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Vittorelli N, Rodríguez de la Vega RC, Snirc A, Levert E, Gautier V, Lalanne C, De Filippo E, Gladieux P, Guillou S, Zhang Y, Tejomurthula S, Grigoriev IV, Debuchy R, Silar P, Giraud T, Hartmann FE. Stepwise recombination suppression around the mating-type locus in an ascomycete fungus with self-fertile spores. PLoS Genet 2023; 19:e1010347. [PMID: 36763677 PMCID: PMC9949647 DOI: 10.1371/journal.pgen.1010347] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2022] [Revised: 02/23/2023] [Accepted: 01/17/2023] [Indexed: 02/12/2023] Open
Abstract
Recombination is often suppressed at sex-determining loci in plants and animals, and at self-incompatibility or mating-type loci in plants and fungi. In fungal ascomycetes, recombination suppression around the mating-type locus is associated with pseudo-homothallism, i.e. the production of self-fertile dikaryotic sexual spores carrying the two opposite mating types. This has been well studied in two species complexes from different families of Sordariales: Podospora anserina and Neurospora tetrasperma. However, it is unclear whether this intriguing association holds in other species. We show here that Schizothecium tetrasporum, a fungus from a third family in the order Sordariales, also produces mostly self-fertile dikaryotic spores carrying the two opposite mating types. This was due to a high frequency of second meiotic division segregation at the mating-type locus, indicating the occurrence of a single and systematic crossing-over event between the mating-type locus and the centromere, as in P. anserina. The mating-type locus has the typical Sordariales organization, plus a MAT1-1-1 pseudogene in the MAT1-2 haplotype. High-quality genome assemblies of opposite mating types and segregation analyses revealed a suppression of recombination in a region of 1.47 Mb around the mating-type locus. We detected three evolutionary strata, indicating a stepwise extension of recombination suppression. The three strata displayed no rearrangement or transposable element accumulation but gene losses and gene disruptions were present, and precisely at the strata margins. Our findings indicate a convergent evolution of self-fertile dikaryotic sexual spores across multiple ascomycete fungi. The particular pattern of meiotic segregation at the mating-type locus was associated with recombination suppression around this locus, that had extended stepwise. This association between pseudo-homothallism and recombination suppression across lineages and the presence of gene disruption at the strata limits are consistent with a recently proposed mechanism of sheltering deleterious alleles to explain stepwise recombination suppression.
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Affiliation(s)
- Nina Vittorelli
- Ecologie Systematique et Evolution, CNRS, Université Paris-Saclay, AgroParisTech, Gif-sur-Yvette, France
- Laboratoire Interdisciplinaire des Energies de Demain, Université Paris Cité, Paris, France
- Département de Biologie, École Normale Supérieure, PSL Université Paris, Paris, France
| | | | - Alodie Snirc
- Ecologie Systematique et Evolution, CNRS, Université Paris-Saclay, AgroParisTech, Gif-sur-Yvette, France
| | - Emilie Levert
- Ecologie Systematique et Evolution, CNRS, Université Paris-Saclay, AgroParisTech, Gif-sur-Yvette, France
- Laboratoire Interdisciplinaire des Energies de Demain, Université Paris Cité, Paris, France
| | - Valérie Gautier
- Laboratoire Interdisciplinaire des Energies de Demain, Université Paris Cité, Paris, France
| | - Christophe Lalanne
- Laboratoire Interdisciplinaire des Energies de Demain, Université Paris Cité, Paris, France
| | - Elsa De Filippo
- Ecologie Systematique et Evolution, CNRS, Université Paris-Saclay, AgroParisTech, Gif-sur-Yvette, France
- Laboratoire Interdisciplinaire des Energies de Demain, Université Paris Cité, Paris, France
| | - Pierre Gladieux
- PHIM Plant Health Institute, Univ Montpellier, INRAE, CIRAD, Institut Agro, IRD, Montpellier, France
| | - Sonia Guillou
- PHIM Plant Health Institute, Univ Montpellier, INRAE, CIRAD, Institut Agro, IRD, Montpellier, France
| | - Yu Zhang
- U.S. Department of Energy Joint Genome Institute, Lawrence Berkeley National Laboratory, Berkeley, California, United States of America
| | - Sravanthi Tejomurthula
- U.S. Department of Energy Joint Genome Institute, Lawrence Berkeley National Laboratory, Berkeley, California, United States of America
| | - Igor V. Grigoriev
- U.S. Department of Energy Joint Genome Institute, Lawrence Berkeley National Laboratory, Berkeley, California, United States of America
- Department of Plant and Microbial Biology, University of California Berkeley, Berkeley, California, United States of America
| | - Robert Debuchy
- Université Paris-Saclay, CEA, CNRS, Institute for Integrative Biology of the Cell (I2BC), Gif-sur-Yvette, France
| | - Philippe Silar
- Laboratoire Interdisciplinaire des Energies de Demain, Université Paris Cité, Paris, France
| | - Tatiana Giraud
- Ecologie Systematique et Evolution, CNRS, Université Paris-Saclay, AgroParisTech, Gif-sur-Yvette, France
| | - Fanny E. Hartmann
- Ecologie Systematique et Evolution, CNRS, Université Paris-Saclay, AgroParisTech, Gif-sur-Yvette, France
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Meunier C, Darolti I, Reimegård J, Mank JE, Johannesson H. Nuclear-specific gene expression in heterokaryons of the filamentous ascomycete Neurospora tetrasperma. Proc Biol Sci 2022; 289:20220971. [PMID: 35946150 PMCID: PMC9363985 DOI: 10.1098/rspb.2022.0971] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Abstract
Heterokaryosis is a system in which genetically distinct nuclei coexist within the same cytoplasm. While heterokaryosis dominates the life cycle of many fungal species, the transcriptomic changes associated with the transition from homokaryosis to heterokaryosis is not well understood. Here, we analyse gene expression profiles of homokaryons and heterokaryons from three phylogenetically and reproductively isolated lineages of the filamentous ascomycete Neurospora tetrasperma. We show that heterokaryons are transcriptionally distinct from homokaryons in the sexual stage of development, but not in the vegetative stage, suggesting that the phenotypic switch to fertility in heterokaryons is associated with major changes in gene expression. Heterokaryon expression is predominantly defined by additive effects of its two nuclear components. Furthermore, allele-specific expression analysis of heterokaryons with varying nuclear ratios show patterns of expression ratios strongly dependent on nuclear ratios in the vegetative stage. By contrast, in the sexual stage, strong deviations of expression ratios indicate a co-regulation of nuclear gene expression in all three lineages. Taken together, our results show two levels of expression control: additive effects suggest a nuclear level of expression, whereas co-regulation of gene expression indicate a heterokaryon level of control.
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Affiliation(s)
- Cécile Meunier
- Department ECOBIO, UMR CNRS 6553, Université Rennes 1, Rennes, France
| | - Iulia Darolti
- Department of Zoology and Biodiversity Research Centre, University of British Columbia, Vancouver, Canada
| | - Johan Reimegård
- Department of Cell and Molecular Biology, National Bioinformatics Infrastructure Sweden, Science for Life Laboratory, Uppsala University, Uppsala, Sweden
| | - Judith E. Mank
- Department of Zoology and Biodiversity Research Centre, University of British Columbia, Vancouver, Canada,Centre for Ecology and Conservation, University of Exeter, Penryn Campus, UK
| | - Hanna Johannesson
- Department of Organismal Biology, Uppsala University, Uppsala, Sweden,The Royal Swedish Academy of Sciences and Department of Ecology, Environment and Plant Sciences, Stockholm University, SE-106 91 Stockholm, Sweden
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3
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Vignolle GA, Schaffer D, Zehetner L, Mach RL, Mach-Aigner AR, Derntl C. FunOrder: A robust and semi-automated method for the identification of essential biosynthetic genes through computational molecular co-evolution. PLoS Comput Biol 2021; 17:e1009372. [PMID: 34570757 PMCID: PMC8476034 DOI: 10.1371/journal.pcbi.1009372] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/13/2021] [Accepted: 08/23/2021] [Indexed: 11/24/2022] Open
Abstract
Secondary metabolites (SMs) are a vast group of compounds with different structures and properties that have been utilized as drugs, food additives, dyes, and as monomers for novel plastics. In many cases, the biosynthesis of SMs is catalysed by enzymes whose corresponding genes are co-localized in the genome in biosynthetic gene clusters (BGCs). Notably, BGCs may contain so-called gap genes, that are not involved in the biosynthesis of the SM. Current genome mining tools can identify BGCs, but they have problems with distinguishing essential genes from gap genes. This can and must be done by expensive, laborious, and time-consuming comparative genomic approaches or transcriptome analyses. In this study, we developed a method that allows semi-automated identification of essential genes in a BGC based on co-evolution analysis. To this end, the protein sequences of a BGC are blasted against a suitable proteome database. For each protein, a phylogenetic tree is created. The trees are compared by treeKO to detect co-evolution. The results of this comparison are visualized in different output formats, which are compared visually. Our results suggest that co-evolution is commonly occurring within BGCs, albeit not all, and that especially those genes that encode for enzymes of the biosynthetic pathway are co-evolutionary linked and can be identified with FunOrder. In light of the growing number of genomic data available, this will contribute to the studies of BGCs in native hosts and facilitate heterologous expression in other organisms with the aim of the discovery of novel SMs. The discovery and description of novel fungal secondary metabolites promises novel antibiotics, pharmaceuticals, and other useful compounds. A way to identify novel secondary metabolites is to express the corresponding genes in a suitable expression host. Consequently, a detailed knowledge or an accurate prediction of these genes is necessary. In fungi, the genes are co-localized in so-called biosynthetic gene clusters. Notably, the clusters may also contain genes that are not necessary for the biosynthesis of the secondary metabolites, so-called gap genes. We developed a method to detect co-evolved genes within the clusters and demonstrated that essential genes are co-evolving and can thus be differentiated from the gap genes. This adds an additional layer of information, which can support researchers with their decisions on which genes to study and express for the discovery of novel secondary metabolites.
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Affiliation(s)
- Gabriel A. Vignolle
- Institute of Chemical, Environmental and Bioscience Engineering, TU Wien, Vienna, Austria
| | - Denise Schaffer
- Institute of Chemical, Environmental and Bioscience Engineering, TU Wien, Vienna, Austria
| | - Leopold Zehetner
- Institute of Chemical, Environmental and Bioscience Engineering, TU Wien, Vienna, Austria
| | - Robert L. Mach
- Institute of Chemical, Environmental and Bioscience Engineering, TU Wien, Vienna, Austria
| | - Astrid R. Mach-Aigner
- Institute of Chemical, Environmental and Bioscience Engineering, TU Wien, Vienna, Austria
| | - Christian Derntl
- Institute of Chemical, Environmental and Bioscience Engineering, TU Wien, Vienna, Austria
- * E-mail:
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Hanson SJ, Cinnéide EÓ, Salzberg LI, Wolfe KH, McGowan J, Fitzpatrick DA, Matlin K. Genomic diversity, chromosomal rearrangements, and interspecies hybridization in the Ogataea polymorpha species complex. G3 (BETHESDA, MD.) 2021; 11:jkab211. [PMID: 34849824 PMCID: PMC8496258 DOI: 10.1093/g3journal/jkab211] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 03/12/2021] [Accepted: 06/11/2021] [Indexed: 11/13/2022]
Abstract
The methylotrophic yeast Ogataea polymorpha has long been a useful system for recombinant protein production, as well as a model system for methanol metabolism, peroxisome biogenesis, thermotolerance, and nitrate assimilation. It has more recently become an important model for the evolution of mating-type switching. Here, we present a population genomics analysis of 47 isolates within the O. polymorpha species complex, including representatives of the species O. polymorpha, Ogataea parapolymorpha, Ogataea haglerorum, and Ogataea angusta. We found low levels of nucleotide sequence diversity within the O. polymorpha species complex and identified chromosomal rearrangements both within and between species. In addition, we found that one isolate is an interspecies hybrid between O. polymorpha and O. parapolymorpha and present evidence for loss of heterozygosity following hybridization.
