1
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Henshaw JM, Bittlingmaier M, Schärer L. Hermaphroditic origins of anisogamy. Philos Trans R Soc Lond B Biol Sci 2023; 378:20220283. [PMID: 36934747 PMCID: PMC10024982 DOI: 10.1098/rstb.2022.0283] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2022] [Accepted: 11/23/2022] [Indexed: 03/21/2023] Open
Abstract
Anisogamy-the size dimorphism of gametes-is the defining difference between the male and female sexual strategies. Game-theoretic thinking led to the first convincing explanation for the evolutionary origins of anisogamy in the 1970s. Since then, formal game-theoretic models have continued to refine our understanding of when and why anisogamy should evolve. Such models typically presume that the earliest anisogamous organisms had separate sexes. However, in most taxa, there is no empirical evidence to support this assumption. Here, we present a model of the coevolution of gamete size and sex allocation, which allows for anisogamy to emerge alongside either hermaphroditism or separate sexes. We show that hermaphroditic anisogamy can evolve directly from isogamous ancestors when the average size of spawning groups is small and fertilization is relatively efficient. Sex allocation under hermaphroditism becomes increasingly female-biased as group size decreases and the degree of anisogamy increases. When spawning groups are very small, our model also predicts the existence of complex isogamous organisms in which individuals allocate resources equally to two large gamete types. We discuss common, but potentially unwarranted, assumptions in the literature that could be relaxed in future models. This article is part of the theme issue 'Half a century of evolutionary games: a synthesis of theory, application and future directions'.
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Affiliation(s)
- Jonathan M. Henshaw
- Institute of Biology I, University of Freiburg, Hauptstraße 1, D-79104 Freiburg, Germany
| | - Markus Bittlingmaier
- Institute of Biology I, University of Freiburg, Hauptstraße 1, D-79104 Freiburg, Germany
- Theoretical and Experimental Ecology Station, CNRS, 2 route du CNRS, 09200 Moulis, France
| | - Lukas Schärer
- Zoological Institute, Department of Environmental Sciences, University of Basel, Basel CH-4051, Switzerland
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2
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da Silva VS, Machado CR. Sex in protists: A new perspective on the reproduction mechanisms of trypanosomatids. Genet Mol Biol 2022; 45:e20220065. [PMID: 36218381 PMCID: PMC9552303 DOI: 10.1590/1678-4685-gmb-2022-0065] [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] [Received: 02/28/2022] [Accepted: 08/07/2022] [Indexed: 11/04/2022] Open
Abstract
The Protist kingdom individuals are the most ancestral representatives of
eukaryotes. They have inhabited Earth since ancient times and are currently
found in the most diverse environments presenting a great heterogeneity of life
forms. The unicellular and multicellular algae, photosynthetic and heterotrophic
organisms, as well as free-living and pathogenic protozoa represents the protist
group. The evolution of sex is directly associated with the origin of eukaryotes
being protists the earliest protagonists of sexual reproduction on earth. In
eukaryotes, the recombination through genetic exchange is a ubiquitous mechanism
that can be stimulated by DNA damage. Scientific evidences support the
hypothesis that reactive oxygen species (ROS) induced DNA damage can promote
sexual recombination in eukaryotes which might have been a decisive factor for
the origin of sex. The fact that some recombination enzymes also participate in
meiotic sex in modern eukaryotes reinforces the idea that sexual reproduction
emerged as consequence of specific mechanisms to cope with mutations and
alterations in genetic material. In this review we will discuss about origin of
sex and different strategies of evolve sexual reproduction in some protists such
that cause human diseases like malaria, toxoplasmosis, sleeping sickness, Chagas
disease, and leishmaniasis.
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Affiliation(s)
- Verônica Santana da Silva
- Universidade Federal de Minas Gerais, Departamento de Genética,
Ecologia e Evolução, Belo Horizonte, MG, Brazil
| | - Carlos Renato Machado
- Universidade Federal de Minas Gerais, Departamento de Bioquímica e
Imunologia, Belo Horizonte, MG, Brazil
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3
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Benites LF, Bucchini F, Sanchez-Brosseau S, Grimsley N, Vandepoele K, Piganeau G. Evolutionary Genomics of Sex-Related Chromosomes at the Base of the Green Lineage. Genome Biol Evol 2021; 13:6380139. [PMID: 34599324 PMCID: PMC8557840 DOI: 10.1093/gbe/evab216] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 09/11/2021] [Indexed: 12/11/2022] Open
Abstract
Although sex is now accepted as a ubiquitous and ancestral feature of eukaryotes, direct observation of sex is still lacking in most unicellular eukaryotic lineages. Evidence of sex is frequently indirect and inferred from the identification of genes involved in meiosis from whole genome data and/or the detection of recombination signatures from genetic diversity in natural populations. In haploid unicellular eukaryotes, sex-related chromosomes are named mating-type (MTs) chromosomes and generally carry large genomic regions where recombination is suppressed. These regions have been characterized in Fungi and Chlorophyta and determine gamete compatibility and fusion. Two candidate MT+ and MT− alleles, spanning 450–650 kb, have recently been described in Ostreococcus tauri, a marine phytoplanktonic alga from the Mamiellophyceae class, an early diverging branch in the green lineage. Here, we investigate the architecture and evolution of these candidate MT+ and MT− alleles. We analyzed the phylogenetic profile and GC content of MT gene families in eight different genomes whose divergence has been previously estimated at up to 640 Myr, and found evidence that the divergence of the two MT alleles predates speciation in the Ostreococcus genus. Phylogenetic profiles of MT trans-specific polymorphisms in gametologs disclosed candidate MTs in two additional species, and possibly a third. These Mamiellales MT candidates are likely to be the oldest mating-type loci described to date, which makes them fascinating models to investigate the evolutionary mechanisms of haploid sex determination in eukaryotes.
