1
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Suzuki S, Yoshida S, Aratani M, Kimura-Kawaguchi MR, Munehara H. A robust system of hybridogenesis that increases genetic variability and promotes evolutionary succession in greenlings (Teleostei: Hexagrammidae, genus Hexagrammos): Regeneration of a new hemiclonal lineage. PLoS One 2024; 19:e0304772. [PMID: 38829848 PMCID: PMC11146738 DOI: 10.1371/journal.pone.0304772] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2024] [Accepted: 05/19/2024] [Indexed: 06/05/2024] Open
Abstract
Unisexual hybrids that reproduce either clonally or hemiclonally are considered to be evolutionarily short-lived as they lack the ability to reduce deleterious mutations and increase genetic diversity. In the greenling (Teleostei: Hexagrammidae, genus Hexagrammos), unisexual hybrids that produce haploid eggs containing only the H. octogrammus (maternal species) genome generate hemiclonal offspring by fertilization with haploid sperm of H. agrammus (paternal species). When hemiclonal hybrids are backcrossed to a male of the maternal species, the offspring (BC-Hoc) are phenotypically similar to the maternal species and produce recombinant gametes through conventional meiosis. BC-Hoc (recombinant generation) individuals referred to as carriers harbor the genetic factor for hybridogenesis, thereby facilitating the production of new hemiclonal lineages through hybridization. Previous studies based on field research have suggested that the carriers produced by two-way backcrossing (mating pattern in which hemiclonal hybrids are backcrossed with both parental species) may overcome the evolutionary dead end imposed by the lack of recombination. The present study verified this hypothesis by regenerating a newly hemiclonal lineage through artificial hybridization. To clarify the genetic mode of hybrids produced by crosses between BC-Hoc and Hag, mature eggs were obtained from 16 individuals and fertilized with either Hag or Hoc sperm. Hybridogenesis was confirmed in one of the 16 individuals. Based on the low occurrence rate, these findings suggest that hemiclonal lineages can be regenerated, and that the hemiclonal factors are likely distributed across multiple genes on different chromosomes. The findings provide important evidence for the retention of a robust system for increasing genetic variability and maintaining evolutionary succession in unisexual hybrids that reproduce hemiclonally.
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Affiliation(s)
- Shota Suzuki
- Graduate School of Environmental Science, Hokkaido University, Sapporo, Japan
- Usujiri Fisheries Station, Field Science Center for Northern Biosphere, Hokkaido University, Hakodate, Japan
| | - Shunsuke Yoshida
- Graduate School of Environmental Science, Hokkaido University, Sapporo, Japan
- Usujiri Fisheries Station, Field Science Center for Northern Biosphere, Hokkaido University, Hakodate, Japan
| | - Misaki Aratani
- Graduate School of Environmental Science, Hokkaido University, Sapporo, Japan
- Usujiri Fisheries Station, Field Science Center for Northern Biosphere, Hokkaido University, Hakodate, Japan
| | - Motoko R. Kimura-Kawaguchi
- Graduate School of Environmental Science, Hokkaido University, Sapporo, Japan
- Usujiri Fisheries Station, Field Science Center for Northern Biosphere, Hokkaido University, Hakodate, Japan
| | - Hiroyuki Munehara
- Usujiri Fisheries Station, Field Science Center for Northern Biosphere, Hokkaido University, Hakodate, Japan
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2
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Lu M, Zhou L, Gui JF. Evolutionary mechanisms and practical significance of reproductive success and clonal diversity in unisexual vertebrate polyploids. SCIENCE CHINA. LIFE SCIENCES 2024; 67:449-459. [PMID: 38198030 DOI: 10.1007/s11427-023-2486-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/04/2023] [Accepted: 11/01/2023] [Indexed: 01/11/2024]
Abstract
Unisexual reproduction is generally relevant to polyploidy, and unisexual vertebrates are often considered an evolutionary "dead end" due to the accumulation of deleterious mutations and absence of genetic diversity. However, some unisexual polyploids have developed strategies to avoid genomic decay, and thus provide ideal models to unveil unexplored evolutionary mechanisms, from the reproductive success to clonal diversity creation. This article reviews the evolutionary mechanisms for overcoming meiotic barrier and generating genetic diversity in unisexual vertebrates, and summarizes recent research advancements in the polyploid Carassius complex. Gynogenetic gibel carp (Carassius gibelio) is a unique amphitriploid that has undergone a recurrent autotriploidy and has overcome the bottleneck of triploid sterility via gynogenesis. Recently, an efficient strategy in which ploidy changes, including from amphitriploid to amphitetraploid, then from amphitetraploid to novel amphitriploid, drive unisexual-sexual-unisexual reproduction transition and clonal diversity has been revealed. Based on this new discovery, multigenomic reconstruction biotechnology has been used to breed a novel strain with superior growth and stronger disease resistance. Moreover, a unique reproduction mode that combines both abilities of ameiotic oogenesis and sperm-egg fusion, termed as ameio-fusiongensis, has been discovered, and it provides an efficient approach to synthesize sterile allopolyploids. In order to avoid ecological risks upon escape and protect the sustainable property rights of the aquaculture seed industry, a controllable fertility biotechnology approach for precise breeding is being developed by integrating sterile allopolyploid synthesis and gene-editing techniques. This review provides novel insights into the origin and evolution of unisexual vertebrates and into the attempts being made to exploit new breeding biotechnologies in aquaculture.
