1
|
Aanen DK, van ’t Padje A, Auxier B. Longevity of Fungal Mycelia and Nuclear Quality Checks: a New Hypothesis for the Role of Clamp Connections in Dikaryons. Microbiol Mol Biol Rev 2023; 87:e0002221. [PMID: 37409939 PMCID: PMC10521366 DOI: 10.1128/mmbr.00022-21] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 07/07/2023] Open
Abstract
This paper addresses the stability of mycelial growth in fungi and differences between ascomycetes and basidiomycetes. Starting with general evolutionary theories of multicellularity and the role of sex, we then discuss individuality in fungi. Recent research has demonstrated the deleterious consequences of nucleus-level selection in fungal mycelia, favoring cheaters with a nucleus-level benefit during spore formation but a negative effect on mycelium-level fitness. Cheaters appear to generally be loss-of-fusion (LOF) mutants, with a higher propensity to form aerial hyphae developing into asexual spores. Since LOF mutants rely on heterokaryosis with wild-type nuclei, we argue that regular single-spore bottlenecks can efficiently select against such cheater mutants. We then zoom in on ecological differences between ascomycetes being typically fast-growing but short-lived with frequent asexual-spore bottlenecks and basidiomycetes being generally slow-growing but long-lived and usually without asexual-spore bottlenecks. We argue that these life history differences have coevolved with stricter nuclear quality checks in basidiomycetes. Specifically, we propose a new function for clamp connections, structures formed during the sexual stage in ascomycetes and basidiomycetes but during somatic growth only in basidiomycete dikaryons. During dikaryon cell division, the two haploid nuclei temporarily enter a monokaryotic phase, by alternatingly entering a retrograde-growing clamp cell, which subsequently fuses with the subapical cell to recover the dikaryotic cell. We hypothesize that clamp connections act as screening devices for nuclear quality, with both nuclei continuously testing each other for fusion ability, a test that LOF mutants will fail. By linking differences in longevity of the mycelial phase to ecology and stringency of nuclear quality checks, we propose that mycelia have a constant and low lifetime cheating risk, irrespective of their size and longevity.
Collapse
Affiliation(s)
- Duur K. Aanen
- Department of Plant Sciences, Laboratory of Genetics, Wageningen University, Wageningen, The Netherlands
| | - Anouk van ’t Padje
- Department of Plant Sciences, Laboratory of Genetics, Wageningen University, Wageningen, The Netherlands
| | - Benjamin Auxier
- Department of Plant Sciences, Laboratory of Genetics, Wageningen University, Wageningen, The Netherlands
| |
Collapse
|
2
|
Auxier B, Czárán TL, Aanen DK. Modelling the consequences of the dikaryotic life cycle of mushroom-forming fungi on genomic conflict. eLife 2022; 11:75917. [PMID: 35441591 PMCID: PMC9084891 DOI: 10.7554/elife.75917] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2021] [Accepted: 04/14/2022] [Indexed: 11/21/2022] Open
Abstract
Generally, sexual organisms contain two haploid genomes, one from each parent, united in a single diploid nucleus of the zygote which links their fate during growth. A fascinating exception to this is Basidiomycete fungi, where the two haploid genomes remain separate in a dikaryon, retaining the option to fertilize subsequent monokaryons encountered. How the ensuing nuclear competition influences the balance of selection within and between individuals is largely unexplored. We test the consequences of the dikaryotic life cycle for mating success and mycelium-level fitness components. We assume a trade-off between mating fitness at the level of the haploid nucleus and fitness of the fungal mycelium. We show that the maintenance of fertilization potential by dikaryons leads to a higher proportion of fertilized monokaryons, but that the ensuing intradikaryon selection for increased nuclear mating fitness leads to reduced mycelium fitness relative to a diploid life cycle. However, this fitness reduction is lower compared to a hypothetical life cycle where dikaryons can also exchange nuclei. Prohibition of fusion between dikaryons therefore reduces the level of nuclear parasitism. The number of loci influencing fitness is an important determinant of the degree to which average mycelium-level fitness is reduced. The results of this study crucially hinge upon a trade-off between nucleus and mycelium-level fitness. We discuss the evidence for this assumption and the implications of an alternative that there is a positive relationship between nucleus and mycelium-level fitness.