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Affiliation(s)
- Luis Felipe Benites
- Integrative Biology of Marine Organisms (BIOM), Sorbonne University, CNRS, Oceanological Observatory of Banyuls, Banyuls-sur-Mer, France
| | - François Bucchini
- Department of Plant Biotechnology and Bioinformatics, Ghent University, Belgium.,VIB Center for Plant Systems Biology, Ghent, Belgium
| | - Sophie Sanchez-Brosseau
- Integrative Biology of Marine Organisms (BIOM), Sorbonne University, CNRS, Oceanological Observatory of Banyuls, Banyuls-sur-Mer, France
| | - Nigel Grimsley
- Integrative Biology of Marine Organisms (BIOM), Sorbonne University, CNRS, Oceanological Observatory of Banyuls, Banyuls-sur-Mer, France
| | - Klaas Vandepoele
- Department of Plant Biotechnology and Bioinformatics, Ghent University, Belgium.,VIB Center for Plant Systems Biology, Ghent, Belgium.,Bioinformatics Institute Ghent, Ghent University, Belgium
| | - Gwenaël Piganeau
- Integrative Biology of Marine Organisms (BIOM), Sorbonne University, CNRS, Oceanological Observatory of Banyuls, Banyuls-sur-Mer, France
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4
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Anders A, Colin R, Banderas A, Sourjik V. Asymmetric mating behavior of isogamous budding yeast. SCIENCE ADVANCES 2021; 7:7/24/eabf8404. [PMID: 34117059 PMCID: PMC8195471 DOI: 10.1126/sciadv.abf8404] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/24/2020] [Accepted: 04/28/2021] [Indexed: 05/12/2023]
Abstract
Anisogamy, the size difference between small male and large female gametes, is known to enable selection for sexual dimorphism and behavioral differences between sexes. Nevertheless, even isogamous species exhibit molecular asymmetries between mating types, which are known to ensure their self-incompatibility. Here, we show that different properties of the pheromones secreted by the MATa and MATα mating types of budding yeast lead to asymmetry in their behavioral responses during mating in mixed haploid populations, which resemble behavioral asymmetries between gametes in anisogamous organisms. MATa behaves as a random searcher that is stimulated in proportion to the fraction of MATα partner cells within the population, whereas MATα behaves as a short-range directional distance sensor. Mathematical modeling suggests that the observed asymmetric responses can enhance efficiency of mating and might thus provide a selective advantage. Our results demonstrate that the emergence of asymmetric mating behavior did not require anisogamy-based sexual selection.
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Affiliation(s)
- Alexander Anders
- Max Planck Institute for Terrestrial Microbiology, Marburg, Germany
- LOEWE Research Center for Synthetic Microbiology (SYNMIKRO), Marburg, Germany
| | - Remy Colin
- Max Planck Institute for Terrestrial Microbiology, Marburg, Germany
- LOEWE Research Center for Synthetic Microbiology (SYNMIKRO), Marburg, Germany
| | - Alvaro Banderas
- Max Planck Institute for Terrestrial Microbiology, Marburg, Germany.
- Laboratoire Physico Chimie Curie, CNRS UMR168, Institut Curie, Paris, France
| | - Victor Sourjik
- Max Planck Institute for Terrestrial Microbiology, Marburg, Germany.
- LOEWE Research Center for Synthetic Microbiology (SYNMIKRO), Marburg, Germany
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5
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Sawka-Gądek N, Potekhin A, Singh DP, Grevtseva I, Arnaiz O, Penel S, Sperling L, Tarcz S, Duret L, Nekrasova I, Meyer E. Evolutionary Plasticity of Mating-Type Determination Mechanisms in Paramecium aurelia Sibling Species. Genome Biol Evol 2021; 13:evaa258. [PMID: 33313646 PMCID: PMC7900874 DOI: 10.1093/gbe/evaa258] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 12/09/2020] [Indexed: 12/15/2022] Open
Abstract
The Paramecium aurelia complex, a group of morphologically similar but sexually incompatible sibling species, is a unique example of the evolutionary plasticity of mating-type systems. Each species has two mating types, O (Odd) and E (Even). Although O and E types are homologous in all species, three different modes of determination and inheritance have been described: genetic determination by Mendelian alleles, stochastic developmental determination, and maternally inherited developmental determination. Previous work in three species of the latter kind has revealed the key roles of the E-specific transmembrane protein mtA and its highly specific transcription factor mtB: type O clones are produced by maternally inherited genome rearrangements that inactivate either mtA or mtB during development. Here we show, through transcriptome analyses in five additional species representing the three determination systems, that mtA expression specifies type E in all cases. We further show that the Mendelian system depends on functional and nonfunctional mtA alleles, and identify novel developmental rearrangements in mtA and mtB which now explain all cases of maternally inherited mating-type determination. Epistasis between these genes likely evolved from less specific interactions between paralogs in the P. aurelia common ancestor, after a whole-genome duplication, but the mtB gene was subsequently lost in three P. aurelia species which appear to have returned to an ancestral regulation mechanism. These results suggest a model accounting for evolutionary transitions between determination systems, and highlight the diversity of molecular solutions explored among sibling species to maintain an essential mating-type polymorphism in cell populations.