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Affiliation(s)
- Meng Lu
- State Key Laboratory of Freshwater Ecology and Biotechnology, Hubei Hongshan Laboratory, the Innovation Academy of Seed Design, Institute of Hydrobiology, Chinese Academy of Sciences, Wuhan, 430072, China
- University of Chinese Academy of Sciences, Beijing, 100049, China
| | - Li Zhou
- State Key Laboratory of Freshwater Ecology and Biotechnology, Hubei Hongshan Laboratory, the Innovation Academy of Seed Design, Institute of Hydrobiology, Chinese Academy of Sciences, Wuhan, 430072, China.
- University of Chinese Academy of Sciences, Beijing, 100049, China.
| | - Jian-Fang Gui
- State Key Laboratory of Freshwater Ecology and Biotechnology, Hubei Hongshan Laboratory, the Innovation Academy of Seed Design, Institute of Hydrobiology, Chinese Academy of Sciences, Wuhan, 430072, China.
- University of Chinese Academy of Sciences, Beijing, 100049, China.
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3
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Dedukh D, Krasikova A. Delete and survive: strategies of programmed genetic material elimination in eukaryotes. Biol Rev Camb Philos Soc 2022; 97:195-216. [PMID: 34542224 PMCID: PMC9292451 DOI: 10.1111/brv.12796] [Citation(s) in RCA: 22] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/26/2021] [Revised: 08/31/2021] [Accepted: 09/02/2021] [Indexed: 02/06/2023]
Abstract
Genome stability is a crucial feature of eukaryotic organisms because its alteration drastically affects the normal development and survival of cells and the organism as a whole. Nevertheless, some organisms can selectively eliminate part of their genomes from certain cell types during specific stages of ontogenesis. This review aims to describe the phenomenon of programmed DNA elimination, which includes chromatin diminution (together with programmed genome rearrangement or DNA rearrangements), B and sex chromosome elimination, paternal genome elimination, parasitically induced genome elimination, and genome elimination in animal and plant hybrids. During programmed DNA elimination, individual chromosomal fragments, whole chromosomes, and even entire parental genomes can be selectively removed. Programmed DNA elimination occurs independently in different organisms, ranging from ciliate protozoa to mammals. Depending on the sequences destined for exclusion, programmed DNA elimination may serve as a radical mechanism of dosage compensation and inactivation of unnecessary or dangerous genetic entities. In hybrids, genome elimination results from competition between parental genomes. Despite the different consequences of DNA elimination, all genetic material destined for elimination must be first recognised, epigenetically marked, separated, and then removed and degraded.
