| 1. |
- Ament-Velásquez, Sandra Lorena, Ph.D. 1988-, et al.
(author)
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The plot thickens : haploid and triploid-like thalli, hybridization, and biased mating type ratios in Letharia
- 2021
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In: Frontiers in Fungal Biology. - : Frontiers Media S.A.. - 2673-6128. ; 2
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Journal article (peer-reviewed)abstract
- The study of the reproductive biology of lichen fungal symbionts has been traditionally challenging due to their complex lifestyles. Against the common belief of haploidy, a recent genomic study found a triploid-like signal in Letharia. Here, we infer the genome organization and reproduction in Letharia by analyzing genomic data from a pure culture and from thalli, and performing a PCR survey of the MAT locus in natural populations. We found that the read count variation in the four Letharia specimens, including the pure culture derived from a single sexual spore of L. lupina, is consistent with haploidy. By contrast, the L. lupina read counts from a thallus’ metagenome are triploid-like. Characterization of the mating-type locus revealed a conserved heterothallic configuration across the genus, along with auxiliary genes that we identified. We found that the mating-type distributions are balanced in North America for L. vulpina and L. lupina, suggesting widespread sexual reproduction, but highly skewed in Europe for L. vulpina, consistent with predominant asexuality. Taken together, we propose that Letharia fungi are heterothallic and typically haploid, and provide evidence that triploid-like individuals are hybrids between L. lupina and an unknown Letharia lineage, reconciling classic systematic and genetic studies with recent genomic observations.
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| 2. |
- Kaasalainen, Ulla, et al.
(author)
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Complex interaction networks among cyanolichens of a tropical biodiversity hotspot
- 2021
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In: Frontiers in Microbiology. - : Frontiers Media S.A.. - 1664-302X. ; 12
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Journal article (peer-reviewed)abstract
- Interactions within lichen communities include, in addition to close mutualistic associations between the main partners of specific lichen symbioses, also more elusive relationships between members of a wider symbiotic community. Here, we analyze association patterns of cyanolichen symbionts in the tropical montane forests of Taita Hills, southern Kenya, which is part of the Eastern Afromontane biodiversity hotspot. The cyanolichen specimens analyzed represent 74 mycobiont taxa within the order Peltigerales (Ascomycota), associating with 115 different variants of the photobionts genus Nostoc (Cyanobacteria). Our analysis demonstrates wide sharing of photobionts and reveals the presence of several photobiont-mediated lichen guilds. Over half of all mycobionts share photobionts with other fungal species, often from different genera or even families, while some others are strict specialists and exclusively associate with a single photobiont variant. The most extensive symbiont network involves 24 different fungal species from five genera associating with 38 Nostoc photobionts. The Nostoc photobionts belong to two main groups, the Nephroma-type Nostoc and the Collema/Peltigera-type Nostoc, and nearly all mycobionts associate only with variants of one group. Among the mycobionts, species that produce cephalodia and those without symbiotic propagules tend to be most promiscuous in photobiont choice. The extent of photobiont sharing and the structure of interaction networks differ dramatically between the two major photobiont-mediated guilds, being both more prevalent and nested among Nephroma guild fungi and more compartmentalized among Peltigera guild fungi. This presumably reflects differences in the ecological characteristics and/or requirements of the two main groups of photobionts. The same two groups of Nostoc have previously been identified from many lichens in various lichen-rich ecosystems in different parts of the world, indicating that photobiont sharing between fungal species is an integral part of lichen ecology globally. In many cases, symbiotically dispersing lichens can facilitate the dispersal of sexually reproducing species, promoting establishment and adaptation into new and marginal habitats and thus driving evolutionary diversification.
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| 3. |
- Kaasalainen, Ulla, et al.
(author)
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Diversity of Leptogium (Collemataceae, Ascomycota) in East African Montane Ecosystems
- 2021
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In: Microorganisms. - : MDPI. - 2076-2607. ; 9:2
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Journal article (peer-reviewed)abstract
- Tropical mountains and especially their forests are hot spots of biodiversity threatened by human population pressure and climate change. The diversity of lichens in tropical Africa is especially poorly known. Here we use the mtSSU and nuITS molecular markers together with morphology and ecology to assess Leptogium (Peltigerales, Ascomycota) diversity in the tropical mountains of Taita Hills and Mt. Kasigau in Kenya and Mt. Kilimanjaro in Tanzania. The sampled habitats cover a wide range of ecosystems from savanna to alpine heath vegetation and from relatively natural forests to agricultural environments and plantation forests. We demonstrate that Leptogium diversity in Africa is much higher than previously known and provide preliminary data on over 70 putative species, including nine established species previously known from the area and over 60 phylogenetically, morphologically, and/or ecologically defined Operational Taxonomic Units (OTUs). Many traditional species concepts are shown to represent morphotypes comprised of several taxa. Many of the species were only found from specific ecosystems and/or restricted habitats and are thus threatened by ongoing habitat fragmentation and degradation of the natural environment. Our results emphasize the importance of molecular markers in species inventories of highly diverse organism groups and geographical areas.