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Affiliation(s)
- Natalia Sawka-Gądek
- Institute of Systematics and Evolution of Animals, Polish Academy of Sciences, Kraków, Poland
| | - Alexey Potekhin
- Department of Microbiology, Faculty of Biology, Saint Petersburg State University, Saint Petersburg, Russia
| | - Deepankar Pratap Singh
- Institut de Biologie de l'Ecole Normale Supérieure (IBENS), Ecole Normale Supérieure, CNRS, INSERM, Université PSL, Paris, France
| | - Inessa Grevtseva
- Department of Microbiology, Faculty of Biology, Saint Petersburg State University, Saint Petersburg, Russia
| | - Olivier Arnaiz
- CEA, CNRS, Institute for Integrative Biology of the Cell (I2BC), Université Paris-Saclay, Gif-sur-Yvette, France
| | - Simon Penel
- CNRS, Laboratoire de Biométrie et Biologie Evolutive UMR 5558, Université de Lyon, Villeurbanne, France
| | - Linda Sperling
- CEA, CNRS, Institute for Integrative Biology of the Cell (I2BC), Université Paris-Saclay, Gif-sur-Yvette, France
| | - Sebastian Tarcz
- Institute of Systematics and Evolution of Animals, Polish Academy of Sciences, Kraków, Poland
| | - Laurent Duret
- CNRS, Laboratoire de Biométrie et Biologie Evolutive UMR 5558, Université de Lyon, Villeurbanne, France
| | - Irina Nekrasova
- Department of Microbiology, Faculty of Biology, Saint Petersburg State University, Saint Petersburg, Russia
| | - Eric Meyer
- Institut de Biologie de l'Ecole Normale Supérieure (IBENS), Ecole Normale Supérieure, CNRS, INSERM, Université PSL, Paris, France
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6
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Seveno J, Even Y, Le Gac M. Strong constitutive expression divergence among strains but no evidence of differential expression associated with sexual reproduction in Alexandrium minutum. HARMFUL ALGAE 2020; 100:101940. [PMID: 33298362 DOI: 10.1016/j.hal.2020.101940] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/30/2020] [Revised: 10/16/2020] [Accepted: 11/01/2020] [Indexed: 06/12/2023]
Abstract
Sexual reproduction remains poorly characterized in dinoflagellates. This is especially the case at the molecular level. Here crossing experiments were performed among strains of the toxic dinoflagellate Alexandrium minutum belonging to two genetically divergent groups. Gene expression was compared between sexually compatible and incompatible crosses at the time of gamete fusion and resting cyst (~zygote) formation. Not a single transcript was identified as differentially expressed between compatible and incompatible crosses at these two crucial time points of the dinoflagellate life cycle. However, several thousands of transcripts displayed constitutive expression differences between strains. This was especially the case between the strains belonging to the genetically divergent groups. A few hundreds of transcripts were also identified as differentially expressed between strains belonging to opposite mating types. Some of these transcripts displayed homology with the SxtA protein, known to be involved in saxitoxin production in cyanobacteria, as well as with proteins potentially involved in mating in fungi.
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Affiliation(s)
- Julie Seveno
- Ifremer, DYNECO PELAGOS, 29280 Plouzané, France; Laboratoire Mer Molécule Santé, Le Mans Université, 72000 Le Mans, France
| | - Yasmine Even
- Laboratoire des Sciences de l'Environnement Marin, UMR 6539 CNRS/UBO - Institut Universitaire Européen de la Mer, Technopôle Brest-Iroise, 29280 Plouzané, France
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7
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Krumbeck Y, Constable GWA, Rogers T. Fitness differences suppress the number of mating types in evolving isogamous species. ROYAL SOCIETY OPEN SCIENCE 2020; 7:192126. [PMID: 32257356 PMCID: PMC7062084 DOI: 10.1098/rsos.192126] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 12/13/2019] [Accepted: 01/31/2020] [Indexed: 06/11/2023]
Abstract
Sexual reproduction is not always synonymous with the existence of two morphologically different sexes; isogamous species produce sex cells of equal size, typically falling into multiple distinct self-incompatible classes, termed mating types. A long-standing open question in evolutionary biology is: what governs the number of these mating types across species? Simple theoretical arguments imply an advantage to rare types, suggesting the number of types should grow consistently; however, empirical observations are very different. While some isogamous species exhibit thousands of mating types, such species are exceedingly rare, and most have fewer than 10. In this paper, we present a mathematical analysis to quantify the role of fitness variation-characterized by different mortality rates-in determining the number of mating types emerging in simple evolutionary models. We predict that the number of mating types decreases as the variance of mortality increases.