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Affiliation(s)
- Dmitrij Dedukh
- Saint‐Petersburg State University7/9 Universitetskaya EmbankmentSaint‐Petersburg199034Russia
| | - Alla Krasikova
- Saint‐Petersburg State University7/9 Universitetskaya EmbankmentSaint‐Petersburg199034Russia
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4
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Kuroda M, Shibata K, Fujimoto T, Murakami M, Yamaha E, Arai K. FISH Identifies Chromosome Differentiation Between Contemporary Genomes of Wild Types and the Ancestral Genome of Unisexual Clones of Dojo Loach, Misgurnus anguillicaudatus. Cytogenet Genome Res 2021; 161:178-186. [PMID: 33971659 DOI: 10.1159/000515107] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2020] [Accepted: 02/08/2021] [Indexed: 11/19/2022] Open
Abstract
In dojo loach (Misgurnus anguillicaudatus), although most wild types are gonochoristic diploids that are genetically differentiated into 2 groups, A and B, clonal lineages appear in certain localities. Clonal loaches have been considered to have hybrid origins between the 2 groups by a series of genetic studies. In this study, using FISH with a newly developed probe (ManDra-A), we identified 26 (1 pair of metacentric and 12 pairs of telocentric chromosomes) of 50 diploid chromosomes in contemporary wild-type group A loach. In contrast, ManDra-A signals were not detected on metacentric chromosomes derived from the ancestral group A of clonal loach. The FISH results clearly showed the presence of certain differentiations in metacentric chromosomes between ancestral and contemporary group A loach. Two-color FISH with ManDra-A and group B-specific ManDra (renamed ManDra-B) probes reconfirmed the hybrid origin of clones by identifying chromosomes from both groups A and B in metaphases. Our results showed the hybrid origin of clonally reproducing fish and the possibility that chromosomal differentiation between ancestral and contemporary fish can affect gametogenesis. In meiotic spermatocytes of sex-reversed clones, ManDra-A, and not ManDra-B, signals were detected in 12 out of 50 bivalents. Thus, the results further support the previous conclusion that clonal gametogenesis was assured by pairing between sister chromosomes duplicated from each ancestral chromosome from group A or B. Our study deepens the knowledge about the association between clonality and hybridity in unisexual vertebrates.
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Affiliation(s)
- Masamichi Kuroda
- Faculty of Fisheries Sciences, Hokkaido University, Hakodate, Japan.,Department of Ocean and Fisheries Sciences, Faculty of Bioindustry, Tokyo University of Agriculture, Abashiri, Japan
| | - Kiko Shibata
- Faculty of Fisheries Sciences, Hokkaido University, Hakodate, Japan
| | | | - Masaru Murakami
- School of Veterinary Medicine, Azabu University, Sagamihara, Japan
| | - Etsuro Yamaha
- Nanae Freshwater Station, Field Science Center for Northern Biosphere, Hokkaido University, Nanae, Japan
| | - Katsutoshi Arai
- Faculty of Fisheries Sciences, Hokkaido University, Hakodate, Japan.,Institute for the Advancement of Higher Education, Hokkaido University, Sapporo, Japan
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5
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Majtánová Z, Dedukh D, Choleva L, Adams M, Ráb P, Unmack PJ, Ezaz T. Uniparental Genome Elimination in Australian Carp Gudgeons. Genome Biol Evol 2021; 13:6137838. [PMID: 33591327 PMCID: PMC8245195 DOI: 10.1093/gbe/evab030] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 02/10/2021] [Indexed: 12/15/2022] Open
Abstract
Metazoans usually reproduce sexually, blending the unique identity of parental genomes for the next generation through functional crossing-over and recombination in meiosis. However, some metazoan lineages have evolved reproductive systems where offspring are either full (clonal) or partial (hemiclonal) genetic replicas. In the latter group, the process of uniparental genome elimination selectively eliminates either the maternal or paternal genome from germ cells, and only one parental genome is selected for transmission. Although fairly common in plants, hybridogenesis (i.e., clonal haploidization via chromosome elimination) remains a poorly understood process in animals. Here, we explore the proximal cytogenomic mechanisms of somatic and germ cell chromosomes in sexual and hybrid genotypes of Australian carp gudgeons (Hypseleotris) by tracing the fate of each set during mitosis (in somatic tissues) and meiosis (in gonads). Our comparative study of diploid hybrid and sexual individuals revealed visually functional gonads in male and female hybrid genotypes and generally high karyotype variability, although the number of chromosome arms remains constant. Our results delivered direct evidence for classic hybridogenesis as a reproductive mode in carp gudgeons. Two parental sets with integral structure in the hybrid soma (the F1 constitution) contrasted with uniparental chromosomal inheritance detected in gonads. The inheritance mode happens through premeiotic genome duplication of the parental genome to be transmitted, whereas the second parental genome is likely gradually eliminated already in juvenile individuals. The role of metacentric chromosomes in hybrid evolution is also discussed.