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Affiliation(s)
- Sara J Hanson
- Department of Molecular Biology, Colorado College, Colorado Springs, CO 80903, USA
| | - Eoin Ó Cinnéide
- School of Medicine, UCD Conway Institute, University College Dublin, Dublin 4, Ireland
| | - Letal I Salzberg
- School of Medicine, UCD Conway Institute, University College Dublin, Dublin 4, Ireland
| | - Kenneth H Wolfe
- School of Medicine, UCD Conway Institute, University College Dublin, Dublin 4, Ireland
| | - Jamie McGowan
- Genome Evolution Laboratory, Department of Biology, Maynooth University, Maynooth, Ireland
- Kathleen Lonsdale Institute for Human Health Research, Maynooth University, Maynooth, Ireland
| | - David A Fitzpatrick
- Genome Evolution Laboratory, Department of Biology, Maynooth University, Maynooth, Ireland
- Kathleen Lonsdale Institute for Human Health Research, Maynooth University, Maynooth, Ireland
| | - Kate Matlin
- Department of Molecular Biology, Colorado College, Colorado Springs, CO 80903, USA
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5
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Hage H, Rosso MN, Tarrago L. Distribution of methionine sulfoxide reductases in fungi and conservation of the free-methionine-R-sulfoxide reductase in multicellular eukaryotes. Free Radic Biol Med 2021; 169:187-215. [PMID: 33865960 DOI: 10.1016/j.freeradbiomed.2021.04.013] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/01/2021] [Revised: 04/06/2021] [Accepted: 04/09/2021] [Indexed: 12/17/2022]
Abstract
Methionine, either as a free amino acid or included in proteins, can be oxidized into methionine sulfoxide (MetO), which exists as R and S diastereomers. Almost all characterized organisms possess thiol-oxidoreductases named methionine sulfoxide reductase (Msr) enzymes to reduce MetO back to Met. MsrA and MsrB reduce the S and R diastereomers of MetO, respectively, with strict stereospecificity and are found in almost all organisms. Another type of thiol-oxidoreductase, the free-methionine-R-sulfoxide reductase (fRMsr), identified so far in prokaryotes and a few unicellular eukaryotes, reduces the R MetO diastereomer of the free amino acid. Moreover, some bacteria possess molybdenum-containing enzymes that reduce MetO, either in the free or protein-bound forms. All these Msrs play important roles in the protection of organisms against oxidative stress. Fungi are heterotrophic eukaryotes that colonize all niches on Earth and play fundamental functions, in organic matter recycling, as symbionts, or as pathogens of numerous organisms. However, our knowledge on fungal Msrs is still limited. Here, we performed a survey of msr genes in almost 700 genomes across the fungal kingdom. We show that most fungi possess one gene coding for each type of methionine sulfoxide reductase: MsrA, MsrB, and fRMsr. However, several fungi living in anaerobic environments or as obligate intracellular parasites were devoid of msr genes. Sequence inspection and phylogenetic analyses allowed us to identify non-canonical sequences with potentially novel enzymatic properties. Finaly, we identified several ocurences of msr horizontal gene transfer from bacteria to fungi.
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Affiliation(s)
- Hayat Hage
- Biodiversité et Biotechnologie Fongiques, UMR1163, INRAE, Aix Marseille Université, Marseille, France
| | - Marie-Noëlle Rosso
- Biodiversité et Biotechnologie Fongiques, UMR1163, INRAE, Aix Marseille Université, Marseille, France
| | - Lionel Tarrago
- Biodiversité et Biotechnologie Fongiques, UMR1163, INRAE, Aix Marseille Université, Marseille, France.
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6
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Hartmann FE, Duhamel M, Carpentier F, Hood ME, Foulongne‐Oriol M, Silar P, Malagnac F, Grognet P, Giraud T. Recombination suppression and evolutionary strata around mating-type loci in fungi: documenting patterns and understanding evolutionary and mechanistic causes. THE NEW PHYTOLOGIST 2021; 229:2470-2491. [PMID: 33113229 PMCID: PMC7898863 DOI: 10.1111/nph.17039] [Citation(s) in RCA: 34] [Impact Index Per Article: 11.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/27/2020] [Accepted: 09/03/2020] [Indexed: 05/08/2023]
Abstract
Genomic regions determining sexual compatibility often display recombination suppression, as occurs in sex chromosomes, plant self-incompatibility loci and fungal mating-type loci. Regions lacking recombination can extend beyond the genes determining sexes or mating types, by several successive steps of recombination suppression. Here we review the evidence for recombination suppression around mating-type loci in fungi, sometimes encompassing vast regions of the mating-type chromosomes. The suppression of recombination at mating-type loci in fungi has long been recognized and maintains the multiallelic combinations required for correct compatibility determination. We review more recent evidence for expansions of recombination suppression beyond mating-type genes in fungi ('evolutionary strata'), which have been little studied and may be more pervasive than commonly thought. We discuss testable hypotheses for the ultimate (evolutionary) and proximate (mechanistic) causes for such expansions of recombination suppression, including (1) antagonistic selection, (2) association of additional functions to mating-type, such as uniparental mitochondria inheritance, (3) accumulation in the margin of nonrecombining regions of various factors, including deleterious mutations or transposable elements resulting from relaxed selection, or neutral rearrangements resulting from genetic drift. The study of recombination suppression in fungi could thus contribute to our understanding of recombination suppression expansion across a broader range of organisms.
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Affiliation(s)
- Fanny E. Hartmann
- Ecologie Systematique EvolutionBatiment 360Université Paris‐SaclayCNRSAgroParisTechOrsay91400France
| | - Marine Duhamel
- Ecologie Systematique EvolutionBatiment 360Université Paris‐SaclayCNRSAgroParisTechOrsay91400France
- Ruhr‐Universität Bochum, Evolution of Plants and Fungi ‐ Gebäude ND 03/174Universitätsstraße150, 44801 BochumGermany
| | - Fantin Carpentier
- Ecologie Systematique EvolutionBatiment 360Université Paris‐SaclayCNRSAgroParisTechOrsay91400France
| | - Michael E. Hood
- Biology Department, Science CentreAmherst CollegeAmherstMA01002USA
| | | | - Philippe Silar
- Lab Interdisciplinaire Energies DemainUniv Paris DiderotSorbonne Paris CiteParis 13F‐75205France
| | - Fabienne Malagnac
- Institute for Integrative Biology of the Cell (I2BC)Université Paris‐SaclayCEACNRSGif‐sur‐Yvette91198France
| | - Pierre Grognet
- Institute for Integrative Biology of the Cell (I2BC)Université Paris‐SaclayCEACNRSGif‐sur‐Yvette91198France
| | - Tatiana Giraud
- Ecologie Systematique EvolutionBatiment 360Université Paris‐SaclayCNRSAgroParisTechOrsay91400France
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7
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van Wyk S, Wingfield BD, De Vos L, van der Merwe NA, Steenkamp ET. Genome-Wide Analyses of Repeat-Induced Point Mutations in the Ascomycota. Front Microbiol 2021; 11:622368. [PMID: 33597932 PMCID: PMC7882544 DOI: 10.3389/fmicb.2020.622368] [Citation(s) in RCA: 24] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/28/2020] [Accepted: 12/29/2020] [Indexed: 11/17/2022] Open
Abstract
The Repeat-Induced Point (RIP) mutation pathway is a fungus-specific genome defense mechanism that mitigates the deleterious consequences of repeated genomic regions and transposable elements (TEs). RIP mutates targeted sequences by introducing cytosine to thymine transitions. We investigated the genome-wide occurrence and extent of RIP with a sliding-window approach. Using genome-wide RIP data and two sets of control groups, the association between RIP, TEs, and GC content were contrasted in organisms capable and incapable of RIP. Based on these data, we then set out to determine the extent and occurrence of RIP in 58 representatives of the Ascomycota. The findings were summarized by placing each of the fungi investigated in one of six categories based on the extent of genome-wide RIP. In silico RIP analyses, using a sliding-window approach with stringent RIP parameters, implemented simultaneously within the same genetic context, on high quality genome assemblies, yielded superior results in determining the genome-wide RIP among the Ascomycota. Most Ascomycota had RIP and these mutations were particularly widespread among classes of the Pezizomycotina, including the early diverging Orbiliomycetes and the Pezizomycetes. The most extreme cases of RIP were limited to representatives of the Dothideomycetes and Sordariomycetes. By contrast, the genomes of the Taphrinomycotina and Saccharomycotina contained no detectable evidence of RIP. Also, recent losses in RIP combined with controlled TE proliferation in the Pezizomycotina subphyla may promote substantial genome enlargement as well as the formation of sub-genomic compartments. These findings have broadened our understanding of the taxonomic range and extent of RIP in Ascomycota and how this pathway affects the genomes of fungi harboring it.
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Affiliation(s)
| | | | | | | | - Emma T. Steenkamp
- Department of Biochemistry, Genetics and Microbiology, Forestry and Agricultural Biotechnology Institute (FABI), University of Pretoria, Pretoria, South Africa
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Barbosa JR, Carvalho Junior RND. Occurrence and possible roles of polysaccharides in fungi and their influence on the development of new technologies. Carbohydr Polym 2020; 246:116613. [PMID: 32747253 PMCID: PMC7293488 DOI: 10.1016/j.carbpol.2020.116613] [Citation(s) in RCA: 19] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2020] [Revised: 05/23/2020] [Accepted: 06/06/2020] [Indexed: 12/12/2022]
Abstract
The article summarizes the roles of polysaccharides in the biology of fungi and their relationship in the development of new technologies. The comparative approach between the evolution of fungi and the chemistry of glycobiology elucidated relevant aspects about the role of polysaccharides in fungi. Also, based on the knowledge of fungal glycobiology, it was possible to address the development of new technologies, such as the production of new anti-tumor drugs, vaccines, biomaterials, and applications in the field of robotics. We conclude that polysaccharides activate pathways of apoptosis, secretion of pro-inflammatory substances, and macrophage, inducing anticancer activity. Also, the activation of the immune system, which opens the way for the production of vaccines. The development of biomaterials and parts for robotics is a promising and little-explored field. Finally, the article is multidisciplinary, with a different and integrated approach to the role of nature in the sustainable development of new technologies.
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Affiliation(s)
- Jhonatas Rodrigues Barbosa
- LABEX/FEA (Extraction Laboratory/Faculty of Food Engineering), ITEC (Institute of Technology), UFPA (Federal University of Para), Rua Augusto Corrêa S/N, Guamá, 66075-900 Belém, PA, Brazil.
| | - Raul Nunes de Carvalho Junior
- LABEX/FEA (Extraction Laboratory/Faculty of Food Engineering), ITEC (Institute of Technology), UFPA (Federal University of Para), Rua Augusto Corrêa S/N, Guamá, 66075-900 Belém, PA, Brazil.
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9
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Hosseini S, Meunier C, Nguyen D, Reimegård J, Johannesson H. Comparative analysis of genome-wide DNA methylation in Neurospora. Epigenetics 2020; 15:972-987. [PMID: 32228351 PMCID: PMC7518705 DOI: 10.1080/15592294.2020.1741758] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/20/2019] [Revised: 02/14/2020] [Accepted: 02/27/2020] [Indexed: 12/18/2022] Open
Abstract
DNA methylation is an epigenetic mark that plays an important role in genetic regulation in eukaryotes. Major progress has been made in dissecting the molecular pathways that regulate DNA methylation. Yet, little is known about DNA methylation variation over evolutionary time. Here we present an investigation of the variation of DNA methylation and transposable element (TE) content in species of the filamentous ascomycetes Neurospora. We generated genome-wide DNA methylation data at single-base resolution, together with genomic TE content and gene expression data, of 10 individuals representing five closely related Neurospora species. We found that the methylation levels were low (ranging from 1.3% to 2.5%) and varied among the genomes in a species-specific way. Furthermore, we found that the TEs over 400 bp long were targeted by DNA methylation, and in all genomes, high methylation correlated with low GC, confirming a conserved link between DNA methylation and Repeat Induced Point (RIP) mutations in this group of fungi. Both TE content and DNA methylation pattern showed phylogenetic signal, and the species with the highest TE load (N. crassa) also exhibited the highest methylation level per TE. Our results suggest that DNA methylation is an evolvable trait and indicate that the genomes of Neurospora are shaped by an evolutionary arms race between TEs and host defence.