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| 4. |
- Kluting, Kerri L., et al.
(author)
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Another dark taxon comes to light: Eludereomycetes, class nov. (Pucciniomycotina, Basidiomycota), and its first known living representative, Eluderea minerophilus, gen. et sp. nov.
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Other publication (other academic/artistic)abstract
- Only a small fraction of the world’s fungi is described, and the large number of unnamed fungal sequences from environmental DNA serves as a significant complication for taxonomic identification in metabarcoding studies. There are several deeply diverged fungal lineages—some hypothesized to represent class and order ranks—currently known only by environmental DNA sequences that represent them. Here, we describe a previously unidentified fungal culture as the first living representative of one of these lineages (previously referred to as ‘clade GS25’, hypothesized as an early diverging lineage sister to the Pucciniomycotina, Basidiomycota) and present its sequenced genome. We used a phylogenomic approach to test the placement and taxonomic rank of this lineage. We formally describe the first known species in Eludereomycetes, class nov. (Pucciniomycotina, Basidiomycota): Eluderea minerophilus, gen. et sp. nov. This species was isolated from Pinus sylvestris roots collected from a Swedish pine forest, where previously published environmental sequencing data from the site indicate that it is almost exclusively found in the deeper mineral soil horizons. Our analysis shows that the most closely related described species to E. minerophilus likely belongs to the Classiculomycetes, a class within the Pucciniomycotina that is morphologically, molecularly, and ecologically distinct from the Eludereomycetes. Identification of a living representative for this lineage previously detected in environmental DNA, ‘clade GS25’, and describing it as a new species was a somewhat serendipitous discovery made possible in part due to characteristics of two previously published studies. We call attention to some of these aspects and propose a set of practices that could be adopted by the research community to help facilitate more connections between living fungus and environmental DNA sequence. The use of such practices would in turn help to alleviate some of the complications associated with unidentified fungal DNA sequences in reference databases and contribute towards a more complete understanding of fungal diversity.
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| 5. |
- Spribille, Toby, et al.
(author)
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3D biofilms : in search of the polysaccharides holding together lichen symbioses
- 2020
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In: FEMS Microbiology Letters. - : Oxford University Press (OUP). - 0378-1097 .- 1574-6968. ; 367:5
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Research review (peer-reviewed)abstract
- Stable, long-term interactions between fungi and algae or cyanobacteria, collectively known as lichens, have repeatedly evolved complex architectures with little resemblance to their component parts. Lacking any central scaffold, the shapes they assume are casts of secreted polymers that cement cells into place, determine the angle of phototropic exposure and regulate water relations. A growing body of evidence suggests that many lichen extracellular polymer matrices harbor unicellular, non-photosynthesizing organisms (UNPOs) not traditionally recognized as lichen symbionts. Understanding organismal input and uptake in this layer is key to interpreting the role UNPOs play in lichen biology. Here, we review both polysaccharide composition determined from whole, pulverized lichens and UNPOs reported from lichens to date. Most reported polysaccharides are thought to be structural cell wall components. The composition of the extracellular matrix is not definitively known. Several lines of evidence suggest some acidic polysaccharides have evaded detection in routine analysis of neutral sugars and may be involved in the extracellular matrix. UNPOs reported from lichens include diverse bacteria and yeasts for which secreted polysaccharides play important biological roles. We conclude by proposing testable hypotheses on the role that symbiont give-and-take in this layer could play in determining or modifying lichen symbiotic outcomes.
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| 6. |
- Spribille, Toby, et al.
(author)
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Basidiomycete yeasts in the cortex of ascomycete macrolichens
- 2016
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In: Science. - : American Association for the Advancement of Science (AAAS). - 0036-8075 .- 1095-9203. ; 353:6298, s. 488-492
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Journal article (peer-reviewed)abstract
- For over 140 years, lichens have been regarded as a symbiosis between a single fungus, usually an ascomycete, and a photosynthesizing partner. Other fungi have long been known to occur as occasional parasites or endophytes, but the one lichen-one fungus paradigm has seldom been questioned. Here we show that many common lichens are composed of the known ascomycete, the photosynthesizing partner, and, unexpectedly, specific basidiomycete yeasts. These yeasts are embedded in the cortex, and their abundance correlates with previously unexplained variations in phenotype. Basidiomycete lineages maintain close associations with specific lichen species over large geographical distances and have been found on six continents. The structurally important lichen cortex, long treated as a zone of differentiated ascomycete cells, appears to consistently contain two unrelated fungi.