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Affiliation(s)
- Zuzana Majtánová
- Laboratory of Fish Genetics, Institute of Animal Physiology and Genetics, Czech Academy of Sciences, Liběchov, Czech Republic
| | - Dmitrij Dedukh
- Laboratory of Fish Genetics, Institute of Animal Physiology and Genetics, Czech Academy of Sciences, Liběchov, Czech Republic
| | - Lukáš Choleva
- Laboratory of Fish Genetics, Institute of Animal Physiology and Genetics, Czech Academy of Sciences, Liběchov, Czech Republic.,Department of Biology and Ecology, Faculty of Science, University of Ostrava, Ostrava, Czech Republic
| | - Mark Adams
- Evolutionary Biology Unit, South Australian Museum, North Terrace, Adelaide, SA, Australia.,School of Biological Sciences, The University of Adelaide, SA, Australia
| | - Petr Ráb
- Laboratory of Fish Genetics, Institute of Animal Physiology and Genetics, Czech Academy of Sciences, Liběchov, Czech Republic
| | - Peter J Unmack
- Centre for Applied Water Science, Institute for Applied Ecology, University of Canberra, ACT, Australia
| | - Tariq Ezaz
- Centre for Conservation Ecology and Genetics, Institute for Applied Ecology, University of Canberra, ACT, Australia
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6
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Dalziel AC, Tirbhowan S, Drapeau HF, Power C, Jonah LS, Gbotsyo YA, Dion‐Côté A. Using asexual vertebrates to study genome evolution and animal physiology: Banded ( Fundulus diaphanus) x Common Killifish ( F. heteroclitus) hybrid lineages as a model system. Evol Appl 2020; 13:1214-1239. [PMID: 32684956 PMCID: PMC7359844 DOI: 10.1111/eva.12975] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2019] [Revised: 03/12/2020] [Accepted: 03/16/2020] [Indexed: 12/27/2022] Open
Abstract
Wild, asexual, vertebrate hybrids have many characteristics that make them good model systems for studying how genomes evolve and epigenetic modifications influence animal physiology. In particular, the formation of asexual hybrid lineages is a form of reproductive incompatibility, but we know little about the genetic and genomic mechanisms by which this mode of reproductive isolation proceeds in animals. Asexual lineages also provide researchers with the ability to produce genetically identical individuals, enabling the study of autonomous epigenetic modifications without the confounds of genetic variation. Here, we briefly review the cellular and molecular mechanisms leading to asexual reproduction in vertebrates and the known genetic and epigenetic consequences of the loss of sex. We then specifically discuss what is known about asexual lineages of Fundulus diaphanus x F. heteroclitus to highlight gaps in our knowledge of the biology of these clones. Our preliminary studies of F. diaphanus and F. heteroclitus karyotypes from Porter's Lake (Nova Scotia, Canada) agree with data from other populations, suggesting a conserved interspecific chromosomal arrangement. In addition, genetic analyses suggest that: (a) the same major clonal lineage (Clone A) of F. diaphanus x F. heteroclitus has remained dominant over the past decade, (b) some minor clones have also persisted, (c) new clones may have recently formed, and iv) wild clones still mainly descend from F. diaphanus ♀ x F. heteroclitus ♂ crosses (96% in 2017-2018). These data suggest that clone formation may be a relatively rare, but continuous process, and there are persistent environmental or genetic factors causing a bias in cross direction. We end by describing our current research on the genomic causes and consequences of a transition to asexuality and the potential physiological consequences of epigenetic variation.
