybridization is common among plants, animals and microbes. However, the ecological consequences of hybridization for microbes are far less understood than for plants and animals. For symbiotic Epichloë fungi, hybridization is widespread and may augment the well-known benefits of the endophytes to their grass hosts, especially in stressful environments. We tested the hybrid fitness hypothesis (HFH) that hybrid endophytes enhance fitness in stressful environments relative to non-hybrid endophytes. In a long-term field experiment, we monitored growth and reproduction of hybrid-infected (H+), non-hybrid infected (NH+), naturally endophyte free (E-) plants and those plants from which the endophyte had been experimentally removed (H- and NH-) in resource-rich and resource-poor environments. Infection by both endophyte species enhanced growth and reproduction. H+ plants outperformed NH+ plants in terms of growth by the end of the experiment, supporting HFH. However, H+ plants only outperformed NH+ plants in the resource-rich treatment, contrary to HFH. Plant genotypes associated with each endophyte species had strong effects on growth and reproduction. Our results provide some support the HFH hypothesis but not based upon adaptation to stressful environments. Our results reinforce the notion of a complex interplay between endophyte and plant genotype and environmental factors that determine fitness of the symbiotum.
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Affiliation(s)
- Stanley H Faeth
- Department of Biology, University of North Carolina at Greensboro, Greensboro, North Carolina, 27402, USA
| | - Martina Oberhofer
- Department of Pharmacognosy, University of Vienna, Althanstrasse 14, 1090, Vienna, Austria
| | - Susanna Saari
- Department of Plant and Environmental Sciences, University of Copenhagen, Thorvaldsensvej 40, 1871, Frederiksberg C, Denmark
| | - Kristin E Haskins
- Department of Biological Sciences, Northern Arizona University, Flagstaff, Arizona, 86011, USA
| | - Tatsiana Shymanovich
- Department of Biology, University of North Carolina at Greensboro, Greensboro, North Carolina, 27402, USA
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Bibian AJ, Rudgers JA, Miller TEX. The Role of Host Demographic Storage in the Ecological Dynamics of Heritable Symbionts. Am Nat 2016; 188:446-59. [PMID: 27622878 DOI: 10.1086/687965] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
Abstract
Heritable symbioses are widespread and ecologically important. Many host organisms have complex life cycles that include diverse opportunities for symbionts to affect their host and be lost during development. Yet, existing theory takes a simplified view of host demography. Here, we generalize symbiosis theory to understand how demographic "storage" in the form of dormant or prereproductive life stages can modify symbiosis dynamics. Using grass-endophyte symbioses as context, we developed models to contrast the role of the seed bank (a storage stage) against the reproductive stage in symbiont persistence and prevalence. We find that the seed bank is as important as or more important than the reproductive stage in driving symbiont dynamics, as long as passage through the seed bank is obligate. Flexible entry to the seed bank substantially weakens its influence on symbiont persistence but can modify prevalence in counterintuitive ways. Our models identify a role for legacy effects, where hosts that lose symbionts retain their demographic influence. The retention of benefits via legacy effects can reduce symbiont prevalence and even cause prevalence to decline with increasing benefits to hosts because symbiont-free hosts carry those benefits. Our results resolve connections between individual-level host-symbiont interactions and population-level patterns, providing guidance for empirical studies.
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Jia T, Oberhofer M, Shymanovich T, Faeth SH. Effects of Hybrid and Non-hybrid Epichloë Endophytes and Their Associated Host Genotypes on the Response of a Native Grass to Varying Environments. MICROBIAL ECOLOGY 2016; 72:185-196. [PMID: 26909796 DOI: 10.1007/s00248-016-0743-7] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/19/2015] [Accepted: 02/15/2016] [Indexed: 06/05/2023]
Abstract
Asexual Epichloë endophytes are prevalent in cool season grasses, and many are of hybrid origin. Hybridization of asexual endophytes is thought to provide a rapid influx of genetic variation that may be adaptive to endophyte-host grass symbiota in stressful environments. For Arizona fescue (Festuca arizonica), hybrid symbiota are commonly found in resource-poor environments, whereas non-hybrid symbiota are more common in resource-rich environments. There have been very few experimental tests where infection, hybrid and non-hybrid status, and plant genotype have been controlled to tease apart their effects on host phenotype and fitness in different environments. We conducted a greenhouse experiment where hybrid (H) and non-hybrid (NH) endophytes were inoculated into plant genotypes that were originally uninfected (E-) or once infected with either the H or NH endophytes. Nine endophyte and plant genotypic group combinations were grown under low and high water and nutrient treatments. Inoculation with the resident H endophyte enhanced growth and altered allocation to roots and shoots, but these effects were greatest in resource-rich environments, contrary to expectations. We found no evidence of co-adaptation between endophyte species and their associated host genotypes. However, naturally E- plants performed better when inoculated with the hybrid endophyte, suggesting these plants were derived from H infected lineages. Our results show complex interactions between endophyte species of hybrid and non-hybrid origin with their host plant genotypes and environmental factors.
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Affiliation(s)
- Tong Jia
- Institute of Loess Plateau, Shanxi University, Taiyuan, 030006, China.
