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Pinello JF, Clark TG. HAP2-Mediated Gamete Fusion: Lessons From the World of Unicellular Eukaryotes. Front Cell Dev Biol 2022; 9:807313. [PMID: 35071241 PMCID: PMC8777248 DOI: 10.3389/fcell.2021.807313] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2021] [Accepted: 11/15/2021] [Indexed: 01/29/2023] Open
Abstract
Most, if not all the cellular requirements for fertilization and sexual reproduction arose early in evolution and are retained in extant lineages of single-celled organisms including a number of important model organism species. In recent years, work in two such species, the green alga, Chlamydomonas reinhardtii, and the free-living ciliate, Tetrahymena thermophila, have lent important new insights into the role of HAP2/GCS1 as a catalyst for gamete fusion in organisms ranging from protists to flowering plants and insects. Here we summarize the current state of knowledge around how mating types from these algal and ciliate systems recognize, adhere and fuse to one another, current gaps in our understanding of HAP2-mediated gamete fusion, and opportunities for applying what we know in practical terms, especially for the control of protozoan parasites.
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Affiliation(s)
- Jennifer F. Pinello
- Department of Cell Biology and Molecular Genetics, University of Maryland, College Park, MD, United States
| | - Theodore G. Clark
- Department of Microbiology and Immunology, Cornell University, Ithaca, NY, United States
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2
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Cronmiller E, Toor D, Shao NC, Kariyawasam T, Wang MH, Lee JH. Cell wall integrity signaling regulates cell wall-related gene expression in Chlamydomonas reinhardtii. Sci Rep 2019; 9:12204. [PMID: 31434930 PMCID: PMC6704257 DOI: 10.1038/s41598-019-48523-4] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/28/2019] [Accepted: 08/02/2019] [Indexed: 11/13/2022] Open
Abstract
An intact cell wall is critical for cellular interactions with the environment and protecting the cell from environmental challenges. Signaling mechanisms are necessary to monitor cell wall integrity and to regulate cell wall production and remodeling during growth and division cycles. The green alga, Chlamydomonas, has a proteinaceous cell wall of defined structure that is readily removed by gametolysin (g-lysin), a metalloprotease released during sexual mating. Naked cells treated with g-lysin induce the mRNA accumulation of >100 cell wall-related genes within an hour, offering a system to study signaling and regulatory mechanisms for de novo cell wall assembly. Combining quantitative RT-PCR and luciferase reporter assays to probe transcript accumulation and promoter activity, we revealed that up to 500-fold upregulation of cell wall-related genes was driven at least partly by transcriptional activation upon g-lysin treatment. To investigate how naked cells trigger this rapid transcriptional activation, we tested whether osmotic stress and cell wall integrity are involved in this process. Under a constant hypotonic condition, comparable levels of cell wall-gene activation were observed by g-lysin treatment. In contrast, cells in an iso- or hypertonic condition showed up to 80% reduction in the g-lysin-induced gene activation, suggesting that osmotic stress is required for full-scale responses to g-lysin treatment. To test whether mechanical perturbation of cell walls is involved, we isolated and examined a new set of cell wall mutants with defective or little cell walls. All cell wall mutants examined showed a constitutive upregulation of cell wall-related genes at a level that is only achieved by treatment with g-lysin in wild-type cells. Our study suggests a cell wall integrity monitoring mechanism that senses both osmotic stress and mechanical defects of cell walls and regulates cell wall-gene expression in Chlamydomonas, which may relate to cell wall integrity signaling mechanisms in other organisms.
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Affiliation(s)
- Evan Cronmiller
- Department of Botany, University of British Columbia, 6270 University Blvd., Vancouver, Canada
| | - Deepak Toor
- Department of Botany, University of British Columbia, 6270 University Blvd., Vancouver, Canada
| | - Nai Chun Shao
- Department of Botany, University of British Columbia, 6270 University Blvd., Vancouver, Canada
| | - Thamali Kariyawasam
- Department of Botany, University of British Columbia, 6270 University Blvd., Vancouver, Canada
| | - Ming Hsiu Wang
- Department of Botany, University of British Columbia, 6270 University Blvd., Vancouver, Canada
| | - Jae-Hyeok Lee
- Department of Botany, University of British Columbia, 6270 University Blvd., Vancouver, Canada.
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3
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Widyaningrum D, Iida D, Tanabe Y, Hayashi Y, Kurniasih SD, Ohama T. Acutely induced cell mortality in the unicellular green alga Chlamydomonas reinhardtii (Chlorophyceae) following exposure to acrylic resin nanoparticles. JOURNAL OF PHYCOLOGY 2019; 55:118-133. [PMID: 30304548 DOI: 10.1111/jpy.12798] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/04/2018] [Accepted: 09/24/2018] [Indexed: 06/08/2023]
Abstract
Nanoparticles have unique properties that make them attractive for use in industrial and medical technology industries but can also be harmful to living organisms, making an understanding of their molecular mechanisms of action essential. We examined the effect of three different sized poly(isobutyl-cyanoacrylate) nanoparticles (iBCA-NPs) on the unicellular green alga Chlamydomonas reinhardtii. We found that exposure to iBCA-NPs immediately caused C. reinhardtii to display abnormal swimming behaviors. Furthermore, after one hour, most of the cells had stopped swimming and 10%-30% of cells were stained with trypan blue, suggesting that these cells had severely impaired plasma membranes. Observation of the cyto-ultrastructure showed that the cell walls had been severely damaged and that many iBCA-NPs were located in the space between the cell wall and plasma membrane, as well as inside the cytosol in some cases. A comparison of three strains of C. reinhardtii with different cell wall conditions further showed that the cell mortality ratio increased more rapidly in the absence of a cell wall. Interestingly, cell mortality over time was essentially identical regardless of iBCA-NP size if the total surface area was the same. Furthermore, direct observation of the trails of iBCA-NPs indicated that the first trigger was their contact with the cell wall, which is most likely accompanied by the inactivation or removal of adsorbed proteins from the cell wall surface. Cell mortality was accompanied by the overproduction of reactive oxygen species, which was detected more readily in cells grown under constant light rather than in the dark.
