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Jiménez-Marín B, Olson BJSC. The Curious Case of Multicellularity in the Volvocine Algae. Front Genet 2022; 13:787665. [PMID: 35295942 PMCID: PMC8919427 DOI: 10.3389/fgene.2022.787665] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2021] [Accepted: 01/20/2022] [Indexed: 11/13/2022] Open
Abstract
The evolution of multicellularity is a major evolutionary transition that underlies the radiation of many species in all domains of life, especially in eukaryotes. The volvocine green algae are an unconventional model system that holds great promise in the field given its genetic tractability, late transition to multicellularity, and phenotypic diversity. Multiple efforts at linking multicellularity-related developmental landmarks to key molecular changes, especially at the genome level, have provided key insights into the molecular innovations or lack thereof that underlie multicellularity. Twelve developmental changes have been proposed to explain the evolution of complex differentiated multicellularity in the volvocine algae. Co-option of key genes, such as cell cycle and developmental regulators has been observed, but with few exceptions, known co-option events do not seem to coincide with most developmental features observed in multicellular volvocines. The apparent lack of "master multicellularity genes" combined with no apparent correlation between gene gains for developmental processes suggest the possibility that many multicellular traits might be the product gene-regulatory and functional innovations; in other words, multicellularity can arise from shared genomic repertoires that undergo regulatory and functional overhauls.
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Affiliation(s)
- Berenice Jiménez-Marín
- Division of Biology, Kansas State University, Manhattan, KS, United States
- Interdepartmental Genetics Graduate Program, Kansas State University, Manhattan, KS, United States
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2
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Hasan AR, Duggal JK, Ness RW. Consequences of recombination for the evolution of the mating type locus in Chlamydomonas reinhardtii. THE NEW PHYTOLOGIST 2019; 224:1339-1348. [PMID: 31222749 DOI: 10.1111/nph.16003] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/28/2019] [Accepted: 06/10/2019] [Indexed: 06/09/2023]
Abstract
Recombination suppression in sex chromosomes and mating type loci can lead to degeneration as a result of reduced selection efficacy and Muller's ratchet effects. However, genetic exchange in the form of noncrossover gene conversions may still take place within crossover-suppressed regions. Recent work has found evidence that gene conversion may explain the low degrees of allelic differentiation in the dimorphic mating-type locus (MT) of the isogamous alga Chlamydomonas reinhardtii. However, no one has tested whether gene conversion is sufficient to avoid the degeneration of functional sequence within MT. Here, we calculate degree of linkage disequilibrium (LD) across MT as a proxy for recombination rate and investigate its relationship to patterns of population genetic variation and the efficacy of selection in the region. We find that degree of LD predicts selection efficacy across MT, and that purifying selection is stronger in shared genes than in MT-limited genes to the point of being equivalent to that of autosomal genes. We argue that while crossover suppression is needed in the mating-type loci of many isogamous systems, these loci are less likely to experience selection to differentiate further. Thus, recombination can act in these regions and prevent degeneration caused by Hill-Robertson effects.
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Affiliation(s)
- Ahmed R Hasan
- Department of Cell and Systems Biology, University of Toronto, Toronto, ON, M5S 3G5, Canada
- Department of Biology, University of Toronto Mississauga, Mississauga, ON, L5L 1C6, Canada
| | - Jaspreet K Duggal
- Department of Biology, University of Toronto Mississauga, Mississauga, ON, L5L 1C6, Canada
| | - Rob W Ness
- Department of Cell and Systems Biology, University of Toronto, Toronto, ON, M5S 3G5, Canada
- Department of Biology, University of Toronto Mississauga, Mississauga, ON, L5L 1C6, Canada
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3
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Abstract
Algae are photosynthetic eukaryotes whose taxonomic breadth covers a range of life histories, degrees of cellular and developmental complexity, and diverse patterns of sexual reproduction. These patterns include haploid- and diploid-phase sex determination, isogamous mating systems, and dimorphic sexes. Despite the ubiquity of sexual reproduction in algae, their mating-type-determination and sex-determination mechanisms have been investigated in only a limited number of representatives. These include volvocine green algae, where sexual cycles and sex-determining mechanisms have shed light on the transition from mating types to sexes, and brown algae, which are a model for UV sex chromosome evolution in the context of a complex haplodiplontic life cycle. Recent advances in genomics have aided progress in understanding sexual cycles in less-studied taxa including ulvophyte, charophyte, and prasinophyte green algae, as well as in diatoms.
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Affiliation(s)
- James Umen
- Donald Danforth Plant Science Center, St. Louis, Missouri 63132, USA;
| | - Susana Coelho
- Algal Genetics Group, Integrative Biology of Marine Models, Station Biologique de Roscoff, Sorbonne Université, UPMC Université Paris 06, CNRS, CS 90074, F-29688 Roscoff, France;
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Featherston J, Arakaki Y, Hanschen ER, Ferris PJ, Michod RE, Olson BJSC, Nozaki H, Durand PM. The 4-Celled Tetrabaena socialis Nuclear Genome Reveals the Essential Components for Genetic Control of Cell Number at the Origin of Multicellularity in the Volvocine Lineage. Mol Biol Evol 2019; 35:855-870. [PMID: 29294063 DOI: 10.1093/molbev/msx332] [Citation(s) in RCA: 28] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
Multicellularity is the premier example of a major evolutionary transition in individuality and was a foundational event in the evolution of macroscopic biodiversity. The volvocine chlorophyte lineage is well suited for studying this process. Extant members span unicellular, simple colonial, and obligate multicellular taxa with germ-soma differentiation. Here, we report the nuclear genome sequence of one of the most morphologically simple organisms in this lineage-the 4-celled colonial Tetrabaena socialis and compare this to the three other complete volvocine nuclear genomes. Using conservative estimates of gene family expansions a minimal set of expanded gene families was identified that associate with the origin of multicellularity. These families are rich in genes related to developmental processes. A subset of these families is lineage specific, which suggests that at a genomic level the evolution of multicellularity also includes lineage-specific molecular developments. Multiple points of evidence associate modifications to the ubiquitin proteasomal pathway (UPP) with the beginning of coloniality. Genes undergoing positive or accelerating selection in the multicellular volvocines were found to be enriched in components of the UPP and gene families gained at the origin of multicellularity include components of the UPP. A defining feature of colonial/multicellular life cycles is the genetic control of cell number. The genomic data presented here, which includes diversification of cell cycle genes and modifications to the UPP, align the genetic components with the evolution of this trait.
