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Ben Chaabene R, Martinez M, Bonavoglia A, Maco B, Chang YW, Lentini G, Soldati-Favre D. Toxoplasma gondii rhoptry discharge factor 3 is essential for invasion and microtubule-associated vesicle biogenesis. PLoS Biol 2024; 22:e3002745. [PMID: 39137211 PMCID: PMC11343613 DOI: 10.1371/journal.pbio.3002745] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/25/2023] [Revised: 08/23/2024] [Accepted: 07/10/2024] [Indexed: 08/15/2024] Open
Abstract
Rhoptries are specialized secretory organelles conserved across the Apicomplexa phylum, essential for host cell invasion and critical for subverting of host cellular and immune functions. They contain proteins and membranous materials injected directly into the host cells, participating in parasitophorous vacuole formation. Toxoplasma gondii tachyzoites harbor 8 to 12 rhoptries, 2 of which are docked to an apical vesicle (AV), a central element associated with a rhoptry secretory apparatus prior to injection into the host cell. This parasite is also equipped with 5 to 6 microtubule-associated vesicles, presumably serving as AV replenishment for iterative rhoptry discharge. Here, we characterized a rhoptry protein, rhoptry discharge factor 3 (RDF3), crucial for rhoptry discharge and invasion. RDF3 enters the secretory pathway, localizing near the AV and associated with the rhoptry bulb. Upon invasion, RDF3 dynamically delocalizes, suggesting a critical role at the time of rhoptry discharge. Cryo-electron tomography analysis of RDF3-depleted parasites reveals irregularity in microtubule-associated vesicles morphology, presumably impacting on their preparedness to function as an AV. Our findings suggest that RDF3 is priming the microtubule-associated vesicles for rhoptry discharge by a mechanism distinct from the rhoptry secretory apparatus contribution.
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Affiliation(s)
- Rouaa Ben Chaabene
- Department of Microbiology and Molecular Medicine, Faculty of Medicine, University of Geneva, Geneva, Switzerland
| | - Matthew Martinez
- Department of Biochemistry and Biophysics, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania, United States of America
| | - Alessandro Bonavoglia
- Department of Microbiology and Molecular Medicine, Faculty of Medicine, University of Geneva, Geneva, Switzerland
| | - Bohumil Maco
- Department of Microbiology and Molecular Medicine, Faculty of Medicine, University of Geneva, Geneva, Switzerland
| | - Yi-Wei Chang
- Department of Biochemistry and Biophysics, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania, United States of America
- Institute of Structural Biology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania, United States of America
| | - Gaëlle Lentini
- Department of Microbiology and Molecular Medicine, Faculty of Medicine, University of Geneva, Geneva, Switzerland
| | - Dominique Soldati-Favre
- Department of Microbiology and Molecular Medicine, Faculty of Medicine, University of Geneva, Geneva, Switzerland
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2
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Zahra I, DeVine L, Cole R, Malik HA, Wu J, Wen J, Hedfi A, Liaqat A, Ijaz R, Ramzan U, Shakoori AR, Shakoori FR, Betenbaugh MJ. Insights into the differential proteome landscape of a newly isolated Paramecium multimicronucleatum in response to cadmium stress. J Proteomics 2024; 300:105178. [PMID: 38636824 DOI: 10.1016/j.jprot.2024.105178] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/29/2024] [Revised: 04/01/2024] [Accepted: 04/12/2024] [Indexed: 04/20/2024]
Abstract
Employing microbial systems for the bioremediation of contaminated waters represent a potential option, however, limited understanding of the underlying mechanisms hampers the implication of microbial-mediated bioremediation. The omics tools offer a promising approach to explore the molecular basis of the bioremediation process. Here, a mass spectrometry-based quantitative proteome profiling approach was conducted to explore the differential protein levels in cadmium-treated Paramecium multimicronucleatum. The Proteome Discoverer software was used to identify and quantify differentially abundant proteins. The proteome profiling generated 7,416 peptide spectral matches, yielding 2824 total peptides, corresponding to 989 proteins. The analysis revealed that 29 proteins exhibited significant (p ≤ 0.05) differential levels, including a higher abundance of 6 proteins and reduced levels of 23 proteins in Cd2+ treated samples. These differentially abundant proteins were associated with stress response, energy metabolism, protein degradation, cell growth, and hormone processing. Briefly, a comprehensive proteome profile in response to cadmium stress of a newly isolated Paramecium has been established that will be useful in future studies identifying critical proteins involved in the bioremediation of metals in ciliates. SIGNIFICANCE: Ciliates are considered a good biological indicator of chemical pollution and relatively sensitive to heavy metal contamination. A prominent ciliate, Paramecium is a promising candidate for the bioremediation of polluted water. The proteins related to metal resistance in Paramecium species are still largely unknown and need further exploration. In order to identify and reveal the proteins related to metal resistance in Paramecia, we have reported differential protein abundance in Paramecium multimicronucleatum in response to cadmium stress. The proteins found in our study play essential roles during stress response, hormone processing, protein degradation, energy metabolism, and cell growth. It seems likely that Paramecia are not a simple sponge for metals but they could also transform them into less toxic derivatives or by detoxification by protein binding. This data will be helpful in future studies to identify critical proteins along with their detailed mechanisms involved in the bioremediation and detoxification of metal ions in Paramecium species.
