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Teresa E. Pawlowska - One of the best experts on this subject based on the ideXlab platform.
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defying muller s ratchet ancient heritable endobacteria escape extinction through retention of recombination and genome plasticity
Mbio, 2016Co-Authors: Mizue Naito, Teresa E. PawlowskaAbstract:ABSTRACT Heritable endobacteria, which are transmitted from one host generation to the next, are subjected to evolutionary forces that are different from those experienced by free-living bacteria. In particular, they suffer consequences of Muller’s ratchet, a mechanism that leads to extinction of small asexual populations due to fixation of slightly deleterious mutations combined with the random loss of the most-fit genotypes, which cannot be recreated without recombination. Mycoplasma-related endobacteria (MRE) are heritable symbionts of fungi from two ancient lineages, Glomeromycota (arbuscular mycorrhizal fungi) and Mucoromycotina . Previous studies revealed that MRE maintain unusually diverse populations inside their hosts and may have been associated with fungi already in the early Paleozoic. Here we show that MRE are vulnerable to genomic degeneration and propose that they defy Muller’s ratchet thanks to retention of recombination and genome plasticity. We suggest that other endobacteria may be capable of raising similar defenses against Muller’s ratchet.
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arbuscular mycorrhizal colonization of giant sequoia sequoiadendron giganteum in response to restoration practices
Mycologia, 2012Co-Authors: Catherine Fahey, Robert A. York, Teresa E. PawlowskaAbstract:Interactions with soil microbiota determine the success of restoring plants to their native habitats. The goal of our study was to understand the effects of restoration practices on interactions of giant sequoia Sequoiadendron giganteum with arbuscular mycorrhizal (AM) fungi (Glomeromycota). Natural regeneration of Sequoiadendron is threatened by the absence of severe fires that create forest canopy gaps. Generating artificial canopy gaps offers an alternative tool for giant sequoia restoration. We investigated the effect of regeneration practices, including (i) sapling location within gaps, (ii) gap size and (iii) soil substrate, on AM fungal colonization of giant sequoia sapling roots in a native giant sequoia grove of the Sierra Nevada, California. We found that the extent of AM fungal root colonization was positively correlated with sapling height and light availability, which were related to the location of the sapling within the gap and the gap size. While colonization frequency by arbuscules in saplings on ash substrate was higher relative to saplings in mineral soil, the total AM fungal root colonization was similar between the substrates. A negative correlation between root colonization by Glomeromycota and non-AM fungal species indicated antagonistic interactions between different classes of root-associated fungi. Using DNA genotyping, we identified six AM fungal taxa representing genera Glomus and Ambispora present in Sequoiadendron roots. Overall, we found that AM fungal colonization of giant sequoia roots was associated with availability of plant-assimilated carbon to the fungus rather than with the AM fungal supply of mineral nutrients to the roots. We conclude that restoration practices affecting light availability and carbon assimilation alter feedbacks between sapling growth and activity of AM fungi in the roots.
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Arbuscular mycorrhizal colonization of giant sequoia (Sequoiadendron giganteum) in response to restoration practices
Mycologia, 2012Co-Authors: Catherine Fahey, Robert A. York, Teresa E. PawlowskaAbstract:Interactions with soil microbiota determine the success of restoring plants to their native habitats. The goal of our study was to understand the effects of restoration practices on interactions of giant sequoia Sequoiadendron giganteum with arbuscular mycorrhizal (AM) fungi (Glomeromycota). Natural regeneration of Sequoiadendron is threatened by the absence of severe fires that create forest canopy gaps. Generating artificial canopy gaps offers an alternative tool for giant sequoia restoration. We investigated the effect of regeneration practices, including (i) sapling location within gaps, (ii) gap size and (iii) soil substrate, on AM fungal colonization of giant sequoia sapling roots in a native giant sequoia grove of the Sierra Nevada, California. We found that the extent of AM fungal root colonization was positively correlated with sapling height and light availability, which were related to the location of the sapling within the gap and the gap size. While colonization frequency by arbuscules in sap...