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Affiliation(s)
- Jonathan Featherston
- Evolutionary Studies Institute, University of the Witwatersrand, Johannesburg, South Africa.,Agricultural Research Council, Biotechnology Platform, Pretoria, South Africa
| | - Yoko Arakaki
- Department of Biological Sciences, Graduate School of Science, University of Tokyo, Bunkyo-ku, Tokyo, Hongo, Japan
| | - Erik R Hanschen
- Department of Ecology and Evolutionary Biology, University of Arizona, Tucson, AZ
| | - Patrick J Ferris
- Department of Ecology and Evolutionary Biology, University of Arizona, Tucson, AZ
| | - Richard E Michod
- Department of Ecology and Evolutionary Biology, University of Arizona, Tucson, AZ
| | | | - Hisayoshi Nozaki
- Department of Biological Sciences, Graduate School of Science, University of Tokyo, Bunkyo-ku, Tokyo, Hongo, Japan
| | - Pierre M Durand
- Evolutionary Studies Institute, University of the Witwatersrand, Johannesburg, South Africa
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5
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Coelho SM, Gueno J, Lipinska AP, Cock JM, Umen JG. UV Chromosomes and Haploid Sexual Systems. TRENDS IN PLANT SCIENCE 2018; 23:794-807. [PMID: 30007571 PMCID: PMC6128410 DOI: 10.1016/j.tplants.2018.06.005] [Citation(s) in RCA: 43] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/01/2018] [Revised: 06/04/2018] [Accepted: 06/07/2018] [Indexed: 05/20/2023]
Abstract
The evolution of sex determination continues to pose major questions in biology. Sex-determination mechanisms control reproductive cell differentiation and development of sexual characteristics in all organisms, from algae to animals and plants. While the underlying processes defining sex (meiosis and recombination) are conserved, sex-determination mechanisms are highly labile. In particular, a flow of new discoveries has highlighted several fascinating features of the previously understudied haploid UV sex determination and related mating systems found in diverse photosynthetic taxa including green algae, bryophytes, and brown algae. Analyses integrating information from these systems and contrasting them with classical XY and ZW systems are providing exciting insights into both the universality and the diversity of sex-determining chromosomes across eukaryotes.
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Affiliation(s)
- Susana Margarida Coelho
- Sorbonne Université, Centre National de la Recherche Scientifique (CNRS), Integrative Biology of Marine Models (LBI2M), Station Biologique de Roscoff (SBR), 29680 Roscoff, France.
| | - Josselin Gueno
- Sorbonne Université, Centre National de la Recherche Scientifique (CNRS), Integrative Biology of Marine Models (LBI2M), Station Biologique de Roscoff (SBR), 29680 Roscoff, France
| | - Agnieszka Paulina Lipinska
- Sorbonne Université, Centre National de la Recherche Scientifique (CNRS), Integrative Biology of Marine Models (LBI2M), Station Biologique de Roscoff (SBR), 29680 Roscoff, France
| | - Jeremy Mark Cock
- Sorbonne Université, Centre National de la Recherche Scientifique (CNRS), Integrative Biology of Marine Models (LBI2M), Station Biologique de Roscoff (SBR), 29680 Roscoff, France
| | - James G Umen
- Donald Danforth Plant Science Center, St. Louis, MO 63132, USA.
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Nozaki H, Ueki N, Takusagawa M, Yamashita S, Misumi O, Matsuzaki R, Kawachi M, Chiang YR, Wu JT. Morphology, taxonomy and mating-type loci in natural populations of Volvox carteri in Taiwan. BOTANICAL STUDIES 2018; 59:10. [PMID: 29616358 PMCID: PMC5882469 DOI: 10.1186/s40529-018-0227-9] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 02/01/2018] [Accepted: 03/29/2018] [Indexed: 06/08/2023]
Abstract
BACKGROUND Volvox carteri f. nagariensis is a model taxon that has been studied extensively at the cellular and molecular level. The most distinctive morphological attribute of V. carteri f. nagariensis within V. carteri is the production of sexual male spheroids with only a 1:1 ratio of somatic cells to sperm packets or androgonidia (sperm packet initials). However, the morphology of male spheroids of V. carteri f. nagariensis has been examined only in Japanese strains. In addition, V. carteri f. nagariensis has heterothallic sexuality; male and female sexes are determined by the sex-determining chromosomal region or mating-type locus composed of a > 1 Mbp linear chromosome. Fifteen sex-specific genes and many sex-based divergent shared genes (gametologs) are present within this region. Thus far, such genes have not been identified in natural populations of this species. RESULTS During a recent fieldwork in Taiwan, we encountered natural populations of V. carteri that had not previously been recorded from Taiwan. In total, 33 strains of this species were established from water samples collected in Northern Taiwan. Based on sequences of the internal transcribed spacer 2 region of nuclear ribosomal DNA and the presence of asexual spheroids with up to 16 gonidia, the species was clearly identified as V. carteri f. nagariensis. However, the sexual male spheroids of the Taiwanese strains generally exhibited a 1:1 to > 50:1 ratio of somatic cells to androgonidia. We also investigated the presence or absence of several sex-specific genes and the sex-based divergent genes MAT3m, MAT3f and LEU1Sm. We did not identify recombination or deletion of such genes between the male and female mating-type locus haplotypes in 32 of the 33 strains. In one putative female strain, the female-specific gene HMG1f was not amplified by genomic polymerase chain reaction. When sexually induced, apparently normal female sexual spheroids developed in this strain. CONCLUSIONS Male spheroids are actually variable within V. carteri f. nagariensis. Therefore, the minimum ratio of somatic cells to androgonidia in male spheroids and the maximum number of gonidia in asexual spheroids may be diagnostic for V. carteri f. nagariensis. HMG1f may not be directly related to the formation of female spheroids in this taxon.