Collapse
Affiliation(s)
- Benjamin Auxier
- Laboratory of Genetics, Wageningen University, Wageningen, Netherlands
| | | | - Duur K Aanen
- Laboratory of Genetics, Wageningen University, Wageningen, Netherlands
| |
Collapse
|
3
|
van de Peppel LJJ, Nieuwenhuis M, Auxier B, Grum-Grzhimaylo AA, Cárdenas ME, de Beer ZW, Lodge DJ, Smith ME, Kuyper TW, Franco-Molano AE, Baroni TJ, Aanen DK. Ancestral predisposition toward a domesticated lifestyle in the termite-cultivated fungus Termitomyces. Curr Biol 2021; 31:4413-4421.e5. [PMID: 34403645 DOI: 10.1016/j.cub.2021.07.070] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2021] [Revised: 06/22/2021] [Accepted: 07/27/2021] [Indexed: 10/20/2022]
Abstract
The ancestor of termites relied on gut symbionts for degradation of plant material, an association that persists in all termite families.1,2 However, the single-lineage Macrotermitinae has additionally acquired a fungal symbiont that complements digestion of food outside the termite gut.3 Phylogenetic analysis has shown that fungi grown by these termites form a clade-the genus Termitomyces-but the events leading toward domestication remain unclear.4 To address this, we reconstructed the lifestyle of the common ancestor of Termitomyces using a combination of ecological data with a phylogenomic analysis of 21 related non-domesticated species and 25 species of Termitomyces. We show that the closely related genera Blastosporella and Arthromyces also contain insect-associated species. Furthermore, the genus Arthromyces produces asexual spores on the mycelium, which may facilitate insect dispersal when growing on aggregated subterranean fecal pellets of a plant-feeding insect. The sister-group relationship between Arthromyces and Termitomyces implies that insect association and asexual sporulation, present in both genera, preceded the domestication of Termitomyces and did not follow domestication as has been proposed previously. Specialization of the common ancestor of these two genera on an insect-fecal substrate is further supported by similar carbohydrate-degrading profiles between Arthromyces and Termitomyces. We describe a set of traits that may have predisposed the ancestor of Termitomyces toward domestication, with each trait found scattered in related taxa outside of the termite-domesticated clade. This pattern indicates that the origin of the termite-fungus symbiosis may not have required large-scale changes of the fungal partner.
Collapse
Affiliation(s)
- Lennart J J van de Peppel
- Laboratory of Genetics, Wageningen University & Research, Droevendaalsesteeg 1, 6708PB Wageningen, the Netherlands.
| | - Mathijs Nieuwenhuis
- Laboratory of Genetics, Wageningen University & Research, Droevendaalsesteeg 1, 6708PB Wageningen, the Netherlands
| | - Benjamin Auxier
- Laboratory of Genetics, Wageningen University & Research, Droevendaalsesteeg 1, 6708PB Wageningen, the Netherlands
| | - Alexey A Grum-Grzhimaylo
- Microbial Ecology Department, Netherlands Institute of Ecology (NIOO-KNAW), Droevendaalsesteeg 10, 6708 PB Wageningen, the Netherlands
| | - Martha E Cárdenas
- Laboratorio de Micología y Fitopatología-LAMFU, Universidad de Los Andes, Carrera 1 # 10A-12, Bogotá, Colombia
| | - Z Wilhelm de Beer
- Department of Biochemistry, Genetics and Microbiology, Forestry and Agricultural Biotechnology Institute (FABI), University of Pretoria, Pretoria, South Africa
| | - D Jean Lodge
- Department of Plant Pathology, 2105 Miller Plant Sciences Building, University of Georgia, Athens, GA 30606, USA
| | - Matthew E Smith
- Department of Plant Pathology, University of Florida, Gainesville, FL 32611, USA
| | - Thomas W Kuyper
- Soil Biology Group, Wageningen University & Research, Box 47, 6700AA Wageningen, the Netherlands
| | - Ana E Franco-Molano
- Laboratorio de Taxonomía y Ecología de Hongos (TEHO), Instituto de Biología, Facultad de Ciencias Exactas y Naturales, Universidad de Antioquia UdeA, Calle 70 No. 52-21, Medellín, Colombia
| | - Timothy J Baroni
- Department of Biological Sciences, State University of New York, College at Cortland, PO Box 2000, Cortland, NY 13045, USA
| | - Duur K Aanen
- Laboratory of Genetics, Wageningen University & Research, Droevendaalsesteeg 1, 6708PB Wageningen, the Netherlands.