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Affiliation(s)
- Yvonne Krumbeck
- Department of Mathematical Sciences, University of Bath, Bath BA2 7AY, UK
| | | | - Tim Rogers
- Department of Mathematical Sciences, University of Bath, Bath BA2 7AY, UK
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8
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Czuppon P, Constable GWA. Invasion and Extinction Dynamics of Mating Types Under Facultative Sexual Reproduction. Genetics 2019; 213:567-580. [PMID: 31391266 PMCID: PMC6781889 DOI: 10.1534/genetics.119.302306] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/09/2019] [Accepted: 08/04/2019] [Indexed: 01/08/2023] Open
Abstract
In sexually reproducing isogamous species, syngamy between gametes is generally not indiscriminate, but rather restricted to occurring between complementary self-incompatible mating types. A longstanding question regards the evolutionary pressures that control the number of mating types observed in natural populations, which ranges from two to many thousands. Here, we describe a population genetic null model of this reproductive system, and derive expressions for the stationary probability distribution of the number of mating types, the establishment probability of a newly arising mating type, and the mean time to extinction of a resident type. Our results yield that the average rate of sexual reproduction in a population correlates positively with the expected number of mating types observed. We further show that the low number of mating types predicted in the rare-sex regime is primarily driven by low invasion probabilities of new mating type alleles, with established resident alleles being very stable over long evolutionary periods. Moreover, our model naturally exhibits varying selection strength dependent on the number of resident mating types. This results in higher extinction and lower invasion rates for an increasing number of residents.
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Affiliation(s)
- Peter Czuppon
- Center for Interdisciplinary Research in Biology, CNRS, Collège de France, PSL Research University, 75231 Paris, France
- Institute of Ecology and Environmental Sciences of Paris, Sorbonne Université, UPEC, CNRS, IRD, INRA, 75252 Paris, France
| | - George W A Constable
- Department of Mathematical Sciences, The University of Bath, BA2 7AY, United Kingdom
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9
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Czuppon P, Rogers DW. Evolution of mating types in finite populations: The precarious advantage of being rare. J Evol Biol 2019; 32:1290-1299. [PMID: 31479547 DOI: 10.1111/jeb.13528] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/04/2019] [Revised: 06/28/2019] [Accepted: 08/19/2019] [Indexed: 01/03/2023]
Abstract
Sexually reproducing populations with self-incompatibility bear the cost of limiting potential mates to individuals of a different type. Rare mating types escape this cost since they are unlikely to encounter incompatible partners, leading to the deterministic prediction of continuous invasion by new mutants and an ever-increasing number of types. However, rare types are also at an increased risk of being lost by random drift. Calculating the number of mating types that a population can maintain requires consideration of both the deterministic advantages and the stochastic risks. By comparing the relative importance of selection and drift, we show that a population of size N can maintain a maximum of approximately N1/3 mating types for intermediate population sizes, whereas for large N, we derive a formal estimate. Although the number of mating types in a population is quite stable, the rare-type advantage promotes turnover of types. We derive explicit formulas for both the invasion and turnover probabilities in finite populations.
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Affiliation(s)
- Peter Czuppon
- Department of Evolutionary Theory, Max Planck Institute for Evolutionary Biology, Plön, Germany.,Centre Interdisciplinaire de Recherche en Biologie, CNRS Collège de France, PSL Research University, Paris, France.,Institut d'Ecologie et des Sciences de l'Environnement (IEES), UPEC, CNRS, IRD, INRA, Sorbonne Université, Paris, France
| | - David W Rogers
- Department of Microbial Population Biology, Max Planck Institute for Evolutionary Biology, Plön, Germany
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10
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Vos M, Buckling A, Kuijper B. Sexual Selection in Bacteria? Trends Microbiol 2019; 27:972-981. [PMID: 31493990 DOI: 10.1016/j.tim.2019.07.009] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/07/2019] [Revised: 07/03/2019] [Accepted: 07/24/2019] [Indexed: 01/05/2023]
Abstract
A main mechanism of lateral gene transfer in bacteria is transformation, where cells take up free DNA from the environment which subsequently can be recombined into the genome. Bacteria are also known to actively release DNA into the environment through secretion or lysis, which could aid uptake via transformation. Various evolutionary benefits of DNA uptake and DNA release have been proposed but these have all been framed in the context of natural selection. Here, we interpret bacterial DNA uptake and release in the context of sexual selection theory, which has been central to our understanding of the bewildering diversity of traits associated with sexual reproduction in the eukaryote world but has never been applied to prokaryotes. Specifically, we explore potential scenarios where bacteria releasing DNA into the environment could compete for successful uptake by other cells, or where bacteria could selectively take up DNA to enhance their fitness. We conclude that there is potential for sexual selection to act in bacteria, and that this might in part explain the considerable diversity in transformation-related behaviours.