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Affiliation(s)
- Dwiyantari Widyaningrum
- School of Environmental Science and Engineering, Kochi University of Technology, 185 Miyanokuchi, Tosayamada, Kami City, Kochi, 782-8502, Japan
| | - Daisuke Iida
- Chikami Miltec Inc, 1-6-3 Ohtesuji, Kochi City, Kochi, 780-0842, Japan
| | - Yuma Tanabe
- Graduate School of Science and Technology, Niigata University, 8050 Ikarashi 2-no-cho, Nishi-ku, Niigata, 950-2181, Japan
| | - Yasuko Hayashi
- Graduate School of Science and Technology, Niigata University, 8050 Ikarashi 2-no-cho, Nishi-ku, Niigata, 950-2181, Japan
| | - Sari Dewi Kurniasih
- School of Environmental Science and Engineering, Kochi University of Technology, 185 Miyanokuchi, Tosayamada, Kami City, Kochi, 782-8502, Japan
- Chemistry Department, Institut Teknologi Bandung, Jalan Ganesha 10, Bandung, West Java, 40132, Indonesia
| | - Takeshi Ohama
- School of Environmental Science and Engineering, Kochi University of Technology, 185 Miyanokuchi, Tosayamada, Kami City, Kochi, 782-8502, Japan
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Geng S, Miyagi A, Umen JG. Evolutionary divergence of the sex-determining gene MID uncoupled from the transition to anisogamy in volvocine algae. Development 2018; 145:dev.162537. [PMID: 29549112 DOI: 10.1242/dev.162537] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2017] [Accepted: 03/13/2018] [Indexed: 12/28/2022]
Abstract
Volvocine algae constitute a unique comparative model for investigating the evolution of oogamy from isogamous mating types. The sex- or mating type-determining gene MID encodes a conserved RWP-RK transcription factor found in either the MT- or male mating locus of dioecious volvocine species. We previously found that MID from the isogamous species Chlamydomonas reinhardtii (CrMID) could not induce ectopic spermatogenesis when expressed heterologously in Volvox carteri females, suggesting coevolution of Mid function with gamete dimorphism. Here we found that ectopic expression of MID from the anisogamous species Pleodorina starrii (PsMID) could efficiently induce spermatogenesis when expressed in V. carteri females and, unexpectedly, that GpMID from the isogamous species Gonium pectorale was also able to induce V. carteri spermatogenesis. Neither VcMID nor GpMID could complement a C. reinhardtii mid mutant, at least partly owing to instability of heterologous Mid proteins. Our data show that Mid divergence was not a major contributor to the transition between isogamy and anisogamy/oogamy in volvocine algae, and instead implicate changes in cis-regulatory interactions and/or trans-acting factors of the Mid network in the evolution of sexual dimorphism.
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Affiliation(s)
- Sa Geng
- Donald Danforth Plant Science Center, 975 N. Warson Rd., St. Louis, MO 63132, USA
| | - Ayano Miyagi
- Donald Danforth Plant Science Center, 975 N. Warson Rd., St. Louis, MO 63132, USA
| | - James G Umen
- Donald Danforth Plant Science Center, 975 N. Warson Rd., St. Louis, MO 63132, USA
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Abstract
Cell-cell fusion is essential for fertilization and organ development. Dedicated proteins known as fusogens are responsible for mediating membrane fusion. However, until recently, these proteins either remained unidentified or were poorly understood at the mechanistic level. Here, we review how fusogens surmount multiple energy barriers to mediate cell-cell fusion. We describe how early preparatory steps bring membranes to a distance of ∼10 nm, while fusogens act in the final approach between membranes. The mechanical force exerted by cell fusogens and the accompanying lipidic rearrangements constitute the hallmarks of cell-cell fusion. Finally, we discuss the relationship between viral and eukaryotic fusogens, highlight a classification scheme regrouping a superfamily of fusogens called Fusexins, and propose new questions and avenues of enquiry.
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Affiliation(s)
- Javier M Hernández
- Department of Structural Biochemistry, Max Planck Institute of Molecular Physiology, D-44227 Dortmund, Germany
| | - Benjamin Podbilewicz
- Department of Biology, Technion - Israel Institute of Technology, Haifa 32000, Israel
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6
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Hadjivasiliou Z, Pomiankowski A. Gamete signalling underlies the evolution of mating types and their number. Philos Trans R Soc Lond B Biol Sci 2017; 371:rstb.2015.0531. [PMID: 27619695 PMCID: PMC5031616 DOI: 10.1098/rstb.2015.0531] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 06/11/2016] [Indexed: 01/02/2023] Open
Abstract
The gametes of unicellular eukaryotes are morphologically identical, but are nonetheless divided into distinct mating types. The number of mating types varies enormously and can reach several thousand, yet most species have only two. Why do morphologically identical gametes need to be differentiated into self-incompatible mating types, and why is two the most common number of mating types? In this work, we explore a neglected hypothesis that there is a need for asymmetric signalling interactions between mating partners. Our review shows that isogamous gametes always interact asymmetrically throughout sex and argue that this asymmetry is favoured because it enhances the efficiency of the mating process. We further develop a simple mathematical model that allows us to study the evolution of the number of mating types based on the strength of signalling interactions between gametes. Novel mating types have an advantage as they are compatible with all others and rarely meet their own type. But if existing mating types coevolve to have strong mutual interactions, this restricts the spread of novel types. Similarly, coevolution is likely to drive out less attractive mating types. These countervailing forces specify the number of mating types that are evolutionarily stable. This article is part of the themed issue ‘Weird sex: the underappreciated diversity of sexual reproduction’.
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Affiliation(s)
- Zena Hadjivasiliou
- Centre for Mathematics and Physics in the Life Sciences and Experimental Biology, University College London, Gower Street, London WC1E 6BT, UK Department of Genetics, Evolution and Environment, University College London, Gower Street, London WC1E 6BT, UK
| | - Andrew Pomiankowski
- Centre for Mathematics and Physics in the Life Sciences and Experimental Biology, University College London, Gower Street, London WC1E 6BT, UK Department of Genetics, Evolution and Environment, University College London, Gower Street, London WC1E 6BT, UK
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7
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Joo S, Nishimura Y, Cronmiller E, Hong RH, Kariyawasam T, Wang MH, Shao NC, El Akkad SED, Suzuki T, Higashiyama T, Jin E, Lee JH. Gene Regulatory Networks for the Haploid-to-Diploid Transition of Chlamydomonas reinhardtii. PLANT PHYSIOLOGY 2017; 175:314-332. [PMID: 28710131 PMCID: PMC5580766 DOI: 10.1104/pp.17.00731] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/05/2017] [Accepted: 07/12/2017] [Indexed: 05/20/2023]
Abstract
The sexual cycle of the unicellular Chlamydomonas reinhardtii culminates in the formation of diploid zygotes that differentiate into dormant spores that eventually undergo meiosis. Mating between gametes induces rapid cell wall shedding via the enzyme g-lysin; cell fusion is followed by heterodimerization of sex-specific homeobox transcription factors, GSM1 and GSP1, and initiation of zygote-specific gene expression. To investigate the genetic underpinnings of the zygote developmental pathway, we performed comparative transcriptome analysis of both pre- and post-fertilization samples. We identified 253 transcripts specifically enriched in early zygotes, 82% of which were not up-regulated in gsp1 null zygotes. We also found that the GSM1/GSP1 heterodimer negatively regulates the vegetative wall program at the posttranscriptional level, enabling prompt transition from vegetative wall to zygotic wall assembly. Annotation of the g-lysin-induced and early zygote genes reveals distinct vegetative and zygotic wall programs, supported by concerted up-regulation of genes encoding cell wall-modifying enzymes and proteins involved in nucleotide-sugar metabolism. The haploid-to-diploid transition in Chlamydomonas is masterfully controlled by the GSM1/GSP1 heterodimer, translating fertilization and gamete coalescence into a bona fide differentiation program. The fertilization-triggered integration of genes required to make related, but structurally and functionally distinct organelles-the vegetative versus zygote cell wall-presents a likely scenario for the evolution of complex developmental gene regulatory networks.