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Affiliation(s)
- Itrat Zahra
- Institute of Zoology, University of the Punjab, New Campus, Lahore 54590, Pakistan.
| | - Lauren DeVine
- Mass Spectrometry and Proteomics Facility, Department of Biological Chemistry, Johns Hopkins University School of Medicine, Baltimore, MD, USA.
| | - Robert Cole
- Mass Spectrometry and Proteomics Facility, Department of Biological Chemistry, Johns Hopkins University School of Medicine, Baltimore, MD, USA.
| | - Hafiza Aroosa Malik
- Bioenergy Research Center, Department of Bioinformatics and Biotechnology, Government College University Faisalabad, Faisalabad 38000, Pakistan.
| | - Jinke Wu
- Department of Chemical and Biomolecular Engineering, Johns Hopkins University, Baltimore, MD, USA.
| | - Junneng Wen
- Department of Chemical and Biomolecular Engineering, Johns Hopkins University, Baltimore, MD, USA.
| | - Amor Hedfi
- Department of Biology, College of Sciences, Taif University, POBox 11099, Taif 21944, Saudi Arabia.
| | - Ayesha Liaqat
- Institute of Zoology, University of the Punjab, New Campus, Lahore 54590, Pakistan.
| | - Roohi Ijaz
- Institute of Zoology, University of the Punjab, New Campus, Lahore 54590, Pakistan.
| | - Uzma Ramzan
- Institute of Zoology, University of the Punjab, New Campus, Lahore 54590, Pakistan.
| | - Abdul Rauf Shakoori
- School of Biological Sciences, University of the Punjab, New Campus, Lahore 54590, Pakistan.
| | - Farah Rauf Shakoori
- Institute of Zoology, University of the Punjab, New Campus, Lahore 54590, Pakistan.
| | - Michael J Betenbaugh
- Department of Chemical and Biomolecular Engineering, Johns Hopkins University, Baltimore, MD, USA.
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3
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Li Z, Chen X, Zhao F, Miao M. Genomic insights into the cellular specialization of predation in raptorial protists. BMC Biol 2024; 22:107. [PMID: 38715037 PMCID: PMC11077807 DOI: 10.1186/s12915-024-01904-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/06/2023] [Accepted: 04/26/2024] [Indexed: 05/12/2024] Open
Abstract
BACKGROUND Predation is a fundamental mechanism for organisms to acquire energy, and various species have evolved diverse tools to enhance their hunting abilities. Among protozoan predators, raptorial Haptorian ciliates are particularly fascinating as they possess offensive extrusomes known as toxicysts, which are rapidly discharged upon prey contact. However, our understanding of the genetic processes and specific toxins involved in toxicyst formation and discharge is still limited. RESULTS In this study, we investigated the predation strategies and subcellular structures of seven Haptoria ciliate species and obtained their genome sequences using single-cell sequencing technology. Comparative genomic analysis revealed distinct gene duplications related to membrane transport proteins and hydrolytic enzymes in Haptoria, which play a crucial role in the production and discharge of toxicysts. Transcriptomic analysis further confirmed the abundant expression of genes related to membrane transporters and cellular toxins in Haptoria compared to Trichostomatia. Notably, polyketide synthases (PKS) and L-amino acid oxidases (LAAO) were identified as potentially toxin genes that underwent extensive duplication events in Haptoria. CONCLUSIONS Our results shed light on the evolutionary and genomic adaptations of Haptorian ciliates for their predation strategies in evolution and provide insights into their toxic mechanisms.
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Affiliation(s)
- Zaihan Li
- University of Chinese Academy of Sciences, Beijing, 100049, China
| | - Xiao Chen
- Laboratory of Marine Protozoan Biodiversity and Evolution, Marine College, Shandong University, Weihai, 264209, China
| | - Fangqing Zhao
- University of Chinese Academy of Sciences, Beijing, 100049, China
- Institute of Zoology, Beijing Institutes of Life Science, Chinese Academy of Sciences, Beijing, 100101, China
| | - Miao Miao
- University of Chinese Academy of Sciences, Beijing, 100049, China.