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Affiliation(s)
- Sara Hosseini
- Department of Organismal Biology, Uppsala University, Uppsala, Sweden
| | - Cécile Meunier
- Department of Organismal Biology, Uppsala University, Uppsala, Sweden
- Department ECOBIO, UMR CNRS 6553, Université Rennes 1, Rennes, France
| | - Diem Nguyen
- Department of Organismal Biology, Uppsala University, Uppsala, Sweden
| | - Johan Reimegård
- Department of Cell and Molecular Biology, National Bioinformatics Infrastructure Sweden, Science for Life Laboratory, Uppsala University, Uppsala, Sweden
| | - Hanna Johannesson
- Department of Organismal Biology, Uppsala University, Uppsala, Sweden
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10
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Xu R, Liu X, Peng B, Liu P, Li Z, Dai Y, Xiao S. Genomic Features of Cladobotryum dendroides, Which Causes Cobweb Disease in Edible Mushrooms, and Identification of Genes Related to Pathogenicity and Mycoparasitism. Pathogens 2020; 9:pathogens9030232. [PMID: 32245129 PMCID: PMC7157644 DOI: 10.3390/pathogens9030232] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2020] [Revised: 03/14/2020] [Accepted: 03/16/2020] [Indexed: 12/16/2022] Open
Abstract
Cladobotryum dendroides, which causes cobweb disease in edible mushrooms, is one of the major fungal pathogens. Our previous studies focused on the genetic and morphological characterization of this fungus, as well as its pathogenicity and the identification of appropriate fungicides. However, little is known about the genome characters, pathogenic genes, and molecular pathogenic mechanisms of C. dendroides. Herein, we reported a high-quality de novo genomic sequence of C. dendroides and compared it with closely-related fungi. The assembled C. dendroides genome was 36.69 Mb, consisting of eight contigs, with an N50 of 4.76 Mb. This genome was similar in size to that of C. protrusum, and shared highly conserved syntenic blocks and a few inversions with C. protrusum. Phylogenetic analysis revealed that, within the Hypocreaceae, Cladobotryum was closer to Mycogone than to Trichoderma, which is consistent with phenotypic evidence. A significant number of the predicted expanded gene families were strongly associated with pathogenicity, virulence, and adaptation. Our findings will be instrumental for the understanding of fungi-fungi interactions, and for exploring efficient management strategies to control cobweb disease.
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Affiliation(s)
- Rong Xu
- Internationally Cooperative Research Center of China for New Germplasm Breeding of Edible Mushroom, Jilin Agricultural University, Changchun 130118, China; (R.X.); (B.P.)
- College of Plant Protection, Jilin Agricultural University, Changchun 130118, China
| | - Xiaochen Liu
- Internationally Cooperative Research Center of China for New Germplasm Breeding of Edible Mushroom, Jilin Agricultural University, Changchun 130118, China; (R.X.); (B.P.)
- College of Plant Protection, Jilin Agricultural University, Changchun 130118, China
| | - Bing Peng
- Internationally Cooperative Research Center of China for New Germplasm Breeding of Edible Mushroom, Jilin Agricultural University, Changchun 130118, China; (R.X.); (B.P.)
- College of Plant Protection, Jilin Agricultural University, Changchun 130118, China
| | - Peibin Liu
- Internationally Cooperative Research Center of China for New Germplasm Breeding of Edible Mushroom, Jilin Agricultural University, Changchun 130118, China; (R.X.); (B.P.)
- College of Plant Protection, Jilin Agricultural University, Changchun 130118, China
| | - Zhuang Li
- Shandong Provincial Key Laboratory for Biology of Vegetable Diseases and Insect Pests, College of Plant Protection, Shandong Agricultural University, Tai’an 271018, China;
| | - Yueting Dai
- Internationally Cooperative Research Center of China for New Germplasm Breeding of Edible Mushroom, Jilin Agricultural University, Changchun 130118, China; (R.X.); (B.P.)
- Correspondence: (Y.D.); (S.X.); Tel.: +86-431-8453-2989 (Y.D. & S.X.)
| | - Shijun Xiao
- Internationally Cooperative Research Center of China for New Germplasm Breeding of Edible Mushroom, Jilin Agricultural University, Changchun 130118, China; (R.X.); (B.P.)
- Correspondence: (Y.D.); (S.X.); Tel.: +86-431-8453-2989 (Y.D. & S.X.)
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11
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van Wyk S, Wingfield BD, De Vos L, van der Merwe NA, Santana QC, Steenkamp ET. Repeat-Induced Point Mutations Drive Divergence between Fusarium circinatum and Its Close Relatives. Pathogens 2019; 8:pathogens8040298. [PMID: 31847413 PMCID: PMC6963459 DOI: 10.3390/pathogens8040298] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/22/2019] [Revised: 12/06/2019] [Accepted: 12/09/2019] [Indexed: 01/01/2023] Open
Abstract
The Repeat-Induced Point (RIP) mutation pathway is a fungal-specific genome defense mechanism that counteracts the deleterious effects of transposable elements. This pathway permanently mutates its target sequences by introducing cytosine to thymine transitions. We investigated the genome-wide occurrence of RIP in the pitch canker pathogen, Fusarium circinatum, and its close relatives in the Fusarium fujikuroi species complex (FFSC). Our results showed that the examined fungi all exhibited hallmarks of RIP, but that they differed in terms of the extent to which their genomes were affected by this pathway. RIP mutations constituted a large proportion of all the FFSC genomes, including both core and dispensable chromosomes, although the latter were generally more extensively affected by RIP. Large RIP-affected genomic regions were also much more gene sparse than the rest of the genome. Our data further showed that RIP-directed sequence diversification increased the variability between homologous regions of related species, and that RIP-affected regions can interfere with homologous recombination during meiosis, thereby contributing to post-mating segregation distortion. Taken together, these findings suggest that RIP can drive the independent divergence of chromosomes, alter chromosome architecture, and contribute to the divergence among F. circinatum and other members of this economically important group of fungi.
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12
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Daskalov A, Gladieux P, Heller J, Glass NL. Programmed Cell Death in Neurospora crassa Is Controlled by the Allorecognition Determinant rcd-1. Genetics 2019; 213:1387-1400. [PMID: 31636083 PMCID: PMC6893366 DOI: 10.1534/genetics.119.302617] [Citation(s) in RCA: 29] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2019] [Accepted: 10/17/2019] [Indexed: 12/31/2022] Open
Abstract
Nonself recognition following cell fusion between genetically distinct individuals of the same species in filamentous fungi often results in a programmed cell death (PCD) reaction, where the heterokaryotic fusion cell is compartmentalized and rapidly killed. The allorecognition process plays a key role as a defense mechanism that restricts genome exploitation, resource plundering, and the spread of deleterious senescence plasmids and mycoviruses. Although a number of incompatibility systems have been described that function in mature hyphae, less is known about the PCD pathways in asexual spores, which represent the main infectious unit in various human and plant fungal pathogens. Here, we report the identification of regulator of cell death-1 (rcd-1), a novel allorecognition gene, controlling PCD in germinating asexual spores of Neurospora crassa; rcd-1 is one of the most polymorphic genes in the genomes of wild N. crassa isolates. The coexpression of two antagonistic rcd-1-1 and rcd-1-2 alleles was necessary and sufficient to trigger cell death in fused germlings and in hyphae. Based on analysis of wild populations of N. crassa and N. discreta, rcd-1 alleles appeared to be under balancing selection and associated with trans-species polymorphisms. We shed light on genomic rearrangements that could have led to the emergence of the incompatibility system in Neurospora and show that rcd-1 belongs to a much larger gene family in fungi. Overall, our work contributes toward a better understanding of allorecognition and PCD in an underexplored developmental stage of filamentous fungi.
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Affiliation(s)
- Asen Daskalov
- Plant and Microbial Biology Department, The University of California, Berkeley, California 94720
| | - Pierre Gladieux
- UMR BGPI, INRA, CIRAD, Montpellier SupAgro, University Montpellier, 34060, France
| | - Jens Heller
- Plant and Microbial Biology Department, The University of California, Berkeley, California 94720
- Environmental Genomics and Systems Biology Division, The Lawrence Berkeley National Laboratory, California 94720
| | - N Louise Glass
- Plant and Microbial Biology Department, The University of California, Berkeley, California 94720
- Environmental Genomics and Systems Biology Division, The Lawrence Berkeley National Laboratory, California 94720
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13
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Atanasova L, Dubey M, Grujić M, Gudmundsson M, Lorenz C, Sandgren M, Kubicek CP, Jensen DF, Karlsson M. Evolution and functional characterization of pectate lyase PEL12, a member of a highly expanded Clonostachys rosea polysaccharide lyase 1 family. BMC Microbiol 2018; 18:178. [PMID: 30404596 PMCID: PMC6223089 DOI: 10.1186/s12866-018-1310-9] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/12/2017] [Accepted: 10/10/2018] [Indexed: 11/29/2022] Open
Abstract
Background Pectin is one of the major and most complex plant cell wall components that needs to be overcome by microorganisms as part of their strategies for plant invasion or nutrition. Microbial pectinolytic enzymes therefore play a significant role for plant-associated microorganisms and for the decomposition and recycling of plant organic matter. Recently, comparative studies revealed significant gene copy number expansion of the polysaccharide lyase 1 (PL1) pectin/pectate lyase gene family in the Clonostachys rosea genome, while only low numbers were found in Trichoderma species. Both of these fungal genera are widely known for their ability to parasitize and kill other fungi (mycoparasitism) and certain species are thus used for biocontrol of plant pathogenic fungi. Results In order to understand the role of the high number of pectin degrading enzymes in Clonostachys, we studied diversity and evolution of the PL1 gene family in C. rosea compared with other Sordariomycetes with varying nutritional life styles. Out of 17 members of C. rosea PL1, we could only detect two to be secreted at acidic pH. One of them, the pectate lyase pel12 gene was found to be strongly induced by pectin and, to a lower degree, by polygalacturonic acid. Heterologous expression of the PEL12 in a PL1-free background of T. reesei revealed direct enzymatic involvement of this protein in utilization of pectin at pH 5 without a requirement for Ca2+. The mutants showed increased utilization of pectin compounds, but did not increase biocontrol ability in detached leaf assay against the plant pathogen Botrytis cinerea compared to the wild type. Conclusions In this study, we aimed to gain insight into diversity and evolution of the PL1 gene family in C. rosea and other Sordariomycete species in relation to their nutritional modes. We show that C. rosea PL1 expansion does not correlate with its mycoparasitic nutritional mode and resembles those of strong plant pathogenic fungi. We further investigated regulation, specificity and function of the C. rosea PEL12 and show that this enzyme is directly involved in degradation of pectin and pectin-related compounds, but not in C. rosea biocontrol. Electronic supplementary material The online version of this article (10.1186/s12866-018-1310-9) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Lea Atanasova
- Forest Mycology and Plant Pathology, Swedish University of Agricultural Sciences, P.O. Box 7026, SE-75007, Uppsala, Sweden. .,Research division of Biochemical Technology, Institute of Chemical, Environmental and Biological Engineering, Vienna University of Technology, Gumpendorferstrasse 1a, 1060, Vienna, Austria. .,Institute of Food Technology, University of Natural Resources and Life Sciences, Muthgasse 11, 1190, Vienna, Austria.
| | - Mukesh Dubey
- Forest Mycology and Plant Pathology, Swedish University of Agricultural Sciences, P.O. Box 7026, SE-75007, Uppsala, Sweden
| | - Marica Grujić
- Research division of Biochemical Technology, Institute of Chemical, Environmental and Biological Engineering, Vienna University of Technology, Gumpendorferstrasse 1a, 1060, Vienna, Austria
| | - Mikael Gudmundsson
- Molecular Sciences, Swedish University of Agricultural Sciences, P.O. Box 7015, SE-75007, Uppsala, Sweden
| | - Cindy Lorenz
- Institute of Food Technology, University of Natural Resources and Life Sciences, Muthgasse 11, 1190, Vienna, Austria
| | - Mats Sandgren
- Molecular Sciences, Swedish University of Agricultural Sciences, P.O. Box 7015, SE-75007, Uppsala, Sweden
| | - Christian P Kubicek
- Research division of Biochemical Technology, Institute of Chemical, Environmental and Biological Engineering, Vienna University of Technology, Gumpendorferstrasse 1a, 1060, Vienna, Austria.,, Present address: Steinschötelgasse 7, 1100, Vienna, Austria
| | - Dan Funck Jensen
- Forest Mycology and Plant Pathology, Swedish University of Agricultural Sciences, P.O. Box 7026, SE-75007, Uppsala, Sweden
| | - Magnus Karlsson
- Forest Mycology and Plant Pathology, Swedish University of Agricultural Sciences, P.O. Box 7026, SE-75007, Uppsala, Sweden
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14
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Svedberg J, Hosseini S, Chen J, Vogan AA, Mozgova I, Hennig L, Manitchotpisit P, Abusharekh A, Hammond TM, Lascoux M, Johannesson H. Convergent evolution of complex genomic rearrangements in two fungal meiotic drive elements. Nat Commun 2018; 9:4242. [PMID: 30315196 PMCID: PMC6185902 DOI: 10.1038/s41467-018-06562-x] [Citation(s) in RCA: 34] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/13/2018] [Accepted: 09/12/2018] [Indexed: 12/31/2022] Open
Abstract
Meiotic drive is widespread in nature. The conflict it generates is expected to be an important motor for evolutionary change and innovation. In this study, we investigated the genomic consequences of two large multi-gene meiotic drive elements, Sk-2 and Sk-3, found in the filamentous ascomycete Neurospora intermedia. Using long-read sequencing, we generated the first complete and well-annotated genome assemblies of large, highly diverged, non-recombining regions associated with meiotic drive elements. Phylogenetic analysis shows that, even though Sk-2 and Sk-3 are located in the same chromosomal region, they do not form sister clades, suggesting independent origins or at least a long evolutionary separation. We conclude that they have in a convergent manner accumulated similar patterns of tandem inversions and dense repeat clusters, presumably in response to similar needs to create linkage between genes causing drive and resistance.