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Affiliation(s)
- Sunjoo Joo
- Department of Botany, University of British Columbia, Vancouver, British Columbia V6T1Z4, Canada
| | - Yoshiki Nishimura
- Department of Botany, Graduate School of Science, Kyoto University, Oiwake-cho, Kita-Shirakawa, Sakyo-ku, Kyoto 606-8502, Japan
| | - Evan Cronmiller
- Department of Botany, University of British Columbia, Vancouver, British Columbia V6T1Z4, Canada
| | - Ran Ha Hong
- Department of Botany, University of British Columbia, Vancouver, British Columbia V6T1Z4, Canada
| | - Thamali Kariyawasam
- Department of Botany, University of British Columbia, Vancouver, British Columbia V6T1Z4, Canada
| | - Ming Hsiu Wang
- Department of Botany, University of British Columbia, Vancouver, British Columbia V6T1Z4, Canada
| | - Nai Chun Shao
- Department of Botany, University of British Columbia, Vancouver, British Columbia V6T1Z4, Canada
| | - Saif-El-Din El Akkad
- Department of Botany, University of British Columbia, Vancouver, British Columbia V6T1Z4, Canada
| | - Takamasa Suzuki
- ERATO, Graduate School of Science, Nagoya University, Furo-cho, Chikusa-ku, Nagoya 464-8602, Japan
| | - Tetsuya Higashiyama
- ERATO, Graduate School of Science, Nagoya University, Furo-cho, Chikusa-ku, Nagoya 464-8602, Japan
| | - Eonseon Jin
- Department Life Sciences, Research Institute for Natural Sciences, Hanyang University, 222 Wangsipri-ro, Sungdong-gu, Seoul 133-791, Republic of Korea
| | - Jae-Hyeok Lee
- Department of Botany, University of British Columbia, Vancouver, British Columbia V6T1Z4, Canada
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8
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9
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Sekimoto H. Sexual reproduction and sex determination in green algae. JOURNAL OF PLANT RESEARCH 2017; 130:423-431. [PMID: 28188480 DOI: 10.1007/s10265-017-0908-6] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/18/2016] [Accepted: 12/26/2016] [Indexed: 06/06/2023]
Abstract
The sexual reproductive processes of some representative freshwater green algae are reviewed. Chlamydomonas reinhardtii is a unicellular volvocine alga having two mating types: mating type plus (mt+) and mating type minus (mt-), which are controlled by a single, complex mating-type locus. Sexual adhesion between the gametes is mediated by sex-specific agglutinin molecules on their flagellar membranes. Cell fusion is initiated by an adhesive interaction between the mt+ and mt- mating structures, followed by localized membrane fusion. The loci of sex-limited genes and the conformation of sex-determining regions have been rearranged during the evolution of volvocine algae; however, the essential function of the sex-determining genes of the isogamous unicellular Chlamydomonas reinhardtii is conserved in the multicellular oogamous Volvox carteri. The sexual reproduction of the unicellular charophycean alga, Closterium peracerosum-strigosum-littorale complex, is also focused on here. The sexual reproductive processes of heterothallic strains are controlled by two multifunctional sex pheromones, PR-IP and PR-IP Inducer, which independently promote multiple steps in conjugation at the appropriate times through different induction mechanisms. The molecules involved in sexual reproduction and sex determination have also been characterized.
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Affiliation(s)
- Hiroyuki Sekimoto
- Department of Chemical and Biological Sciences, Faculty of Science, Japan Women's University, 2-8-1 Mejirodai, Bunkyo-ku, Tokyo, 112-8681, Japan.
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10
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Demuez M, Mahdy A, Tomás-Pejó E, González-Fernández C, Ballesteros M. Enzymatic cell disruption of microalgae biomass in biorefinery processes. Biotechnol Bioeng 2015; 112:1955-66. [DOI: 10.1002/bit.25644] [Citation(s) in RCA: 111] [Impact Index Per Article: 12.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/17/2015] [Revised: 05/05/2015] [Accepted: 05/06/2015] [Indexed: 11/08/2022]
Affiliation(s)
- Marie Demuez
- IMDEA Energy Institute; Biotechnological Processes for Energy Production Unit; Av. Ramón de la Sagra 3 28935 Móstoles Spain
| | - Ahmed Mahdy
- IMDEA Energy Institute; Biotechnological Processes for Energy Production Unit; Av. Ramón de la Sagra 3 28935 Móstoles Spain
- Department of Agricultural Microbiology; Faculty of Agriculture; Zagazig University; 44511 Zagazig Egypt
| | - Elia Tomás-Pejó
- IMDEA Energy Institute; Biotechnological Processes for Energy Production Unit; Av. Ramón de la Sagra 3 28935 Móstoles Spain
| | - Cristina González-Fernández
- IMDEA Energy Institute; Biotechnological Processes for Energy Production Unit; Av. Ramón de la Sagra 3 28935 Móstoles Spain
| | - Mercedes Ballesteros
- IMDEA Energy Institute; Biotechnological Processes for Energy Production Unit; Av. Ramón de la Sagra 3 28935 Móstoles Spain
- CIEMAT; Renewable Energy Division; Biofuels Unit; Av. Complutense 40 28040 Madrid Spain
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11
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Brueggeman AJ, Kuehler D, Weeks DP. Evaluation of three herbicide resistance genes for use in genetic transformations and for potential crop protection in algae production. PLANT BIOTECHNOLOGY JOURNAL 2014; 12:894-902. [PMID: 24796724 DOI: 10.1111/pbi.12192] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/26/2013] [Revised: 03/03/2014] [Accepted: 03/10/2014] [Indexed: 05/09/2023]
Abstract
Genes conferring resistance to the herbicides glyphosate, oxyfluorfen and norflurazon were developed and tested for use as dominant selectable markers in genetic transformation of Chlamydomonas reinhardtii and as potential tools for the protection of commercial-scale algal production facilities against contamination by organisms sensitive to these broad-spectrum herbicides. A synthetic glyphosate acetyltransferase (GAT) gene, when fitted with a strong Chlamydomonas promoter, conferred a 2.7×-fold increase in tolerance to the EPSPS inhibitor, glyphosate, in transgenic cells compared with progenitor WT cells. A mutant Chlamydomonas protoporphyrinogen oxidase (protox, PPO) gene previously shown to produce an enzyme insensitive to PPO-inhibiting herbicides, when genetically engineered, generated transgenic cells able to tolerate up to 136× higher levels of the PPO inhibitor, oxyfluorfen, than nontransformed cells. Genetic modification of the Chlamydomonas phytoene desaturase (PDS) gene-based gene sequences found in various norflurazon-resistant organisms allowed production of transgenic cells tolerant to 40× higher levels of norflurazon than nontransgenic cells. The high efficiency of all three herbicide resistance genes in producing transgenic cells demonstrated their suitability as dominant selectable markers for genetic transformation of Chlamydomonas and, potentially, other eukaryotic algae. However, the requirement for high concentrations of glyphosate and its associated negative effects on cell growth rates preclude its consideration for use in large-scale production facilities. In contrast, only low doses of norflurazon and oxyfluorfen (~1.5 μm and ~0.1 μm, respectively) are required for inhibition of cell growth, suggesting that these two herbicides may prove effective in large-scale algal production facilities in suppressing growth of organisms sensitive to these herbicides.