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4
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Gao Y, Solberg T, Wang R, Yu Y, Al-Rasheid KAS, Gao F. Application of RNA interference and protein localization to investigate housekeeping and developmentally regulated genes in the emerging model protozoan Paramecium caudatum. Commun Biol 2024; 7:204. [PMID: 38374195 PMCID: PMC10876655 DOI: 10.1038/s42003-024-05906-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/25/2023] [Accepted: 02/09/2024] [Indexed: 02/21/2024] Open
Abstract
Unicellular eukaryotes represent tremendous evolutionary diversity. However, the molecular mechanisms underlying this diversity remain largely unexplored, partly due to a limitation of genetic tools to only a few model species. Paramecium caudatum is a well-known unicellular eukaryote with an unexpectedly large germline genome, of which only two percent is retained in the somatic genome following sexual processes, revealing extensive DNA elimination. However, further progress in understanding the molecular mechanisms governing this process is hampered by a lack of suitable genetic tools. Here, we report the successful application of gene knockdown and protein localization methods to interrogate the function of both housekeeping and developmentally regulated genes in P. caudatum. Using these methods, we achieved the expected phenotypes upon RNAi by feeding, and determined the localization of these proteins by microinjection of fusion constructs containing fluorescent protein or antibody tags. Lastly, we used these methods to reveal that P. caudatum PiggyMac, a domesticated piggyBac transposase, is essential for sexual development, and is likely to be an active transposase directly involved in DNA cleavage. The application of these methods lays the groundwork for future studies of gene function in P. caudatum and can be used to answer important biological questions in the future.
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Affiliation(s)
- Yunyi Gao
- Key Laboratory of Evolution & Marine Biodiversity (Ministry of Education), and Institute of Evolution & Marine Biodiversity, Ocean University of China, Qingdao, 266003, China
| | - Therese Solberg
- Department of Molecular Biology, Keio University School of Medicine, Tokyo, 160-8582, Japan
- Human Biology Microbiome Quantum Research Center (WPI-Bio2Q), Keio University, Tokyo, 108-8345, Japan
| | - Rui Wang
- Key Laboratory of Evolution & Marine Biodiversity (Ministry of Education), and Institute of Evolution & Marine Biodiversity, Ocean University of China, Qingdao, 266003, China
| | - Yueer Yu
- Key Laboratory of Evolution & Marine Biodiversity (Ministry of Education), and Institute of Evolution & Marine Biodiversity, Ocean University of China, Qingdao, 266003, China
| | - Khaled A S Al-Rasheid
- Zoology Department, College of Science, King Saud University, Riyadh, 11451, Saudi Arabia
| | - Feng Gao
- Key Laboratory of Evolution & Marine Biodiversity (Ministry of Education), and Institute of Evolution & Marine Biodiversity, Ocean University of China, Qingdao, 266003, China.
- Laoshan Laboratory, Qingdao, 266237, China.
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5
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Mocaer K, Mizzon G, Gunkel M, Halavatyi A, Steyer A, Oorschot V, Schorb M, Le Kieffre C, Yee DP, Chevalier F, Gallet B, Decelle J, Schwab Y, Ronchi P. Targeted volume correlative light and electron microscopy of an environmental marine microorganism. J Cell Sci 2023; 136:jcs261355. [PMID: 37455654 PMCID: PMC10445747 DOI: 10.1242/jcs.261355] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/22/2023] [Accepted: 07/06/2023] [Indexed: 07/18/2023] Open
Abstract
Photosynthetic microalgae are responsible for an important fraction of CO2 fixation and O2 production on Earth. Three-dimensional (3D) ultrastructural characterization of these organisms in their natural environment can contribute to a deeper understanding of their cell biology. However, the low throughput of volume electron microscopy (vEM) methods along with the complexity and heterogeneity of environmental samples pose great technical challenges. In the present study, we used a workflow based on a specific electron microscopy sample preparation method compatible with both light and vEM imaging in order to target one cell among a complex natural community. This method revealed the 3D subcellular landscape of a photosynthetic dinoflagellate, which we identified as Ensiculifera tyrrhenica, with quantitative characterization of multiple organelles. We show that this cell contains a single convoluted chloroplast and show the arrangement of the flagellar apparatus with its associated photosensitive elements. Moreover, we observed partial chromatin unfolding, potentially associated with transcription activity in these organisms, in which chromosomes are permanently condensed. Together with providing insights in dinoflagellate biology, this proof-of-principle study illustrates an efficient tool for the targeted ultrastructural analysis of environmental microorganisms in heterogeneous mixes.