| | - Martina Oberhofer
- Department of Biology, University of North Carolina Greensboro, 321 McIver Street, Greensboro, NC, 27412, USA
| | - Tatsiana Shymanovich
- Department of Biology, University of North Carolina Greensboro, 321 McIver Street, Greensboro, NC, 27412, USA
| | - Stanley H Faeth
- Department of Biology, University of North Carolina Greensboro, 321 McIver Street, Greensboro, NC, 27412, USA
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Ueno AC, Gundel PE, Omacini M, Ghersa CM, Bush LP, Martínez‐Ghersa MA. Mutualism effectiveness of a fungal endophyte in an annual grass is impaired by ozone. Funct Ecol 2015. [DOI: 10.1111/1365-2435.12519] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Andrea C. Ueno
- Facultad de Agronomía (UBA) IFEVA‐CONICET, Cátedra de Ecología Av. San Martín 4453 Buenos Aires 1417 CP Argentina
| | - Pedro E. Gundel
- Facultad de Agronomía (UBA) IFEVA‐CONICET, Cátedra de Ecología Av. San Martín 4453 Buenos Aires 1417 CP Argentina
| | - Marina Omacini
- Facultad de Agronomía (UBA) IFEVA‐CONICET, Cátedra de Ecología Av. San Martín 4453 Buenos Aires 1417 CP Argentina
| | - Claudio M. Ghersa
- Facultad de Agronomía (UBA) IFEVA‐CONICET, Cátedra de Ecología Av. San Martín 4453 Buenos Aires 1417 CP Argentina
| | - Lowell P. Bush
- Department of Plant & Soil Sciences University of Kentucky Lexington KY 40546‐0091 USA
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Song H, Nan Z. Origin, divergence, and phylogeny of asexual Epichloë endophyte in Elymus species from western China. PLoS One 2015; 10:e0127096. [PMID: 25970178 PMCID: PMC4430518 DOI: 10.1371/journal.pone.0127096] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/03/2014] [Accepted: 04/10/2015] [Indexed: 11/29/2022] Open
Abstract
Asexual Epichloë species are likely derived directly from sexual Epichloë species that then lost their capacity for sexual reproduction or lost sexual reproduction because of interspecific hybridization between distinct lineages of sexual Epichloë and/or asexual Epichloë species. In this study we isolated asexual Epichloë endophytes from Elymus species in western China and sequenced intron-rich regions in the genes encoding β-tubulin (tubB) and translation elongation factor 1-α (tefA). Our results showed that there are no gene copies of tubB and tefA in any of the isolates. Phylogenetic analysis showed that sequences in this study formed a single clade with asexual Epichloë bromicola from Hordeum brevisubulatum, which implies asexual Epichloë endophytes that are symbionts in a western Chinese Elymus species likely share a common ancestor with asexual E. bromicola from European H. brevisubulatum. In addition, our results revealed that asexual E. bromicola isolates that are symbionts in a western Chinese Elymus species and sexual Epichloë species that are symbionts in a North American Elymus species have a different origin. Further analysis found that Epichloë species likely originated in Eurasia. In addition, the results support the hypothesis that migratory birds or humans might have aided the dispersal of these fungal endophytes to other continents.
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Affiliation(s)
- Hui Song
- Key Laboratory of Grassland Agro-Ecosystems, Lanzhou, 730020, P. R. China
- College of Pastoral Agriculture Science and Technology, Lanzhou University, Lanzhou, 730020, P. R. China
| | - Zhibiao Nan
- Key Laboratory of Grassland Agro-Ecosystems, Lanzhou, 730020, P. R. China
- College of Pastoral Agriculture Science and Technology, Lanzhou University, Lanzhou, 730020, P. R. China
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Shoji JY, Charlton ND, Yi M, Young CA, Craven KD. Vegetative hyphal fusion and subsequent nuclear behavior in Epichloë grass endophytes. PLoS One 2015; 10:e0121875. [PMID: 25837972 PMCID: PMC4383479 DOI: 10.1371/journal.pone.0121875] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2014] [Accepted: 02/18/2015] [Indexed: 01/18/2023] Open
Abstract
Epichloë species (including the former genus Neotyphodium) are fungal symbionts of many agronomically important forage grasses, and provide their grass hosts with protection from a wide range of biotic and abiotic stresses. Epichloë species include many interspecific hybrids with allodiploid-like genomes, which may provide the potential for combined traits or recombination to generate new traits. Though circumstantial evidence suggests that such interspecific hybrids might have arisen from nuclear fusion events following vegetative hyphal fusion between different Epichloë strains, this hypothesis has not been addressed empirically. Here, we investigated vegetative hyphal fusion and subsequent nuclear behavior in Epichloë species. A majority of Epichloë strains, especially those having a sexual stage, underwent self vegetative hyphal fusion. Vegetative fusion also occurred between two hyphae from different Epichloë strains. Though Epichloë spp. are uninucleate fungi, hyphal fusion resulted in two nuclei stably sharing the same cytoplasm, which might ultimately lead to nuclear fusion. In addition, protoplast fusion experiments gave rise to uninucleate putative hybrids, which apparently had two markers, one from each parent within the same nucleus. These results are consistent with the notion that interspecific hybrids arise from vegetative hyphal fusion. However, we also discuss additional factors, such as post-hybridization selection, that may be important to explain the recognized prevalence of hybrids in Epichloë species.
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Affiliation(s)
- Jun-ya Shoji
- The Samuel Roberts Noble Foundation, Plant Biology Division, 2510 Sam Noble Parkway, Ardmore, Oklahoma 73401, United States of America
| | - Nikki D. Charlton
- The Samuel Roberts Noble Foundation, Forage Improvement Division, 2510 Sam Noble Parkway, Ardmore, Oklahoma 73401, United States of America
| | - Mihwa Yi
- The Samuel Roberts Noble Foundation, Forage Improvement Division, 2510 Sam Noble Parkway, Ardmore, Oklahoma 73401, United States of America
| | - Carolyn A. Young
- The Samuel Roberts Noble Foundation, Forage Improvement Division, 2510 Sam Noble Parkway, Ardmore, Oklahoma 73401, United States of America
| | - Kelly D. Craven
- The Samuel Roberts Noble Foundation, Plant Biology Division, 2510 Sam Noble Parkway, Ardmore, Oklahoma 73401, United States of America
- * E-mail:
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Li X, Zhou Y, Zhu M, Qin J, Ren A, Gao Y. Stroma-bearing endophyte and its potential horizontal transmission ability in Achnatherum sibiricum. Mycologia 2014; 107:21-31. [PMID: 25344262 DOI: 10.3852/13-355] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
Stromata occasionally are observed in Achnatherum sibiricum distributed in northern China. However, endophyte species that form stromata on that host have not been studied. Here we identified the first Epichloë sp. endophyte in stroma-bearing A. sibiricum. Isolated colonies of this Epichloë sp. were smoother and more compact than previously described for Epichloë gansuensis and also had longer phialides and faster growth in culture. However, phylogenetic relationships based on intron sequences of genes encoding β-tubulin (tubB) and translation elongation factor 1-α (tefA) grouped all isolates from the stromata in a clade with a close relationship to E. gansuensis. We identified the new isolates as E. gansuensis. The analysis of the stromata revealed no perithecium or ascospores during morphological and paraffin section observation. Furthermore, the ability of conidia formed on stromata to germinate and initiate infection of new seedlings was tested. After 3 mo 20% endophyte-free seedlings became infected by E. gansuensis, whereas the control group showed no endophyte infection. The results indicated the potential of cultures from conidia to mediate horizontal transmission.