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Affiliation(s)
- Jesper Svedberg
- Department of Organismal Biology, Uppsala University, Norbyvägen 18D, 752 36, Uppsala, Sweden
| | - Sara Hosseini
- Department of Organismal Biology, Uppsala University, Norbyvägen 18D, 752 36, Uppsala, Sweden
| | - Jun Chen
- Department of Ecology and Genetics, Science for Life Laboratory, Uppsala University, Norbyvägen 18D, 752 36, Uppsala, Sweden
| | - Aaron A Vogan
- Department of Organismal Biology, Uppsala University, Norbyvägen 18D, 752 36, Uppsala, Sweden
| | - Iva Mozgova
- Department of Plant Biology and Linnean Center for Plant Biology, Swedish University of Agricultural Sciences, PO-Box 7080, SE-75007, Uppsala, Sweden
- Institute of Microbiology of the Czech Academy of Sciences, Centre Algatech, Opatovický mlýn, CZ-37981, Třeboň, Czech Republic
| | - Lars Hennig
- Department of Plant Biology and Linnean Center for Plant Biology, Swedish University of Agricultural Sciences, PO-Box 7080, SE-75007, Uppsala, Sweden
| | | | - Anna Abusharekh
- School of Biological Sciences, Illinois State University, Normal, IL, 61790, USA
| | - Thomas M Hammond
- School of Biological Sciences, Illinois State University, Normal, IL, 61790, USA
| | - Martin Lascoux
- Department of Ecology and Genetics, Science for Life Laboratory, Uppsala University, Norbyvägen 18D, 752 36, Uppsala, Sweden
| | - Hanna Johannesson
- Department of Organismal Biology, Uppsala University, Norbyvägen 18D, 752 36, Uppsala, Sweden.
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15
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Simpson MC, Coetzee MPA, van der Nest MA, Wingfield MJ, Wingfield BD. Ceratocystidaceae exhibit high levels of recombination at the mating-type (MAT) locus. Fungal Biol 2018; 122:1184-1191. [PMID: 30449356 DOI: 10.1016/j.funbio.2018.09.003] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/10/2017] [Revised: 07/11/2018] [Accepted: 09/12/2018] [Indexed: 12/29/2022]
Abstract
Mating is central to many fungal life cycles and is controlled by genes at the mating-type (MAT) locus. These genes determine whether the fungus will be self-sterile (heterothallic) or self-fertile (homothallic). Species in the ascomycete family Ceratocystidaceae have different mating strategies, making them interesting to consider with regards to their MAT loci. The aim of this study was to compare the composition of the MAT locus flanking regions in 11 species of Ceratocystidaceae representing four genera. Genome assemblies for each species were examined to identify the MAT locus and determine the structure of the flanking regions. Large contigs containing the MAT locus were then functionally annotated and analysed for the presence of transposable elements. Genes typically flanking the MAT locus in sordariomycetes were found to be highly conserved in the Ceratocystidaceae. The different genera in the Ceratocystidaceae displayed little synteny outside of the immediate MAT locus flanking genes. Even though species ofCeratocystis did not show much synteny outside of the immediate MAT locus flanking genes, species of Huntiella and Endoconidiophora were comparatively syntenic. Due to the high number of transposable elements present in Ceratocystis MAT flanking regions, we hypothesise that Ceratocystis species may have undergone recombination in this region.
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Affiliation(s)
- Melissa C Simpson
- Department of Biochemistry, Genetics and Microbiology, Forestry and Agricultural Biotechnology Institute, University of Pretoria, Pretoria, 0002, South Africa.
| | - Martin P A Coetzee
- Department of Biochemistry, Genetics and Microbiology, Forestry and Agricultural Biotechnology Institute, University of Pretoria, Pretoria, 0002, South Africa.
| | - Magriet A van der Nest
- Department of Biochemistry, Genetics and Microbiology, Forestry and Agricultural Biotechnology Institute, University of Pretoria, Pretoria, 0002, South Africa.
| | - Michael J Wingfield
- Department of Biochemistry, Genetics and Microbiology, Forestry and Agricultural Biotechnology Institute, University of Pretoria, Pretoria, 0002, South Africa.
| | - Brenda D Wingfield
- Department of Biochemistry, Genetics and Microbiology, Forestry and Agricultural Biotechnology Institute, University of Pretoria, Pretoria, 0002, South Africa.
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16
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Bertazzoni S, Williams AH, Jones DA, Syme RA, Tan KC, Hane JK. Accessories Make the Outfit: Accessory Chromosomes and Other Dispensable DNA Regions in Plant-Pathogenic Fungi. MOLECULAR PLANT-MICROBE INTERACTIONS : MPMI 2018; 31:779-788. [PMID: 29664319 DOI: 10.1094/mpmi-06-17-0135-fi] [Citation(s) in RCA: 60] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/16/2023]
Abstract
Fungal pathogen genomes can often be divided into core and accessory regions. Accessory regions ARs) may be comprised of either ARs (within core chromosomes (CCs) or wholly dispensable (accessory) chromosomes (ACs). Fungal ACs and ARs typically accumulate mutations and structural rearrangements more rapidly over time than CCs and many harbor genes relevant to host-pathogen interactions. These regions are of particular interest in plant pathology and include host-specific virulence factors and secondary metabolite synthesis gene clusters. This review outlines known ACs and ARs in fungal genomes, methods used for their detection, their common properties that differentiate them from the core genome, and what is currently known of their various roles in pathogenicity. Reports on the evolutionary processes generating and shaping AC and AR compartments are discussed, including repeat induced point mutation and breakage fusion bridge cycles. Previously ACs have been studied extensively within key genera, including Fusarium, Zymoseptoria, and Alternaria, but are growing in frequency of observation and perceived importance across a wider range of fungal species. Recent advances in sequencing technologies permit affordable genome assembly and resequencing of populations that will facilitate further discovery and routine screening of ACs.
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Affiliation(s)
- Stefania Bertazzoni
- 1 Centre for Crop & Disease Management, Curtin University, Perth, Western Australia, Australia; and
| | - Angela H Williams
- 1 Centre for Crop & Disease Management, Curtin University, Perth, Western Australia, Australia; and
| | - Darcy A Jones
- 1 Centre for Crop & Disease Management, Curtin University, Perth, Western Australia, Australia; and
| | - Robert A Syme
- 1 Centre for Crop & Disease Management, Curtin University, Perth, Western Australia, Australia; and
| | - Kar-Chun Tan
- 1 Centre for Crop & Disease Management, Curtin University, Perth, Western Australia, Australia; and
| | - James K Hane
- 1 Centre for Crop & Disease Management, Curtin University, Perth, Western Australia, Australia; and
- 2 Curtin Institute for Computation, Curtin University, Perth, Western Australia, Australia
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17
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Charlesworth D. Evolution of recombination rates between sex chromosomes. Philos Trans R Soc Lond B Biol Sci 2018; 372:rstb.2016.0456. [PMID: 29109220 DOI: 10.1098/rstb.2016.0456] [Citation(s) in RCA: 90] [Impact Index Per Article: 15.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 05/24/2017] [Indexed: 11/12/2022] Open
Abstract
In species with genetic sex-determination, the chromosomes carrying the sex-determining genes have often evolved non-recombining regions and subsequently evolved the full set of characteristics denoted by the term 'sex chromosomes'. These include size differences, creating chromosomal heteromorphism, and loss of gene functions from one member of the chromosome pair. Such characteristics and changes have been widely reviewed, and underlie molecular genetic approaches that can detect sex chromosome regions. This review deals mainly with the evolution of new non-recombining regions, focusing on how certain evolutionary situations select for suppressed recombination (rather than the proximate mechanisms causing suppressed recombination between sex chromosomes). Particularly important is the likely involvement of sexually antagonistic polymorphisms in genome regions closely linked to sex-determining loci. These may be responsible for the evolutionary strata of sex chromosomes that have repeatedly formed by recombination suppression evolving across large genome regions. More studies of recently evolved non-recombining sex-determining regions should help to test this hypothesis empirically, and may provide evidence about whether other situations can sometimes lead to sex-linked regions evolving. Similarities with other non-recombining genome regions are discussed briefly, to illustrate common features of the different cases, though no general properties apply to all of them.This article is part of the themed issue 'Evolutionary causes and consequences of recombination rate variation in sexual organisms'.
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Affiliation(s)
- Deborah Charlesworth
- Institute of Evolutionary Biology, School of Biological Sciences, Ashworth Laboratory, University of Edinburgh, King's Buildings, Edinburgh EH9 3FL, UK
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18
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Abstract
The first eukaryotic genome to be sequenced was fungal, and there continue to be more sequenced genomes in the kingdom Fungi than in any other eukaryotic kingdom. Comparison of these genomes reveals many sources of genetic variation, from single nucleotide polymorphisms to horizontal gene transfer and on to changes in the arrangement and number of chromosomes, not to mention endofungal bacteria and viruses. Population genomics shows that all sources generate variation all the time and implicate natural selection as the force maintaining genome stability. Variation in wild populations is a rich resource for associating genetic variation with phenotypic variation, whether through quantitative trait locus mapping, genome-wide association studies, or reverse ecology. Subjects of studies associating genetic and phenotypic variation include model fungi, e.g., Saccharomyces and Neurospora, but pioneering studies have also been made with fungi pathogenic to plants, e.g., Pyricularia (= Magnaporthe), Zymoseptoria, and Fusarium, and to humans, e.g., Coccidioides, Cryptococcus, and Candida.
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19
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Meunier C, Hosseini S, Heidari N, Maryush Z, Johannesson H. Multilevel Selection in the Filamentous Ascomycete Neurospora tetrasperma. Am Nat 2018. [DOI: 10.1086/695803] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
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20
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Sun Y, Svedberg J, Hiltunen M, Corcoran P, Johannesson H. Large-scale suppression of recombination predates genomic rearrangements in Neurospora tetrasperma. Nat Commun 2017; 8:1140. [PMID: 29074958 PMCID: PMC5658415 DOI: 10.1038/s41467-017-01317-6] [Citation(s) in RCA: 36] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2017] [Accepted: 09/08/2017] [Indexed: 12/21/2022] Open
Abstract
A common feature of eukaryote genomes is large chromosomal regions where recombination is absent or strongly reduced, but the factors that cause this reduction are not well understood. Genomic rearrangements have often been implicated, but they may also be a consequence of recombination suppression rather than a cause. In this study, we generate eight high-quality genomic data sets of the filamentous ascomycete Neurospora tetrasperma, a fungus that lacks recombination over most of its largest chromosome. The genomes surprisingly reveal collinearity of the non-recombining regions and although large inversions are enriched in these regions, we conclude these inversions to be derived and not the cause of the suppression. To our knowledge, this is the first time that non-recombining, genic regions as large as 86% of a full chromosome (or 8 Mbp), are shown to be collinear. These findings are of significant interest for our understanding of the evolution of sex chromosomes and other supergene complexes.
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Affiliation(s)
- Yu Sun
- Guangdong Provincial Key Laboratory of Protein Function and Regulation in Agricultural Organisms, College of Life Sciences, South China Agricultural University, Guangzhou, 510642, China
| | - Jesper Svedberg
- Department of Organismal Biology, Uppsala University, Norbyvägen 18D, 752 36, Uppsala, Sweden
| | - Markus Hiltunen
- Department of Organismal Biology, Uppsala University, Norbyvägen 18D, 752 36, Uppsala, Sweden
| | - Pádraic Corcoran
- Department of Animal and Plant Sciences, University of Sheffield, Sheffield, S10 2TN, UK
| | - Hanna Johannesson
- Department of Organismal Biology, Uppsala University, Norbyvägen 18D, 752 36, Uppsala, Sweden.