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Affiliation(s)
- Hisayoshi Nozaki
- Department of Biological Sciences, Graduate School of Science, University of Tokyo, Hongo, Bunkyo-ku, Tokyo, 113-0033 Japan
| | - Noriko Ueki
- Department of Biology, Brooklyn College, City University of New York, Brooklyn, NY 11210 USA
| | - Mari Takusagawa
- Department of Botany, Graduate School of Science, Kyoto University, Sakyo-ku, Kyoto, 606-8502 Japan
| | - Shota Yamashita
- Department of Biological Sciences, Graduate School of Science, University of Tokyo, Hongo, Bunkyo-ku, Tokyo, 113-0033 Japan
| | - Osami Misumi
- Department of Biological Science and Chemistry, Faculty of Science, Graduate School of Medicine, Yamaguchi University, Yoshida, Yamaguchi, 753-8512 Japan
| | - Ryo Matsuzaki
- Center for Environmental Biology and Ecosystem Studies, National Institute for Environmental Studies, Onogawa, Tsukuba, Ibaraki 305-8506 Japan
| | - Masanobu Kawachi
- Center for Environmental Biology and Ecosystem Studies, National Institute for Environmental Studies, Onogawa, Tsukuba, Ibaraki 305-8506 Japan
| | - Yin-Ru Chiang
- Biodiversity Research Center, Academia Sinica, Nankang, Taipei, 11529 Taiwan
| | - Jiunn-Tzong Wu
- Biodiversity Research Center, Academia Sinica, Nankang, Taipei, 11529 Taiwan
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Hamaji T, Kawai-Toyooka H, Uchimura H, Suzuki M, Noguchi H, Minakuchi Y, Toyoda A, Fujiyama A, Miyagishima SY, Umen JG, Nozaki H. Anisogamy evolved with a reduced sex-determining region in volvocine green algae. Commun Biol 2018; 1:17. [PMID: 30271904 PMCID: PMC6123790 DOI: 10.1038/s42003-018-0019-5] [Citation(s) in RCA: 26] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/16/2017] [Accepted: 02/08/2018] [Indexed: 11/09/2022] Open
Abstract
Male and female gametes differing in size-anisogamy-emerged independently from isogamous ancestors in various eukaryotic lineages, although genetic bases of this emergence are still unknown. Volvocine green algae are a model lineage for investigating the transition from isogamy to anisogamy. Here we focus on two closely related volvocine genera that bracket this transition-isogamous Yamagishiella and anisogamous Eudorina. We generated de novo nuclear genome assemblies of both sexes of Yamagishiella and Eudorina to identify the dimorphic sex-determining chromosomal region or mating-type locus (MT) from each. In contrast to the large (>1 Mb) and complex MT of oogamous Volvox, Yamagishiella and Eudorina MT are smaller (7-268 kb) and simpler with only two sex-limited genes-the minus/male-limited MID and the plus/female-limited FUS1. No prominently dimorphic gametologs were identified in either species. Thus, the first step to anisogamy in volvocine algae presumably occurred without an increase in MT size and complexity.
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Affiliation(s)
- Takashi Hamaji
- Department of Biological Sciences, Graduate School of Science, The University of Tokyo, Bunkyo-ku, Tokyo, 113-0033, Japan
- Department of Biological Sciences, Graduate School of Science, Kyoto University, Kitashirakawa-Oiwakecho, Sakyo-ku, Kyoto, 606-8502, Japan
| | - Hiroko Kawai-Toyooka
- Department of Biological Sciences, Graduate School of Science, The University of Tokyo, Bunkyo-ku, Tokyo, 113-0033, Japan.
| | - Haruka Uchimura
- Department of Biological Sciences, Graduate School of Science, The University of Tokyo, Bunkyo-ku, Tokyo, 113-0033, Japan
| | - Masahiro Suzuki
- Kobe University Research Center for Inland Seas, Awaji, Hyogo, 656-2401, Japan
| | - Hideki Noguchi
- Center for Genome Informatics, Joint Support-Center for Data Science Research, Research Organization of Information and Systems, Mishima, Shizuoka, 411-8540, Japan
- Advanced Genomics Center, National Institute of Genetics, Mishima, Shizuoka, 411-8540, Japan
| | - Yohei Minakuchi
- Center for Information Biology, National Institute of Genetics, Mishima, Shizuoka, 411-8540, Japan
| | - Atsushi Toyoda
- Advanced Genomics Center, National Institute of Genetics, Mishima, Shizuoka, 411-8540, Japan
- Center for Information Biology, National Institute of Genetics, Mishima, Shizuoka, 411-8540, Japan
| | - Asao Fujiyama
- Advanced Genomics Center, National Institute of Genetics, Mishima, Shizuoka, 411-8540, Japan
| | - Shin-Ya Miyagishima
- Department of Cell Genetics, National Institute of Genetics, Mishima, Shizuoka, 411-8540, Japan
| | - James G Umen
- Donald Danforth Plant Science Center, 975 N Warson Rd, St. Louis, MO, 63132, USA
| | - Hisayoshi Nozaki
- Department of Biological Sciences, Graduate School of Science, The University of Tokyo, Bunkyo-ku, Tokyo, 113-0033, Japan.
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Klein B, Wibberg D, Hallmann A. Whole transcriptome RNA-Seq analysis reveals extensive cell type-specific compartmentalization in Volvox carteri. BMC Biol 2017; 15:111. [PMID: 29179763 PMCID: PMC5704591 DOI: 10.1186/s12915-017-0450-y] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/07/2017] [Accepted: 10/30/2017] [Indexed: 12/20/2022] Open
Abstract
Background One of evolution’s most important achievements is the development and radiation of multicellular organisms with different types of cells. Complex multicellularity has evolved several times in eukaryotes; yet, in most lineages, an investigation of its molecular background is considerably challenging since the transition occurred too far in the past and, in addition, these lineages evolved a large number of cell types. However, for volvocine green algae, such as Volvox carteri, multicellularity is a relatively recent innovation. Furthermore, V. carteri shows a complete division of labor between only two cell types – small, flagellated somatic cells and large, immotile reproductive cells. Thus, V. carteri provides a unique opportunity to study multicellularity and cellular differentiation at the molecular level. Results This study provides a whole transcriptome RNA-Seq analysis of separated cell types of the multicellular green alga V. carteri f. nagariensis to reveal cell type-specific components and functions. To this end, 246 million quality filtered reads were mapped to the genome and valid expression data were obtained for 93% of the 14,247 gene loci. In the subsequent search for protein domains with assigned molecular function, we identified 9435 previously classified domains in 44% of all gene loci. Furthermore, in 43% of all gene loci we identified 15,254 domains that are involved in biological processes. All identified domains were investigated regarding cell type-specific expression. Moreover, we provide further insight into the expression pattern of previously described gene families (e.g., pherophorin, extracellular matrix metalloprotease, and VARL families). Our results demonstrate an extensive compartmentalization of the transcriptome between cell types: More than half of all genes show a clear difference in expression between somatic and reproductive cells. Conclusions This study constitutes the first transcriptome-wide RNA-Seq analysis of separated cell types of V. carteri focusing on gene expression. The high degree of differential expression indicates a strong differentiation of cell types despite the fact that V. carteri diverged relatively recently from its unicellular relatives. Our expression dataset and the bioinformatic analyses provide the opportunity to further investigate and understand the mechanisms of cell type-specific expression and its transcriptional regulation. Electronic supplementary material The online version of this article (doi:10.1186/s12915-017-0450-y) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Benjamin Klein
- Department of Cellular and Developmental Biology of Plants, University of Bielefeld, Universitätsstr. 25, 33615, Bielefeld, Germany
| | - Daniel Wibberg
- Center for Biotechnology (CeBiTec), University of Bielefeld, Bielefeld, Germany
| | - Armin Hallmann
- Department of Cellular and Developmental Biology of Plants, University of Bielefeld, Universitätsstr. 25, 33615, Bielefeld, Germany.