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Affiliation(s)
| | - Svetlana Tirbhowan
- Department of BiologySaint Mary's UniversityHalifaxNSCanada
- Département de biologieUniversité de MonctonMonctonNBCanada
| | | | - Claude Power
- Département de biologieUniversité de MonctonMonctonNBCanada
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7
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Endoh M, Shima F, Havelka M, Asanuma R, Yamaha E, Fujimoto T, Arai K. Hybrid between Danio rerio female and Danio nigrofasciatus male produces aneuploid sperm with limited fertilization capacity. PLoS One 2020; 15:e0233885. [PMID: 32470029 PMCID: PMC7259755 DOI: 10.1371/journal.pone.0233885] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/05/2020] [Accepted: 05/14/2020] [Indexed: 12/23/2022] Open
Abstract
In the Danio species, interspecific hybridization has been conducted in several combinations. Among them, only the hybrid between a zebrafish (D. rerio) female and a spotted danio (D. nigrofasciatus) male was reported to be fertile. However, beyond these investigations, by means of reproductive biology, gametes of the hybrid have also not been investigated genetically. For this study, we induced a hybrid of the D. rerio female and D. nigrofasciatus male in order to study its developmental capacity, reproductive performance and gametic characteristics. Its hybrid nature was genetically verified by polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) analysis of the rhodopsin gene. Almost all the hybrids (36/37) were males, and only one was female. Developing oocytes were observed in the hybrid female, but ovulated eggs have not been obtained thus far. Microscopic observation revealed various head sizes of sperm in the hybrid males. Flow cytometry showed that the hybrid males generated aneuploid sperm with various ploidy levels up to diploidy. In backcrosses between D. rerio females and hybrid males, fertilization rates were significantly lower than the control D. rerio, and most resultant progeny with abnormal appearance exhibited various kinds of aneuploidies ranging from haploidy to triploidy, but only one viable progeny, which survived more than four months, was triploid. This suggested the contribution of fertile diploid sperm of the hybrid male to successful fertilization and development.
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Affiliation(s)
- Mitsuru Endoh
- Laboratory of Aquaculture Genetics and Genomics, Division of Marine Life Science, Faculty and Graduate School of Fisheries Sciences, Hokkaido University, Hakodate, Hokkaido, Japan
- Research Fellow of Japan Society for the Promotion of Science, Tokyo, Japan
- * E-mail:
| | - Fumika Shima
- Laboratory of Aquaculture Genetics and Genomics, Division of Marine Life Science, Faculty and Graduate School of Fisheries Sciences, Hokkaido University, Hakodate, Hokkaido, Japan
| | - Miloš Havelka
- Laboratory of Aquaculture Genetics and Genomics, Division of Marine Life Science, Faculty and Graduate School of Fisheries Sciences, Hokkaido University, Hakodate, Hokkaido, Japan
| | - Rei Asanuma
- Laboratory of Aquaculture Genetics and Genomics, Division of Marine Life Science, Faculty and Graduate School of Fisheries Sciences, Hokkaido University, Hakodate, Hokkaido, Japan
| | - Etsuro Yamaha
- Nanae Fresh-Water Station, Field Science Center for Northern Biosphere, Hokkaido University, Nanae, Hokkaido, Japan
| | - Takafumi Fujimoto
- Laboratory of Aquaculture Genetics and Genomics, Division of Marine Life Science, Faculty and Graduate School of Fisheries Sciences, Hokkaido University, Hakodate, Hokkaido, Japan
| | - Katsutoshi Arai
- Laboratory of Aquaculture Genetics and Genomics, Division of Marine Life Science, Faculty and Graduate School of Fisheries Sciences, Hokkaido University, Hakodate, Hokkaido, Japan
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8
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Suzuki S, Miyake S, Arai K, Munehara H. Unisexual hybrids break through an evolutionary dead end by two-way backcrossing. Evolution 2020; 74:392-403. [PMID: 31873961 DOI: 10.1111/evo.13903] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/18/2019] [Accepted: 12/06/2019] [Indexed: 11/29/2022]
Abstract
Unisexual vertebrates (i.e., those produced through clonal or hemiclonal reproduction) are typically incapable of purging deleterious mutations, and, as a result, are considered short-lived in evolutionary terms. In hemiclonal reproduction (hybridogenesis), one parental genome is eliminated during oogenesis, producing haploid eggs containing the genome of a single parent. Hemiclonal hybrids are usually produced by backcrossing hemiclonal hybrids with males of the paternal species. When hemiclonal hybrids from a genus of greenlings (Hexagrammos) are crossed with males of the maternal species, the progeny are phenotypically similar to the maternal species and produce recombinant gametes by regular meiosis. The present study was conducted to determine if the hemiclonal genome is returned to the gene pool of the maternal species in the wild. Using a specific cytogenetic marker to discriminate between such progeny and the maternal species, we observed that Hexagrammos hybrids mated with maternal and paternal ancestors at the same frequency. This two-way backcrossing in which clonal genomes are returned to the gene pool where they can undergo recombination plays an important role in increasing the genetic variability of the hemiclonal genome and reducing the extinction risk. In this way, hybrid lineages may have survived longer than predicted through occasional recombinant generation.