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multinucleate spores contribute to evolutionary longevity of asexual Glomeromycota
The American Naturalist, 2010Co-Authors: Jeanluc Jany, Teresa E. PawlowskaAbstract:Abstract: Arbuscular mycorrhizal fungi (Glomeromycota) are the dominant symbionts of land plants and one of the oldest multicellular lineages that exist without evidence of sexual reproduction. The mechanisms that protect these organisms from extinction due to accumulation of deleterious mutations in the absence of sexual recombination are unclear. Glomeromycota reproduce by spores containing hundreds of nuclei, which represents a departure from the typical eukaryotic developmental pattern, where a multicellular organism is re‐created from a uninucleate propagule. To understand whether the multinucleate spore makeup may have contributed to the evolutionary success of Glomeromycota, we examined the dynamics of spore nuclei in Glomus etunicatum using live three‐dimensional imaging and mathematical models. We show that the spores are populated by an influx of a stream of nuclei from the surrounding mycelium rather than by divisions of a single founder nucleus. We present evidence that mechanisms of selection...
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organization of genetic variation in individuals of arbuscular mycorrhizal fungi
Nature, 2004Co-Authors: Teresa E. Pawlowska, John W TaylorAbstract:Arbuscular mycorrhizal (AM) fungi (Glomeromycota) are thought to be the oldest group of asexual multicellular organisms. They colonize the roots of most land plants, where they facilitate mineral uptake from the soil in exchange for plant-assimilated carbon1. Cells of AM fungi contain hundreds of nuclei. Unusual polymorphism of ribosomal DNA observed in individual spores of AM fungi inspired a hypothesis that heterokaryosis—that is, the coexistence of many dissimilar nuclei in cells—occurs throughout the AM fungal life history2,3. Here we report a genetic approach to test the hypothesis of heterokaryosis in AM fungi. Our study of the transmission of polymorphic genetic markers in natural isolates of Glomus etunicatum, coupled with direct amplification of rDNA from microdissected nuclei by polymerase chain reaction, supports the alternative hypothesis of homokaryosis, in which nuclei populating AM fungal individuals are genetically uniform. Intrasporal rDNA polymorphism contained in each nucleus signals a relaxation of concerted evolution4, a recombination-driven process that is responsible for homogenizing rDNA repeats5. Polyploid organization of Glomeromycotan genomes could accommodate intranuclear rDNA polymorphism and buffer these apparently asexual organisms against the effects of accumulating mutations.
Christopher Walker - One of the best experts on this subject based on the ideXlab platform.
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the early devonian fungus mycokidstonia sphaerialoides from the rhynie chert is a member of the ambisporaceae Glomeromycota archaeosporales not an ascomycete
Review of Palaeobotany and Palynology, 2021Co-Authors: Michael Krings, Christopher Walker, Carla J Harper, Mark BrundrettAbstract:Abstract Glomeromycotan propagules (spores) are morphologically diverse in the Early Devonian Rhynie chert; however, only relatively few of these fossils have been documented and critically evaluated. This study re-examines propagules previously described informally as ‘reproductive unit 1’, and identified as Glomeromycotan acaulospores borne within the neck of a sporiferous saccule. Size and morphology, spore wall structure, and the close association of specimens in land plant axes with small glomoid spores, are solid arguments for affinities of ‘reproductive unit 1’ to the Ambisporaceae (Archaeosporales). Moreover, the acaulospores correspond morphologically to Mycokidstonia sphaerialoides, a Rhynie chert fossil originally interpreted as an ascomycete perithecium that, consequently, is redefined here as a member of the Glomeromycota conspecific with ‘reproductive unit 1’. The diagnosis for M. sphaerialoides is emended to be compliant with Glomeromycotan taxonomy; features of the saccule, acaulospore wall, and associated glomoid spores are included. An epitype is also designated. Mycokidstonia sphaerialoides adds to an increasing body of fossil data depicting Devonian Glomeromycota as a diverse fungal lineage which is likely to have been an ecologically important constituent of early terrestrial ecosystems.