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Yamamoto K, Kawai-Toyooka H, Hamaji T, Tsuchikane Y, Mori T, Takahashi F, Sekimoto H, Ferris PJ, Nozaki H. Molecular evolutionary analysis of a gender-limited MID ortholog from the homothallic species Volvox africanus with male and monoecious spheroids. PLoS One 2017; 12:e0180313. [PMID: 28665990 PMCID: PMC5493378 DOI: 10.1371/journal.pone.0180313] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2017] [Accepted: 06/13/2017] [Indexed: 11/18/2022] Open
Abstract
Volvox is a very interesting oogamous organism that exhibits various types of sexuality and/or sexual spheroids depending upon species or strains. However, molecular bases of such sexual reproduction characteristics have not been studied in this genus. In the model species V. carteri, an ortholog of the minus mating type-determining or minus dominance gene (MID) of isogamous Chlamydomonas reinhardtii is male-specific and determines the sperm formation. Male and female genders are genetically determined (heterothallism) in V. carteri, whereas in several other species of Volvox both male and female gametes (sperm and eggs) are formed within the same clonal culture (homothallism). To resolve the molecular basis of the evolution of Volvox species with monoecious spheroids, we here describe a MID ortholog in the homothallic species V. africanus that produces both monoecious and male spheroids within a single clonal culture. Comparison of synonymous and nonsynonymous nucleotide substitutions in MID genes between V. africanus and heterothallic volvocacean species suggests that the MID gene of V. africanus evolved under the same degree of functional constraint as those of the heterothallic species. Based on semi quantitative reverse transcription polymerase chain reaction analyses using the asexual, male and monoecious spheroids isolated from a sexually induced V. africanus culture, the MID mRNA level was significantly upregulated in the male spheroids, but suppressed in the monoecious spheroids. These results suggest that the monoecious spheroid-specific down regulation of gene expression of the MID homolog correlates with the formation of both eggs and sperm in the same spheroid in V. africanus.
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Affiliation(s)
- Kayoko Yamamoto
- Department of Biological Sciences, Graduate School of Science, the University of Tokyo, Bunkyo-ku, Tokyo, Japan
| | - Hiroko Kawai-Toyooka
- Department of Biological Sciences, Graduate School of Science, the University of Tokyo, Bunkyo-ku, Tokyo, Japan
| | - Takashi Hamaji
- Department of Biological Sciences, Graduate School of Science, the University of Tokyo, Bunkyo-ku, Tokyo, Japan
| | - Yuki Tsuchikane
- Department of Chemical and Biological Sciences, Faculty of Science, Japan Women's University, Bunkyo-ku, Tokyo, Japan
| | - Toshiyuki Mori
- Department of Tropical Medicine and Parasitology, School of Medicine, Juntendo University School of Medicine, Bunkyo-ku, Tokyo, Japan
| | - Fumio Takahashi
- College of Life Sciences, Ritsumeikan University, Kusatsu-shi, Shiga, Japan
| | - Hiroyuki Sekimoto
- Department of Chemical and Biological Sciences, Faculty of Science, Japan Women's University, Bunkyo-ku, Tokyo, Japan
| | - Patrick J. Ferris
- Department of Ecology and Evolutionary Biology, University of Arizona, Tucson, Arizona, United States of America
| | - Hisayoshi Nozaki
- Department of Biological Sciences, Graduate School of Science, the University of Tokyo, Bunkyo-ku, Tokyo, Japan
- * E-mail:
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10
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Douglas TE, Queller DC, Strassmann JE. Social amoebae mating types do not invest unequally in sexual offspring. J Evol Biol 2017; 30:926-937. [PMID: 28211207 DOI: 10.1111/jeb.13056] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2016] [Revised: 01/30/2017] [Accepted: 02/10/2017] [Indexed: 11/29/2022]
Abstract
Unequal investment by different sexes in their progeny is common and includes differential investment in the zygote and differential care of the young. The social amoeba Dictyostelium discoideum has a sexual stage in which isogamous cells of any two of the three mating types fuse to form a zygote which then attracts hundreds of other cells to the macrocyst. The latter cells are cannibalized and so make no genetic contribution to reproduction. Previous literature suggests that this sacrifice may be induced in cells of one mating type by cells of another, resulting in a higher than expected production of macrocysts when the inducing type is rare and giving a reproductive advantage to this social cheat. We tested this hypothesis in eight trios of field-collected clones of each of the three D. discoideum mating types by measuring macrocyst production at different pairwise frequencies. We found evidence that supported differential contribution in only two of the 24 clone pairs, so this pattern is rare and clone-specific. In general, we did not reject the hypothesis that the mating types contribute cells relative to their proportion in the population. We also found a significant quadratic relationship between partner frequency and macrocyst production, suggesting that when one clone is rare, macrocyst production is limited by partner availability. We were also unable to replicate previous findings that macrocyst production could be induced in the absence of a compatible mating partner. Overall, mating type-specific differential investment during sex is unlikely in microbial eukaryotes like D. discoideum.
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Affiliation(s)
- T E Douglas
- Department of Biology, Washington University in St. Louis, St. Louis, MO, USA
| | - D C Queller
- Department of Biology, Washington University in St. Louis, St. Louis, MO, USA
| | - J E Strassmann
- Department of Biology, Washington University in St. Louis, St. Louis, MO, USA
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11
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Nozaki H, Mahakham W, Athibai S, Yamamoto K, Takusagawa M, Misumi O, Herron MD, Rosenzweig F, Kawachi M. Rediscovery of the species of 'ancestral Volvox': morphology and phylogenetic position of Pleodorina sphaerica (Volvocales, Chlorophyceae) from Thailand. PHYCOLOGIA 2017; 56:469-475. [PMID: 29375162 PMCID: PMC5785936 DOI: 10.2216/17-3.1] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/13/2023]
Abstract
Pleodorina sphaerica Iyengar was considered to be a phylogenetic link between Volvox and the type species Pleodorina californica Shaw because it has small somatic cells distributed from the anterior to posterior poles in 64- or 128-celled vegetative colonies. However, cultural studies and molecular and ultrastructural data are lacking in P. sphaerica, and this species has not been recorded since 1951. Here, we performed light and electron microscopy and molecular phylogeny of P. sphaerica based on newly established culture strains originating from Thailand. Morphological features of the present Thai species agreed well with those of the previous studies of the Indian material of P. sphaerica and with those of the current concept of the advanced members of the Volvocaceae. The present P. sphaerica strains exhibited homothallic sexuality; male and facultative female colonies developed within a single clonal culture. Chloroplast multigene phylogeny demonstrated that P. sphaerica was sister to two other species of Pleodorina (P. californica and Pleodorina japonica Nozaki) without posterior somatic cells, and these three species of Pleodorina formed a robust clade, which was positioned distally in the large monophyletic group including nine taxa of Volvox sect. Merrillosphaera and Volvox (sect. Janetosphaera) aureus Ehrenberg. Based on the present phylogenetic results, evolutionary losses of posterior somatic cells might have occurred in the ancestor of P. californica and P. japonica. Thus, P. sphaerica might represent an ancestral morphology of Pleodorina, rather than of Volvox.