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21
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Yamazaki T, Ichihara K, Suzuki R, Oshima K, Miyamura S, Kuwano K, Toyoda A, Suzuki Y, Sugano S, Hattori M, Kawano S. Genomic structure and evolution of the mating type locus in the green seaweed Ulva partita. Sci Rep 2017; 7:11679. [PMID: 28916791 PMCID: PMC5601483 DOI: 10.1038/s41598-017-11677-0] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/07/2016] [Accepted: 08/29/2017] [Indexed: 01/08/2023] Open
Abstract
The evolution of sex chromosomes and mating loci in organisms with UV systems of sex/mating type determination in haploid phases via genes on UV chromosomes is not well understood. We report the structure of the mating type (MT) locus and its evolutionary history in the green seaweed Ulva partita, which is a multicellular organism with an isomorphic haploid-diploid life cycle and mating type determination in the haploid phase. Comprehensive comparison of a total of 12.0 and 16.6 Gb of genomic next-generation sequencing data for mt- and mt+ strains identified highly rearranged MT loci of 1.0 and 1.5 Mb in size and containing 46 and 67 genes, respectively, including 23 gametologs. Molecular evolutionary analyses suggested that the MT loci diverged over a prolonged period in the individual mating types after their establishment in an ancestor. A gene encoding an RWP-RK domain-containing protein was found in the mt- MT locus but was not an ortholog of the chlorophycean mating type determination gene MID. Taken together, our results suggest that the genomic structure and its evolutionary history in the U. partita MT locus are similar to those on other UV chromosomes and that the MT locus genes are quite different from those of Chlorophyceae.
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Affiliation(s)
- Tomokazu Yamazaki
- Department of Integrated Biosciences, Graduate School of Frontier Sciences, University of Tokyo, Kashiwa, Chiba, Japan
| | - Kensuke Ichihara
- Department of Integrated Biosciences, Graduate School of Frontier Sciences, University of Tokyo, Kashiwa, Chiba, Japan
| | - Ryogo Suzuki
- Department of Integrated Biosciences, Graduate School of Frontier Sciences, University of Tokyo, Kashiwa, Chiba, Japan
| | - Kenshiro Oshima
- Department of Medical Genome Sciences, Graduate School of Frontier Sciences, University of Tokyo, Kashiwa, Chiba, Japan
| | - Shinichi Miyamura
- Faculty of Life and Environmental Sciences, University of Tsukuba, Tsukuba, Ibaraki, Japan
| | - Kazuyoshi Kuwano
- Graduate School of Fisheries and Environmental Sciences, Nagasaki University, Nagasaki, Japan
| | - Atsushi Toyoda
- Center for Information Biology, National Institute of Genetics, Shizuoka, Japan
| | - Yutaka Suzuki
- Department of Medical Genome Sciences, Graduate School of Frontier Sciences, University of Tokyo, Kashiwa, Chiba, Japan
| | - Sumio Sugano
- Department of Medical Genome Sciences, Graduate School of Frontier Sciences, University of Tokyo, Kashiwa, Chiba, Japan
| | - Masahira Hattori
- Department of Medical Genome Sciences, Graduate School of Frontier Sciences, University of Tokyo, Kashiwa, Chiba, Japan
- Graduate School of Advanced Science and Engineering, Waseda University, Tokyo, Japan
| | - Shigeyuki Kawano
- Department of Integrated Biosciences, Graduate School of Frontier Sciences, University of Tokyo, Kashiwa, Chiba, Japan.
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A-to-I RNA editing is developmentally regulated and generally adaptive for sexual reproduction in Neurospora crassa. Proc Natl Acad Sci U S A 2017; 114:E7756-E7765. [PMID: 28847945 DOI: 10.1073/pnas.1702591114] [Citation(s) in RCA: 64] [Impact Index Per Article: 9.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Although fungi lack adenosine deaminase acting on RNA (ADAR) enzymes, adenosine to inosine (A-to-I) RNA editing was reported recently in Fusarium graminearum during sexual reproduction. In this study, we profiled the A-to-I editing landscape and characterized its functional and adaptive properties in the model filamentous fungus Neurospora crassa A total of 40,677 A-to-I editing sites were identified, and approximately half of them displayed stage-specific editing or editing levels at different sexual stages. RNA-sequencing analysis with the Δstc-1 and Δsad-1 mutants confirmed A-to-I editing occurred before ascus development but became more prevalent during ascosporogenesis. Besides fungal-specific sequence and secondary structure preference, 63.5% of A-to-I editing sites were in the coding regions and 81.3% of them resulted in nonsynonymous recoding, resulting in a significant increase in the proteome complexity. Many genes involved in RNA silencing, DNA methylation, and histone modifications had extensive recoding, including sad-1, sms-3, qde-1, and dim-2. Fifty pseudogenes harbor premature stop codons that require A-to-I editing to encode full-length proteins. Unlike in humans, nonsynonymous editing events in N. crassa are generally beneficial and favored by positive selection. Almost half of the nonsynonymous editing sites in N. crassa are conserved and edited in Neurospora tetrasperma Furthermore, hundreds of them are conserved in F. graminearum and had higher editing levels. Two unknown genes with editing sites conserved between Neurospora and Fusarium were experimentally shown to be important for ascosporogenesis. This study comprehensively analyzed A-to-I editing in N. crassa and showed that RNA editing is stage-specific and generally adaptive, and may be functionally related to repeat induced point mutation and meiotic silencing by unpaired DNA.
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Abstract
This article provides an overview of sexual reproduction in the ascomycetes, a phylum of fungi that is named after the specialized sacs or "asci" that hold the sexual spores. They have therefore also been referred to as the Sac Fungi due to these characteristic structures that typically contain four to eight ascospores. Ascomycetes are morphologically diverse and include single-celled yeasts, filamentous fungi, and more complex cup fungi. The sexual cycles of many species, including those of the model yeasts Saccharomyces cerevisiae and Schizosaccharomyces pombe and the filamentous saprobes Neurospora crassa, Aspergillus nidulans, and Podospora anserina, have been examined in depth. In addition, sexual or parasexual cycles have been uncovered in important human pathogens such as Candida albicans and Aspergillus fumigatus, as well as in plant pathogens such as Fusarium graminearum and Cochliobolus heterostrophus. We summarize what is known about sexual fecundity in ascomycetes, examine how structural changes at the mating-type locus dictate sexual behavior, and discuss recent studies that reveal that pheromone signaling pathways can be repurposed to serve cellular roles unrelated to sex.
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McCluskey K, Baker SE. Diverse data supports the transition of filamentous fungal model organisms into the post-genomics era. Mycology 2017; 8:67-83. [PMID: 30123633 PMCID: PMC6059044 DOI: 10.1080/21501203.2017.1281849] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/14/2016] [Accepted: 01/10/2017] [Indexed: 01/14/2023] Open
Abstract
Filamentous fungi have been important as model organisms since the beginning of modern biological inquiry and have benefitted from open data since the earliest genetic maps were shared. From early origins in simple Mendelian genetics of mating types, parasexual genetics of colony colour, and the foundational demonstration of the segregation of a nutritional requirement, the contribution of research systems utilising filamentous fungi has spanned the biochemical genetics era, through the molecular genetics era, and now are at the very foundation of diverse omics approaches to research and development. Fungal model organisms have come from most major taxonomic groups although Ascomycete filamentous fungi have seen the most major sustained effort. In addition to the published material about filamentous fungi, shared molecular tools have found application in every area of fungal biology. Similarly, shared data has contributed to the success of model systems. The scale of data supporting research with filamentous fungi has grown by 10 to 12 orders of magnitude. From genetic to molecular maps, expression databases, and finally genome resources, the open and collaborative nature of the research communities has assured that the rising tide of data has lifted all of the research systems together.
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Affiliation(s)
- Kevin McCluskey
- Department of Plant Pathology, Kansas State University, Manhattan, KS, USA
| | - Scott E. Baker
- Environmental Molecular Science Laboratory, Pacific Northwest National Laboratory, Richland, WA, USA
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25
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Roy SW. Is Genome Complexity a Consequence of Inefficient Selection? Evidence from Intron Creation in Nonrecombining Regions. Mol Biol Evol 2016; 33:3088-3094. [DOI: 10.1093/molbev/msw172] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
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26
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Testa AC, Oliver RP, Hane JK. OcculterCut: A Comprehensive Survey of AT-Rich Regions in Fungal Genomes. Genome Biol Evol 2016; 8:2044-64. [PMID: 27289099 PMCID: PMC4943192 DOI: 10.1093/gbe/evw121] [Citation(s) in RCA: 83] [Impact Index Per Article: 10.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 05/14/2016] [Indexed: 12/03/2022] Open
Abstract
We present a novel method to measure the local GC-content bias in genomes and a survey of published fungal species. The method, enacted as "OcculterCut" (https://sourceforge.net/projects/occultercut, last accessed April 30, 2016), identified species containing distinct AT-rich regions. In most fungal taxa, AT-rich regions are a signature of repeat-induced point mutation (RIP), which targets repetitive DNA and decreases GC-content though the conversion of cytosine to thymine bases. RIP has in turn been identified as a driver of fungal genome evolution, as RIP mutations can also occur in single-copy genes neighboring repeat-rich regions. Over time RIP perpetuates "two speeds" of gene evolution in the GC-equilibrated and AT-rich regions of fungal genomes. In this study, genomes showing evidence of this process are found to be common, particularly among the Pezizomycotina. Further analysis highlighted differences in amino acid composition and putative functions of genes from these regions, supporting the hypothesis that these regions play an important role in fungal evolution. OcculterCut can also be used to identify genes undergoing RIP-assisted diversifying selection, such as small, secreted effector proteins that mediate host-microbe disease interactions.
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Affiliation(s)
- Alison C Testa
- Department of Environment & Agriculture, Centre for Crop and Disease Management, Curtin University, Perth, Australia
| | - Richard P Oliver
- Department of Environment & Agriculture, Centre for Crop and Disease Management, Curtin University, Perth, Australia
| | - James K Hane
- Department of Environment & Agriculture, Centre for Crop and Disease Management, Curtin University, Perth, Australia Curtin Institute for Computation, Curtin University, Perth, Australia
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Kracher D, Scheiblbrandner S, Felice AKG, Breslmayr E, Preims M, Ludwicka K, Haltrich D, Eijsink VGH, Ludwig R. Extracellular electron transfer systems fuel cellulose oxidative degradation. Science 2016; 352:1098-101. [DOI: 10.1126/science.aaf3165] [Citation(s) in RCA: 257] [Impact Index Per Article: 32.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2016] [Accepted: 04/15/2016] [Indexed: 01/19/2023]
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The Fast-Evolving phy-2 Gene Modulates Sexual Development in Response to Light in the Model Fungus Neurospora crassa. mBio 2016; 7:e02148. [PMID: 26956589 PMCID: PMC4810495 DOI: 10.1128/mbio.02148-15] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023] Open
Abstract
Rapid responses to changes in incident light are critical to the guidance of behavior and development in most species. Phytochrome light receptors in particular play key roles in bacterial physiology and plant development, but their functions and regulation are less well understood in fungi. Nevertheless, genome-wide expression measurements provide key information that can guide experiments that reveal how genes respond to environmental signals and clarify their role in development. We performed functional genomic and phenotypic analyses of the two phytochromes in Neurospora crassa, a fungal model adapted to a postfire environment that experiences dramatically variable light conditions. Expression of phy-1 and phy-2 was low in early sexual development and in the case of phy-2 increased in late sexual development. Under light stimulation, strains with the phytochromes deleted exhibited increased expression of sexual development-related genes. Moreover, under red light, the phy-2 knockout strain commenced sexual development early. In the evolution of phytochromes within ascomycetes, at least two duplications have occurred, and the faster-evolving phy-2 gene has frequently been lost. Additionally, the three key cysteine sites that are critical for bacterial and plant phytochrome function are not conserved within fungal phy-2 homologs. Through the action of phytochromes, transitions between asexual and sexual reproduction are modulated by light level and light quality, presumably as an adaptation for fast asexual growth and initiation of sexual reproduction of N. crassa in exposed postfire ecosystems. Environmental signals, including light, play critical roles in regulating fungal growth and pathogenicity, and balance of asexual and sexual reproduction is critical in fungal pathogens’ incidence, virulence, and distribution. Red light sensing by phytochromes is well known to play critical roles in bacterial physiology and plant development. Homologs of phytochromes were first discovered in the fungal model Neurospora crassa and then subsequently in diverse other fungi, including many plant pathogens. Our study investigated the evolution of red light sensors in ascomycetes and confirmed—using the model fungus Neurospora crassa—their roles in modulating the asexual-sexual reproduction balance in fungi. Our findings also provide a key insight into one of the most poorly understood aspects of fungal biology, suggesting that further study of the function of phytochromes in fungi is critical to reveal the genetic basis of the asexual-sexual switch responsible for fungal growth and distribution, including diverse and destructive plant pathogens.