| |
Collapse
|
4
|
Auxier B, Bazzicalupo A. Comment on 'Single nucleus sequencing reveals evidence of inter-nucleus recombination in arbuscular mycorrhizal fungi'. eLife 2019; 8:e47301. [PMID: 31650958 PMCID: PMC6814362 DOI: 10.7554/elife.47301] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/09/2019] [Accepted: 10/09/2019] [Indexed: 01/02/2023] Open
Abstract
Chen et al. recently reported evidence for inter-nucleus recombination in arbuscular mycorrhizal fungi (Chen et al., 2018a). Here, we report a reanalysis of their data. After filtering the data by excluding heterozygous sites in haploid nuclei, duplicated regions of the genome, and low-coverage depths base calls, we find the evidence for recombination to be very sparse.
Collapse
Affiliation(s)
- Benjamin Auxier
- Laboratory of GeneticsWageningen UniversityWageningenNetherlands
| | - Anna Bazzicalupo
- Department of Microbiology and ImmunologyMontana State UniversityBozemanUnited States
| |
Collapse
|
5
|
Auxier B, Dee J, Berbee ML, Momany M. Diversity of opisthokont septin proteins reveals structural constraints and conserved motifs. BMC Evol Biol 2019; 19:4. [PMID: 30616529 PMCID: PMC6323724 DOI: 10.1186/s12862-018-1297-8] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2018] [Accepted: 11/19/2018] [Indexed: 01/22/2023] Open
Abstract
BACKGROUND Septins are cytoskeletal proteins important in cell division and in establishing and maintaining cell polarity. Although septins are found in various eukaryotes, septin genes had the richest history of duplication and diversification in the animals, fungi and protists that comprise opisthokonts. Opisthokont septin paralogs encode modular proteins that assemble into heteropolymeric higher order structures. The heteropolymers can create physical barriers to diffusion or serve as scaffolds organizing other morphogenetic proteins. How the paralogous septin modules interact to form heteropolymers is still unclear. Through comparative analyses, we hoped to clarify the evolutionary origin of septin diversity and to suggest which amino acid residues were responsible for subunit binding specificity. RESULTS Here we take advantage of newly sequenced genomes to reconcile septin gene trees with a species phylogeny from 22 animals, fungi and protists. Our phylogenetic analysis divided 120 septins representing the 22 taxa into seven clades (Groups) of paralogs. Suggesting that septin genes duplicated early in opisthokont evolution, animal and fungal lineages share septin Groups 1A, 4 and possibly also 1B and 2. Group 5 septins were present in fungi but not in animals and whether they were present in the opisthokont ancestor was unclear. Protein homology folding showed that previously identified conserved septin motifs were all located near interface regions between the adjacent septin monomers. We found specific interface residues associated with each septin Group that are candidates for providing subunit binding specificity. CONCLUSIONS This work reveals that duplication of septin genes began in an ancestral opisthokont more than a billion years ago and continued through the diversification of animals and fungi. Evidence for evolutionary conservation of ~ 49 interface residues will inform mutagenesis experiments and lead to improved understanding of the rules guiding septin heteropolymer formation and from there, to improved understanding of development of form in animals and fungi.
Collapse
Affiliation(s)
- Benjamin Auxier
- Department of Botany, University of British Columbia, Vancouver, Canada
- current address: Laboratory of Genetics, Wageningen University and Research, P.O. Box 16, 6700AA, Wageningen, The Netherlands
| | - Jaclyn Dee
- Department of Botany, University of British Columbia, Vancouver, Canada
| | - Mary L. Berbee
- Department of Botany, University of British Columbia, Vancouver, Canada
| | - Michelle Momany
- Fungal Biology Group and Plant Biology Department, University of Georgia, Athens, USA
| |
Collapse
|