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Affiliation(s)
- Xia Li
- Department of Plant Biology and Ecology, College of Life Sciences, Nankai University, Tianjin, P.R. China
| | - Yong Zhou
- Department of Plant Biology and Ecology, College of Life Sciences, Nankai University, Tianjin, P.R. China
| | - Minjie Zhu
- Department of Plant Biology and Ecology, College of Life Sciences, Nankai University, Tianjin, P.R. China
| | - Junhua Qin
- Department of Plant Biology and Ecology, College of Life Sciences, Nankai University, Tianjin, P.R. China
| | - Anzhi Ren
- Department of Plant Biology and Ecology, College of Life Sciences, Nankai University, Tianjin, P.R. China
| | - Yubao Gao
- Department of Plant Biology and Ecology, College of Life Sciences, Nankai University, Tianjin, P.R. China
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Saari S, Richter S, Robbins M, Faeth SH. Bottom-up regulates top-down: the effects of hybridization of grass endophytes on an aphid herbivore and its generalist predator. OIKOS 2014. [DOI: 10.1111/j.1600-0706.2013.00690.x] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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Oberhofer M, Güsewell S, Leuchtmann A. Effects of natural hybrid and non-hybrid Epichloë endophytes on the response of Hordelymus europaeus to drought stress. THE NEW PHYTOLOGIST 2014; 201:242-253. [PMID: 24102453 DOI: 10.1111/nph.12496] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/20/2013] [Accepted: 08/02/2013] [Indexed: 06/02/2023]
Abstract
Interspecific hybrid endophytes of the genus Epichloë (Ascomycota, Clavicipitaceae) are prevalent in wild grass populations, possibly because of their larger gene variation, resulting in increased fitness benefits for host plants; however, the reasons are not yet known. We tested hypotheses regarding niche expansion mediated by hybrid endophytes, population-dependent interactions and local co-adaptation in the woodland grass Hordelymus europaeus, which naturally hosts both hybrid and non-hybrid endophyte taxa. Seedlings derived from seeds of four grass populations made endophyte free were re-inoculated with hybrid or non-hybrid endophyte strains, or left endophyte free. Plants were grown in the glasshouse with or without drought treatment. Endophyte infection increased plant biomass and tiller production by 10-15% in both treatments. Endophyte types had similar effects on growth, but opposite effects on reproduction: non-hybrid endophytes increased seed production, whereas hybrid endophytes reduced or prevented it completely. The results are consistent with the observation that non-hybrid endophytes in H. europaeus prevail at dry sites, but cannot explain the prevalence of hybrid endophytes. Thus, our results do not support the hypothesis of niche expansion of hybrid-infected plants. Moreover, plants inoculated with native relative to foreign endophytes yielded higher infections, but both showed similar growth and survival, suggesting weak co-adaptation.
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Affiliation(s)
- Martina Oberhofer
- Plant Ecological Genetics, Institute of Integrative Biology, ETH Zürich, Universitätstrasse 16, CH-8092, Zürich, Switzerland
- Department of Biology, University of North Carolina Greensboro, 321 McIver Street, Greensboro, NC, 27412, USA
| | - Sabine Güsewell
- Plant Ecology, Institute of Integrative Biology, ETH Zürich, Universitätstrasse 16, CH-8092, Zürich, Switzerland
| | - Adrian Leuchtmann
- Plant Ecological Genetics, Institute of Integrative Biology, ETH Zürich, Universitätstrasse 16, CH-8092, Zürich, Switzerland
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Schardl CL, Young CA, Pan J, Florea S, Takach JE, Panaccione DG, Farman ML, Webb JS, Jaromczyk J, Charlton ND, Nagabhyru P, Chen L, Shi C, Leuchtmann A. Currencies of mutualisms: sources of alkaloid genes in vertically transmitted epichloae. Toxins (Basel) 2013; 5:1064-88. [PMID: 23744053 PMCID: PMC3717770 DOI: 10.3390/toxins5061064] [Citation(s) in RCA: 81] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2013] [Revised: 05/17/2013] [Accepted: 05/29/2013] [Indexed: 11/17/2022] Open
Abstract
The epichloae (Epichloë and Neotyphodium species), a monophyletic group of fungi in the family Clavicipitaceae, are systemic symbionts of cool-season grasses (Poaceae subfamily Poöideae). Most epichloae are vertically transmitted in seeds (endophytes), and most produce alkaloids that attack nervous systems of potential herbivores. These protective metabolites include ergot alkaloids and indole-diterpenes (tremorgens), which are active in vertebrate systems, and lolines and peramine, which are more specific against invertebrates. Several Epichloë species have been described which are sexual and capable of horizontal transmission, and most are vertically transmissible also. Asexual epichloae are mainly or exclusively vertically transmitted, and many are interspecific hybrids with genomic contributions from two or three ancestral Epichloë species. Here we employ genome-scale analyses to investigate the origins of biosynthesis gene clusters for ergot alkaloids (EAS), indole-diterpenes (IDT), and lolines (LOL) in 12 hybrid species. In each hybrid, the alkaloid-gene and housekeeping-gene relationships were congruent. Interestingly, hybrids frequently had alkaloid clusters that were rare in their sexual ancestors. Also, in those hybrids that had multiple EAS, IDT or LOL clusters, one cluster lacked some genes, usually for late pathway steps. Possible implications of these findings for the alkaloid profiles and endophyte ecology are discussed.