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Corcoran P, Anderson JL, Jacobson DJ, Sun Y, Ni P, Lascoux M, Johannesson H. Introgression maintains the genetic integrity of the mating-type determining chromosome of the fungus Neurospora tetrasperma. Genome Res 2016; 26:486-98. [PMID: 26893460 PMCID: PMC4817772 DOI: 10.1101/gr.197244.115] [Citation(s) in RCA: 35] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2015] [Accepted: 02/16/2016] [Indexed: 01/01/2023]
Abstract
Genome evolution is driven by a complex interplay of factors, including selection, recombination, and introgression. The regions determining sexual identity are particularly dynamic parts of eukaryotic genomes that are prone to molecular degeneration associated with suppressed recombination. In the fungus Neurospora tetrasperma, it has been proposed that this molecular degeneration is counteracted by the introgression of nondegenerated DNA from closely related species. In this study, we used comparative and population genomic analyses of 92 genomes from eight phylogenetically and reproductively isolated lineages of N. tetrasperma, and its three closest relatives, to investigate the factors shaping the evolutionary history of the genomes.We found that suppressed recombination extends across at least 6 Mbp (∼ 63%) of the mating-type (mat) chromosome in N. tetrasperma and is associated with decreased genetic diversity, which is likely the result primarily of selection at linked sites. Furthermore, analyses of molecular evolution revealed an increased mutational load in this region, relative to recombining regions. However, comparative genomic and phylogenetic analyses indicate that the mat chromosomes are temporarily regenerated via introgression from sister species; six of eight lineages show introgression into one of their mat chromosomes, with multiple Neurospora species acting as donors. The introgressed tracts have been fixed within lineages, suggesting that they confer an adaptive advantage in natural populations, and our analyses support the presence of selective sweeps in at least one lineage. Thus, these data strongly support the previously hypothesized role of introgression as a mechanism for the maintenance of mating-type determining chromosomal regions.
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Affiliation(s)
- Pádraic Corcoran
- Department of Organismal Biology, Uppsala University, 752 36 Uppsala, Sweden; Department of Animal and Plant Sciences, University of Sheffield, Sheffield S10 2TN, United Kingdom
| | - Jennifer L Anderson
- Department of Organismal Biology, Uppsala University, 752 36 Uppsala, Sweden
| | - David J Jacobson
- Department of Organismal Biology, Uppsala University, 752 36 Uppsala, Sweden
| | - Yu Sun
- Department of Cell and Molecular Biology, Uppsala University, 752 36 Uppsala, Sweden
| | | | - Martin Lascoux
- Department of Ecology and Genetics, Science for Life Laboratory, Uppsala University, 752 36 Uppsala, Sweden
| | - Hanna Johannesson
- Department of Organismal Biology, Uppsala University, 752 36 Uppsala, Sweden
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30
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Heitman J. Evolution of sexual reproduction: a view from the Fungal Kingdom supports an evolutionary epoch with sex before sexes. FUNGAL BIOL REV 2015; 29:108-117. [PMID: 26834823 DOI: 10.1016/j.fbr.2015.08.002] [Citation(s) in RCA: 63] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
Sexual reproduction is conserved throughout each supergroup within the eukaryotic tree of life, and therefore thought to have evolved once and to have been present in the last eukaryotic common ancestor (LECA). Given the antiquity of sex, there are features of sexual reproduction that are ancient and ancestral, and thus shared in diverse extant organisms. On the other hand, the vast evolutionary distance that separates any given extant species from the LECA necessarily implies that other features of sex will be derived. While most types of sex we are familiar with involve two opposite sexes or mating types, recent studies in the fungal kingdom have revealed novel and unusual patterns of sexual reproduction, including unisexual reproduction. In this mode of reproduction a single mating type can on its own undergo self-fertile/homothallic reproduction, either with itself or with other members of the population of the same mating type. Unisexual reproduction has arisen independently as a derived feature in several different lineages. That a myriad of different types of sex determination and sex determinants abound in animals, plants, protists, and fungi suggests that sex specification itself may not be ancestral and instead may be a derived trait. If so, then the original form of sexual reproduction may have been unisexual, onto which sexes were superimposed as a later feature. In this model, unisexual reproduction is both an ancestral and a derived trait. In this review, we consider what is new and what is old about sexual reproduction from the unique vantage point of the fungal kingdom.
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Affiliation(s)
- Joseph Heitman
- Department of Molecular Genetics and Microbiology, Duke University Medical Center, Durham, NC 27710 USA
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31
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Idnurm A, Hood ME, Johannesson H, Giraud T. Contrasted patterns in mating-type chromosomes in fungi: hotspots versus coldspots of recombination. FUNGAL BIOL REV 2015; 29:220-229. [PMID: 26688691 PMCID: PMC4680991 DOI: 10.1016/j.fbr.2015.06.001] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
It is striking that, while central to sexual reproduction, the genomic regions determining sex or mating-types are often characterized by suppressed recombination that leads to a decrease in the efficiency of selection, shelters genetic load, and inevitably contributes to their genic degeneration. Research on model and lesser-explored fungi has revealed similarities in recombination suppression of the genomic regions involved in mating compatibility across eukaryotes, but fungi also provide opposite examples of enhanced recombination in the genomic regions that determine their mating types. These contrasted patterns of genetic recombination (sensu lato, including gene conversion and ectopic recombination) in regions of the genome involved in mating compatibility point to important yet complex processes occurring in their evolution. A number of pieces in this puzzle remain to be solved, in particular on the unclear selective forces that may cause the patterns of recombination, prompting theoretical developments and experimental studies. This review thus points to fungi as a fascinating group for studying the various evolutionary forces at play in the genomic regions involved in mating compatibility.
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Affiliation(s)
- Alexander Idnurm
- School of BioSciences, University of Melbourne, VIC 3010, Australia
| | - Michael E. Hood
- Department of Biology, Amherst College, Amherst, Massachusetts 01002 USA
| | - Hanna Johannesson
- Department of Evolutionary Biology, Uppsala University, Norbyvägen 18D, 752 36 Uppsala, Sweden
| | - Tatiana Giraud
- Laboratoire Ecologie, Systématique et Evolution, UMR 8079 CNRS-UPS-AgroParisTech, Bâtiment 360, Université Paris-Sud, 91405 Orsay cedex, France
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32
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Abstract
Research over the past two decades shows that both recombination and clonality are likely to contribute to the reproduction of all fungi. This view of fungi is different from the historical and still commonly held view that a large fraction of fungi are exclusively clonal and that some fungi have been exclusively clonal for hundreds of millions of years. Here, we first will consider how these two historical views have changed. Then we will examine the impact on fungal research of the concept of restrained recombination [Tibayrenc M, Ayala FJ (2012) Proc Natl Acad Sci USA 109 (48):E3305-E3313]. Using animal and human pathogenic fungi, we examine extrinsic restraints on recombination associated with bottlenecks in genetic variation caused by geographic dispersal and extrinsic restraints caused by shifts in reproductive mode associated with either disease transmission or hybridization. Using species of the model yeast Saccharomyces and the model filamentous fungus Neurospora, we examine intrinsic restraints on recombination associated with mating systems that range from strictly clonal at one extreme to fully outbreeding at the other and those that lie between, including selfing and inbreeding. We also consider the effect of nomenclature on perception of reproductive mode and a means of comparing the relative impact of clonality and recombination on fungal populations. Last, we consider a recent hypothesis suggesting that fungi thought to have the most severe intrinsic constraints on recombination actually may have the fewest.
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33
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Grognet P, Silar P. Maintaining heterokaryosis in pseudo-homothallic fungi. Commun Integr Biol 2015; 8:e994382. [PMID: 26479494 PMCID: PMC4594319 DOI: 10.4161/19420889.2014.994382] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/24/2014] [Accepted: 11/06/2014] [Indexed: 01/09/2023] Open
Abstract
Among all the strategies displayed by fungi to reproduce and propagate, some species have adopted a peculiar behavior called pseudo-homothallism. Pseudo-homothallic fungi are true heterothallics, i.e., they need 2 genetically-compatible partners to mate, but they produce self-fertile mycelium in which the 2 different nuclei carrying the compatible mating types are present. This lifestyle not only enables the fungus to reproduce without finding a compatible partner, but also to cross with any mate it may encounter. However, to be fully functional, pseudo-homothallism requires maintaining heterokaryosis at every stage of the life cycle. We recently showed that neither the structure of the mating-type locus nor hybrid-enhancing effect due to the presence of the 2 mating types accounts for the maintenance of heterokaryosis in the pseudo-homothallic fungus P. anserina. In this addendum, we summarize the mechanisms creating heterokaryosis in P. anserina and 2 other well-known pseudo-homothallic fungi, Neurospora tetrasperma and Agaricus bisporus. We also discuss mechanisms potentially involved in maintaining heterokaryosis in these 3 species.
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Affiliation(s)
- Pierre Grognet
- Univ Paris Diderot; Sorbonne Paris Cité; Institut des Energies de Demain ; Paris, France
| | - Philippe Silar
- Univ Paris Diderot; Sorbonne Paris Cité; Institut des Energies de Demain ; Paris, France
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34
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Charlesworth D. The status of supergenes in the 21st century: recombination suppression in Batesian mimicry and sex chromosomes and other complex adaptations. Evol Appl 2015; 9:74-90. [PMID: 27087840 PMCID: PMC4780387 DOI: 10.1111/eva.12291] [Citation(s) in RCA: 90] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/24/2015] [Accepted: 06/16/2015] [Indexed: 02/06/2023] Open
Abstract
I review theoretical models for the evolution of supergenes in the cases of Batesian mimicry in butterflies, distylous plants and sex chromosomes. For each of these systems, I outline the genetic evidence that led to the proposal that they involve multiple genes that interact during ‘complex adaptations’, and at which the mutations involved are not unconditionally advantageous, but show advantages that trade‐off against some disadvantages. I describe recent molecular genetic studies of these systems and questions they raise about the evolution of suppressed recombination. Nonrecombining regions of sex chromosomes have long been known, but it is not yet fully understood why recombination suppression repeatedly evolved in systems in distantly related taxa, but does not always evolve. Recent studies of distylous plants are tending to support the existence of recombination‐suppressed genome regions, which may include modest numbers of genes and resemble recently evolved sex‐linked regions. For Batesian mimicry, however, molecular genetic work in two butterfly species suggests a new supergene scenario, with a single gene mutating to produce initial adaptive phenotypes, perhaps followed by modifiers specifically refining and perfecting the new phenotype.
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35
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Abstract
Genome defense likely evolved to curtail the spread of transposable elements and invading viruses. A combination of effective defense mechanisms has been shown to limit colonization of the Neurospora crassa genome by transposable elements. A novel DNA transposon named Sly1-1 was discovered in the genome of the most widely used laboratory "wild-type" strain FGSC 2489 (OR74A). Meiotic silencing by unpaired DNA, also simply called meiotic silencing, prevents the expression of regions of the genome that are unpaired during karyogamy. This mechanism is posttranscriptional and is proposed to involve the production of small RNA, so-called masiRNAs, by proteins homologous to those involved in RNA interference-silencing pathways in animals, fungi, and plants. Here, we demonstrate production of small RNAs when Sly1-1 was unpaired in a cross between two wild-type strains. These small RNAs are dependent on SAD-1, an RNA-dependent RNA polymerase necessary for meiotic silencing. We present the first case of endogenously produced masiRNA from a novel N. crassa DNA transposable element.
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36
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Chaos of Rearrangements in the Mating-Type Chromosomes of the Anther-Smut Fungus Microbotryum lychnidis-dioicae. Genetics 2015; 200:1275-84. [PMID: 26044594 PMCID: PMC4574255 DOI: 10.1534/genetics.115.177709] [Citation(s) in RCA: 59] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/02/2015] [Accepted: 06/02/2015] [Indexed: 12/02/2022] Open
Abstract
Sex chromosomes in plants and animals and fungal mating-type chromosomes often show exceptional genome features, with extensive suppression of homologous recombination and cytological differentiation between members of the diploid chromosome pair. Despite strong interest in the genetics of these chromosomes, their large regions of suppressed recombination often are enriched in transposable elements and therefore can be challenging to assemble. Here we show that the latest improvements of the PacBio sequencing yield assembly of the whole genome of the anther-smut fungus, Microbotryum lychnidis-dioicae (the pathogenic fungus causing anther-smut disease of Silene latifolia), into finished chromosomes or chromosome arms, even for the repeat-rich mating-type chromosomes and centromeres. Suppressed recombination of the mating-type chromosomes is revealed to span nearly 90% of their lengths, with extreme levels of rearrangements, transposable element accumulation, and differentiation between the two mating types. We observed no correlation between allelic divergence and physical position in the nonrecombining regions of the mating-type chromosomes. This may result from gene conversion or from rearrangements of ancient evolutionary strata, i.e., successive steps of suppressed recombination. Centromeres were found to be composed mainly of copia-like transposable elements and to possess specific minisatellite repeats identical between the different chromosomes. We also identified subtelomeric motifs. In addition, extensive signs of degeneration were detected in the nonrecombining regions in the form of transposable element accumulation and of hundreds of gene losses on each mating-type chromosome. Furthermore, our study highlights the potential of the latest breakthrough PacBio chemistry to resolve complex genome architectures.