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12
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The cilium secretes bioactive ectosomes. Curr Biol 2013; 23:906-11. [PMID: 23623554 DOI: 10.1016/j.cub.2013.04.019] [Citation(s) in RCA: 167] [Impact Index Per Article: 15.2] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2013] [Revised: 04/03/2013] [Accepted: 04/09/2013] [Indexed: 12/19/2022]
Abstract
The release of membrane vesicles from the surface of cells into their surrounding environment is now recognized as an important pathway for the delivery of proteins to extracellular sites of biological function. Membrane vesicles of this kind, termed exosomes and ectosomes, are the result of active processes and have been shown to carry a wide array of biological effector molecules that can play roles in cell-to-cell communication and remodeling of the extracellular space. Degradation of the extracellular matrix (ECM) through the regulated release of proteolytic enzymes is a key process for development, morphogenesis, and cell migration in animal and plant cells. Here we show that the unicellular alga Chlamydomonas achieves the timely degradation of its mother cell wall, a type of ECM, through the budding of ectosomes directly from the membranes of its flagella. Using a combination of immunoelectron microscopy, immunofluorescence microscopy, and functional analysis, we demonstrate that these vesicles, which we term ciliary ectosomes, act as carriers of the proteolytic enzyme necessary for the liberation of daughter cells following mitosis. Chlamydomonas has proven to be the key unicellular model for the highly conserved mechanisms of mammalian cilia, and our results suggest that cilia may be an underappreciated source of bioactive, extracellular membrane vesicles.
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Kubo T, Kaida S, Abe J, Saito T, Fukuzawa H, Matsuda Y. The Chlamydomonas hatching enzyme, sporangin, is expressed in specific phases of the cell cycle and is localized to the flagella of daughter cells within the sporangial cell wall. PLANT & CELL PHYSIOLOGY 2009; 50:572-83. [PMID: 19179351 DOI: 10.1093/pcp/pcp016] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/08/2023]
Abstract
The timely breakdown of the extracellular matrix by proteolytic enzymes is essential for development, morphogenesis and cell proliferation in plant and animal cells. Sporangin of the unicellular green alga Chlamydomonas reinhardtii that mediates breakdown of the sporangial cell wall to liberate the daughter cells after cell division is characterized as a subtilase-like serine protease. The sporangin gene is specifically transcribed during S/M phase in a synchronized vegetative cell cycle. In immunoblot analyses using a polyclonal antibody raised against the sporangin polypeptide, the enzyme is synthesized after mitotic cell division and accumulated in the daughter cells before hatching. Immunofluorescence analyses showed that sporangin is localized to the flagella of the daughter cells within the sporangial cell wall, and released into the culture medium. The data suggest that sporangin is released from flagella concurrently with the digestion of sporangial cell wall, and then the daughter cells are hatched from the sporangia in the Chlamydomonas vegetative cell cycle.
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Affiliation(s)
- Takeaki Kubo
- Division of Integrated Life Science, Graduate School of Biostudies, Kyoto University, Kyoto 606-8502, Japan.
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14
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Liu Y, Tewari R, Ning J, Blagborough AM, Garbom S, Pei J, Grishin NV, Steele RE, Sinden RE, Snell WJ, Billker O. The conserved plant sterility gene HAP2 functions after attachment of fusogenic membranes in Chlamydomonas and Plasmodium gametes. Genes Dev 2008; 22:1051-68. [PMID: 18367645 DOI: 10.1101/gad.1656508] [Citation(s) in RCA: 239] [Impact Index Per Article: 14.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
The cellular and molecular mechanisms that underlie species-specific membrane fusion between male and female gametes remain largely unknown. Here, by use of gene discovery methods in the green alga Chlamydomonas, gene disruption in the rodent malaria parasite Plasmodium berghei, and distinctive features of fertilization in both organisms, we report discovery of a mechanism that accounts for a conserved protein required for gamete fusion. A screen for fusion mutants in Chlamydomonas identified a homolog of HAP2, an Arabidopsis sterility gene. Moreover, HAP2 disruption in Plasmodium blocked fertilization and thereby mosquito transmission of malaria. HAP2 localizes at the fusion site of Chlamydomonas minus gametes, yet Chlamydomonas minus and Plasmodium hap2 male gametes retain the ability, using other, species-limited proteins, to form tight prefusion membrane attachments with their respective gamete partners. Membrane dye experiments show that HAP2 is essential for membrane merger. Thus, in two distantly related eukaryotes, species-limited proteins govern access to a conserved protein essential for membrane fusion.
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Affiliation(s)
- Yanjie Liu
- Department of Cell Biology, University of Texas Southwestern Medical Center, Dallas, Texas 75390, USA
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15
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Wilson NF. Isolation and in vitro binding of mating type plus fertilization tubules from Chlamydomonas. Methods Mol Biol 2008; 475:213-222. [PMID: 18979246 DOI: 10.1007/978-1-59745-250-2_12] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/27/2023]
Abstract
During fertilization in Chlamydomonas, adhesion and fusion of gametes occur at the tip of specialized regions of the plasma membrane, known as mating structures. The mating type minus (mt[-]) structure is a slightly raised dome-shaped region located at the apical end of the cell body. In contrast, the activated mating type plus (mt[+]) structure is an actin-filled, microvillouslike organelle. Interestingly, a similar type of "fusion organelle" is conserved across diverse groups. Chlamydomonas provides an ideal model system for studying the process of gametic cell fusion in that it is amenable to genetic manipulations as well as cell and molecular biological approaches. Moreover, the ease of culturing Chlamydomonas combined with the ability to isolate the mt(+) fertilization tubule and the development of in vitro assays for adhesion makes it an ideal system for biochemical studies focused on dissecting the molecular mechanisms that underlie the complex process of gametic cell fusion.