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Affiliation(s)
- Christopher L. Schardl
- Department of Plant Pathology, University of Kentucky, Lexington, KY 40546, USA; E-Mails: (J.P.); (S.F.); (M.L.F.); (P.N.); (L.C.); (C.S.)
| | - Carolyn A. Young
- Forage Improvement Division, The Samuel Roberts Noble Foundation, Ardmore, OK 73401, USA; E-Mails: (C.A.Y.); (J.E.T.); (N.D.C.)
| | - Juan Pan
- Department of Plant Pathology, University of Kentucky, Lexington, KY 40546, USA; E-Mails: (J.P.); (S.F.); (M.L.F.); (P.N.); (L.C.); (C.S.)
| | - Simona Florea
- Department of Plant Pathology, University of Kentucky, Lexington, KY 40546, USA; E-Mails: (J.P.); (S.F.); (M.L.F.); (P.N.); (L.C.); (C.S.)
| | - Johanna E. Takach
- Forage Improvement Division, The Samuel Roberts Noble Foundation, Ardmore, OK 73401, USA; E-Mails: (C.A.Y.); (J.E.T.); (N.D.C.)
| | - Daniel G. Panaccione
- Division of Plant and Soil Sciences, West Virginia University, Morgantown, WV 26506, USA; E-Mail:
| | - Mark L. Farman
- Department of Plant Pathology, University of Kentucky, Lexington, KY 40546, USA; E-Mails: (J.P.); (S.F.); (M.L.F.); (P.N.); (L.C.); (C.S.)
| | - Jennifer S. Webb
- Advanced Genetic Technologies Center, University of Kentucky, Lexington, KY 40546, USA; E-Mails: (J.S.W.); (J.J.)
| | - Jolanta Jaromczyk
- Advanced Genetic Technologies Center, University of Kentucky, Lexington, KY 40546, USA; E-Mails: (J.S.W.); (J.J.)
| | - Nikki D. Charlton
- Forage Improvement Division, The Samuel Roberts Noble Foundation, Ardmore, OK 73401, USA; E-Mails: (C.A.Y.); (J.E.T.); (N.D.C.)
| | - Padmaja Nagabhyru
- Department of Plant Pathology, University of Kentucky, Lexington, KY 40546, USA; E-Mails: (J.P.); (S.F.); (M.L.F.); (P.N.); (L.C.); (C.S.)
| | - Li Chen
- Department of Plant Pathology, University of Kentucky, Lexington, KY 40546, USA; E-Mails: (J.P.); (S.F.); (M.L.F.); (P.N.); (L.C.); (C.S.)
- School of Pastoral Agriculture Science and Technology, Lanzhou University, Lanzhou 730020, China
| | - Chong Shi
- Department of Plant Pathology, University of Kentucky, Lexington, KY 40546, USA; E-Mails: (J.P.); (S.F.); (M.L.F.); (P.N.); (L.C.); (C.S.)
- School of Grassland & Environmental Science, Xinjiang Agricultural University, Urumqi 830052, China
| | - Adrian Leuchtmann
- Institute of Integrative Biology, ETH Zürich, Zürich CH-8092, Switzerland; E-Mail:
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Gundel PE, Martínez-Ghersa MA, Omacini M, Cuyeu R, Pagano E, Ríos R, Ghersa CM. Mutualism effectiveness and vertical transmission of symbiotic fungal endophytes in response to host genetic background. Evol Appl 2013; 5:838-49. [PMID: 23346228 PMCID: PMC3552401 DOI: 10.1111/j.1752-4571.2012.00261.x] [Citation(s) in RCA: 53] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/25/2012] [Accepted: 03/06/2012] [Indexed: 12/01/2022] Open
Abstract
Certain species of the Pooideae subfamily develop stress tolerance and herbivory resistance through symbiosis with vertically transmitted, asexual fungi. This symbiosis is specific, and genetic factors modulate the compatibility between partners. Although gene flow is clearly a fitness trait in allogamous grasses, because it injects hybrid vigor and raw material for evolution, it could reduce compatibility and thus mutualism effectiveness. To explore the importance of host genetic background in modulating the performance of symbiosis, Lolium multiflorum plants, infected and noninfected with Neotyphodium occultans, were crossed with genetically distant plants of isolines (susceptible and resistant to diclofop-methyl herbicide) bred from two cultivars and exposed to stress. The endophyte improved seedling survival in genotypes susceptible to herbicide, while it had a negative effect on one of the genetically resistant crosses. Mutualism provided resistance to herbivory independently of the host genotype, but this effect vanished under stress. While no endophyte effect was observed on host reproductive success, it was increased by interpopulation plant crosses. Neither gene flow nor herbicide had an important impact on endophyte transmission. Host fitness improvements attributable to gene flow do not appear to result in direct conflict with mutualism while this seems to be an important mechanism for the ecological and contemporary evolution of the symbiotum.
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Affiliation(s)
- Pedro E Gundel
- IFEVA-Facultad de Agronomía (UBA)/CONICET Argentina ; MTT Agrifood Research, Plant Protection Finland
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White JF, Crawford H, Torres MS, Mattera R, Irizarry I, Bergen M. A proposed mechanism for nitrogen acquisition by grass seedlings through oxidation of symbiotic bacteria. Symbiosis 2012; 57:161-171. [PMID: 23087539 PMCID: PMC3473182 DOI: 10.1007/s13199-012-0189-8] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/30/2012] [Accepted: 09/22/2012] [Indexed: 12/01/2022]
Abstract
In this paper we propose and provide evidence for a mechanism, oxidative nitrogen scavenging (ONS), whereby seedlings of some grass species may extract nitrogen from symbiotic diazotrophic bacteria through oxidation by plant-secreted reactive oxygen species (ROS). Experiments on this proposed mechanism employ tall fescue (Festuca arundinaceae) seedlings to elucidate features of the oxidative mechanism. We employed 15N2 gas assimilation experiments to demonstrate nitrogen fixation, direct microscopic visualization of bacteria on seedling surfaces to visualize the bacterial oxidation process, reactive oxygen probes to test for the presence of H2O2 and cultural experiments to assess conditions under which H2O2 is secreted by seedlings. We also made surveys of the seedlings of several grass species to assess the distribution of the phenomenon of microbial oxidation in the Poaceae. Key elements of the proposed mechanism for nitrogen acquisition in seedlings include: 1) diazotrophic bacteria are vectored on or within seeds; 2) at seed germination bacteria colonize seedling roots and shoots; 3) seedling tissues secrete ROS onto bacteria; 4) bacterial cell walls, membranes, nucleic acids, proteins and other biological molecules are oxidized; 5) nitrates and/or smaller fragments of organic nitrogen-containing molecules resulting from oxidation may be absorbed by seedling tissues and larger peptide fragments may be further processed by secreted or cell wall plant proteases until they are small enough for transport into cells. Hydrogen peroxide secretion from seedling roots and bacterial oxidation was observed in several species in subfamily Pooideae where seeds possessed adherent paleas and lemmas, but was not seen in grasses that lacked this feature or long-cultivated crop species.