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Affiliation(s)
- Shota Suzuki
- Graduate School of Environmental Science, Hokkaido University, Sapporo, 060-0810, Japan.,Usujiri Fisheries Station, Field Science Center for Northern Biosphere, Hokkaido University, Hakodate, 041-1613, Japan
| | - Shota Miyake
- Tokyo Metropolitan Ogasawara Fisheries Center, Tokyo, 100-2101, Japan
| | - Katsutoshi Arai
- Graduate School of Fisheries Sciences, Hokkaido University, Hakodate, 041-8611, Japan
| | - Hiroyuki Munehara
- Usujiri Fisheries Station, Field Science Center for Northern Biosphere, Hokkaido University, Hakodate, 041-1613, Japan
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9
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The programmed DNA elimination and formation of micronuclei in germ line cells of the natural hybridogenetic water frog Pelophylax esculentus. Sci Rep 2018; 8:7870. [PMID: 29777142 PMCID: PMC5959867 DOI: 10.1038/s41598-018-26168-z] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2017] [Accepted: 04/30/2018] [Indexed: 01/15/2023] Open
Abstract
DNA elimination is a radical form of gene silencing and occurs both in somatic and germ cells. The programmed DNA elimination occurs during gametogenesis in interspecies hybrids that reproduce by hybridogenesis (stick insects, fishes, and amphibians) and concerns removal of whole genomes of one of the parental species and production of clonal gametes propagating the genome of the other species. The cellular mechanisms differ considerably in hybridogenetic insects and fishes but remains unknown in edible frogs Pelophylax esculentus, natural hybrids between Pelophylax lessonae and Pelophylax ridibundus. Here we report DNA elimination mechanism in early developing gonads of diploid and triploid hybrid frogs, studied by TEM, immunofluorescence, and cytochemistry. In gonocytes of both sexes (primary oogonia and prespermatogonia), micronuclei emerge as detached nuclear buds formed during interphase. We found depletion of nuclear pore complexes in micronuclear membrane and chromatin inactivation via heterochromatinization followed by degradation of micronuclei by autophagy. Micronuclei formation does not lead to apoptotic cell death showing that genome elimination is a physiological process. Chromatin elimination via micronuclei in P. esculentus is unique among hybridogenetic animals and contributes to broadening the knowledge about reproductive modes in animals.
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10
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Suzuki S, Arai K, Munehara H. Karyological evidence of hybridogenesis in Greenlings (Teleostei: Hexagrammidae). PLoS One 2017; 12:e0180626. [PMID: 28678883 PMCID: PMC5498075 DOI: 10.1371/journal.pone.0180626] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/05/2017] [Accepted: 06/18/2017] [Indexed: 11/18/2022] Open
Abstract
Two types of natural hybrids were discovered in populations of three Hexagrammos species (Teleostei: Hexagrammidae) distributed off the southern coast of Hokkaido in the North Pacific Ocean. Both hybrids reproduce by hybridogenesis, in which the maternal haploid genome is transmitted to offspring without recombination and the paternal haploid genome is eliminated during gametogenesis. While natural hybrids are unisexual and reproduce hemiclonally by backcrossing with the paternal species (BC-P), artificial F1-hybrids between the pure species produce recombinant gametes. Thus, despite having the same genome composition, the natural hybrids and the F1-hybrids are not genetically identical. Here, to clarify the differences between both hybrids, we examined the karyotypes of the three Hexagrammos species, their natural hybrids, the artificial F1-hybrids, and several backcrosses. Artificial F1-hybrids have karyotypes and chromosome numbers that are intermediate between those of the parental species. Conversely, the natural hybrids differed from F1-hybrids by having several large metacentric chromosomes and microchromosomes. Since the entire maternal haploid genome is inherited by the natural hybrids, maternal backcrosses (BC-M) between natural hybrids and males of the maternal species (H. octogrammus; Hoc) have a hemiclonal Hoc genome with large chromosomes from the mother and a normal Hoc genome from the father. However, the large chromosomes disappear in offspring of BC-M, probably due to fissuring during gametogenesis. Similarly, microsatellite DNA analysis revealed that chromosomes of BC-M undergo recombination. These findings suggest that genetic factors associated with hemiclonal reproduction may be located on the large metacentric chromosomes of natural hybrids.