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Affiliation(s)
- Nedra F Wilson
- Department of Anatomy and Cell Biology, Oklahoma State University Center for Health Sciences, Tulsa, OK, USA
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16
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Abstract
Differentiation of vegetative cells of the haploid eukaryote Chlamydomonas is dependent on environmental conditions. Upon depletion of nitrogen and exposure to light, vegetative cells undergo a mitotic division, generating gametes that are either mating-type plus (mt[+]) or mating-type minus (mt[-]). As gametes of opposite mating type encounter one another, an initial adhesive interaction mediated by flagella induces a signal transduction pathway that results in activation of gametes. Gametic activation results in the exposure of previously cryptic regions of the plasma membrane (mating structures) that contain the molecules required for gametic cell adhesion and fusion. Recent studies have identified new steps in this signal transduction pathway, including the tyrosine phosphorylation of a cyclic guanosine monophosphate-dependent protein kinase, a requirement for a novel microtubular motility known as intraflagellar transport, and a mt(+)-specific molecule that mediates adhesion between mating structures.
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Affiliation(s)
- Nedra F Wilson
- Department of Anatomy and Cell Biology, Oklahoma State University Center for Health Sciences, Tulsa, OK, USA
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17
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Goodenough U, Lin H, Lee JH. Sex determination in Chlamydomonas. Semin Cell Dev Biol 2007; 18:350-61. [PMID: 17643326 DOI: 10.1016/j.semcdb.2007.02.006] [Citation(s) in RCA: 100] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2007] [Accepted: 02/15/2007] [Indexed: 02/07/2023]
Abstract
The sex-determination system of the unicellular green alga, Chlamydomonas reinhardtii, is governed by genes in the mating-type (MT) locus and entails additional genes located in autosomes. Gene expression is initiated by nitrogen starvation, and cells differentiate into plus or minus gametes within 6h. Reviewed is our current understanding of gametic differentiation and fertilization, initiation of zygote development, and the uniparental inheritance of organelle genomes.
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Affiliation(s)
- Ursula Goodenough
- Department of Biology, Washington University, St. Louis, MO 63130, United States.
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18
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Hoffmann XK, Beck CF. Mating-induced shedding of cell walls, removal of walls from vegetative cells, and osmotic stress induce presumed cell wall genes in Chlamydomonas. PLANT PHYSIOLOGY 2005; 139:999-1014. [PMID: 16183845 PMCID: PMC1256013 DOI: 10.1104/pp.105.065037] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/10/2005] [Revised: 07/05/2005] [Accepted: 07/15/2005] [Indexed: 05/04/2023]
Abstract
The first step in sexual differentiation of the unicellular green alga Chlamydomonas reinhardtii is the formation of gametes. Three genes, GAS28, GAS30, and GAS31, encoding Hyp-rich glycoproteins that presumably are cell wall constituents, are expressed in the late phase of gametogenesis. These genes, in addition, are activated by zygote formation and cell wall removal and by the application of osmotic stress. The induction by zygote formation could be traced to cell wall shedding prior to gamete fusion since it was seen in mutants defective in cell fusion. However, it was absent in mutants defective in the initial steps of mating, i.e. in flagellar agglutination and in accumulation of adenosine 3',5'-cyclic monophosphate in response to this agglutination. Induction of the three GAS genes was also observed when cultures were exposed to hypoosmotic or hyperosmotic stress. To address the question whether the induction seen upon cell wall removal from both gametes and vegetative cells was elicited by osmotic stress, cell wall removal was performed under isosmotic conditions. Also under such conditions an activation of the genes was observed, suggesting that the signaling pathway(s) is (are) activated by wall removal itself.
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MESH Headings
- Amino Acid Sequence
- Animals
- Base Sequence
- Cell Wall/genetics
- Chlamydomonas reinhardtii/cytology
- Chlamydomonas reinhardtii/genetics
- Chlamydomonas reinhardtii/growth & development
- Chlamydomonas reinhardtii/metabolism
- DNA, Algal/genetics
- DNA, Protozoan/genetics
- Gene Expression Regulation, Developmental
- Genes, Protozoan
- Glycoproteins/genetics
- Models, Biological
- Molecular Sequence Data
- Mutation
- Osmotic Pressure
- Protozoan Proteins/biosynthesis
- Protozoan Proteins/genetics
- RNA, Algal/genetics
- RNA, Algal/metabolism
- RNA, Messenger/genetics
- RNA, Messenger/metabolism
- RNA, Protozoan/genetics
- RNA, Protozoan/metabolism
- Sequence Homology, Amino Acid
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19
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Pan J, Misamore MJ, Wang Q, Snell WJ. Protein transport and signal transduction during fertilization in chlamydomonas. Traffic 2003; 4:452-9. [PMID: 12795690 DOI: 10.1034/j.1600-0854.2003.00105.x] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
Fertilization in Chlamydomonas begins with flagellar adhesion between mating type plus and mating type minus gametes and is consummated within minutes by zygote formation. Once fusion occurs, the newly merged gametes cease existence as distinct entities, and the diploid zygote immediately initiates transcription of zygote-specific genes. Accomplishing fertilization within such a short time requires the rapid and signaled movement of pre-existing membrane and cytoplasmic proteins between and within several cellular compartments. Generation within the adhering flagella of the initial signals for protein movement, as well as movement itself of at least one cytoplasmic protein from the cell body to the flagella, depend on the microtubule motor, kinesin-II and presumably on intraflagellar transport (IFT). Adhesion and fusion of the two gametes depend on a second translocation event, the movement of an adhesion/fusion protein onto the surface of a rapidly elongating, microvillous-like fusion organelle. Finally, the merging of the two separate gametes, each containing sex-specific proteins, into a single cell allows the formerly separate proteins to form new interactions that regulate zygote development. Two proteins - a nuclease and a homeodomain protein - which were present only in the plus gamete, are 'delivered' to the cytoplasm of the zygote during gamete fusion. The nuclease is selectively imported into the minus chloroplast, where it degrades the chloroplast DNA, thereby ensuring uniparental inheritance of plus chloroplast traits. The homeodomain protein binds with an as yet unidentified protein delivered by the minus gamete, and the new complex activates transcription of zygote-specific genes.