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| 7. |
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| 8. |
- Thor, Göran, et al.
(author)
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Vad är en lav?
- 2017
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In: Fauna och flora. - 0014-8903. ; 112, s. 22-26
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Journal article (pop. science, debate, etc.)
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| 9. |
- Tuovinen, Veera
(author)
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Basidiomycete yeasts as hidden partners in ascomycete lichens
- 2016
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Conference paper (other academic/artistic)abstract
- For 140 years lichens have been described as a symbiosis between a fungus and photosynthesising partners. Lichens repeatedly host a wide range of additional fungi and bacterial communities but their role has been considered nonessential for the formation of the symbiosis. We found that previously unknown basidiomycete fungi (Cyphobasidium spp.) are widespread components of several macrolichens and that their abundance explains phenotypic variation in some cases. We could locate these fungi into the lichen cortex. With this study, the role and diversity of the different organisms involved in one of the oldest known symbioses need to be reconsidered.
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| 10. |
- Tuovinen, Veera
(author)
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Hidden complexity of lichen symbiosis : insights into functionality, reproduction and composition
- 2017
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Doctoral thesis (other academic/artistic)abstract
- Lichens are tremendously diverse physical outcomes of symbiotic relationships involving fungi, algae and bacteria. This thesis aims to give insight into the functionality, composition and reproduction of lichens from the fungal perspective. When previous results from a barcoding study were re-evaluated, no support for a free-living life phase of Cladonia mycobionts could be found. Genomic and transcriptomic data were used to identify the fungal partners in thalli, and a fluorescent in situ hybridization (FISH) method for the simultaneous visualization of the different fungi was developed. This approach led to the discovery of previously unknown basidiomycetes, Cyphobasidium spp., which are widespread components of the cortex of lichens in Parmeliaceae. In some cases, the abundance of Cyphobasidium correlates with previously unexplained phenotypic variation of the lichens. In the case example Bryoria capillaris, Cyphobasidium yeasts are the dominant cells in the cortex and hence the fungus that meets the eye when looking at the lichen. With the help of hologenomic data and FISH, it could also be shown that Tremella lethariae, a lichenicolous heterobasidiomycete known to induce galls on Letharia, is dimorphic and frequently occupies the cortex of asymptomatic Letharia thalli in its anamorphic state. Finally, genomic and transcriptomic data was used to investigate the mating system of the genus Letharia, which includes species with different reproductive strategies. All studied Letharia species have a heterothallic mating system, meaning they need to find a compatible mate in order to sexually reproduce. Thus, the variation of reproduction strategies within the genus cannot be explained only by the mating system of the Letharia mycobiont. Our data on the mating-type ratios indicates that no potential for sexual reproduction exists for the red-listed L. vulpina in Sweden, as only one mating type is found in the populations. The roles the secondary fungi have in the symbiosis is not yet fully understood. However, the results indicate that we should not automatically assume that some of the organisms are negligible for the function of the holobiont, or that all functions assigned to fungal origin are conducted by the primary mycobiont. Altogether, the findings presented in this thesis support the view of lichens as a community of bionts with complex interactions and calls for a more holistic approach for the study of the symbiosis.
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| 11. |
- Tuovinen, Veera, et al.
(author)
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No support for occurrence of free-living Cladonia mycobionts in dead wood
- 2015
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In: Fungal Ecology. - : Elsevier BV. - 1754-5048 .- 1878-0083. ; 14, s. 130-132
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Journal article (peer-reviewed)abstract
- Lichenised fungi are traditionally assumed to form obligate symbioses with algae or cyanobacteria and to be confined to the surface of their growing substratum. However, in a recent 454 pyrosequencing study of fungal communities in Picea abies logs, lichen-forming fungi were detected at a depth of more than 6 cm in dead wood, implying the existence of free-living lichen mycobionts. To determine whether this was the case, we investigated whether Cladonia spp., the most frequently encountered mycobionts, occurred in wood without their photobionts. We detected green algae in all samples with records of Cladonia spp. Hence, we found no evidence for free-living Cladonia mycobionts in wood. We suggest that the detected Cladonia DNA in these logs originates from vegetative propagules or thallus fragments dispersed into the logs by animals or water. However, the occurrence of free-living stages of other lichen-forming fungal taxa in dead wood cannot be excluded. (C) 2014 The Authors. Published by Elsevier Ltd.
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| 12. |
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| 13. |
- Tuovinen, Veera, et al.