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Affiliation(s)
- Hisayoshi Nozaki
- Department of Biological Sciences, Graduate School of Science, University of Tokyo, Hongo 7-3-1, Bunkyo-ku, Tokyo 113-0033, Japan
- Corresponding author ()
| | - Wuttipong Mahakham
- Applied Taxonomic Research Center, Department of Biology, Faculty of Science, Khon Kaen University, Nai-Muang, Muang District, Khon Kaen 40002, Thailand
| | - Sujeephon Athibai
- Applied Taxonomic Research Center, Department of Biology, Faculty of Science, Khon Kaen University, Nai-Muang, Muang District, Khon Kaen 40002, Thailand
| | - Kayoko Yamamoto
- Department of Biological Sciences, Graduate School of Science, University of Tokyo, Hongo 7-3-1, Bunkyo-ku, Tokyo 113-0033, Japan
| | - Mari Takusagawa
- Department of Biological Science and Chemistry, Faculty of Science, Graduate School of Medicine, Yamaguchi University, 1677-1 Yoshida, Yamaguchi 753-8512, Japan
| | - Osami Misumi
- Department of Biological Science and Chemistry, Faculty of Science, Graduate School of Medicine, Yamaguchi University, 1677-1 Yoshida, Yamaguchi 753-8512, Japan
| | - Matthew D. Herron
- Division of Biological Sciences, University of Montana, Missoula, MT 59812, USA
| | - Frank Rosenzweig
- Division of Biological Sciences, University of Montana, Missoula, MT 59812, USA
| | - Masanobu Kawachi
- Center for Environmental Biology and Ecosystem Studies, National Institute for Environmental Studies, Onogawa 16-2, Tsukuba-shi, Ibaraki 305-8506, Japan
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12
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Yamashita S, Arakaki Y, Kawai-Toyooka H, Noga A, Hirono M, Nozaki H. Alternative evolution of a spheroidal colony in volvocine algae: developmental analysis of embryogenesis in Astrephomene (Volvocales, Chlorophyta). BMC Evol Biol 2016; 16:243. [PMID: 27829356 PMCID: PMC5103382 DOI: 10.1186/s12862-016-0794-x] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/12/2016] [Accepted: 10/07/2016] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Volvocine algae, which range from the unicellular Chlamydomonas to the multicellular Volvox with a germ-soma division of labor, are a model for the evolution of multicellularity. Within this group, the spheroidal colony might have evolved in two independent lineages: Volvocaceae and the goniacean Astrephomene. Astrephomene produces spheroidal colonies with posterior somatic cells. The feature that distinguishes Astrephomene from the volvocacean algae is lack of inversion during embryogenesis; the volvocacean embryo undergoes inversion after successive divisions to orient flagella toward the outside. The mechanisms of inversion at the molecular and cellular levels in volvocacean algae have been assessed in detail, particularly in Volvox carteri. However, embryogenesis in Astrephomene has not been subjected to such investigations. RESULTS This study relied on light microscopy time-lapse imaging using an actively growing culture of a newly established strain to conduct a developmental analysis of Astrephomene as well as to perform a comparison with the similar spheroidal volvocacean Eudorina. During the successive divisions involved in Astrephomene embryogenesis, gradual rotation of daughter protoplasts resulted in movement of their apical portions toward the embryonic posterior, forming a convex-to-spheroidal cell sheet with the apical ends of protoplasts on the outside. Differentiation of the posterior somatic cells from the embryo periphery was traced based on cell lineages during embryogenesis. In contrast, in Eudorina, the rotation of daughter protoplasts did not occur during successive cell divisions; however, inversion occurred after such divisions, and a spheroidal embryo was formed. Indirect immunofluorescence microscopy of basal bodies and nuclei verified this difference between Astrephomene and Eudorina in the movement of embryonic protoplasts. CONCLUSIONS These results suggest different tactics for spheroidal colony formation between the two lineages: rotation of daughter protoplasts during successive cell divisions in Astrephomene, and inversion after cell divisions in Eudorina. This study will facilitate further research into the molecular and genetic mechanisms of the parallel evolution of the spheroidal colony in volvocine algae.
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Affiliation(s)
- Shota Yamashita
- Department of Biological Sciences, Graduate School of Science, University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo, 113-0033, Japan
| | - Yoko Arakaki
- Department of Biological Sciences, Graduate School of Science, University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo, 113-0033, Japan
| | - Hiroko Kawai-Toyooka
- Department of Biological Sciences, Graduate School of Science, University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo, 113-0033, Japan
| | - Akira Noga
- Department of Biological Sciences, Graduate School of Science, University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo, 113-0033, Japan
| | - Masafumi Hirono
- Department of Frontier Bioscience, Faculty of Bioscience and Applied Chemistry, Hosei University, 3-7-2 Kajino-cho, Koganei-shi, Tokyo, 184-8584, Japan
| | - Hisayoshi Nozaki
- Department of Biological Sciences, Graduate School of Science, University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo, 113-0033, Japan.
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13
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Matt G, Umen J. Volvox: A simple algal model for embryogenesis, morphogenesis and cellular differentiation. Dev Biol 2016; 419:99-113. [PMID: 27451296 PMCID: PMC5101179 DOI: 10.1016/j.ydbio.2016.07.014] [Citation(s) in RCA: 48] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2016] [Revised: 07/15/2016] [Accepted: 07/15/2016] [Indexed: 11/20/2022]
Abstract
Patterning of a multicellular body plan involves a coordinated set of developmental processes that includes cell division, morphogenesis, and cellular differentiation. These processes have been most intensively studied in animals and land plants; however, deep insight can also be gained by studying development in simpler multicellular organisms. The multicellular green alga Volvox carteri (Volvox) is an excellent model for the investigation of developmental mechanisms and their evolutionary origins. Volvox has a streamlined body plan that contains only a few thousand cells and two distinct cell types: reproductive germ cells and terminally differentiated somatic cells. Patterning of the Volvox body plan is achieved through a stereotyped developmental program that includes embryonic cleavage with asymmetric cell division, morphogenesis, and cell-type differentiation. In this review we provide an overview of how these three developmental processes give rise to the adult form in Volvox and how developmental mutants have provided insights into the mechanisms behind these events. We highlight the accessibility and tractability of Volvox and its relatives that provide a unique opportunity for studying development.
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Affiliation(s)
- Gavriel Matt
- Donald Danforth Plant Science Center, 975 N Warson Rd, St. Louis, MO 63132, USA; Washington University in St. Louis, Division of Biology & Biomedical Science, Campus Box 8226, 660 South Euclid Ave, St. Louis, MO 63110, USA.
| | - James Umen
- Donald Danforth Plant Science Center, 975 N Warson Rd, St. Louis, MO 63132, USA.