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Affiliation(s)
- Karel Mocaer
- Cell Biology and Biophysics Unit, European Molecular Biology Laboratory, 69117 Heidelberg, Germany
- Collaboration for joint PhD degree between the European Molecular Biology Laboratory and the Heidelberg University, Faculty of Biosciences, 69120 Heidelberg, Germany
| | - Giulia Mizzon
- Electron Microscopy Core Facility, European Molecular Biology Laboratory, 69117 Heidelberg, Germany
- Department of Infectious Diseases, Molecular Virology, CIID, 69120 Heidelberg, Germany
- German Center for Infection Research, Heidelberg partner site, 69120 Heidelberg, Germany
| | - Manuel Gunkel
- Advanced Light Microscopy Facility, European Molecular Biology Laboratory, 69117 Heidelberg, Germany
| | - Aliaksandr Halavatyi
- Advanced Light Microscopy Facility, European Molecular Biology Laboratory, 69117 Heidelberg, Germany
| | - Anna Steyer
- EMBL Imaging Centre, European Molecular Biology Laboratory, 69117 Heidelberg, Germany
| | - Viola Oorschot
- Electron Microscopy Core Facility, European Molecular Biology Laboratory, 69117 Heidelberg, Germany
| | - Martin Schorb
- Electron Microscopy Core Facility, European Molecular Biology Laboratory, 69117 Heidelberg, Germany
| | | | - Daniel P. Yee
- Université Grenoble Alpes, CNRS, CEA, INRAe, IRIG-LPCV, 38054 Grenoble, France
| | - Fabien Chevalier
- Université Grenoble Alpes, CNRS, CEA, INRAe, IRIG-LPCV, 38054 Grenoble, France
| | - Benoit Gallet
- Institut de Biologie Structurale (IBS), Université Grenoble Alpes, CEA, CNRS, 38000 Grenoble, France
| | - Johan Decelle
- Université Grenoble Alpes, CNRS, CEA, INRAe, IRIG-LPCV, 38054 Grenoble, France
| | - Yannick Schwab
- Cell Biology and Biophysics Unit, European Molecular Biology Laboratory, 69117 Heidelberg, Germany
- Electron Microscopy Core Facility, European Molecular Biology Laboratory, 69117 Heidelberg, Germany
| | - Paolo Ronchi
- Electron Microscopy Core Facility, European Molecular Biology Laboratory, 69117 Heidelberg, Germany
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6
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Van Houten J. A Review for the Special Issue on Paramecium as a Modern Model Organism. Microorganisms 2023; 11:microorganisms11040937. [PMID: 37110360 PMCID: PMC10143506 DOI: 10.3390/microorganisms11040937] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2023] [Revised: 03/28/2023] [Accepted: 03/29/2023] [Indexed: 04/07/2023] Open
Abstract
This review provides background and perspective for the articles contributing to the Special Issue of MDPI Micro-organisms on Paramecium as a Modern Model Organism. The six articles cover a variety of topics, each taking advantage of an important aspect of Paramecium biology: peripheral surface proteins that are developmentally regulated, endosymbiont algae and bacteria, ion channel regulation by calmodulin, regulation of cell mating reactivity and senescence, and the introns that dwell in the large genome. Each article highlights a significant aspect of Paramecium and its versatility.
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Affiliation(s)
- Judith Van Houten
- Department of Biology, University of Vermont, Burlington, VT 05405, USA
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7
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Ganser MH, Bartel H, Fedrizzi M, Agatha S. A comparative ultrastructural study on the nanoscale extrusomes of tintinnids (Alveolata, Ciliophora, Spirotricha) and their phylogenetic significance. Eur J Protistol 2023; 87:125953. [PMID: 36638556 DOI: 10.1016/j.ejop.2022.125953] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/10/2022] [Revised: 12/14/2022] [Accepted: 12/19/2022] [Indexed: 12/24/2022]
Abstract
The capsules, putative extrusomes in tintinnid ciliates, are known since 1971. Based on their ultrastructure, shape, and size, five capsule types were distinguished and suggested to be of phylogenetic significance. However, detailed morphometric data and transmission electron micrographs are lacking to verify former conclusions. In the current study, comprehensive analyses of transmission electron microscopic data were performed, investigating 14 species from 13 genera and more than seven families collected in European coastal waters and in the Northeast Pacific. Our data suggest two main capsule types (large and ampulliform vs small and ellipsoidal/ovoidal) each including two subtypes characterised by their internal structures. Species groupings inferred from the capsule (sub-)types emerge also as closely related in gene trees. Additionally, the ampulliform type unites the Undellidae, Xystonellidae, and Tintinnid clade 2, while the shared possession of the small ellipsoidal type proposes a close relationship of Tintinnid clade 11 with the Rhabdonellidae and Cyttarocylididae. Thus, the capsules provide promising features to shed light on several unresolved evolutionary relationships among tintinnid genera and families; yet, information on capsules is still missing for many monophyletic groupings. Finally, we provide the first ultrastructural clues for the extrusive character of these organelles.