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Affiliation(s)
- Michiel Vos
- European Centre for Environment and Human Health, University of Exeter Medical School, University of Exeter, Penryn Campus, Penryn, TR10 9FE, UK.
| | - Angus Buckling
- Department of Biosciences, University of Exeter, Penryn Campus, Penryn, TR10 9FE, UK
| | - Bram Kuijper
- Department of Biosciences, University of Exeter, Penryn Campus, Penryn, TR10 9FE, UK
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11
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Hadjivasiliou Z, Pomiankowski A. Evolution of asymmetric gamete signaling and suppressed recombination at the mating type locus. eLife 2019; 8:48239. [PMID: 31464685 PMCID: PMC6715347 DOI: 10.7554/elife.48239] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/07/2019] [Accepted: 07/25/2019] [Indexed: 11/24/2022] Open
Abstract
The two partners required for sexual reproduction are rarely the same. This pattern extends to species which lack sexual dimorphism yet possess self-incompatible gametes determined at mating-type regions of suppressed recombination, likely precursors of sex chromosomes. Here we investigate the role of cellular signaling in the evolution of mating-types. We develop a model of ligand-receptor dynamics, and identify factors that determine the capacity of cells to send and receive signals. The model specifies conditions favoring the evolution of gametes producing ligand and receptor asymmetrically and shows how these are affected by recombination. When the recombination rate evolves, the conditions favoring asymmetric signaling also favor tight linkage of ligand and receptor loci in distinct linkage groups. These results suggest that selection for asymmetric gamete signaling could be the first step in the evolution of non-recombinant mating-type loci, paving the road for the evolution of anisogamy and sexes. Sexual reproduction, from birds to bees, relies on distinct classes of sex cells, known as gametes, fusing together. Most single cell organisms, rather than producing eggs and sperm, have similar sized gametes that fall into distinct ‘mating types’. However, only sex cells belonging to different mating types can fuse together and sexually reproduce. At first glance, it seems illogical that cells from the same mating type cannot reproduce with each other, as this restricts eligible partners within a population and makes finding a mate more difficult. Yet the typical pattern amongst single cell organisms is still two distinct classes of sex cells, just as in birds and bees. How did the obsession with mating between two different types become favored during evolution? One possibility is that cells with different mating types can recognize and communicate with each other more easily. Cells communicate by releasing proteins known as ligands, which bind to specific receptors found on the cell’s surface. Using mathematical modelling, Hadjivasiliou and Pomiankowski showed that natural selection typically favors ‘asymmetric’ signaling, whereby cells evolve to either produce receptor A with ligand B, or have the reverse pattern and produce receptor B with ligand A. These asymmetric mutants are favored because they avoid producing ligands that clog or activate the receptors on their own surface. As a result, different types of cells are better at recognizing each other and mating more quickly. When cells sexually reproduce they exchange genetic material with each other to produce offspring with a combination of genes that differ to their own. However, if the genes coding for ligand and receptor pairs were constantly being ‘swapped’, this could lead to new combinations, and a loss of asymmetric signaling. Hadjivasiliou and Pomiankowski showed that for asymmetric signaling to evolve, natural selection favors the genes encoding these non-compatible ligand and receptor pairs to be closely linked within the genome. This ensures that the mis-matching ligand and receptor are inherited together, preventing cells from producing pairs which can bind to themselves. This study provides an original way to address an evolutionary question which has long puzzled biologists. These findings raise further questions about how gametes evolved to become the sperm and egg, and how factors such as signaling between cells can determine the sex of more complex organisms, such as ourselves.
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Affiliation(s)
- Zena Hadjivasiliou
- Department of Biochemistry, University of Geneva, Geneva, Switzerland.,Centre for Mathematics and Physics in the Life Sciences and Experimental Biology (CoMPLEX), University College London, London, United Kingdom.,Department of Genetics, Evolution and Environment, University College London, London, United Kingdom
| | - Andrew Pomiankowski
- Centre for Mathematics and Physics in the Life Sciences and Experimental Biology (CoMPLEX), University College London, London, United Kingdom.,Department of Genetics, Evolution and Environment, University College London, London, United Kingdom
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12
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Ennos RA, Hu XS. Estimating the number of sexual events per generation in a facultatively sexual haploid population. Heredity (Edinb) 2019; 122:729-741. [PMID: 30531814 PMCID: PMC6781114 DOI: 10.1038/s41437-018-0171-1] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2018] [Revised: 11/22/2018] [Accepted: 11/24/2018] [Indexed: 12/18/2022] Open
Abstract
In populations of facultatively sexual organisms, the proportion of sexually produced offspring contributed to each generation is a critical determinant of their evolutionary potential. However, estimating this parameter in natural populations has proved difficult. Here we develop a population genetic model for estimating the number of sexual events occurring per generation for facultatively sexual haploids possessing a biallelic mating-type locus (e.g., Chlamydomonas, ascomycete fungi). Our model treats the population as two subpopulations possessing opposite mating-type alleles, which exchange genes only when a sexual event takes place. Where mating types are equally abundant, we show that, for a neutral genetic marker, genetic differentiation between mating-type subpopulations is a simple function of the effective population size, the frequency of sexual reproduction, and the recombination fraction between the genetic marker and the mating-type locus. We employ simulations to examine the effects of linkage of markers to the mating-type locus, inequality of mating-type frequencies, mutation rate, and selection on this relationship. Finally, we apply our model to estimate the number of sexual reproduction events per generation in populations of four species of facultatively sexual ascomycete fungi, which have been jointly scored for mating type and a range of polymorphic molecular markers. Relative estimates are in line with expectations based on the known reproductive biology of these species.