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14
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Olson BJ, Nedelcu AM. Co-option during the evolution of multicellular and developmental complexity in the volvocine green algae. Curr Opin Genet Dev 2016; 39:107-115. [PMID: 27379901 DOI: 10.1016/j.gde.2016.06.003] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/29/2016] [Revised: 06/02/2016] [Accepted: 06/07/2016] [Indexed: 11/19/2022]
Abstract
Despite its major impact on the evolution of Life on Earth, the transition to multicellularity remains poorly understood, especially in terms of its genetic basis. The volvocine algae are a group of closely related species that range in morphology from unicellular individuals (Chlamydomonas) to undifferentiated multicellular forms (Gonium) and complex organisms with distinct developmental programs and one (Pleodorina) or two (Volvox) specialized cell types. Modern genetic approaches, complemented by the recent sequencing of genomes from several key species, revealed that co-option of existing genes and pathways is the primary driving force for the evolution of multicellularity in this lineage. The initial transition to undifferentiated multicellularity, as typified by the extant Gonium, was driven primarily by the co-option of cell cycle regulation. Further morphological and developmental innovations in the lineage leading to Volvox resulted from additional co-option events involving genes important for embryonic inversion, asymmetric cell division, somatic and germ cell differentiation and the structure and function of the extracellular matrix. Because of their relatively low but variable levels of morphological and developmental complexity, simple underlying genetics and recent evolutionary history, the volvocine algae are providing significant insight into our understanding of the genetics and evolution of major developmental and morphological traits.
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Affiliation(s)
| | - Aurora M Nedelcu
- Department of Biology, University of New Brunswick, Fredericton, NB, Canada
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15
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Sequence of the Gonium pectorale Mating Locus Reveals a Complex and Dynamic History of Changes in Volvocine Algal Mating Haplotypes. G3-GENES GENOMES GENETICS 2016; 6:1179-89. [PMID: 26921294 PMCID: PMC4856071 DOI: 10.1534/g3.115.026229] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
Sex-determining regions (SDRs) or mating-type (MT) loci in two sequenced volvocine algal species, Chlamydomonas reinhardtii and Volvox carteri, exhibit major differences in size, structure, gene content, and gametolog differentiation. Understanding the origin of these differences requires investigation of MT loci from related species. Here, we determined the sequences of the minus and plus MT haplotypes of the isogamous 16-celled volvocine alga, Gonium pectorale, which is more closely related to the multicellular V. carteri than to C. reinhardtii. Compared to C. reinhardtii MT, G. pectorale MT is moderately larger in size, and has a less complex structure, with only two major syntenic blocs of collinear gametologs. However, the gametolog content of G. pectorale MT has more overlap with that of V. carteri MT than with C. reinhardtii MT, while the allelic divergence between gametologs in G. pectorale is even lower than that in C. reinhardtii. Three key sex-related genes are conserved in G. pectorale MT: GpMID and GpMTD1 in MT–, and GpFUS1 in MT+. GpFUS1 protein exhibited specific localization at the plus-gametic mating structure, indicating a conserved function in fertilization. Our results suggest that the G. pectorale–V. carteri common ancestral MT experienced at least one major reformation after the split from C. reinhardtii, and that the V. carteri ancestral MT underwent a subsequent expansion and loss of recombination after the divergence from G. pectorale. These data begin to polarize important changes that occurred in volvocine MT loci, and highlight the potential for discontinuous and dynamic evolution in SDRs.
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16
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The Gonium pectorale genome demonstrates co-option of cell cycle regulation during the evolution of multicellularity. Nat Commun 2016; 7:11370. [PMID: 27102219 PMCID: PMC4844696 DOI: 10.1038/ncomms11370] [Citation(s) in RCA: 102] [Impact Index Per Article: 12.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/26/2016] [Accepted: 03/18/2016] [Indexed: 12/30/2022] Open
Abstract
The transition to multicellularity has occurred numerous times in all domains of life, yet its initial steps are poorly understood. The volvocine green algae are a tractable system for understanding the genetic basis of multicellularity including the initial formation of cooperative cell groups. Here we report the genome sequence of the undifferentiated colonial alga, Gonium pectorale, where group formation evolved by co-option of the retinoblastoma cell cycle regulatory pathway. Significantly, expression of the Gonium retinoblastoma cell cycle regulator in unicellular Chlamydomonas causes it to become colonial. The presence of these changes in undifferentiated Gonium indicates extensive group-level adaptation during the initial step in the evolution of multicellularity. These results emphasize an early and formative step in the evolution of multicellularity, the evolution of cell cycle regulation, one that may shed light on the evolutionary history of other multicellular innovations and evolutionary transitions.
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17
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Nozaki H, Matsuzaki R, Yamamoto K, Kawachi M, Takahashi F. Delineating a New Heterothallic Species of Volvox (Volvocaceae, Chlorophyceae) Using New Strains of "Volvox africanus". PLoS One 2015; 10:e0142632. [PMID: 26562165 PMCID: PMC4643018 DOI: 10.1371/journal.pone.0142632] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/02/2015] [Accepted: 10/23/2015] [Indexed: 11/18/2022] Open
Abstract
The volvocine algae represent an excellent model lineage in which to study evolution of female and male genders based on comparative analyses of related species. Among these species, Volvox carteri has been extensively studied as a model of an oogamous and complex organism. However, it may have unique derived features that are not present in other species of Volvox. Therefore, information regarding the characteristics of sexual reproduction of other species of Volvox is also important. In 1971, Starr studied four types of sexuality in several global strains identified as Volvox africanus; however, further taxonomic studies of these strains have been lacking, and strains of three of the four sexual types are not available. Here, we studied the morphology, sexual reproduction, and taxonomy of two V. africanus-like species isolated recently from Lake Biwa, Japan. These two species were very similar to two sexual types described by Starr in 1971: one producing dioecious sexual spheroids in heterothallic strains and the other forming both male spheroids and monoecious spheroids in a single strain. The former species produced zygotes with a reticulate cell wall, whereas a smooth zygote wall was observed in the latter species as in V. africanus previously reported from various localities around the world. Our multigene phylogenetic analysis demonstrated that these are sister species to each other. However, the presence of a compensatory base change in the most conserved region of the secondary structure of nuclear ribosomal DNA internal transcribed spacer-2, hybrid inviability demonstrated by intercrossing experiments, and morphological differences in the density of abutment between the gelatinous material of adjacent cells (individual sheaths) in the spheroid supported the recognition of the two species, V. africanus having a smooth zygote wall and V. reticuliferus Nozaki sp. nov. having a reticulate zygote wall.