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A new genus, Planticonsortium (Mucoromycotina), and new combination (P. tenue), for the fine root endophyte, Glomus tenue (basionym Rhizophagus tenuis)
Mycorrhiza, 2018Co-Authors: Christopher Walker, Armelle Gollotte, Dirk RedeckerAbstract:In 1977, the fine root endophyte, originally named Rhizophagus tenuis , was transferred into the genus Glomus as G. tenue , thus positioning the species with all other known arbuscular mycorrhizal fungi ( Glomeromycota , Glomeromycotina ). Recent molecular evidence, however, places it in a different subphylum, Mucoromycotina in the Mucoromycota . No suitable genus exists in the Mucoromycotina to accommodate G. tenue , so it is moved to Planticonsortium gen. nov. as P. tenue comb. nov.
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Acaulosporoid Glomeromycotan spores with a germination shield from the 400-million-year-old Rhynie chert
Mycological Progress, 2009Co-Authors: Nora Dotzler, Michael Krings, Thomas N. Taylor, Christopher Walker, Hagen Hass, Hans Kerp, Reinhard AgererAbstract:Scutellosporites devonicus from the Early Devonian Rhynie chert is the only fossil Glomeromycotan spore taxon known to produce a germination shield. This paper describes a second type of Glomeromycotan spore with a germination shield from the Rhynie chert. In contrast to S. devonicus , however, these spores are acaulosporoid and develop laterally in the neck of the sporiferous saccule. Germination shield morphology varies, from plate-like with single or double lobes to tongue-shaped structures usually with infolded margins that are distally fringed or palmate. Spore walls are complex and appear to be constructed of at least three wall groups, the outermost of which includes the remains of the saccule. The complement of features displayed by the fossils suggests a relationship with the extant genera Ambispora, Otospora, Acaulospora or Archaeospora , but which of these is the closest extant relative cannot be determined. The acaulosporoid spores from the Rhynie chert document that this spore type was in existence already ∼400 mya, and thus contribute to a more complete understanding of the evolutionary history of the Glomeromycota. This discovery pushes back the evolutionary origin of all main Glomeromycotan groups, revealing that they had evolved before rooted land plants had emerged.
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a new fungal phylum the Glomeromycota phylogeny and evolution
Fungal Biology, 2001Co-Authors: Arthur Schuβler, Daniel Schwarzott, Christopher WalkerAbstract:The ecologically and economically important arbuscular mycorrhizal (AM) fungi, crucial in the ecology and physiology of land plants, and the endocytobiotic fungus, Geosiphon pyriformis, are phylogenetically analysed by their small subunit (SSU) rRNA gene sequences. They can, from molecular, morphological and ecological characteristics, unequivocally be separated from all other major fungal groups in a monophyletic clade. Consequently they are removed from the polyphyletic Zygomycota, and placed into a new monophyletic phylum, the Glomeromycota. The recognition of this monophyletic group, which probably diverged from the same common ancestor as the Ascomycota and Basidiomycota, gives these fungi their proper status, and provides a basis for a new and natural systematics of these fascinating, yet largely hidden organisms, with three new orders (Archaeosporales, Paraglomerales, Diversisporales) described herein. Additionally, several clades resolve at family level; their formal description is in progress.
Dirk Redecker - One of the best experts on this subject based on the ideXlab platform.
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A new genus, Planticonsortium (Mucoromycotina), and new combination (P. tenue), for the fine root endophyte, Glomus tenue (basionym Rhizophagus tenuis)
Mycorrhiza, 2018Co-Authors: Christopher Walker, Armelle Gollotte, Dirk RedeckerAbstract:In 1977, the fine root endophyte, originally named Rhizophagus tenuis , was transferred into the genus Glomus as G. tenue , thus positioning the species with all other known arbuscular mycorrhizal fungi ( Glomeromycota , Glomeromycotina ). Recent molecular evidence, however, places it in a different subphylum, Mucoromycotina in the Mucoromycota . No suitable genus exists in the Mucoromycotina to accommodate G. tenue , so it is moved to Planticonsortium gen. nov. as P. tenue comb. nov.