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Affiliation(s)
- Maximilian H Ganser
- Department of Environment & Biodiversity, Paris Lodron University of Salzburg, Hellbrunnerstraße 34, 5020 Salzburg, Austria.
| | - Heidi Bartel
- Department of Environment & Biodiversity, Paris Lodron University of Salzburg, Hellbrunnerstraße 34, 5020 Salzburg, Austria
| | - Mattia Fedrizzi
- Department of Environment & Biodiversity, Paris Lodron University of Salzburg, Hellbrunnerstraße 34, 5020 Salzburg, Austria
| | - Sabine Agatha
- Department of Environment & Biodiversity, Paris Lodron University of Salzburg, Hellbrunnerstraße 34, 5020 Salzburg, Austria.
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8
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Kodama Y, Fujishima M. Role of host ciliate Paramecium bursaria mitochondria and trichocysts for symbiotic Chlorella variabilis attachment beneath the host cell cortex. FEMS Microbiol Lett 2023; 370:fnad088. [PMID: 37660246 DOI: 10.1093/femsle/fnad088] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2023] [Revised: 08/08/2023] [Accepted: 08/25/2023] [Indexed: 09/04/2023] Open
Abstract
Symbiotic Chlorella variabilis is encased in the perialgal vacuole (PV) membrane of ciliate Paramecium bursaria. The PV membrane is stably anchored below the host cell cortex by adhesion to host mitochondria. Host trichocysts, which are defensive organelles against predators, are present in the mitochondria and PV membrane vicinity. The mechanism by which PV attaches beneath the host cell cortex remains unknown. When P. bursaria is centrifuged at high speed, the symbiotic algae are displaced from the host cell cortex and concentrate at the posterior end. When centrifugation is stopped, the dislocated algae reattach beneath the host cell cortex with fast cytoplasmic streaming. The densities of mitochondria and trichocysts before and after centrifugation were compared using indirect immunofluorescence microscopy with monoclonal antibodies. Almost all trichocysts were shed by high-speed centrifugation, but dislocated algae could reattach even in the absence of trichocysts. In contrast, host mitochondria were unaffected in localization and number, and the dislocated algae also reattached. These findings suggest trichocysts are unnecessary for algal relocalization and that mitochondria are colocalized with the algae. However, many mitochondria were also present in the cell's anterior region without symbiotic algae. Therefore, not all areas with mitochondria contained algae, but there was an algal localization bias within the host cell.
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Affiliation(s)
- Yuuki Kodama
- Institute of Agricultural and Life Sciences, Academic Assembly, Shimane University, 1060 Nishikawatsu-cho, Matsue-shi, Shimane 690-8504, Japan
| | - Masahiro Fujishima
- Department of Environmental Science and Engineering, Graduate School of Science and Engineering, Yamaguchi University, Yoshida 1677-1, Yamaguchi 753-8512, Japan
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9
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Calmodulin in Paramecium: Focus on Genomic Data. Microorganisms 2022; 10:microorganisms10101915. [PMID: 36296191 PMCID: PMC9608856 DOI: 10.3390/microorganisms10101915] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2022] [Revised: 09/14/2022] [Accepted: 09/22/2022] [Indexed: 11/26/2022] Open
Abstract
Calcium (Ca2+) is a universal second messenger that plays a key role in cellular signaling. However, Ca2+ signals are transduced with the help of Ca2+-binding proteins, which serve as sensors, transducers, and elicitors. Among the collection of these Ca2+-binding proteins, calmodulin (CaM) emerged as the prototypical model in eukaryotic cells. This is a small protein that binds four Ca2+ ions and whose functions are multiple, controlling many essential aspects of cell physiology. CaM is universally distributed in eukaryotes, from multicellular organisms, such as human and land plants, to unicellular microorganisms, such as yeasts and ciliates. Here, we review most of the information gathered on CaM in Paramecium, a group of ciliates. We condense the information here by mentioning that mature Paramecium CaM is a 148 amino acid-long protein codified by a single gene, as in other eukaryotic microorganisms. In these ciliates, the protein is notoriously localized and regulates cilia function and can stimulate the activity of some enzymes. When Paramecium CaM is mutated, cells show flawed locomotion and/or exocytosis. We further widen this and additional information in the text, focusing on genomic data.