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Affiliation(s)
- Hisayoshi Nozaki
- Department of Biological Sciences, Graduate school of Science, University of Tokyo, Tokyo, Japan
- * E-mail:
| | - Ryo Matsuzaki
- Department of Biological Sciences, Graduate school of Science, University of Tokyo, Tokyo, Japan
| | - Kayoko Yamamoto
- Department of Biological Sciences, Graduate school of Science, University of Tokyo, Tokyo, Japan
| | - Masanobu Kawachi
- Center for Environmental Biology and Ecosystem Studies, National Institute for Environmental Studies, Tsukuba, Ibaraki, Japan
| | - Fumio Takahashi
- Ritsumeikan University, College of Life Sciences, Kusatsu, Shiga, Japan
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18
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Mori T, Kawai-Toyooka H, Igawa T, Nozaki H. Gamete Dialogs in Green Lineages. MOLECULAR PLANT 2015; 8:1442-54. [PMID: 26145252 DOI: 10.1016/j.molp.2015.06.008] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/04/2015] [Revised: 06/15/2015] [Accepted: 06/28/2015] [Indexed: 05/20/2023]
Abstract
Gamete fusion is a core process of sexual reproduction and, in both plants and animals, different sex gametes fuse within species. Although most of the molecular factors involved in gamete interaction are still unknown in various sex-possessing eukaryotes, reports of such factors in algae and land plants have been increasing in the past decade. In particular, knowledge of gamete interaction in flowering plants and green algae has increased since the identification of the conserved gamete fusion factor generative cell specific 1/hapless 2 (GCS1/HAP2). GCS1 was first identified as a pollen generative cell-specific transmembrane protein in the lily (Lilium longiflorum), and was then shown to function not only in flowering plant gamete fusion but also in various eukaryotes, including unicellular protists and metazoans. In addition, although initially restricted to Chlamydomonas, knowledge of gamete attachment in flowering plants was also acquired. This review focuses on recent progress in the study of gamete interaction in volvocine green algae and flowering plants and discusses conserved mechanisms of gamete recognition, attachment, and fusion leading to zygote formation.
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Affiliation(s)
- Toshiyuki Mori
- Department of Biological Sciences, Graduate School of Science, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033, Japan.
| | - Hiroko Kawai-Toyooka
- Department of Biological Sciences, Graduate School of Science, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033, Japan
| | - Tomoko Igawa
- Graduate School of Horticulture, Chiba University, 648 Matsudo, Matsudo, Chiba 271-8510, Japan
| | - Hisayoshi Nozaki
- Department of Biological Sciences, Graduate School of Science, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033, Japan.
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19
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Kawafune K, Hongoh Y, Hamaji T, Sakamoto T, Kurata T, Hirooka S, Miyagishima SY, Nozaki H. Two different rickettsial bacteria invading Volvox carteri. PLoS One 2015; 10:e0116192. [PMID: 25671568 PMCID: PMC4324946 DOI: 10.1371/journal.pone.0116192] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/17/2014] [Accepted: 12/02/2014] [Indexed: 12/02/2022] Open
Abstract
BACKGROUND Bacteria of the family Rickettsiaceae are principally associated with arthropods. Recently, endosymbionts of the Rickettsiaceae have been found in non-phagotrophic cells of the volvocalean green algae Carteria cerasiformis, Pleodorina japonica, and Volvox carteri. Such endosymbionts were present in only C. cerasiformis strain NIES-425 and V. carteri strain UTEX 2180, of various strains of Carteria and V. carteri examined, suggesting that rickettsial endosymbionts may have been transmitted to only a few algal strains very recently. However, in preliminary work, we detected a sequence similar to that of a rickettsial gene in the nuclear genome of V. carteri strain EVE. METHODOLOGY/PRINCIPAL FINDINGS Here we explored the origin of the rickettsial gene-like sequences in the endosymbiont-lacking V. carteri strain EVE, by performing comparative analyses on 13 strains of V. carteri. By reference to our ongoing genomic sequence of rickettsial endosymbionts in C. cerasiformis strain NIES-425 cells, we confirmed that an approximately 9-kbp DNA sequence encompassing a region similar to that of four rickettsial genes was present in the nuclear genome of V. carteri strain EVE. Phylogenetic analyses, and comparisons of the synteny of rickettsial gene-like sequences from various strains of V. carteri, indicated that the rickettsial gene-like sequences in the nuclear genome of V. carteri strain EVE were closely related to rickettsial gene sequences of P. japonica, rather than those of V. carteri strain UTEX 2180. CONCLUSION/SIGNIFICANCE At least two different rickettsial organisms may have invaded the V. carteri lineage, one of which may be the direct ancestor of the endosymbiont of V. carteri strain UTEX 2180, whereas the other may be closely related to the endosymbiont of P. japonica. Endosymbiotic gene transfer from the latter rickettsial organism may have occurred in an ancestor of V. carteri. Thus, the rickettsiae may be widely associated with V. carteri, and likely have often been lost during host evolution.
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Affiliation(s)
- Kaoru Kawafune
- Department of Biological Sciences, Graduate School of Science, University of Tokyo, Bunkyo-ku, Tokyo, Japan
| | - Yuichi Hongoh
- Department of Biological Sciences, Graduate School of Bioscience and Biotechnology, Tokyo Institute of Technology, Ookayama, Meguro-ku, Tokyo, Japan
| | - Takashi Hamaji
- Donald Danforth Plant Science Center, Saint Louis, Missouri, United States of America
| | - Tomoaki Sakamoto
- Plant Global Education Project, Graduate School of Biological Sciences, Nara Institute of Science and Technology, Ikoma, Nara, Japan
| | - Tetsuya Kurata
- Plant Global Education Project, Graduate School of Biological Sciences, Nara Institute of Science and Technology, Ikoma, Nara, Japan
| | - Shunsuke Hirooka
- Center for Frontier Research, National Institute of Genetics, Mishima, Shizuoka, Japan
| | - Shin-ya Miyagishima
- Center for Frontier Research, National Institute of Genetics, Mishima, Shizuoka, Japan
| | - Hisayoshi Nozaki
- Department of Biological Sciences, Graduate School of Science, University of Tokyo, Bunkyo-ku, Tokyo, Japan
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20
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Function of the male-gamete-specific fusion protein HAP2 in a seven-sexed ciliate. Curr Biol 2014; 24:2168-2173. [PMID: 25155508 DOI: 10.1016/j.cub.2014.07.064] [Citation(s) in RCA: 47] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/27/2014] [Revised: 06/20/2014] [Accepted: 07/23/2014] [Indexed: 01/04/2023]
Abstract
HAP2, a male-gamete-specific protein conserved across vast evolutionary distances, has garnered considerable attention as a potential membrane fusogen required for fertilization in taxa ranging from protozoa and green algae to flowering plants and invertebrate animals [1-6]. However, its presence in Tetrahymena thermophila, a ciliated protozoan with seven sexes or mating types that bypasses the production of male gametes, raises interesting questions regarding the evolutionary origins of gamete-specific functions in sexually dimorphic species. Here we show that HAP2 is expressed in all seven mating types of T. thermophila and that fertility is only blocked when the gene is deleted from both cells of a mating pair. HAP2 deletion strains of complementary mating types can recognize one another and form pairs; however, pair stability is compromised and membrane pore formation at the nuclear exchange junction is blocked. The absence of pore formation is consistent with previous studies suggesting a role for HAP2 in gamete fusion in other systems. We propose a model in which each of the several hundred membrane pores established at the conjugation junction of mating Tetrahymena represents the equivalent of a male/female interface, and that pore formation is driven on both sides of the junction by the presence of HAP2. Such a model supports the idea that many of the disparate functions of sperm and egg were shared by the "isogametes" of early eukaryotes and became partitioned to either male or female sex cells later in evolution.