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Affiliation(s)
- Junmin Pan
- Department of Cell Biology, University of Texas South-western Medical Center, Dallas, Texas 75390-9039, USA
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20
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Misamore MJ, Gupta S, Snell WJ. The Chlamydomonas Fus1 protein is present on the mating type plus fusion organelle and required for a critical membrane adhesion event during fusion with minus gametes. Mol Biol Cell 2003; 14:2530-42. [PMID: 12808049 PMCID: PMC194900 DOI: 10.1091/mbc.e02-12-0790] [Citation(s) in RCA: 76] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Abstract
The molecular mechanisms of the defining event in fertilization, gamete fusion, remain poorly understood. The FUS1 gene in the unicellular, biflagellated green alga Chlamydomonas is one of the few sex-specific eukaryotic genes shown by genetic analysis to be essential for gamete fusion during fertilization. In Chlamydomonas, adhesion and fusion of the plasma membranes of activated mt+ and mt- gametes is accomplished via specialized fusion organelles called mating structures. Herein, we identify the endogenous Fus1 protein, test the idea that Fus1 is at the site of fusion, and identify the step in fusion that requires Fus1. Our results show that Fus1 is a approximately 95-kDa protein present on the external surface of both unactivated and activated mt+ gametes. Bioassays indicate that adhesion between mating type plus and mating type minus fusion organelles requires Fus1 and that Fus1 is functional only after gamete activation. Finally, immunofluorescence demonstrates that the Fus1 protein is present as an apical patch on unactivated gametes and redistributes during gamete activation over the entire surface of the microvillous-like activated plus mating structure, the fertilization tubule. Thus, Fus1 is present on mt+ gametes at the site of cell-cell fusion and essential for an early step in the fusion process.
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Affiliation(s)
- Michael J Misamore
- Department of Cell Biology, University of Texas Southwestern Medical Center, Dallas 75390-9039, USA
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21
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Grobe K, Pöppelmann M, Becker WM, Petersen A. Properties of group I allergens from grass pollen and their relation to cathepsin B, a member of the C1 family of cysteine proteinases. EUROPEAN JOURNAL OF BIOCHEMISTRY 2002; 269:2083-92. [PMID: 11985585 DOI: 10.1046/j.1432-1033.2002.02856.x] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Expansins are a family of proteins that catalyze pH-dependent long-term extension of isolated plant cell walls. They are divided into two groups, alpha and beta, the latter consisting of the grass group I pollen allergens and their vegetative homologs. Expansins are suggested to mediate plant cell growth by interfering with either structural proteins or the polysaccharide network in the cell wall. Our group reported papain-like properties of beta-expansin of Timothy grass (Phleum pratense) pollen, Phl p 1, and suggested that cleavage of cell wall structural proteins may be the underlying mechanism of expansin-mediated wall extension. Here, we report additional data showing that beta-expansins resemble ancient and modern cathepsin B, which is a member of the papain (C1) family of cysteine proteinases. Using the Pichia pastoris expression system, we show that cleavage of inhibitory prosequences from the recombinant allergen is facilitated by its N-glycosylation and that the truncated, activated allergen shows proteolytic activity, resulting in very low stability of the protein. We also show that deglycosylated, full-length allergen is not activated efficiently and therefore is relatively stable. Motif and homology search tools detected significant similarity between beta-expansins and cathepsins of modern animals as well as the archezoa Giardia lamblia, confirming the presence of inhibitory prosequences, active site and other functional amino-acid residues, as well as a conserved location of these features within these molecules. Lastly, we demonstrate by site-directed mutagenesis that the conserved His104 residue is involved in the catalytic activity of beta-expansins. These results indicate a common origin of cathepsin B and beta-expansins, especially if taken together with their previously known biochemical properties.
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Affiliation(s)
- Kay Grobe
- University of California San Diego, La Jolla 92093-0687, USA.
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22
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Pan J, Snell WJ. Signal transduction during fertilization in the unicellular green alga, Chlamydomonas. Curr Opin Microbiol 2000; 3:596-602. [PMID: 11121779 DOI: 10.1016/s1369-5274(00)00146-6] [Citation(s) in RCA: 70] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
Sexual reproduction in the green alga, Chlamydomonas, is regulated by environmental conditions and by cell-cell interactions. After gametogenesis, flagellar adhesion between gametes triggers gamete activation, leading to cell fusion and zygote formation. Recent studies have identified new molecular events that underlie signal transduction during Chlamydomonas fertilization, including expression of a sex-determining protein, phosphorylation of a homeodomain protein, activity of a kinesin II and regulated translocation of an aurora/Ip11-like protein kinase from the cell body to the flagella.
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Affiliation(s)
- J Pan
- Department of Cell Biology, University of Texas, Southwestern Medical Center at Dallas, 5323 Harry Hines Boulevard, Dallas, TX 75390-9039, USA
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23
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Wilson NF, O'Connell JS, Lu M, Snell WJ. Flagellar adhesion between mt(+) and mt(-) Chlamydomonas gametes regulates phosphorylation of the mt(+)-specific homeodomain protein GSP1. J Biol Chem 1999; 274:34383-8. [PMID: 10567416 DOI: 10.1074/jbc.274.48.34383] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
During fertilization in Chlamydomonas, flagellar adhesion between mt(+) and mt(-) gametes induces a cAMP-dependent signal transduction pathway that prepares the gametes for cell fusion and zygote formation. Previously, our laboratory identified a homeodomain protein (GSP1) whose expression was restricted to the cell bodies of mt(+) gametes and whose transcript level was up-regulated during flagellar adhesion. In this report, we describe a new form of GSP1 that appears early during gamete interactions. Immunoblot analysis showed that in addition to the 120-kDa form of GSP1 normally present in mt(+) gametes, a 122-kDa form was detected when the cells were mixed with mt(-) gametes. The more slowly migrating form of GSP1 was detectable within minutes after gametes were mixed together, and its appearance did not require new protein synthesis. Thus, the 122-kDa form represents a post-translational modification of the pre-existing 120-kDa form of GSP1. Moreover, conversion to the 122-kDa form did not require cell fusion. Although the 120-kDa form was expressed 10 h after vegetative cells were transferred to gametic induction medium, the 122-kDa form was detected only after mt(+) gametes were induced to undergo the sexual signaling that accompanies fertilization. Incubation of mt(+) gametes with dibutyryl cAMP led to the appearance of the 122-kDa form of GSP1, and the cyclic nucleotide-dependent protein kinase inhibitor H-8 inhibited the adhesion-induced conversion. Incubation of GSP1 immunoprecipitated from signaling mt(+) gametes with alkaline phosphatase showed that the conversion was due to phosphorylation. The results indicate that flagellar adhesion induces a rapid, cAMP-dependent phosphorylation of the homeodomain protein GSP1 early during fertilization in Chlamydomonas.