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Neurospora Heterokaryons with Complementary Duplications and Deficiencies in Their Constituent Nuclei Provide an Approach to Identify Nucleus-Limited Genes. G3-GENES GENOMES GENETICS 2015; 5:1263-72. [PMID: 25897010 PMCID: PMC4478554 DOI: 10.1534/g3.115.017616] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
Introgression is the transfer of genes or genomic regions from one species into another via hybridization and back-crosses. We have introgressed four translocations (EB4, IBj5, UK14-1, and B362i) from Neurospora crassa into N. tetrasperma. This enabled us to construct two general types of heterokaryons with mat-A and mat-a nuclei of different genotypes: one type is [T + N] (with one translocation nucleus and one normal sequence nucleus), and the other is [Dp + Df] (with one nucleus carrying a duplication of the translocation region and the other being deleted for the translocation region). Self-crossing these heterokaryons again produced [T + N] and [Dp + Df] progeny. From conidia (vegetative spores) produced by the heterokaryotic mycelia, we obtained self-fertile (heterokaryotic) and self-sterile (homokaryotic) derivative strains. [T + N] heterokaryons produced homokaryotic conidial derivatives of both mating types, but [Dp + Df] heterokaryons produced viable conidial homokaryons of only the mating type of the Dp nucleus. All four [T + N] heterokaryons and three [Dp + Df] heterokaryons produced both self-sterile and self-fertile conidial derivatives, but the [Dp(B362i) + Df(B362i)] heterokaryons produced only self-sterile ones. Conceivably, the Df(B362i) nuclei may be deleted for a nucleus-limited gene required for efficient mitosis or nuclear division, and whose deficit is not complemented by the neighboring Dp(B362i) nuclei. A cross involving Dp(EB4) showed repeat-induced point mutation (RIP). Because RIP can occur in self-crosses of [Dp + Df] but not [T + N] heterokaryons, RIP alteration of a translocated segment would depend on the relative numbers of [Dp + Df] vs. [T + N] ancestors.
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38
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Fontanillas E, Hood ME, Badouin H, Petit E, Barbe V, Gouzy J, de Vienne DM, Aguileta G, Poulain J, Wincker P, Chen Z, Toh SS, Cuomo CA, Perlin MH, Gladieux P, Giraud T. Degeneration of the nonrecombining regions in the mating-type chromosomes of the anther-smut fungi. Mol Biol Evol 2015; 32:928-43. [PMID: 25534033 PMCID: PMC4379399 DOI: 10.1093/molbev/msu396] [Citation(s) in RCA: 45] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023] Open
Abstract
Dimorphic mating-type chromosomes in fungi are excellent models for understanding the genomic consequences of recombination suppression. Their suppressed recombination and reduced effective population size are expected to limit the efficacy of natural selection, leading to genomic degeneration. Our aim was to identify the sequences of the mating-type chromosomes (a1 and a2) of the anther-smut fungi and to investigate degeneration in their nonrecombining regions. We used the haploid a1 Microbotryum lychnidis-dioicae reference genome sequence. The a1 and a2 mating-type chromosomes were both isolated electrophoretically and sequenced. Integration with restriction-digest optical maps identified regions of recombination and nonrecombination in the mating-type chromosomes. Genome sequence data were also obtained for 12 other Microbotryum species. We found strong evidence of degeneration across the genus in the nonrecombining regions of the mating-type chromosomes, with significantly higher rates of nonsynonymous substitution (dN/dS) than in nonmating-type chromosomes or in recombining regions of the mating-type chromosomes. The nonrecombining regions of the mating-type chromosomes also showed high transposable element content, weak gene expression, and gene losses. The levels of degeneration did not differ between the a1 and a2 mating-type chromosomes, consistent with the lack of homogametic/heterogametic asymmetry between them, and contrasting with X/Y or Z/W sex chromosomes.
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Affiliation(s)
- Eric Fontanillas
- Ecologie, Systématique et Evolution, Bâtiment 360, Université Paris-Sud, Orsay, France CNRS, Orsay, France
| | | | - Hélène Badouin
- Ecologie, Systématique et Evolution, Bâtiment 360, Université Paris-Sud, Orsay, France CNRS, Orsay, France
| | - Elsa Petit
- Ecologie, Systématique et Evolution, Bâtiment 360, Université Paris-Sud, Orsay, France CNRS, Orsay, France Department of Biology, Amherst College
| | - Valérie Barbe
- Commissariat à l'Energie Atomique (CEA), Institut de Génomique (IG), Genoscope, Evry, France
| | - Jérôme Gouzy
- INRA, Laboratoire des Interactions Plantes-Microorganismes (LIPM), UMR441, Castanet-Tolosan, France CNRS, Laboratoire des Interactions Plantes-Microorganismes (LIPM), UMR2594, Castanet-Tolosan, France
| | - Damien M de Vienne
- Laboratoire de Biométrie et Biologie Evolutive, Centre National de la Recherche Scientifique, Unité Mixte de Recherche 5558, Université Lyon 1, Villeurbanne, France Université de Lyon, Lyon, France Bioinformatics and Genomics Programme, Centre for Genomic Regulation (CRG), Dr. Aiguader 88, Barcelona, Spain Universitat Pompeu Fabra (UPF), Barcelona, Spain
| | - Gabriela Aguileta
- Bioinformatics and Genomics Programme, Centre for Genomic Regulation (CRG), Dr. Aiguader 88, Barcelona, Spain Universitat Pompeu Fabra (UPF), Barcelona, Spain
| | | | - Patrick Wincker
- Commissariat à l'Energie Atomique (CEA), Institut de Génomique (IG), Genoscope, Evry, France CNRS UMR 8030, Evry, France
| | - Zehua Chen
- Broad Institute of MIT and Harvard, Cambridge, MA
| | - Su San Toh
- Department of Biology, Program on Disease Evolution, University of Louisville
| | | | - Michael H Perlin
- Department of Biology, Program on Disease Evolution, University of Louisville
| | - Pierre Gladieux
- Ecologie, Systématique et Evolution, Bâtiment 360, Université Paris-Sud, Orsay, France CNRS, Orsay, France
| | - Tatiana Giraud
- Ecologie, Systématique et Evolution, Bâtiment 360, Université Paris-Sud, Orsay, France CNRS, Orsay, France
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39
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Whittle CA, Votintseva A, Ridout K, Filatov DA. Recent and massive expansion of the mating-type-specific region in the smut fungus Microbotryum. Genetics 2015; 199:809-16. [PMID: 25567990 PMCID: PMC4349073 DOI: 10.1534/genetics.114.171702] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/21/2014] [Accepted: 12/22/2014] [Indexed: 12/25/2022] Open
Abstract
The presence of large genomic regions with suppressed recombination (SR) is a key shared property of some sex- and mating-type determining (mat) chromosomes identified to date in animals, plants, and fungi. Why such regions form and how they evolve remain central questions in evolutionary genetics. The smut fungus Microbotryum lychnis-dioicae is a basidiomycete fungus in which dimorphic mat chromosomes have been reported, but the size, age, and evolutionary dynamics of the SR region remains unresolved. To identify the SR region in M. lychnis-dioicae and to study its evolution, we sequenced 12 genomes (6 per mating type) of this species and identified the genomic contigs that show fixed sequence differences between the mating types. We report that the SR region spans more than half of the mat chromosome (>2.3 Mbp) and that it is of very recent origin (∼2 × 10(6) years) as the average sequence divergence between mating types was only 2% in the SR region. This contrasts with a much higher divergence in and around the mating-type determining pheromone receptor locus in the SR, suggesting a recent and massive expansion of the SR region. Our results comprise the first reported case of recent massive SR expansion documented in a basidiomycete fungus.
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Affiliation(s)
- Carrie A Whittle
- Department of Plant Sciences, University of Oxford, Oxford OX1 3RB, United Kingdom
| | - Antonina Votintseva
- Department of Plant Sciences, University of Oxford, Oxford OX1 3RB, United Kingdom
| | - Kate Ridout
- Department of Plant Sciences, University of Oxford, Oxford OX1 3RB, United Kingdom
| | - Dmitry A Filatov
- Department of Plant Sciences, University of Oxford, Oxford OX1 3RB, United Kingdom
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40
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Abstract
Owing to their small size and paucity of phenotypic characters, progress in the evolutionary biology of microbes in general, and human pathogenic fungi in particular, has been linked to a series of advances in DNA sequencing over the past quarter century. Phylogenetics was the first area to benefit, with the achievement of a basic understanding of fungal phylogeny. Population genetics was the next advance, finding cryptic species everywhere, and recombination in species previously thought to be asexual. Comparative genomics saw the next advance, in which variation in gene content and changes in gene family size were found to be important sources of variation. Fungal population genomics is showing that gene flow among closely related populations and species provides yet another source of adaptive, genetic variation. Now, two means to associate genetic variation with phenotypic variation, "reverse ecology" for adaptive phenotypes, and genome-wide association of any phenotype, are letting evolutionary biology make a profound contribution to molecular developmental biology of pathogenic fungi.
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Affiliation(s)
- John W Taylor
- University of California, Berkeley, California 94720-3102
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41
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Abstract
We used comparative and population genomics to study intron evolutionary dynamics in the fungal model genus Neurospora. For our investigation, we used well-annotated genomes of N. crassa, N. discreta, and N. tetrasperma, and 92 resequenced genomes of N. tetrasperma from natural populations. By analyzing the four well-annotated genomes, we identified 9495 intron sites in 7619 orthologous genes. Our data supports nonhomologous end joining (NHEJ) and tandem duplication as mechanisms for intron gains in the genus and the RT-mRNA process as a mechanism for intron loss. We found a moderate intron gain rate (5.78–6.89 × 10−13 intron gains per nucleotide site per year) and a high intron loss rate (7.53–13.76 × 10−10 intron losses per intron sites per year) as compared to other eukaryotes. The derived intron gains and losses are skewed to high frequencies, relative to neutral SNPs, in natural populations of N. tetrasperma, suggesting that selection is involved in maintaining a high intron turnover. Furthermore, our analyses of the association between intron population-level frequency and genomic features suggest that selection is involved in shaping a 5′ intron position bias and a low intron GC content. However, intron sequence analyses suggest that the gained introns were not exposed to recent selective sweeps. Taken together, this work contributes to our understanding of the importance of mutational bias and selection in shaping the intron distribution in eukaryotic genomes.
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Corcoran P, Dettman JR, Sun Y, Luque EM, Corrochano LM, Taylor JW, Lascoux M, Johannesson H. A global multilocus analysis of the model fungus Neurospora reveals a single recent origin of a novel genetic system. Mol Phylogenet Evol 2014; 78:136-47. [PMID: 24845789 DOI: 10.1016/j.ympev.2014.05.007] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/28/2013] [Revised: 02/13/2014] [Accepted: 05/06/2014] [Indexed: 10/25/2022]
Abstract
The large diversity of mating systems observed in the fungal kingdom underlines the importance of mating system change in fungal evolution. The selfing species Neurospora tetrasperma has evolved a novel method of achieving self-fertility by a mating system referred to as pseudohomothallism. However, little is known about the origin of N. tetrasperma and its relationship to the self-sterile, heterothallic, Neurospora species. In this study, we used a combination of phylogenetic and population genetic analyses to reconstruct the evolutionary history of N. tetrasperma and its heterothallic relatives. We sequenced 9 unlinked nuclear loci from 106 strains of N. tetrasperma sampled from across the globe, and a sample of 28 heterothallic strains of Neurospora. Our analyses provide strong support for monophyly of N. tetrasperma, but reject the monophyly of N. crassa. We estimate that N. tetrasperma is of a recent origin and that it diverged from the heterothallic species ∼1 million years ago. We also extend previous findings on the diversification within the N. tetrasperma clade, with 10 lineages identified. Taken together, these findings indicate that N. tetrasperma is younger than has been previously reported and that a rapid diversification of lineages has occurred within the N. tetrasperma clade.