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Affiliation(s)
- James F White
- Department of Plant Biology and Pathology, Rutgers University, New Brunswick, NJ USA
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Saari S, Faeth SH. Hybridization of Neotyphodium endophytes enhances competitive ability of the host grass. THE NEW PHYTOLOGIST 2012; 195:231-236. [PMID: 22489964 DOI: 10.1111/j.1469-8137.2012.04140.x] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
• Associations with microbial symbionts may lead to niche differentiation of their host. Vertically transmitted Neotyphodium endophytes of grasses often hybridize in nature. Infection by these hybrid symbionts may result in different host-plant phenotypes from those caused as a result of infection by nonhybrid symbionts. Observations of wild Arizona fescue (Festuca arizonica) populations show that hybrid Neotyphodium-infected (H+) grasses dominate in resource-poor environments, whereas nonhybrid endophyte-infected (NH+) grasses dominate in environments with more resources. We studied the hypothesis that hybridization of endophytes increases stress tolerance of the host. • To test whether hybridization of Neotyphodium affects performance and competitive abilities of the host depending on resources, we conducted a glasshouse experiment where competition, nutrients and watering were manipulated. • H+ plants had greater wet biomass than NH+ and endophyte-free plants, when grown in competition, but only in low-water and low-nutrient treatments. By contrast, NH+ plants did not perform better than H+ or endophyte-free plants regardless of the treatment combination. • Our results suggest that hybridization of symbiotic Neotyphodium endophytes may increase competitive potential of the host in stressful environments and that this hybridization may be underlying niche expansion of Arizona fescue in the environments with low resources.
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Affiliation(s)
- S Saari
- Department of Biology, University of North Carolina at Greensboro, Greensboro, NC 27402, USA.
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29
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Taxonomic placement of Epichloë poae sp. nov. and horizontal dissemination to seedlings via conidia. FUNGAL DIVERS 2012. [DOI: 10.1007/s13225-012-0170-0] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/28/2022]
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Gibert A, Volaire F, Barre P, Hazard L. A fungal endophyte reinforces population adaptive differentiation in its host grass species. THE NEW PHYTOLOGIST 2012; 194:561-571. [PMID: 22404479 DOI: 10.1111/j.1469-8137.2012.04073.x] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/29/2023]
Abstract
Hereditary symbioses between fungal endophytes and grasses are relatively recent in the history of plant life. Given < 80 million yr of co-evolution, symbioses are likely to have impacted plant microevolutionary rather than macroevolutionary processes. Therefore, we investigated the microevolutionary role of the fungal endophyte Neotyphodium lolii in the adaptive differentiation of its host species Lolium perenne. Endophyte frequency in 22 natural L. perenne populations was established across a water availability gradient. Adaptive differentiation among five populations, and between symbiotic (S) and nonsymbiotic (NS) plants, was examined in a glasshouse experiment under nonlimiting and limiting water conditions. Genetic differentiation was subsequently assessed among populations, and between S and NS individuals, using 14 simple sequence repeats (SSR). Symbiosis frequencies were positively correlated to water availability. Adaptive population differentiation occurred following a trade-off between biomass production under nonlimiting water conditions and survivorship under water stress. Endophytic symbiosis increased plant survival in xeric populations, and reinforced competitiveness in mesic populations. No genetic difference was detected between S and NS plants within populations. Therefore, we conclude that the endophyte relationship is responsible for these effects. Local adaptation of the host plant, appears to be supported by the fungal endophyte.
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Affiliation(s)
- Anaïs Gibert
- INRA - UMR 1248 AGIR, BP 52627, F-31326 Castanet-Tolosan Cedex, France
| | - Florence Volaire
- INRA - UMR 5175 CEFE, Route De Mende, F-34293 Montpellier, Cedex 5, France
| | | | - Laurent Hazard
- INRA - UMR 1248 AGIR, BP 52627, F-31326 Castanet-Tolosan Cedex, France
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31
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Rudgers JA, Miller TEX, Ziegler SM, Craven KD. There are many ways to be a mutualist: Endophytic fungus reduces plant survival but increases population growth. Ecology 2012; 93:565-74. [DOI: 10.1890/11-0689.1] [Citation(s) in RCA: 46] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
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32
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Conspicuous epiphytic growth of an interspecific hybrid Neotyphodium sp. endophyte on distorted host inflorescences. Fungal Biol 2012; 116:42-8. [DOI: 10.1016/j.funbio.2011.09.007] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2011] [Revised: 09/28/2011] [Accepted: 09/29/2011] [Indexed: 11/22/2022]
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33
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GARCÍA PARISI PABLOA, CASAS CECILIA, GUNDEL PEDROE, OMACINI MARINA. Consequences of grazing on the vertical transmission of a fungal Neotyphodium symbiont in an annual grass population. AUSTRAL ECOL 2011. [DOI: 10.1111/j.1442-9993.2011.02325.x] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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34
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Gundel PE, Rudgers JA, Ghersa CM. Incorporating the process of vertical transmission into understanding of host-symbiont dynamics. OIKOS 2011. [DOI: 10.1111/j.1600-0706.2011.19299.x] [Citation(s) in RCA: 86] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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35
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Inderbitzin P, Davis RM, Bostock RM, Subbarao KV. The ascomycete Verticillium longisporum is a hybrid and a plant pathogen with an expanded host range. PLoS One 2011; 6:e18260. [PMID: 21455321 PMCID: PMC3063834 DOI: 10.1371/journal.pone.0018260] [Citation(s) in RCA: 134] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/10/2011] [Accepted: 02/23/2011] [Indexed: 01/24/2023] Open
Abstract
Hybridization plays a central role in plant evolution, but its overall importance in fungi is unknown. New plant pathogens are thought to arise by hybridization between formerly separated fungal species. Evolution of hybrid plant pathogens from non-pathogenic ancestors in the fungal-like protist Phytophthora has been demonstrated, but in fungi, the most important group of plant pathogens, there are few well-characterized examples of hybrids. We focused our attention on the hybrid and plant pathogen Verticillium longisporum, the causal agent of the Verticillium wilt disease in crucifer crops. In order to address questions related to the evolutionary origin of V. longisporum, we used phylogenetic analyses of seven nuclear loci and a dataset of 203 isolates of V. longisporum, V. dahliae and related species. We confirmed that V. longisporum was diploid, and originated three different times, involving four different lineages and three different parental species. All hybrids shared a common parent, species A1, that hybridized respectively with species D1, V. dahliae lineage D2 and V. dahliae lineage D3, to give rise to three different lineages of V. longisporum. Species A1 and species D1 constituted as yet unknown taxa. Verticillium longisporum likely originated recently, as each V. longisporum lineage was genetically homogenous, and comprised species A1 alleles that were identical across lineages.