(author)
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Two Basidiomycete Fungi in the Cortex of Wolf
- 2019
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In: Current Biology. - : CELL PRESS. - 0960-9822 .- 1879-0445. ; 29:3, s. 476-
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Journal article (peer-reviewed)abstract
- Since the late 1800s, mycologists have been detecting fungi above and beyond the assumed single fungus in lichen thalli [1-6]. Over the last century, these fungi have been accorded roles ranging from commensalists to pathogens. Recently, Cyphobasidiales yeasts were shown to be ubiquitous in the cortex layer of many macrolichens [7], but for most species, little is known of their cellular distribution and constancy beyond visible fruiting structures. Here, we demonstrate the occurrence of an additional and distantly related basidiomycete, Tremella, in 95% of studied thalli in a global sample of one of the most intensively studied groups of lichens, the wolf lichens (genus Letharia). Tremella species are reported from a wide range of lichen genera [8], but until now, their biology was deduced from fruiting bodies (basidiomata) formed on lichen thalli. Based on this, they have been thought to be uncommon to rare, to occur exclusively in a hyphal form, and to be parasitic on the dominant fungal partner [9, 10]. We show that, in wolf lichens, Tremella occurs as yeast cells also in thalli that lack basidiomata and infer that this is its dominant stage in nature. We further show that the hyphal stage, when present in Letharia, is in close contact with algal cells, challenging the assumption that lichen-associated Tremella species are uniformly mycoparasites. Our results suggest that extent of occurrence and cellular interactions of known fungi within lichens have historically been underestimated and raise new questions about their function in specific lichen symbioses.
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| 14. |
- Tuovinen, Veera, et al.
(author)
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Visualizing fungal communities in lichens by fluorescent in situ hybridization
- 2016
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Conference paper (other academic/artistic)abstract
- Lichens are communities of different groups of fungi, photosynthetic organisms and bacteria. Distinguishing between different fungi with light microscopy can be challenging, even when the occurrence of lichenicolous fungi is known based on molecular data. Fluorescent in situ hybridization (FISH) is a method to visualize different structures, species or specific RNA targets but has rarely been used in lichenology. We developed general protocols for FISH in lichens, accounting for cortical polysaccharide matrix and cell wall permeabilization as well as autofluorescence of different parts of thalli. We also designed specific probes for simultaneous visualization of Ascomycota and Basidiomycota. Cyphobasidium hypogymniicola (Pucciniomycotina, Basidiomycota) is a lichenicolous fungus occurring on Hypogymnia physodes, one of the most common lichens in Scandinavia. Cyphobasidium hypogymniicola forms its sexual stage in thalline galls. We used Cyphobasidium-targeted FISH to reveal previously unrecognized details of the fungal teleomorph as well as a previously unknown anamorphic (yeast) state of C. hypogymniicola occurring on the cortical layer of apparently uninfected H. physodes. FISH with its many applications appears as a powerful tool for the study of communities within lichens.
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| 15. |
- Zamora, Juan Carlos, et al.
(author)
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Considerations and consequences of allowing DNA sequence data as types of fungal taxa
- 2018
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In: IMA Fungus. - : INT MYCOLOGICAL ASSOC. - 2210-6340 .- 2210-6359. ; 9:1, s. 167-185
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Journal article (peer-reviewed)abstract
- Nomenclatural type definitions are one of the most important concepts in biological nomenclature. Being physical objects that can be re-studied by other researchers, types permanently link taxonomy (an artificial agreement to classify biological diversity) with nomenclature (an artificial agreement to name biological diversity). Two proposals to amend the International Code of Nomenclature for algae, fungi, and plants (ICN), allowing DNA sequences alone (of any region and extent) to serve as types of taxon names for voucherless fungi (mainly putative taxa from environmental DNA sequences), have been submitted to be voted on at the 11th International Mycological Congress (Puerto Rico, July 2018). We consider various genetic processes affecting the distribution of alleles among taxa and find that alleles may not consistently and uniquely represent the species within which they are contained. Should the proposals be accepted, the meaning of nomenclatural types would change in a fundamental way from physical objects as sources of data to the data themselves. Such changes are conducive to irreproducible science, the potential typification on artefactual data, and massive creation of names with low information content, ultimately causing nomenclatural instability and unnecessary work for future researchers that would stall future explorations of fungal diversity. We conclude that the acceptance of DNA sequences alone as types of names of taxa, under the terms used in the current proposals, is unnecessary and would not solve the problem of naming putative taxa known only from DNA sequences in a scientifically defensible way. As an alternative, we highlight the use of formulas for naming putative taxa (candidate taxa) that do not require any modification of the ICN.
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