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10
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Martinez M, Chen WD, Cova MM, Molnár P, Mageswaran SK, Guérin A, John ARO, Lebrun M, Chang YW. Rhoptry secretion system structure and priming in Plasmodium falciparum revealed using in situ cryo-electron tomography. Nat Microbiol 2022; 7:1230-1238. [PMID: 35817892 PMCID: PMC7613239 DOI: 10.1038/s41564-022-01171-3] [Citation(s) in RCA: 16] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2022] [Accepted: 06/07/2022] [Indexed: 01/13/2023]
Abstract
Apicomplexan parasites secrete contents of the rhoptries, club-shaped organelles in the apical region, into host cells to permit their invasion and establishment of infection. The rhoptry secretory apparatus (RSA), which is critical for rhoptry secretion, was recently discovered in Toxoplasma and Cryptosporidium. It is unknown whether a similar molecular machinery exists in the malaria parasite Plasmodium. In this study, we use in situ cryo-electron tomography to investigate the rhoptry secretion system in P. falciparum merozoites. We identify the presence of an RSA at the cell apex and a morphologically distinct apical vesicle docking the tips of the two rhoptries to the RSA. We also discover two additional rhoptry organizations that lack the apical vesicle. Using subtomogram averaging, we reveal different conformations of the RSA structure corresponding to different rhoptry organizations. Our results highlight previously unknown steps in the process of rhoptry secretion and indicate a regulatory role for the conserved apical vesicle in host invasion by apicomplexan parasites.
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Affiliation(s)
- Matthew Martinez
- Department of Biochemistry and Biophysics, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA, USA
| | - William David Chen
- Department of Biochemistry and Biophysics, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA, USA
| | | | - Petra Molnár
- Department of Pediatrics, Division of Infectious Diseases, Children's Hospital of Philadelphia, Philadelphia, PA, USA
| | - Shrawan Kumar Mageswaran
- Department of Biochemistry and Biophysics, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA, USA
| | - Amandine Guérin
- Department of Pathobiology, School of Veterinary Medicine, University of Pennsylvania, Philadelphia, PA, USA
| | - Audrey R Odom John
- Department of Pediatrics, Division of Infectious Diseases, Children's Hospital of Philadelphia, Philadelphia, PA, USA
- Department of Pediatrics, Perelman School of Medicine, University of Pennsylvania, Children's Hospital of Philadelphia, Philadelphia, PA, USA
| | - Maryse Lebrun
- LPHI, UMR 5235 CNRS, Université de Montpellier, Montpellier, France
| | - Yi-Wei Chang
- Department of Biochemistry and Biophysics, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA, USA.
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11
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Plattner H. Membrane Traffic and Ca 2+ -Signals in Ciliates. J Eukaryot Microbiol 2022; 69:e12895. [PMID: 35156735 DOI: 10.1111/jeu.12895] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/03/2021] [Revised: 02/01/2022] [Accepted: 02/01/2022] [Indexed: 11/30/2022]
Abstract
A Paramecium cell has as many types of membrane interactions as mammalian cells, as established with monoclonal antibodies by R. Allen and A. Fok. Since then, we have identified key-players, such as SNARE-proteins, Ca2+ -regulating proteins, including Ca2+ -channels, Ca2+ -pumps, Ca2+ -binding proteins of different affinity etc. at the molecular level, probed their function and localized them at the light and electron microscopy level. SNARE-proteins, in conjunction with a synaptotagmin-like Ca2+ -sensor protein, mediate membrane fusion. This interaction is additionally regulated by monomeric GTPases whose spectrum in Tetrahymena and Paramecium has been established by A. Turkewitz. As known from mammalian cells, GTPases are activated on membranes in conjunction with lumenal acidification by an H+ -ATPase. For these complex molecules we found in Paramecium an unsurpassed number of 17 a-subunit paralogs which connect the polymeric head and basis part, V1 and V0. (This multitude may reflect different local functional requirements.) Together with plasmalemmal Ca2+ -influx-channels, locally enriched intracellular InsP3 -type (InsP3 R, mainly in osmoregulatory system) and ryanodine receptor-like Ca2+ -release channels (ryanodine receptor-like proteins, RyR-LP), this complexity mediates Ca2+ signals for most flexible local membrane-to-membrane interactions. As we found, the latter channel types miss a substantial portion of the N-terminal part. Caffeine and 4-chloro-meta-cresol (the agent used to probe mutations of RyRs in man during surgery in malignant insomnia patients) initiate trichocyst exocytosis by activating Ca2+ -release channels type CRC-IV in the peripheral part of alveolar sacs. This is superimposed by Ca2+ -influx, i.e. a mechanism called "store-operated Ca2+ -entry" (SOCE). For the majority of key players, we have mapped paralogs throughout the Paramecium cell, with features in common or at variance in the different organelles participating in vesicle trafficking. Local values of free Ca2+ -concentration, [Ca2+ ]i , and their change, e.g. upon exocytosis stimulation, have been registered by flurochromes and chelator effects. In parallel we have registered release of Ca2+ from alveolar sacs by quenched-flow analysis combined with cryofixation and x-ray microanalysis.