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Affiliation(s)
- Shota Suzuki
- Graduate School of Environmental Science, Hokkaido University, Sapporo, Japan
- Usujiri Fisheries Station, Field Science Center for Northern Biosphere, Hokkaido University, Hakodate, Japan
- * E-mail:
| | - Katsutoshi Arai
- Graduate School of Fisheries Sciences, Hokkaido University, Hakodate, Japan
| | - Hiroyuki Munehara
- Usujiri Fisheries Station, Field Science Center for Northern Biosphere, Hokkaido University, Hakodate, Japan
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11
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Munehara H, Horita M, Kimura-Kawaguchi MR, Yamazaki A. Origins of two hemiclonal hybrids among three Hexagrammos species (Teleostei: Hexagrammidae): genetic diversification through host switching. Ecol Evol 2016; 6:7126-7140. [PMID: 28725387 PMCID: PMC5513241 DOI: 10.1002/ece3.2446] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2016] [Revised: 08/09/2016] [Accepted: 08/12/2016] [Indexed: 12/03/2022] Open
Abstract
Two natural, hemiclonal hybrid strains were discovered in three Hexagrammos species. The natural hybrids, all of which were females that produced haploid eggs containing only the Hexagrammos octogrammus genome (maternal ancestor; hereafter Hoc), generated F1 hybrid‐type offspring by fertilization with haploid sperm of Hexagrammos agrammus or Hexagrammos otakii (paternal species; Hag and Hot, respectively). This study was performed to clarify the extent of diversification between the two hybrids and the maternal ancestor. Genealogical analysis using mtDNA revealed that all 38 Hoc/Hot hybrids formed a branch (Branch I) with 18 of the 33 Hoc/Hag hybrids. No haplotype sharing was observed with the maternal ancestor. Further, microsatellite DNA analysis suggested that the members of Branch I shared the same hemiclonal genome set. The results suggested that Hoc/Hot hybrids originated by anomalous hybridization, or “host switching,” between Hoc/Hag and Hot, and not from interspecific hybridization between Hoc and Hot. The remaining 9 of 11 Hoc/Hag haplotypes and all of the 27 Hoc haplotypes were mixed within the genealogical tree, as if they had originated from multiple mutations. However, Hoc/Hag could also mate with Hoc. Although offspring from this host switch (Backcross‐Hoc) have the same genome as normal Hoc, a part of their genome retains genetic factors capable of producing hemiclones. Consequently, when a descendant of a BC‐Hoc hybrid mates with Hag males, a new hemiclone lineage will arise. Multiple haplotype revival through host switching from a single mutation in hybrids is another possible hypothesis for the observed mixing of Hoc/Hag haplotypes within the mtDNA genealogical tree.
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Affiliation(s)
- Hiroyuki Munehara
- Field Science Center for Northern Biosphere Hokkaido University Hakodate Hokkaido Japan
| | - Miho Horita
- Field Science Center for Northern Biosphere Hokkaido University Hakodate Hokkaido Japan.,Graduate School of Environmental Science Hokkaido University Hakodate Hokkaido Japan.,Division of Analytical Bio-Medicine Advanced Research Support Center Ehime University Toon City Ehime Japan
| | - Motoko R Kimura-Kawaguchi
- Field Science Center for Northern Biosphere Hokkaido University Hakodate Hokkaido Japan.,Graduate School of Environmental Science Hokkaido University Hakodate Hokkaido Japan
| | - Aya Yamazaki
- Field Science Center for Northern Biosphere Hokkaido University Hakodate Hokkaido Japan.,Graduate School of Environmental Science Hokkaido University Hakodate Hokkaido Japan
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