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21
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Geng S, De Hoff P, Umen JG. Evolution of sexes from an ancestral mating-type specification pathway. PLoS Biol 2014; 12:e1001904. [PMID: 25003332 PMCID: PMC4086717 DOI: 10.1371/journal.pbio.1001904] [Citation(s) in RCA: 52] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/24/2014] [Accepted: 05/30/2014] [Indexed: 01/20/2023] Open
Abstract
Male and female sexes have evolved repeatedly in eukaryotes but the origins of dimorphic sexes and their relationship to mating types in unicellular species are not understood. Volvocine algae include isogamous species such as Chlamydomonas reinhardtii, with two equal-sized mating types, and oogamous multicellular species such as Volvox carteri with sperm-producing males and egg-producing females. Theoretical work predicts genetic linkage of a gamete cell-size regulatory gene(s) to an ancestral mating-type locus as a possible step in the evolution of dimorphic gametes, but this idea has not been tested. Here we show that, contrary to predictions, a single conserved mating locus (MT) gene in volvocine algae-MID, which encodes a RWP-RK domain transcription factor-evolved from its ancestral role in C. reinhardtii as a mating-type specifier, to become a determinant of sperm and egg development in V. carteri. Transgenic female V. carteri expressing male MID produced functional sperm packets during sexual development. Transgenic male V. carteri with RNA interference (RNAi)-mediated knockdowns of VcMID produced functional eggs, or self-fertile hermaphrodites. Post-transcriptional controls were found to regulate cell-type-limited expression and nuclear localization of VcMid protein that restricted its activity to nuclei of developing male germ cells and sperm. Crosses with sex-reversed strains uncoupled sex determination from sex chromosome identity and revealed gender-specific roles for male and female mating locus genes in sexual development, gamete fitness and reproductive success. Our data show genetic continuity between the mating-type specification and sex determination pathways of volvocine algae, and reveal evidence for gender-specific adaptations in the male and female mating locus haplotypes of Volvox. These findings will enable a deeper understanding of how a master regulator of mating-type determination in an ancestral unicellular species was reprogrammed to control sexually dimorphic gamete development in a multicellular descendant.
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Affiliation(s)
- Sa Geng
- Donald Danforth Plant Science Center, St. Louis, Missouri, United States of America
| | - Peter De Hoff
- The Salk Institute for Biological Studies, La Jolla, California, United States of America
| | - James G. Umen
- Donald Danforth Plant Science Center, St. Louis, Missouri, United States of America
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22
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Sex-specific posttranslational regulation of the gamete fusogen GCS1 in the isogamous volvocine alga Gonium pectorale. EUKARYOTIC CELL 2014; 13:648-56. [PMID: 24632243 DOI: 10.1128/ec.00330-13] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
Male and female, generally defined based on differences in gamete size and motility, likely have multiple independent origins, appearing to have evolved from isogamous organisms in various eukaryotic lineages. Recent studies of the gamete fusogen GCS1/HAP2 indicate that this protein is deeply conserved across eukaryotes, and its exclusive and/or functional expression generally resides in males or in male homologues. However, little is known regarding the conserved or primitive molecular traits of males and females within eukaryotes. Here, using morphologically indistinguishable isogametes of the colonial volvocine Gonium pectorale, we demonstrated that GCS1 is differently regulated between the sexes. G. pectorale GCS1 molecules in one sex (homologous to male) are transported from the gamete cytoplasm to the protruded fusion site, whereas those of the other sex (females) are quickly degraded within the cytoplasm upon gamete activation. This molecular trait difference might be conserved across various eukaryotic lineages and may represent male and female prototypes originating from a common eukaryotic ancestor.
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Nozaki H, Yamada TK, Takahashi F, Matsuzaki R, Nakada T. New "missing link" genus of the colonial volvocine green algae gives insights into the evolution of oogamy. BMC Evol Biol 2014; 14:37. [PMID: 24589311 PMCID: PMC4015742 DOI: 10.1186/1471-2148-14-37] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2013] [Accepted: 02/25/2014] [Indexed: 11/17/2022] Open
Abstract
Background The evolution of oogamy from isogamy, an important biological event, can be summarized as follows: morphologically similar gametes (isogametes) differentiated into small “male” and large “female” motile gametes during anisogamy, from which immotile female gametes (eggs) evolved. The volvocine green algae represent a model lineage to study this type of sex evolution and show two types of gametic unions: conjugation between isogametes outside the parental colonies (external fertilization during isogamy) and fertilization between small motile gametes (sperm) and large gametes (eggs) inside the female colony (internal fertilization during anisogamy and oogamy). Although recent cultural studies on volvocine algae revealed morphological diversity and molecular genetic data of sexual reproduction, an intermediate type of union between these two gametic unions has not been identified. Results We identified a novel colonial volvocine genus, Colemanosphaera, which produces bundles of spindle-shaped male gametes through successive divisions of colonial cells. Obligately anisogamous conjugation between male and female motile gametes occurred outside the female colony (external fertilization during anisogamy). This new genus contains 16- or 32-celled spheroidal colonies similar to those of the volvocine genera Yamagishiella and Eudorina. However, Colemanosphaera can be clearly distinguished from these two genera based on its sister phylogenetic position to the enigmatic flattened colonial volvocine Platydorina and external fertilization during anisogamy. Two species of Colemanosphaera were found in a Japanese lake; these species are also distributed in European freshwaters based on a published sequence of an Austrian strain and the original description of Pandorina charkowiensis from Ukraine. Conclusions Based on phylogeny and morphological data, this novel genus exhibits a missing link between Platydorina and the typical spheroidal colonial volvocine members such as Pandorina or Yamagishiella. Considering the external obligate anisogamy, oogamy evolution may have been preceded by the transition from external to internal fertilization during anisogamy within the volvocine green algae.
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Affiliation(s)
- Hisayoshi Nozaki
- Department of Biological Sciences, Graduate School of Science, University of Tokyo, 7-3-1 Hongo, Bunkyo, Tokyo 113-0033, Japan.
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