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12
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Wiser MF. Unique Endomembrane Systems and Virulence in Pathogenic Protozoa. Life (Basel) 2021; 11:life11080822. [PMID: 34440567 PMCID: PMC8401336 DOI: 10.3390/life11080822] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2021] [Revised: 08/10/2021] [Accepted: 08/10/2021] [Indexed: 02/06/2023] Open
Abstract
Virulence in pathogenic protozoa is often tied to secretory processes such as the expression of adhesins on parasite surfaces or the secretion of proteases to assisted in tissue invasion and other proteins to avoid the immune system. This review is a broad overview of the endomembrane systems of pathogenic protozoa with a focus on Giardia, Trichomonas, Entamoeba, kinetoplastids, and apicomplexans. The focus is on unique features of these protozoa and how these features relate to virulence. In general, the basic elements of the endocytic and exocytic pathways are present in all protozoa. Some of these elements, especially the endosomal compartments, have been repurposed by the various species and quite often the repurposing is associated with virulence. The Apicomplexa exhibit the most unique endomembrane systems. This includes unique secretory organelles that play a central role in interactions between parasite and host and are involved in the invasion of host cells. Furthermore, as intracellular parasites, the apicomplexans extensively modify their host cells through the secretion of proteins and other material into the host cell. This includes a unique targeting motif for proteins destined for the host cell. Most notable among the apicomplexans is the malaria parasite, which extensively modifies and exports numerous proteins into the host erythrocyte. These modifications of the host erythrocyte include the formation of unique membranes and structures in the host erythrocyte cytoplasm and on the erythrocyte membrane. The transport of parasite proteins to the host erythrocyte involves several unique mechanisms and components, as well as the generation of compartments within the erythrocyte that participate in extraparasite trafficking.
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Affiliation(s)
- Mark F Wiser
- Department of Tropical Medicine, Tulane University School of Public Health and Tropical Medicine, New Orleans, LA 70112, USA
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Hu K. The art of the steal. Nat Microbiol 2021; 6:421-422. [PMID: 33782557 DOI: 10.1038/s41564-021-00886-z] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Affiliation(s)
- Ke Hu
- Biodesign Institute - Center for Mechanisms of Evolution/School of Life Sciences, Arizona State University, Tempe, AZ, USA.
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Sparvoli D, Lebrun M. Unraveling the Elusive Rhoptry Exocytic Mechanism of Apicomplexa. Trends Parasitol 2021; 37:622-637. [PMID: 34045149 DOI: 10.1016/j.pt.2021.04.011] [Citation(s) in RCA: 14] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/12/2021] [Revised: 04/19/2021] [Accepted: 04/19/2021] [Indexed: 12/11/2022]
Abstract
Apicomplexan parasites are unicellular eukaryotes that invade the cells in which they proliferate. The development of genetic tools in Toxoplasma, and then in Plasmodium, in the 1990s allowed the first description of the molecular machinery used for motility and invasion, revealing a crucial role for two different secretory organelles, micronemes and rhoptries. Rhoptry proteins are injected directly into the host cytoplasm not only to promote invasion but also to manipulate host functions. Nonetheless, the injection machinery has remained mysterious, a major conundrum in the field. Here we review recent progress in uncovering structural components and proteins implicated in rhoptry exocytosis and explain how revisiting early findings and considering the evolutionary origins of Apicomplexa contributed to some of these discoveries.
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Affiliation(s)
- Daniela Sparvoli
- LPHI UMR5235, Univ Montpellier, CNRS, F-34095 Montpellier, France
| | - Maryse Lebrun
- LPHI UMR5235, Univ Montpellier, CNRS, F-34095 Montpellier, France.
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An Alveolata secretory machinery adapted to parasite host cell invasion. Nat Microbiol 2021; 6:425-434. [PMID: 33495622 PMCID: PMC8886610 DOI: 10.1038/s41564-020-00854-z] [Citation(s) in RCA: 39] [Impact Index Per Article: 13.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/09/2020] [Accepted: 12/14/2020] [Indexed: 01/29/2023]
Abstract
Apicomplexa are unicellular eukaryotes and obligate intracellular parasites, including Plasmodium (the causative agent of malaria) and Toxoplasma (one of the most widespread zoonotic pathogens). Rhoptries, one of their specialized secretory organelles, undergo regulated exocytosis during invasion1. Rhoptry proteins are injected directly into the host cell to support invasion and subversion of host immune function2. The mechanism by which they are discharged is unclear and appears distinct from those in bacteria, yeast, animals and plants. Here, we show that rhoptry secretion in Apicomplexa shares structural and genetic elements with the exocytic machinery of ciliates, their free-living relatives. Rhoptry exocytosis depends on intramembranous particles in the shape of a rosette embedded into the plasma membrane of the parasite apex. Formation of this rosette requires multiple non-discharge (Nd) proteins conserved and restricted to Ciliata, Dinoflagellata and Apicomplexa that together constitute the superphylum Alveolata. We identified Nd6 at the site of exocytosis in association with an apical vesicle. Sandwiched between the rosette and the tip of the rhoptry, this vesicle appears as a central element of the rhoptry secretion machine. Our results describe a conserved secretion system that was adapted to provide defence for free-living unicellular eukaryotes and host cell injection in intracellular parasites.