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Affiliation(s)
- Patrik Inderbitzin
- Department of Plant Pathology, University of California Davis, Davis, California, United States of America
| | - R. Michael Davis
- Department of Plant Pathology, University of California Davis, Davis, California, United States of America
| | - Richard M. Bostock
- Department of Plant Pathology, University of California Davis, Davis, California, United States of America
| | - Krishna V. Subbarao
- Department of Plant Pathology, University of California Davis, Davis, California, United States of America
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36
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Gundel PE, Omacini M, Sadras VO, Ghersa CM. The interplay between the effectiveness of the grass-endophyte mutualism and the genetic variability of the host plant. Evol Appl 2010; 3:538-46. [PMID: 25567945 PMCID: PMC3352510 DOI: 10.1111/j.1752-4571.2010.00152.x] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2010] [Accepted: 07/09/2010] [Indexed: 11/27/2022] Open
Abstract
Neotyphodium endophytic fungi, the asexual state of Epichloë species, protect cool-season grasses against stresses. The outcomes of Neotyphodium-grass symbioses are agronomically relevant as they may affect the productivity of pastures. It has been suggested that the mutualism is characteristic of agronomic grasses and that differential rates of gene flow between both partners’ populations are expected to disrupt the specificity of the association and, thus, the mutualism in wild grasses. We propose that compatibility is necessary but not sufficient to explain the outcomes of Neotyphodium-grass symbiosis, and advance a model that links genetic compatibility, mutualism effectiveness, and endophyte transmission efficiency. For endophytes that reproduce clonally and depend on allogamous hosts for reproduction and dissemination, we propose that this symbiosis works as an integrated entity where gene flow promotes its fitness and evolution. Compatibility between the host plant and the fungal endophyte would be high in genetically close parents; however, mutualism effectiveness and transmission efficiency would be low in fitness depressed host plants. Increasing the genetic distance of mating parents would increase mutualism effectiveness and transmission efficiency. This tendency would be broken when the genetic distance between parents is high (out-breeding depression). Our model allows for testable hypotheses that would contribute to understand the coevolutionary origin and future of the endophyte-grass mutualism.
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Affiliation(s)
- Pedro E Gundel
- IFEVA-Facultad de Agronomía (UBA)/CONICET, Cátedra de Ecología Buenos Aires, Argentina
| | - Marina Omacini
- IFEVA-Facultad de Agronomía (UBA)/CONICET, Cátedra de Ecología Buenos Aires, Argentina
| | - Victor O Sadras
- South Australian Research and Development Institute Adelaide, Australia
| | - Claudio M Ghersa
- IFEVA-Facultad de Agronomía (UBA)/CONICET, Cátedra de Ecología Buenos Aires, Argentina
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37
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Hamilton CE, Dowling TE, Faeth SH. Hybridization in endophyte symbionts alters host response to moisture and nutrient treatments. MICROBIAL ECOLOGY 2010; 59:768-775. [PMID: 19921327 DOI: 10.1007/s00248-009-9606-9] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/24/2009] [Accepted: 10/17/2009] [Indexed: 05/28/2023]
Abstract
When a host organism is infected by a symbiont, the resulting symbiotum has a phenotype distinct from uninfected hosts. Genotypic interactions between the partners may increase phenotypic variation of the host at the population level. Neotyphodium is an asexual, vertically transmitted endophytic symbiont of grasses often existing in hybrid form. Hybridization in Neotyphodium rapidly increases the symbiotum's genomic content and is likely to increase the phenotypic variation of the host. This phenotypic variation is predicted to enhance host performance, especially in stressful environments. We tested this hypothesis by comparing the growth, survival, and resource allocation of hybrid and nonhybrid infected host plants exposed to controlled variation in soil moisture and nutrients. Infection by a hybrid endophyte did not fit our predictions of comparatively higher root and total biomass production under low moisture/low nutrient treatments. Regardless of whether the host was infected by a hybrid or nonhybrid endophyte, both produced significantly higher root/total biomass when both nutrient and moisture were high compared to limited nutrient/moisture treatments. However, infection by hybrid Neotyphodium did result in significantly higher total biomass and host survival compared to nonhybrid infected hosts, regardless of treatment. Endophyte hybridization alters host strategies in response to stress by increasing survival in depauperate habitats and thus, potentially increasing the relative long-term host fitness.
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Affiliation(s)
- Cyd E Hamilton
- Arizona State University, School of Life Sciences, Tempe, AZ 85287, USA.
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38
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Collado-Romero M, Jiménez-Díaz RM, Mercado-Blanco J. DNA sequence analysis of conserved genes reveals hybridization events that increase genetic diversity in Verticillium dahliae. Fungal Biol 2010; 114:209-18. [PMID: 20943131 DOI: 10.1016/j.funbio.2009.12.005] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2009] [Revised: 12/13/2009] [Accepted: 12/30/2009] [Indexed: 10/19/2022]
Abstract
The hybrid origin of a Verticillium dahliae isolate belonging to the vegetative compatibility group (VCG) 3 is reported in this work. Moreover, new data supporting the hybrid origin of two V. dahliae var. longisporum (VDLSP) isolates are provided as well as information about putative parentals. Thus, isolates of VDLSP and V. dahliae VCG3 were found harboring multiple sequences of actin (Act), β-tubulin (β-tub), calmodulin (Cal) and histone 3 (H3) genes. Phylogenetic analysis of these sequences, the internal transcribed sequences (ITS-1 and ITS-2) of the rRNA genes and of a V. dahliae-specific sequence provided molecular evidences for the interspecific hybrid origin of those isolates. Sequence analysis suggests that some of VDLSP isolates may have resulted from hybridization events between a V. dahliae isolate of VCG1 and/or VCG4A and, probably, a closely related taxon to Verticillium alboatrum but not this one. Similarly, phylogenetic analysis and PCR markers indicated that a V. dahliae VCG3 isolate might have arisen from a hybridization event between a V. dahliae VCG1B isolate and as yet unidentified parent. This second parental probably does not belong to the Verticillium genus according to the gene sequences dissimilarities found between the VCG3 isolate and Verticillium spp. These results suggest an important role of parasexuality in diversity and evolution in the genus Verticillium and show that interspecific hybrids within this genus may not be rare in nature.