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Affiliation(s)
- Richard A Ennos
- Institute of Evolutionary Biology, University of Edinburgh, Ashworth Building, Charlotte Auerbach Road, Edinburgh, EH9 3FL, UK.
| | - Xin-Sheng Hu
- Guangdong Key Laboratory for Innovative Development and Utilization of Forest Plant Germplasm, South China Agricultural University, 510642, Guangdong, China.
- College of Forestry and Landscape Architecture, South China Agricultural University, 510642, Guangdong, China.
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13
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Kutschera U, Hoppe T. Plasmodial slime molds and the evolution of microbial husbandry. Theory Biosci 2019; 138:127-132. [PMID: 30809766 DOI: 10.1007/s12064-019-00285-3] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/05/2018] [Accepted: 01/16/2019] [Indexed: 11/24/2022]
Abstract
Detailed analyses into the life cycle of the soil-dwelling microbe Dictyostelium discoideum led to the conclusion that this "social amoeba" practices some form of "non-monoculture farming" via the transfer of bacteria to novel environments. Herein, we show that in myxomycetes (plasmodial slime molds or myxogastrids) a similar "farming symbiosis" has evolved. Based on laboratory studies of two representative species in the genera Fuligo and Didymium, the sexual life cycle of these enigmatic microbes that feed on bacteria was reconstructed, with reference to plasmo- and karyogamy. We document that the spores carry and transfer bacteria and hence may inoculate new habitats. The significance of this finding with respect to Ernst Haeckel's work on myxomycetes and his concept of ecology are addressed.
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Affiliation(s)
- Ulrich Kutschera
- Institute of Biology, University of Kassel, Heinrich-Plett-Strasse 40, 34132, Kassel, Germany.
| | - Thomas Hoppe
- Museum für Naturkunde, Nicolaiberg 3, 07545, Gera, Germany
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14
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The rate of facultative sex governs the number of expected mating types in isogamous species. Nat Ecol Evol 2018; 2:1168-1175. [DOI: 10.1038/s41559-018-0580-9] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/06/2017] [Accepted: 05/16/2018] [Indexed: 01/30/2023]
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15
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Figueroa RI, Estrada M, Garcés E. Life histories of microalgal species causing harmful blooms: Haploids, diploids and the relevance of benthic stages. HARMFUL ALGAE 2018; 73:44-57. [PMID: 29602506 DOI: 10.1016/j.hal.2018.01.006] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/29/2017] [Revised: 01/18/2018] [Accepted: 01/18/2018] [Indexed: 05/25/2023]
Abstract
In coastal and offshore waters, Harmful Algal Blooms (HABs) currently threaten the well-being of coastal countries. These events, which can be localized or involve wide-ranging areas, pose risks to human health, marine ecosystems, and economic resources, such as tourism, fisheries, and aquaculture. Dynamics of HABs vary from one site to another, depending on the hydrographic and ecological conditions. The challenge in investigating HABs is that they are caused by organisms from multiple algal classes, each with its own unique features, including different life histories. The complete algal life cycle has been determined in <1% of the described species, although elucidation of the life cycles of bloom-forming species is essential in developing preventative measures. The knowledge obtained thus far has confirmed the complexity of the algal life cycle, which is composed of discrete life stages whose morphology, ecological niche (plankton/benthos), function, and lifespan vary. The factors that trigger transitions between the different stages in nature are mostly unknown, but it is clear that an understanding of this process provides the key to effectively forecasting bloom recurrence, maintenance, and decline. Planktonic stages constitute an ephemeral phase of the life cycle of most species whereas resistant, benthic stages enable a species to withstand adverse conditions for prolonged periods, thus providing dormant reservoirs for eventual blooms and facilitating organismal dispersal. Here we review current knowledge of the life cycle strategies of major groups of HAB producers in marine and brackish waters. Rather than providing a comprehensive discussion, the objective was to highlight several of the research milestones that have changed our understanding of the plasticity and frequency of the different life cycle stages as well as the transitions between them. We also discuss the relevance of benthic and planktonic forms and their implications for HAB dynamics.