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Indicator species and co-occurrence in communities of arbuscular mycorrhizal fungi at the European scale
Soil Biology and Biochemistry, 2016Co-Authors: Marie-lara Bouffaud, Diederik Van Tuinen, Daniel Wipf, Rachel E. Creamer, Dote Stone, Pierre Plassart, Philippe Lemanceau, Dirk RedeckerAbstract:Utilizing a European transect of 54 soil samples, comprising of grasslands, arable and forest sites, we analyzed community composition of Arbuscular Mycorrhizal Fungi (AMF, Glomeromycota) using pyrosequencing of the Internal Transcribed Spacer region. We found a significant influence of environmental factors (soil pH and organic carbon or land use) on the community composition, but these factors did not fully explain the overall amount of AMF diversity. Geographical distance of sites also significantly affected community structure, indicating significant dispersal limitations of Glomeromycota at the European scale. Indicator species have been proposed by land use and physicochemical soil parameters. Generalist species were also identified, that were found occurring in a large proportion of the sample sites. By co-occurrence analysis of species pairs we show that, at this spatial scale, closely-related species are more likely to co-occur than distantly-related ones. This suggests that environmental filtering is a more dominant driving force in community assembly than fungal competition.
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A novel clade of sporocarp-forming species of Glomeromycotan fungi in the Diversisporales lineage
Mycological Progress, 2007Co-Authors: Dirk Redecker, Philipp Raab, Fritz Oehl, Francisco J. Camacho, Regis CourtecuisseAbstract:In the early times of taxonomy of arbuscular mycorrhizal fungi (Glomeromycota), exclusively sporocarpic species were described. Since then the focus has mainly shifted to species forming spores singly. For many of the sporocarpic species, no molecular data have been made available, and their phylogenetic position has remained unclear. We obtained small subunit ribosomal rDNA and internal transcribed spacer data from specimens of Glomeromycotan sporocarps from tropical areas that were assigned to three morphospecies. The complete sequence of the 18S small rDNA subunit sequence, internal transcribed spacers (ITS) 1 and 2 and 5.8S rDNA subunit, was determined from a sporocarp of Glomus fulvum . Partial sequences of the small subunit and the other regions were obtained from Glomus pulvinatum and the newly described species Glomus megalocarpum . Molecular phylogenetic analyses placed all species analyzed as a monophyletic sister group to the Diversispora spurca / Glomus versiforme clade group (“ Glomus group C”) within the Diversisporales. The phylogenetic divergence from other known species suggests that this clade may constitute a new genus. These findings will have important consequences for taxon definition in the Diversisporales. They will facilitate identification of these fungi using rDNA sequences within colonized roots or the environment.
Michael Krings - One of the best experts on this subject based on the ideXlab platform.
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the early devonian fungus mycokidstonia sphaerialoides from the rhynie chert is a member of the ambisporaceae Glomeromycota archaeosporales not an ascomycete
Review of Palaeobotany and Palynology, 2021Co-Authors: Michael Krings, Christopher Walker, Carla J Harper, Mark BrundrettAbstract:Abstract Glomeromycotan propagules (spores) are morphologically diverse in the Early Devonian Rhynie chert; however, only relatively few of these fossils have been documented and critically evaluated. This study re-examines propagules previously described informally as ‘reproductive unit 1’, and identified as Glomeromycotan acaulospores borne within the neck of a sporiferous saccule. Size and morphology, spore wall structure, and the close association of specimens in land plant axes with small glomoid spores, are solid arguments for affinities of ‘reproductive unit 1’ to the Ambisporaceae (Archaeosporales). Moreover, the acaulospores correspond morphologically to Mycokidstonia sphaerialoides, a Rhynie chert fossil originally interpreted as an ascomycete perithecium that, consequently, is redefined here as a member of the Glomeromycota conspecific with ‘reproductive unit 1’. The diagnosis for M. sphaerialoides is emended to be compliant with Glomeromycotan taxonomy; features of the saccule, acaulospore wall, and associated glomoid spores are included. An epitype is also designated. Mycokidstonia sphaerialoides adds to an increasing body of fossil data depicting Devonian Glomeromycota as a diverse fungal lineage which is likely to have been an ecologically important constituent of early terrestrial ecosystems.