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Affiliation(s)
- Melania Collado-Romero
- Departamento Protección de Cultivos, Instituto de Agricultura Sostenible, Consejo Superior de Investigaciones Científicas, Apartado 4084, 14080 Córdoba, Spain.
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39
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Rudgers JA, Afkhami ME, Rúa MA, Davitt AJ, Hammer S, Huguet VM. A fungus among us: broad patterns of endophyte distribution in the grasses. Ecology 2009; 90:1531-9. [DOI: 10.1890/08-0116.1] [Citation(s) in RCA: 102] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
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40
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Rodriguez RJ, White JF, Arnold AE, Redman RS. Fungal endophytes: diversity and functional roles. THE NEW PHYTOLOGIST 2009; 182:314-330. [PMID: 19236579 DOI: 10.1111/j.1469-8137.2009.02773.x] [Citation(s) in RCA: 1298] [Impact Index Per Article: 86.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/20/2023]
Abstract
All plants in natural ecosystems appear to be symbiotic with fungal endophytes. This highly diverse group of fungi can have profound impacts on plant communities through increasing fitness by conferring abiotic and biotic stress tolerance, increasing biomass and decreasing water consumption, or decreasing fitness by altering resource allocation. Despite more than 100 yr of research resulting in thousands of journal articles, the ecological significance of these fungi remains poorly characterized. Historically, two endophytic groups (clavicipitaceous (C) and nonclavicipitaceous (NC)) have been discriminated based on phylogeny and life history traits. Here, we show that NC-endophytes represent three distinct functional groups based on host colonization and transmission, in planta biodiversity and fitness benefits conferred to hosts. Using this framework, we contrast the life histories, interactions with hosts and potential roles in plant ecophysiology of C- and NC-endophytes, and highlight several key questions for future work in endophyte biology.
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Affiliation(s)
- R J Rodriguez
- US Geological Survey, Seattle, WA, USA
- University of Washington, Seattle, WA, USA
| | - J F White
- Rutgers University, New Brunswick, NJ, USA
| | - A E Arnold
- Division of Plant Pathology & Microbiology, Department of Plant Sciences, University of Arizona, Tucson, AZ 85721, USA
| | - R S Redman
- University of Washington, Seattle, WA, USA
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41
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Klosterman SJ, Atallah ZK, Vallad GE, Subbarao KV. Diversity, pathogenicity, and management of verticillium species. ANNUAL REVIEW OF PHYTOPATHOLOGY 2009; 47:39-62. [PMID: 19385730 DOI: 10.1146/annurev-phyto-080508-081748] [Citation(s) in RCA: 393] [Impact Index Per Article: 26.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/21/2023]
Abstract
The genus Verticillium encompasses phytopathogenic species that cause vascular wilts of plants. In this review, we focus on Verticillium dahliae, placing emphasis on the controversy surrounding the elevation of a long-spored variant as a new species, recent advances in the analysis of compatible and incompatible interactions, highlighted by the use of strains expressing fluorescent proteins, and the genetic diversity among Verticillium spp. A synthesis of the approaches to explore genetic diversity, gene flow, and the potential for cryptic recombination is provided. Control of Verticillium wilt has relied on a panoply of chemical and nonchemical strategies, but is beset with environmental or site-specific efficacy problems. Host resistance remains the most logical choice, but is unavailable in most crops. The genetic basis of resistance to Verticillium wilt is unknown in most crops, as are the subcellular signaling mechanisms associated with Ve-mediated, race-specific resistance. Increased understanding in each of these areas promises to facilitate management of Verticillium wilts across a broad range of crops.
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42
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Gundel PE, Batista WB, Texeira M, Martínez-Ghersa MA, Omacini M, Ghersa CM. Neotyphodium endophyte infection frequency in annual grass populations: relative importance of mutualism and transmission efficiency. Proc Biol Sci 2008; 275:897-905. [PMID: 18198146 DOI: 10.1098/rspb.2007.1494] [Citation(s) in RCA: 80] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Persistence and ubiquity of vertically transmitted Neotyphodium endophytes in grass populations is puzzling because infected plants do not consistently exhibit increased fitness. Using an annual grass population model, we show that the problems for matching endophyte infection and mutualism are likely to arise from difficulties in detecting small mutualistic effects, variability in endophyte transmission efficiency and an apparent prevalence of non-equilibrium in the dynamics of infection. Although endophytes would ultimately persist only if the infection confers some fitness increase to the host plants, such an increase can be very small, as long as the transmission efficiency is sufficiently high. In addition, imperfect transmission limits effectively the equilibrium infection level if the infected plants exhibit small or large reproductive advantage. Under frequent natural conditions, the equilibrium infection level is very sensitive to small changes in transmission efficiency and host reproductive advantage, while convergence to such an equilibrium is slow. As a consequence, seed immigration and environmental fluctuation are likely to keep local infection levels away from equilibrium. Transient dynamics analysis suggests that, when driven by environmental fluctuation, infection frequency increases would often be larger than decreases. By contrast, when due to immigration, overrepresentation of infected individuals tends to vanish faster than equivalent overrepresentation of non-infected individuals.
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Affiliation(s)
- Pedro E Gundel
- IFEVA-Facultad de Agronomía UBA/CONICET, Cátedra de Ecología, C1417DSE Buenos Aires, Argentina.