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Affiliation(s)
- Rosa Isabel Figueroa
- Instituto Español de Oceanografía (IEO), C.O. Vigo, 36280 Vigo, Spain; Aquatic Ecology Division, Department of Biology, Lund University, S-22362 Lund, Sweden.
| | - Marta Estrada
- Departament de Biología Marina i Oceanografía, Institut de Ciències del Mar, Consejo Superior de Investigaciones Científicas (CSIC), Pg. Marítim de la Barceloneta 37-49, 08003 Barcelona, Spain
| | - Esther Garcés
- Departament de Biología Marina i Oceanografía, Institut de Ciències del Mar, Consejo Superior de Investigaciones Científicas (CSIC), Pg. Marítim de la Barceloneta 37-49, 08003 Barcelona, Spain
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16
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Aanen D, Beekman M, Kokko H. Weird sex: the underappreciated diversity of sexual reproduction. Philos Trans R Soc Lond B Biol Sci 2018; 371:rstb.2016.0262. [PMID: 27619706 DOI: 10.1098/rstb.2016.0262] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 07/20/2016] [Indexed: 11/12/2022] Open
Affiliation(s)
- Duur Aanen
- Plant Sciences Group, Laboratory of Genetics, Wageningen University, Wageningen, The Netherlands
| | - Madeleine Beekman
- School of Life and Environmental Sciences, The University of Sydney, Sydney, Australia
| | - Hanna Kokko
- Institute of Evolutionary Biology and Environmental Studies, University of Zurich, Zurich, Switzerland
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17
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Radzvilavicius AL, Lane N, Pomiankowski A. Sexual conflict explains the extraordinary diversity of mechanisms regulating mitochondrial inheritance. BMC Biol 2017; 15:94. [PMID: 29073898 PMCID: PMC5658935 DOI: 10.1186/s12915-017-0437-8] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2017] [Accepted: 10/10/2017] [Indexed: 01/08/2023] Open
Abstract
BACKGROUND Mitochondria are predominantly inherited from the maternal gamete, even in unicellular organisms. Yet an extraordinary array of mechanisms enforce uniparental inheritance, which implies shifting selection pressures and multiple origins. RESULTS We consider how this high turnover in mechanisms controlling uniparental inheritance arises using a novel evolutionary model in which control of mitochondrial transmission occurs either during spermatogenesis (by paternal nuclear genes) or at/after fertilization (by maternal nuclear genes). The model treats paternal leakage as an evolvable trait. Our evolutionary analysis shows that maternal control consistently favours strict uniparental inheritance with complete exclusion of sperm mitochondria, whereas some degree of paternal leakage of mitochondria is an expected outcome under paternal control. This difference arises because mito-nuclear linkage builds up with maternal control, allowing the greater variance created by asymmetric inheritance to boost the efficiency of purifying selection and bring benefits in the long term. In contrast, under paternal control, mito-nuclear linkage tends to be much weaker, giving greater advantage to the mixing of cytotypes, which improves mean fitness in the short term, even though it imposes a fitness cost to both mating types in the long term. CONCLUSIONS Sexual conflict is an inevitable outcome when there is competition between maternal and paternal control of mitochondrial inheritance. If evolution has led to complete uniparental inheritance through maternal control, it creates selective pressure on the paternal nucleus in favour of subversion through paternal leakage, and vice versa. This selective divergence provides a reason for the repeated evolution of novel mechanisms that regulate the transmission of paternal mitochondria, both in the fertilized egg and spermatogenesis. Our analysis suggests that the widespread occurrence of paternal leakage and prevalence of heteroplasmy are natural outcomes of this sexual conflict.
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Affiliation(s)
- Arunas L Radzvilavicius
- Centre for Mathematics and Physics in the Life Sciences and Experimental Biology, University College London, Gower Street, London, WC1E 6BT, UK
- Department of Genetics, Evolution and Environment, University College London, Gower Street, London, WC1E 6BT, UK
- Department of Biology, University of Pennsylvania, Philadelphia, PA, 19104, USA
| | - Nick Lane
- Centre for Mathematics and Physics in the Life Sciences and Experimental Biology, University College London, Gower Street, London, WC1E 6BT, UK
- Department of Genetics, Evolution and Environment, University College London, Gower Street, London, WC1E 6BT, UK
| | - Andrew Pomiankowski
- Centre for Mathematics and Physics in the Life Sciences and Experimental Biology, University College London, Gower Street, London, WC1E 6BT, UK.
- Department of Genetics, Evolution and Environment, University College London, Gower Street, London, WC1E 6BT, UK.
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18
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Brandeis M. New-age ideas about age-old sex: separating meiosis from mating could solve a century-old conundrum. Biol Rev Camb Philos Soc 2017; 93:801-810. [PMID: 28913952 DOI: 10.1111/brv.12367] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/10/2017] [Revised: 08/17/2017] [Accepted: 08/18/2017] [Indexed: 12/01/2022]
Abstract
Ever since Darwin first addressed it, sexual reproduction reigns as the 'queen' of evolutionary questions. Multiple theories tried to explain how this apparently costly and cumbersome method has become the universal mode of eukaryote reproduction. Most theories stress the adaptive advantages of sex by generating variation, they fail however to explain the ubiquitous persistence of sexual reproduction also where adaptation is not an issue. I argue that the obstacle for comprehending the role of sex stems from the conceptual entanglement of two distinct processes - gamete production by meiosis and gamete fusion by mating (mixis). Meiosis is an ancient, highly rigid and evolutionary conserved process identical and ubiquitous in all eukaryotes. Mating, by contrast, shows tremendous evolutionary variability even in closely related clades and exhibits wonderful ecological adaptability. To appreciate the respective roles of these two processes, which are normally linked and alternating, we require cases where one takes place without the other. Such cases are rather common. The heteromorphic sex chromosomes Y and W, that do not undergo meiotic recombination are an evolutionary test case for demonstrating the role of meiosis. Substantial recent genomic evidence highlights the accelerated rates of change and attrition these chromosomes undergo in comparison to those of recombining autosomes. I thus propose that the most basic role of meiosis is conserving integrity of the genome. A reciprocal case of meiosis without bi-parental mating, is presented by self-fertilization, which is fairly common in flowering plants, as well as most types of apomixis. I argue that deconstructing sex into these two distinct processes - meiosis and mating - will greatly facilitate their analysis and promote our understanding of sexual reproduction.