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Acaulosporoid Glomeromycotan spores with a germination shield from the 400-million-year-old Rhynie chert
Mycological Progress, 2009Co-Authors: Nora Dotzler, Michael Krings, Thomas N. Taylor, Christopher Walker, Hagen Hass, Hans Kerp, Reinhard AgererAbstract:Scutellosporites devonicus from the Early Devonian Rhynie chert is the only fossil Glomeromycotan spore taxon known to produce a germination shield. This paper describes a second type of Glomeromycotan spore with a germination shield from the Rhynie chert. In contrast to S. devonicus , however, these spores are acaulosporoid and develop laterally in the neck of the sporiferous saccule. Germination shield morphology varies, from plate-like with single or double lobes to tongue-shaped structures usually with infolded margins that are distally fringed or palmate. Spore walls are complex and appear to be constructed of at least three wall groups, the outermost of which includes the remains of the saccule. The complement of features displayed by the fossils suggests a relationship with the extant genera Ambispora, Otospora, Acaulospora or Archaeospora , but which of these is the closest extant relative cannot be determined. The acaulosporoid spores from the Rhynie chert document that this spore type was in existence already ∼400 mya, and thus contribute to a more complete understanding of the evolutionary history of the Glomeromycota. This discovery pushes back the evolutionary origin of all main Glomeromycotan groups, revealing that they had evolved before rooted land plants had emerged.
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Germination shields in Scutellospora (Glomeromycota: Diversisporales, Gigasporaceae) from the 400 million-year-old Rhynie chert
Mycological Progress, 2006Co-Authors: Nora Dotzler, Michael Krings, Thomas N. Taylor, Reinhard AgererAbstract:Glomeromycotan spores from the Lower Devonian Rhynie chert provide the first evidence for germination shields in fossil fungi and demonstrate that this complex mode of germination was in place in some fungi at least 400 million years ago. Moreover, they represent the first direct marker relative to the precise systematic position of an Early Devonian endomycorrhizal fungus. In extant fungi, germination shields occur exclusively in the genus Scutellospora (Glomeromycota: Diversisporales, Gigasporaceae). These structures are regarded as a derived feature within the phylum Glomeromycota, and hence their presence in the Rhynie chert suggests that major diversification within this group of fungi occurred before the Early Devonian.
Reinhard Agerer - One of the best experts on this subject based on the ideXlab platform.
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Acaulosporoid Glomeromycotan spores with a germination shield from the 400-million-year-old Rhynie chert
Mycological Progress, 2009Co-Authors: Nora Dotzler, Michael Krings, Thomas N. Taylor, Christopher Walker, Hagen Hass, Hans Kerp, Reinhard AgererAbstract:Scutellosporites devonicus from the Early Devonian Rhynie chert is the only fossil Glomeromycotan spore taxon known to produce a germination shield. This paper describes a second type of Glomeromycotan spore with a germination shield from the Rhynie chert. In contrast to S. devonicus , however, these spores are acaulosporoid and develop laterally in the neck of the sporiferous saccule. Germination shield morphology varies, from plate-like with single or double lobes to tongue-shaped structures usually with infolded margins that are distally fringed or palmate. Spore walls are complex and appear to be constructed of at least three wall groups, the outermost of which includes the remains of the saccule. The complement of features displayed by the fossils suggests a relationship with the extant genera Ambispora, Otospora, Acaulospora or Archaeospora , but which of these is the closest extant relative cannot be determined. The acaulosporoid spores from the Rhynie chert document that this spore type was in existence already ∼400 mya, and thus contribute to a more complete understanding of the evolutionary history of the Glomeromycota. This discovery pushes back the evolutionary origin of all main Glomeromycotan groups, revealing that they had evolved before rooted land plants had emerged.
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Germination shields in Scutellospora (Glomeromycota: Diversisporales, Gigasporaceae) from the 400 million-year-old Rhynie chert
Mycological Progress, 2006Co-Authors: Nora Dotzler, Michael Krings, Thomas N. Taylor, Reinhard AgererAbstract:Glomeromycotan spores from the Lower Devonian Rhynie chert provide the first evidence for germination shields in fossil fungi and demonstrate that this complex mode of germination was in place in some fungi at least 400 million years ago. Moreover, they represent the first direct marker relative to the precise systematic position of an Early Devonian endomycorrhizal fungus. In extant fungi, germination shields occur exclusively in the genus Scutellospora (Glomeromycota: Diversisporales, Gigasporaceae). These structures are regarded as a derived feature within the phylum Glomeromycota, and hence their presence in the Rhynie chert suggests that major diversification within this group of fungi occurred before the Early Devonian.