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Affiliation(s)
- N F Wilson
- Department of Cell Biology, University of Texas Southwestern Medical Center, Dallas, Texas 75235-9039, USA
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24
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Wilson NF, Foglesong MJ, Snell WJ. The Chlamydomonas mating type plus fertilization tubule, a prototypic cell fusion organelle: isolation, characterization, and in vitro adhesion to mating type minus gametes. J Cell Biol 1997; 137:1537-53. [PMID: 9199169 PMCID: PMC2137821 DOI: 10.1083/jcb.137.7.1537] [Citation(s) in RCA: 40] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023] Open
Abstract
In the biflagellated alga Chlamydomonas, adhesion and fusion of the plasma membranes of gametes during fertilization occurs via an actin-filled, microvillus-like cell protrusion. Formation of this approximately 3-microm-long fusion organelle, the Chlamydomonas fertilization tubule, is induced in mating type plus (mt+) gametes during flagellar adhesion with mating type minus (mt-) gametes. Subsequent adhesion between the tip of the mt+ fertilization tubule and the apex of a mating structure on mt- gametes is followed rapidly by fusion of the plasma membranes and zygote formation. In this report, we describe the isolation and characterization of fertilization tubules from mt+ gametes activated for cell fusion. Fertilization tubules were detached by homogenization of activated mt+ gametes in an EGTA-containing buffer and purified by differential centrifugation followed by fractionation on sucrose and Percoll gradients. As determined by fluorescence microscopy of samples stained with a fluorescent probe for filamentous actin, the method yielded 2-3 x 10(6) fertilization tubules/microg protein, representing up to a 360-fold enrichment of these organelles. Examination by negative stain electron microscopy demonstrated that the purified fertilization tubules were morphologically indistinguishable from fertilization tubules on intact, activated mt+ gametes, retaining both the extracellular fringe and the internal array of actin filaments. Several proteins, including actin as well as two surface proteins identified by biotinylation studies, copurified with the fertilization tubules. Most importantly, the isolated mt+ fertilization tubules bound to the apical ends of activated mt- gametes between the two flagella, the site of the mt- mating structure; a single fertilization tubule bound per cell, binding was specific for gametes, and fertilization tubules isolated from trypsin-treated, activated mt+ gametes did not bind to activated mt- gametes.
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Affiliation(s)
- N F Wilson
- Department of Cell Biology and Neuroscience, The University of Texas Southwestern Medical Center, Dallas, Texas 75235, USA
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25
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Beck CF, Haring MA. Gametic Differentiation of Chlamydomonas. INTERNATIONAL REVIEW OF CYTOLOGY 1996. [DOI: 10.1016/s0074-7696(08)60886-4] [Citation(s) in RCA: 40] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
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26
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Sekimoto H, Sone Y, Fujii T. Regulation of expression of the genes for a sex pheromone by an inducer of the sex pheromone in the Closterium peracerosum-strigosum-littorale complex. PLANTA 1994; 193:137-144. [PMID: 7764622 DOI: 10.1007/bf00191617] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/22/2023]
Abstract
A sex pheromone, protoplast-release-inducing protein (PR-IP), of the Closterium peracerosum-strigosum-littorale complex is known to induce the release of protoplasts from mating-type minus (Mt-) cells during sexual reproduction and to have two subunit polypeptides of 19 and 42 kDa. Here, we describe the regulation mechanism for the release of the PR-IP. The sex pheromone was fractionated to yield subunits of 19 and 42 kDa, respectively, and each subunit was treated with V8 protease and with CNBr. By reference to the partial amino-acid sequences of the digested polypeptides, oligo nucleotides were synthesized and used as primers for the combined reverse transcription-polymerase chain reaction. Amplified fragments of DNA, of 130 bp in the case of the 19-kDa subunit and of 330 bp in the case of the 42-kDa subunit, were obtained, sequenced, and used as probes to identify the respective transcripts. From the results of Northern hybridization, the sizes of transcripts were estimated to be 1.2 kb for the 19-kDa subunit and 1.4 kb for the 42-kDa subunit. These transcripts appeared transiently only when mating-type plus (mt+) cells were treated with another sex pheromone (PR-IP Inducer) for more than 4 h in the light. By immunoblotting with anti-42-kDa-subunit antiserum, it was shown that PR-IP accumulated gradually in the medium but not in the mt+ cells after treatment with PR-IP inducer in the light.(ABSTRACT TRUNCATED AT 250 WORDS)
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Affiliation(s)
- H Sekimoto
- Institute of Biological Sciences, University of Tsukuba, Ibaraki, Japan
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27
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Zhang Y, Snell W. Differential regulation of adenylylcyclases in vegetative and gametic flagella of Chlamydomonas. J Biol Chem 1993. [DOI: 10.1016/s0021-9258(18)53922-3] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022] Open
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28
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Kinoshita T, Fukuzawa H, Shimada T, Saito T, Matsuda Y. Primary structure and expression of a gamete lytic enzyme in Chlamydomonas reinhardtii: similarity of functional domains to matrix metalloproteases. Proc Natl Acad Sci U S A 1992; 89:4693-7. [PMID: 1584806 PMCID: PMC49149 DOI: 10.1073/pnas.89.10.4693] [Citation(s) in RCA: 68] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022] Open
Abstract
A gamete lytic enzyme (GLE) of Chlamydomonas reinhardtii is a zinc metalloprotease and mediates digestion of the cell walls of the two mating-type gametes during mating as a necessary prelude to cell fusion. The nucleotide sequence analysis of a cDNA revealed that GLE is synthesized in a preproenzyme form, a 638-amino acid polypeptide (Mr, 69,824) with a 28-amino acid signal peptide, a 155-amino acid propolypeptide, and a 455-amino acid mature polypeptide (Mr, 49,633). A potential site for autocatalytic activation was contained within the propolypeptide and a zinc binding site found within the mature polypeptide; both sites were highly homologous to those in mammalian collagenase. A putative calcium binding site was present in the near C-terminal region of the mature GLE. Both propolypeptide and mature polypeptide had potential sites for asparagine-linked glycosylation, and the Arg-(Pro)3 and Arg-(Pro)2 motifs, which are known to exist in hydroxyproline-rich glycoproteins of the Chlamydomonas cell wall. Northern blot analysis revealed that steady-state levels of the 2.4-kilobase GLE mRNA increased during growth and mitotic cell division in the vegetative cell cycle and also increased markedly during gametogenesis under nitrogen-starved conditions.