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Affiliation(s)
- Michael Brandeis
- The Department of Genetics, The Alexander Silberman Institute of Life Sciences, The Hebrew University of Jerusalem, Edmond J. Safra Campus, Jerusalem, 9190401, Israel
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19
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Lehtonen J, Kokko H, Parker GA. What do isogamous organisms teach us about sex and the two sexes? Philos Trans R Soc Lond B Biol Sci 2016; 371:20150532. [PMID: 27619696 PMCID: PMC5031617 DOI: 10.1098/rstb.2015.0532] [Citation(s) in RCA: 35] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 06/24/2016] [Indexed: 11/12/2022] Open
Abstract
Isogamy is a reproductive system where all gametes are morphologically similar, especially in terms of size. Its importance goes beyond specific cases: to this day non-anisogamous systems are common outside of multicellular animals and plants, they can be found in all eukaryotic super-groups, and anisogamous organisms appear to have isogamous ancestors. Furthermore, because maleness is synonymous with the production of small gametes, an explanation for the initial origin of males and females is synonymous with understanding the transition from isogamy to anisogamy. As we show here, this transition may also be crucial for understanding why sex itself remains common even in taxa with high costs of male production (the twofold cost of sex). The transition to anisogamy implies the origin of male and female sexes, kickstarts the subsequent evolution of sex roles, and has a major impact on the costliness of sexual reproduction. Finally, we combine some of the consequences of isogamy and anisogamy in a thought experiment on the maintenance of sexual reproduction. We ask what happens if there is a less than twofold benefit to sex (not an unlikely scenario as large short-term benefits have proved difficult to find), and argue that this could lead to a situation where lineages that evolve anisogamy-and thus the highest costs of sex-end up being associated with constraints that make invasion by asexual reproduction unlikely (the 'anisogamy gateway' hypothesis).This article is part of the themed issue 'Weird sex: the underappreciated diversity of sexual reproduction'.
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Affiliation(s)
- Jussi Lehtonen
- Evolution and Ecology Research Centre, School of Biological, Earth and Environmental Sciences, University of New South Wales, Sydney, New South Wales 2052, Australia
| | - Hanna Kokko
- Department of Evolutionary Biology and Environmental Studies, University of Zurich, Winterthurerstrasse 190, 8057 Zurich, Switzerland
| | - Geoff A Parker
- Institute of Integrative Biology, University of Liverpool, Liverpool L69 7ZB, UK
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Hadjivasiliou Z, Pomiankowski A, Kuijper B. The evolution of mating type switching. Evolution 2016; 70:1569-81. [PMID: 27271362 PMCID: PMC5008120 DOI: 10.1111/evo.12959] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/27/2016] [Accepted: 05/09/2016] [Indexed: 01/01/2023]
Abstract
Predictions about the evolution of sex determination mechanisms have mainly focused on animals and plants, whereas unicellular eukaryotes such as fungi and ciliates have received little attention. Many taxa within the latter groups can stochastically switch their mating type identity during vegetative growth. Here, we investigate the hypothesis that mating type switching overcomes distortions in the distribution of mating types due to drift during asexual growth. Using a computational model, we show that smaller population size, longer vegetative periods and more mating types lead to greater distortions in the distribution of mating types. However, the impact of these parameters on optimal switching rates is not straightforward. We find that longer vegetative periods cause reductions and considerable fluctuations in the switching rate over time. Smaller population size increases the strength of selection for switching but has little impact on the switching rate itself. The number of mating types decreases switching rates when gametes can freely sample each other, but increases switching rates when there is selection for speedy mating. We discuss our results in light of empirical work and propose new experiments that could further our understanding of sexuality in isogamous eukaryotes.
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Affiliation(s)
- Zena Hadjivasiliou
- CoMPLEX, Centre for Mathematics and Physics in the Life sciences and Experimental biology, University College London, Gower Street, London, United Kingdom. .,Department of Genetics, Evolution and Environment, University College London, Gower Street, London, United Kingdom.
| | - Andrew Pomiankowski
- CoMPLEX, Centre for Mathematics and Physics in the Life sciences and Experimental biology, University College London, Gower Street, London, United Kingdom.,Department of Genetics, Evolution and Environment, University College London, Gower Street, London, United Kingdom
| | - Bram Kuijper
- CoMPLEX, Centre for Mathematics and Physics in the Life sciences and Experimental biology, University College London, Gower Street, London, United Kingdom.,Department of Genetics, Evolution and Environment, University College London, Gower Street, London, United Kingdom
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