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Affiliation(s)
- Pádraic Corcoran
- Department of Evolutionary Biology, Uppsala University, Uppsala, Sweden.
| | - Jeremy R Dettman
- Department of Biology, University of Ottawa, Ottawa, Ontario, Canada
| | - Yu Sun
- Department of Evolutionary Biology, Uppsala University, Uppsala, Sweden
| | - Eva M Luque
- Departamento de Genética, Universidad de Sevilla, Sevilla, Spain
| | | | - John W Taylor
- Department of Plant and Microbial Biology, University of California Berkeley, Berkeley, CA, USA
| | - Martin Lascoux
- Department of Plant Ecology and Evolution, Uppsala University, Uppsala, Sweden
| | - Hanna Johannesson
- Department of Evolutionary Biology, Uppsala University, Uppsala, Sweden
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43
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Todd RB, Zhou M, Ohm RA, Leeggangers HACF, Visser L, de Vries RP. Prevalence of transcription factors in ascomycete and basidiomycete fungi. BMC Genomics 2014; 15:214. [PMID: 24650355 PMCID: PMC3998117 DOI: 10.1186/1471-2164-15-214] [Citation(s) in RCA: 82] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2013] [Accepted: 03/11/2014] [Indexed: 12/18/2022] Open
Abstract
Background Gene regulation underlies fungal physiology and therefore is a major factor in fungal biodiversity. Analysis of genome sequences has revealed a large number of putative transcription factors in most fungal genomes. The presence of fungal orthologs for individual regulators has been analysed and appears to be highly variable with some regulators widely conserved and others showing narrow distribution. Although genome-scale transcription factor surveys have been performed before, no global study into the prevalence of specific regulators across the fungal kingdom has been presented. Results In this study we have analysed the number of members for 37 regulator classes in 77 ascomycete and 31 basidiomycete fungal genomes and revealed significant differences between ascomycetes and basidiomycetes. In addition, we determined the presence of 64 regulators characterised in ascomycetes across these 108 genomes. This demonstrated that overall the highest presence of orthologs is in the filamentous ascomycetes. A significant number of regulators lacked orthologs in the ascomycete yeasts and the basidiomycetes. Conversely, of seven basidiomycete regulators included in the study, only one had orthologs in ascomycetes. Conclusions This study demonstrates a significant difference in the regulatory repertoire of ascomycete and basidiomycete fungi, at the level of both regulator class and individual regulator. This suggests that the current regulatory systems of these fungi have been mainly developed after the two phyla diverged. Most regulators detected in both phyla are involved in central functions of fungal physiology and therefore were likely already present in the ancestor of the two phyla.
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Affiliation(s)
- Richard B Todd
- Department of Plant Pathology, Kansas State University, 4024 Throckmorton Plant Sciences Center, Manhattan, KS 66506, USA.
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Maintaining two mating types: structure of the mating type locus and its role in heterokaryosis in Podospora anserina. Genetics 2014; 197:421-32. [PMID: 24558260 DOI: 10.1534/genetics.113.159988] [Citation(s) in RCA: 50] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Pseudo-homothallism is a reproductive strategy elected by some fungi producing heterokaryotic sexual spores containing genetically different but sexually compatible nuclei. This lifestyle appears as a compromise between true homothallism (self-fertility with predominant inbreeding) and complete heterothallism (with exclusive outcrossing). However, pseudohomothallic species face the problem of maintaining heterokaryotic mycelia to fully benefit from this lifestyle, as homokaryons are self-sterile. Here, we report on the structure of chromosome 1 in mat+ and mat- isolates of strain S of the pseudohomothallic fungus Podospora anserina. Chromosome 1 contains either one of the mat+ and mat- mating types of P. anserina, which is mostly found in nature as a mat+/mat- heterokaryotic mycelium harboring sexually compatible nuclei. We identified a "mat" region ∼0.8 Mb long, devoid of meiotic recombination and containing the mating-type idiomorphs, which is a candidate to be involved in the maintenance of the heterokaryotic state, since the S mat+ and S mat- strains have different physiology that may enable hybrid-vigor-like phenomena in the heterokaryons. The mat region contains 229 coding sequences. A total of 687 polymorphisms were detected between the S mat+ and S mat- chromosomes. Importantly, the mat region is colinear between both chromosomes, which calls for an original mechanism of recombination inhibition. Microarray analyses revealed that 10% of the P. anserina genes have different transcriptional profiles in S mat+ and S mat-, in line with their different phenotypes. Finally, we show that the heterokaryotic state is faithfully maintained during mycelium growth of P. anserina, yet mat+/mat+ and mat-/mat- heterokaryons are as stable as mat+/mat- ones, evidencing a maintenance of heterokaryosis that does not rely on fitness-enhancing complementation between the S mat+ and S mat- strains.
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Leducq JB. Ecological Genomics of Adaptation and Speciation in Fungi. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2014; 781:49-72. [DOI: 10.1007/978-94-007-7347-9_4] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
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Species and population level molecular profiling reveals cryptic recombination and emergent asymmetry in the dimorphic mating locus of C. reinhardtii. PLoS Genet 2013; 9:e1003724. [PMID: 24009520 PMCID: PMC3757049 DOI: 10.1371/journal.pgen.1003724] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/12/2013] [Accepted: 06/28/2013] [Indexed: 12/12/2022] Open
Abstract
Heteromorphic sex-determining regions or mating-type loci can contain large regions of non-recombining sequence where selection operates under different constraints than in freely recombining autosomal regions. Detailed studies of these non-recombining regions can provide insights into how genes are gained and lost, and how genetic isolation is maintained between mating haplotypes or sex chromosomes. The Chlamydomonas reinhardtii mating-type locus (MT) is a complex polygenic region characterized by sequence rearrangements and suppressed recombination between its two haplotypes, MT+ and MT−. We used new sequence information to redefine the genetic contents of MT and found repeated translocations from autosomes as well as sexually controlled expression patterns for several newly identified genes. We examined sequence diversity of MT genes from wild isolates of C. reinhardtii to investigate the impacts of recombination suppression. Our population data revealed two previously unreported types of genetic exchange in Chlamydomonas MT—gene conversion in the rearranged domains, and crossover exchanges in flanking domains—both of which contribute to maintenance of genetic homogeneity between haplotypes. To investigate the cause of blocked recombination in MT we assessed recombination rates in crosses where the parents were homozygous at MT. While normal recombination was restored in MT+×MT+ crosses, it was still suppressed in MT−×MT− crosses. These data revealed an underlying asymmetry in the two MT haplotypes and suggest that sequence rearrangements are insufficient to fully account for recombination suppression. Together our findings reveal new evolutionary dynamics for mating loci and have implications for the evolution of heteromorphic sex chromosomes and other non-recombining genomic regions. Sex chromosomes and mating-type loci are often atypical in their structure and evolutionary dynamics. One distinguishing feature is the absence of recombination that results in genetic isolation and promotes rapid evolution and sometimes degeneration. We investigated gene content, sex-regulated expression, and recombination of mating locus (MT) genes in the unicellular alga Chlamydomonas reinhardtii. Despite the lack of observable recombination in and around Chlamydomonas MT, genes from its two mating types are far more similar to each other than expected for a non-recombining region. This discrepancy is explained by our finding evidence of genetic exchange between the two mating types within wild populations. In addition, we observed an unexpected asymmetry in the recombination behavior of the two mating types that may have contributed to the preferential expansion of one MT haplotype over the other through insertion of new genes. Our data suggest a mechanism to explain the emergence of heteromorphic sex chromosomes in haploid organisms by asymmetric expansion rather than by loss or degeneration as occurs in some Y or W chromosomes from diploid organisms. Our observations support a revised view of recombination in sex-determining regions as a quantitative phenomenon that can significantly affect rates of evolution and sex-linked genetic diversification.
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47
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Gioti A, Stajich JE, Johannesson H. Neurospora and the dead-end hypothesis: genomic consequences of selfing in the model genus. Evolution 2013; 67:3600-16. [PMID: 24299411 DOI: 10.1111/evo.12206] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/31/2012] [Accepted: 06/24/2013] [Indexed: 12/24/2022]
Abstract
It is becoming increasingly evident that adoption of different reproductive strategies, such as sexual selfing and asexuality, greatly impacts genome evolution. In this study, we test theoretical predictions on genomic maladaptation of selfing lineages using empirical data from the model fungus Neurospora. We sequenced the genomes of four species representing distinct transitions to selfing within the history of the genus, as well as the transcriptome of one of these, and compared with available data from three outcrossing species. Our results provide evidence for a relaxation of purifying selection in protein-coding genes and for a reduced efficiency of transposable element silencing by Repeat Induced Point mutation. A reduction in adaptive evolution was also identified in the form of reduced codon usage bias in highly expressed genes of selfing Neurospora, but this result may be confounded by mutational bias. Potentially counteracting these negative effects, the nucleotide substitution rate and the spread of transposons is reduced in selfing species. We suggest that differences in substitution rate relate to the absence, in selfing Neurospora, of the asexual pathway producing conidia. Our results support the dead-end theory and show that Neurospora genomes bear signatures of both sexual and asexual reproductive mode.
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Affiliation(s)
- Anastasia Gioti
- Department of Evolutionary Biology, Uppsala University, Norbyvägen 18D, 752 36 Uppsala, Sweden.
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Samils N, Gioti A, Karlsson M, Sun Y, Kasuga T, Bastiaans E, Wang Z, Li N, Townsend JP, Johannesson H. Sex-linked transcriptional divergence in the hermaphrodite fungus Neurospora tetrasperma. Proc Biol Sci 2013; 280:20130862. [PMID: 23782882 PMCID: PMC3712418 DOI: 10.1098/rspb.2013.0862] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
In the filamentous ascomycete Neurospora tetrasperma, a large (approx. 7 Mbp) region of suppressed recombination surrounds the mating-type (mat) locus. While the remainder of the genome is largely homoallelic, this region of recombinational suppression, extending over 1500 genes, is associated with sequence divergence. Here, we used microarrays to examine how the molecular phenotype of gene expression level is linked to this divergent region, and thus to the mating type. Culturing N. tetrasperma on agar media that induce sexual/female or vegetative/male tissue, we found 196 genes significantly differentially expressed between mat A and mat a mating types. Our data show that the genes exhibiting mat-linked expression are enriched in the region genetically linked to mating type, and sequence and expression divergence are positively correlated. Our results indicate that the phenotype of mat A strains is optimized for traits promoting sexual/female development and the phenotype of mat a strains for vegetative/male development. This discovery of differentially expressed genes associated with mating type provides a link between genotypic and phenotypic divergence in this taxon and illustrates a fungal analogue to sexual dimorphism found among animals and plants.
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Affiliation(s)
- Nicklas Samils
- Department of Forest Mycology and Plant Pathology, Swedish University of Agricultural Sciences, PO Box 7026, 75007 Uppsala, Sweden
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Abstract
Trimethylated lysine 27 on histone H3 (H3K27me3) is present in Drosophila, Arabidopsis, worms, and mammals, but is absent from yeasts that have been examined. We identified and analyzed H3K27me3 in the filamentous fungus Neurospora crassa and in other Neurospora species. H3K27me3 covers 6.8% of the N. crassa genome, encompassing 223 domains, including 774 genes, all of which are transcriptionally silent. N. crassa H3K27me3-marked genes are less conserved than unmarked genes and only ∼35% of genes marked by H3K27me3 in N. crassa are also H3K27me3-marked in Neurospora discreta and Neurospora tetrasperma. We found that three components of the Neurospora Polycomb repressive complex 2 (PRC2)--[Su-(var)3-9; E(z); Trithorax] (SET)-7, embryonic ectoderm development (EED), and SU(Z)12 (suppressor of zeste12)--are required for H3K27me3, whereas the fourth component, Neurospora protein 55 (an N. crassa homolog of p55/RbAp48), is critical for H3K27me3 only at subtelomeric domains. Loss of H3K27me3, caused by deletion of the gene encoding the catalytic PRC2 subunit, set-7, resulted in up-regulation of 130 genes, including genes in both H3K27me3-marked and unmarked regions.
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50
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Abstract
It is now well established that plants have an important place in studies of sex chromosome evolution because of the repeated independent evolution of separate sexes and sex chromosomes. There has been considerable recent progress in studying plant sex chromosomes. In this review, I focus on how these recent studies have helped clarify or answer several important questions about sex chromosome evolution, and I shall also try to clarify some common misconceptions. I also outline future work that will be needed to make further progress, including testing some important ideas by genetic, molecular, and developmental approaches. Systems with different ages can clearly help show the time course of events during changes from an ancestral co-sexual state (hermaphroditism or monoecy), and I will also explain how different questions can be studied in lineages whose dioecy or sex chromosomes evolved at different times in the past.
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Affiliation(s)
- Deborah Charlesworth
- Institute of Evolutionary Biology, School of Biological Sciences, The University of Edinburgh, The King's Buildings, West Mains Road, Edinburgh EH9 3JT, UK.
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