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Affiliation(s)
- T Kinoshita
- Department of Biology, Faculty of Science, Kobe University, Japan
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29
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ATP-dependent regulation of flagellar adenylylcyclase in gametes of Chlamydomonas reinhardtii. J Biol Chem 1991. [DOI: 10.1016/s0021-9258(18)54447-1] [Citation(s) in RCA: 30] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
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30
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Hunnicutt GR, Snell WJ. Rapid and slow mechanisms for loss of cell adhesiveness during fertilization in Chlamydomonas. Dev Biol 1991; 147:216-24. [PMID: 1879608 DOI: 10.1016/s0012-1606(05)80019-3] [Citation(s) in RCA: 23] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
Although vegetative cells, gametes, and zygotes of the biflagellated alga Chlamydomonas bear flagella, only the flagella of mt+ and mt- gametes are adhesive. The molecules responsible for adhesiveness, mt+ and mt- agglutinins, are long rod-shaped glycoproteins displayed on the flagellar membrane. These flagellar agglutinins, which gametes use both as adhesion and signaling molecules during the early events of fertilization, are lost from the flagella during adhesion. Flagellar adhesiveness can be maintained, however, by recruitment and activation of preexisting, inactive agglutinins from the plasma membrane of the cell body (Hunnicutt et al, 1990, J. Cell Biol. 111, 1605-1616) unless the gametes of opposite mating types fuse to form zygotes. Upon cell fusion, flagellar adhesiveness is lost. In the studies presented here, we have employed an in vitro bioassay to measure agglutinins in both cell bodies and flagella at various times during gametogenesis, during fertilization, and after zygote-formation. By use of the bioassay, which can detect agglutinins that are functionally inactive in vivo, we found that vegetative cells are devoid of agglutinins. These adhesion molecules appear only after gametogenesis is underway with the cell body agglutinins appearing first and then the flagellar agglutinins. Surprisingly, 30 min after zygote formation, when the zygotes' flagella are no longer adhesive, the flagellar agglutinin activity detectable with the bioassay remains high. One interpretation of these results is that zygotes continue to recruit agglutinins from the cell body to the flagella, but cell fusion abrogates activation of the agglutinins. Within 45-90 min after fusion both the cell body and flagellar agglutinins are lost and can be detected in the medium. These mechanisms, which render the zygotes nonadhesive to other zygotes and unmated gametes, contribute to the Chlamydomonas equivalent of a block to polyspermy.
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Affiliation(s)
- G R Hunnicutt
- Department of Cell Biology and Neuroscience, University of Texas Southwestern Medical Center, Dallas 75235
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31
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Protein Sorting in the Secretory System of Plant Cells. ACTA ACUST UNITED AC 1991. [DOI: 10.1016/s0074-7696(08)61215-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 04/10/2023]
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32
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Snell WJ. Adhesion and signalling during fertilization in multicellular and unicellular organisms. Curr Opin Cell Biol 1990; 2:821-32. [PMID: 2083083 DOI: 10.1016/0955-0674(90)90079-t] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Affiliation(s)
- W J Snell
- Department of Cell Biology and Neuroscience, University of Texas Southwestern Medical Center, Dallas
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33
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Hunnicutt GR, Kosfiszer MG, Snell WJ. Cell body and flagellar agglutinins in Chlamydomonas reinhardtii: the cell body plasma membrane is a reservoir for agglutinins whose migration to the flagella is regulated by a functional barrier. J Biophys Biochem Cytol 1990; 111:1605-16. [PMID: 2170424 PMCID: PMC2116248 DOI: 10.1083/jcb.111.4.1605] [Citation(s) in RCA: 86] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022] Open
Abstract
Fertilization in Chlamydomonas reinhardtii is initiated when gametes of opposite mating types adhere to each other via adhesion molecules (agglutinins) on their flagella. Adhesion leads to loss of active agglutinins from the flagella and recruitment of new agglutinins from a pool associated with the cell body. We have been interested in determining the precise cellular location of the pool and learning more about the relationship between agglutinins in the two domains. In the studies reported here we describe methods for purification of mt+ cell body agglutinins by use of ammonium sulfate precipitation, chromatography (molecular sieve, ion exchange, and hydrophobic interaction), and sucrose gradient centrifugation. About 90% of the total agglutinins were associated with the cell body and the remainder were on the flagella. Cell body agglutinins were indistinguishable from mt+ flagellar agglutinins by SDS-PAGE, elution properties on a hydrophobic interaction column, and in sedimentation properties on sucrose gradients. The nonadhesiveness of cell bodies suggested that the cell body agglutinins would be intracellular, but our results are not consistent with this interpretation. We have demonstrated that brief trypsin treatment of deflagellated gametes destroyed all of the cell body agglutinins and, in addition, we showed that the cell body agglutinins were accessible to surface iodination. These results indicated that C. reinhardtii agglutinins have a novel cellular disposition: active agglutinins, representing approximately 10% of the total cellular agglutinins, are found only on the flagella, whereas the remaining 90% of these molecules are on the external surface of the cell body plasma membrane in a nonfunctional form. This segregation of cell adhesion molecules into distinct membrane domains before gametic interactions has been demonstrated in sperm of multicellular organisms and may be a common mechanism for sequestering these critical molecules until gametes are activated for fusion. In experiments in which surface-iodinated cell bodies were permitted to regenerate new flagella, we found that the agglutinins (as well as the 350,000 Mr, major flagellar membrane protein) on the newly regenerated flagella were iodinated. These results indicate that proteins destined for the flagella can reside on the external surface of the cell body plasma membrane and are recruited onto newly forming flagella as well as onto preexisting flagella during fertilization.
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Affiliation(s)
- G R Hunnicutt
- Department of Cell Biology and Neuroscience, University of Texas Southwestern Medical Center, Dallas 75235
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34
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Waffenschmidt S, Jaenicke L. Autolysins in Chlamydomonas. CELL WALLS AND SURFACES, REPRODUCTION, PHOTOSYNTHESIS 1990. [DOI: 10.1007/978-3-642-48652-4_5] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
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35
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Snell WJ, Eskue WA, Buchanan MJ. Regulated secretion of a serine protease that activates an extracellular matrix-degrading metalloprotease during fertilization in Chlamydomonas. J Cell Biol 1989; 109:1689-94. [PMID: 2551910 PMCID: PMC2115817 DOI: 10.1083/jcb.109.4.1689] [Citation(s) in RCA: 38] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
During fertilization in the biflagellated alga, Chlamydomonas reinhardtii, gametes of opposite mating types adhere to each other via agglutinin molecules located on their flagellar surfaces, generating a sexual signal that induces several cellular responses including cell wall release. This cell contact-generated signal is mediated by cAMP and release of the wall, which is devoid of cellulose and contains several hydroxyproline-rich glycoproteins, is due to the activation of a metalloprotease, lysin. Although we originally assumed that lysin would be stored intracellularly in a compartment structurally separate from its substrate, recently we showed that lysin is stored in the periplasm as an inactive, higher relative molecular mass precursor, prolysin (Buchanan, M.J., S. H. Imam, W. A. Eskue, and W. J. Snell. 1989. J. Cell Biol. 108:199-207). Here we show that conversion of prolysin to lysin is due to a cellular, nonperiplasmic enzyme that has the properties of a serine protease. Release of this serine protease into the periplasm is induced by incubation of gametes in dibutyryl cAMP. This may be one of the few examples of regulated secretion of a protease in a eucaryotic microorganism and a novel example of regulated secretion in a plant system.
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Affiliation(s)
- W J Snell
- University of Texas Southwestern Medical School, Department of Cell Biology, Dallas 75235-9039
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