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43
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Afkhami M, Rudgers J. Symbiosis Lost: Imperfect Vertical Transmission of Fungal Endophytes in Grasses. Am Nat 2008; 172:405-16. [DOI: 10.1086/589893] [Citation(s) in RCA: 105] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
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44
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Fehrer J, Slavíková-Bayerová Š, Orange A. Large genetic divergence of new, morphologically similar species of sterile lichens from Europe (Lepraria, Stereocaulaceae, Ascomycota): concordance of DNA sequence data with secondary metabolites. Cladistics 2008; 24:443-458. [DOI: 10.1111/j.1096-0031.2008.00216.x] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022] Open
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Sullivan TJ, Faeth SH. Local adaptation in Festuca arizonica infected by hybrid and nonhybrid Neotyphodium endophytes. MICROBIAL ECOLOGY 2008; 55:697-704. [PMID: 17943341 DOI: 10.1007/s00248-007-9312-4] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/16/2007] [Accepted: 08/06/2007] [Indexed: 05/25/2023]
Abstract
Cool-season grasses often harbor obligate fungal symbionts from the genus Neotyphodium, and these symbiota can function as a single ecological unit. Previous studies have shown that gene flow in Neotyphodium in Festuca arizonica is low enough such that populations could diverge and form local adaptations. A reciprocal transplant experiment was performed between two F. arizonica/Neotyphodium populations in Arizona, Clint's Well and Flagstaff, using symbiota with the most common Neotyphodium genotypes in each population, to test for local adaptations. The genetic difference between populations is potentially large as Neotyphodium from Clint's Well are of hybrid origin. Local environmental variation was the most important source of variation for F. arizonica/Neotyphodium symbiota growth, with individuals at Flagstaff growing larger and individuals at Clint's Well not reproducing. Local environment and the source population of the symbiota interacted to affect vegetative growth. Symbiota from Clint's Well, which harbor hybrid Neotyphodium, had higher volume/wet mass and volume/dry mass ratios but only in the marginal Clint's Well habitat. The local environment also affected F. arizonica/Neotyphodium reproduction because only symbiota transplanted to Flagstaff reproduced. Symbiota from Clint's Well produced more panicles, whereas symbiota from Flagstaff with nonhybrid Neotyphodium produced greater seed mass per panicle. Overall seed mass production was not different, suggesting that the two strategies are functionally equivalent. We find that F. arizonica/Neotyphodium symbiota vary geographically, but potential local adaptations are only apparent in marginal habitats and may be related to the evolutionary history of the Neotyphodium part of the symbiota.
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Affiliation(s)
- T J Sullivan
- School of Life Sciences, Arizona State University, Tempe, AZ 85287-4501, USA.
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46
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Tintjer T, Leuchtmann A, Clay K. Variation in horizontal and vertical transmission of the endophyte Epichloë elymi infecting the grass Elymus hystrix. THE NEW PHYTOLOGIST 2008; 179:236-246. [PMID: 18422901 DOI: 10.1111/j.1469-8137.2008.02441.x] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/26/2023]
Abstract
Systemic fungal endophytes (Clavicipitaceae) of grasses reproduce sexually when the fungus forms stromata and contagious ascospores, or asexually by vertical transmission of hyphae into seeds and seedlings. Vertical transmission is predicted to favor reduced virulence compared with horizontal transmission in systems with both types of transmission. Here, variation in vertical and horizontal transmission and its potential heritability in a host grass-endophyte interaction, Elymus hystrix infected with Epichloë elymi, were examined in natural populations and two common garden experiments using field-collected host tillers and seed progeny of maternal plants with known infection phenotypes. Transmission mode exhibited year-to-year variation in field and common garden environments. In the common garden there were consistent differences among maternal plant families in stroma production and significant correlations between stroma production in the common garden and in natural populations. Transmission mode differed among maternal families, spanning a continuum from pure vertical transmission to a high proportion of stroma production and horizontal transmission potential. Vertical transmission to seeds occurred at high rates in all maternal families regardless of their stroma production. Observed patterns of variation indicate that endophyte transmission mode and correlated changes in virulence can respond to selection by biotic and abiotic factors.
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Affiliation(s)
- Tammy Tintjer
- Department of Biology, Indiana University, Bloomington, IN 47405, USA
- Present address: Department of Sciences and Mathematics, St. Mary of the Woods College, St. Mary of the Woods, IN 47876, USA
| | - Adrian Leuchtmann
- Institute of Integrative Biology, Plant Ecological Genetics, ETH Zürich, Universitätstrasse 16, CH-8092 Zürich, Switzerland
| | - Keith Clay
- Department of Biology, Indiana University, Bloomington, IN 47405, USA
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Abstract
In this review on fungal speciation, we first contrast the issues of species definition and species criteria and show that by distinguishing the two concepts the approaches to studying the speciation can be clarified. We then review recent developments in the understanding of modes of speciation in fungi. Allopatric speciation raises no theoretical problem and numerous fungal examples exist from nature. We explain the theoretical difficulties raised by sympatric speciation, review the most recent models, and provide some natural examples consistent with speciation in sympatry. We describe the nature of prezygotic and postzygotic reproductive isolation in fungi and examine their evolution as functions of temporal and of the geographical distributions. We then review the theory and evidence for roles of cospeciation, host shifts, hybridization, karyotypic rearrangement, and epigenetic mechanisms in fungal speciation. Finally, we review the available data on the genetics of speciation in fungi and address the issue of speciation in asexual species.
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Hossaert-McKey M, McKey D, Dormont L. Fungal sex as a private matter: odour signals in a specialized pollination-like insect-fungus mutualism. THE NEW PHYTOLOGIST 2008; 178:225-227. [PMID: 18371002 DOI: 10.1111/j.1469-8137.2008.02428.x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/26/2023]
Affiliation(s)
- Martine Hossaert-McKey
- Centre d'Ecologie Fonctionnelle et Evolutive (CEFE), UMR CNRS 5175, 1919 route de Mende, F-34293 Montpellier Cedex 5, France (*Author for correspondence: tel +33 4 67 61 32 30; fax +33 4 67 41 21 38; email )
| | - Doyle McKey
- Centre d'Ecologie Fonctionnelle et Evolutive (CEFE), UMR CNRS 5175, 1919 route de Mende, F-34293 Montpellier Cedex 5, France (*Author for correspondence: tel +33 4 67 61 32 30; fax +33 4 67 41 21 38; email )
| | - Laurent Dormont
- Centre d'Ecologie Fonctionnelle et Evolutive (CEFE), UMR CNRS 5175, 1919 route de Mende, F-34293 Montpellier Cedex 5, France (*Author for correspondence: tel +33 4 67 61 32 30; fax +33 4 67 41 21 38; email )
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Clewes E, Barbara DJ. Two allopolyploid ascomycete fungal plant pathogens were not rescued by vertical transmission. THE NEW PHYTOLOGIST 2007; 177:583-585. [PMID: 18086225 DOI: 10.1111/j.1469-8137.2007.02327.x] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/25/2023]
Affiliation(s)
- E Clewes
- Warwick HRI, University of Warwick, Wellesbourne, Warwick, UK
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