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Dubois DJ, Soldati-Favre D. Biogenesis and secretion of micronemes in Toxoplasma gondii. Cell Microbiol 2019; 21:e13018. [PMID: 30791192 DOI: 10.1111/cmi.13018] [Citation(s) in RCA: 61] [Impact Index Per Article: 12.2] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/08/2018] [Revised: 02/11/2019] [Accepted: 02/17/2019] [Indexed: 12/20/2022]
Abstract
One of the hallmarks of the parasitic phylum of Apicomplexa is the presence of highly specialised, apical secretory organelles, called the micronemes and rhoptries that play critical roles in ensuring survival and dissemination. Upon exocytosis, the micronemes release adhesin complexes, perforins, and proteases that are crucially implicated in egress from infected cells, gliding motility, migration across biological barriers, and host cell invasion. Recent studies on Toxoplasma gondii and Plasmodium species have shed more light on the signalling events and the machinery that trigger microneme secretion. Intracellular cyclic nucleotides, calcium level, and phosphatidic acid act as key mediators of microneme exocytosis, and several downstream effectors have been identified. Here, we review the key steps of microneme biogenesis and exocytosis, summarising the still fractal knowledge at the molecular level regarding the fusion event with the parasite plasma membrane.
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Affiliation(s)
- David J Dubois
- Department of Microbiology and Molecular Medicine, University of Geneva CMU, Geneva, Switzerland
| | - Dominique Soldati-Favre
- Department of Microbiology and Molecular Medicine, University of Geneva CMU, Geneva, Switzerland
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Abstract
Imagine that in 1678 you are Christiaan Huygens or Antonie van Leeuwenhoek seeing paramecia swim gracefully across the field of view of your new microscope. These unicellular, free-living, and swimming cells might have remained a curiosity if not for the ability of H.S. Jennings (Behavior of the lower organisms. Indiana University Press, Bloomington, 1906) and T.M. Sonneborn (Proc Natl Acad Sci USA 23:378-385, 1937) to recognize them for their behavior and genetics, both Mendelian and non-Mendelian. Following many years of painstaking work by Sonneborn and other researchers, Paramecium now serves as a modern model organism that has made specific contributions to cell and molecular biology and development. We will review the continuing usefulness and contributions of Paramecium species in this chapter.Even without a microscope, Paramecium species is visible to the naked eye because of their size (50-300 μ long). Paramecia are holotrichous ciliates, that is, unicellular organisms in the phylum Ciliophora that are covered with cilia. It was the beating of these cilia that propelled them across the slides of the first microscopes and continue to fascinate us today. Over time, Paramecium became a favorite model organism for a large variety of studies. Denis Lyn has called Paramecium the "white rat" of the Ciliophora for their manipulability and amenity to research. We will touch upon the use of Paramecium species to examine swimming behavior, ciliary structure and function, ion channel function, basal body duplication and patterning, non-Mendelian cortical inheritance, programmed DNA rearrangements, regulated secretion and exocytosis, and cell trafficking. In particular, we will focus on the use of P. tetraurelia and P. caudatum.
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Heidari-Zefreh AA, Shariatpanahi ME, Mousavi A, Kalatejari S. Enhancement of microspore embryogenesis induction and plantlet regeneration of sweet pepper (Capsicum annuum L.) using putrescine and ascorbic acid. PROTOPLASMA 2019; 256:459-469. [PMID: 29922944 DOI: 10.1007/s00709-018-1308-z] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/25/2018] [Accepted: 09/10/2018] [Indexed: 05/26/2023]
Abstract
Production of doubled haploid (DH) plants is an efficient tool in genetic and plant breeding programs; however, sweet pepper (Capsicum annuum L.) is recalcitrant to microspore embryogenesis and DH production. Trying to break the barrier of DH production, three independent experiments were conducted on microspore embryogenesis of sweet pepper. In the first experiment, the effect of cold (4 °C) and heat (32 °C) pretreatments were investigated on microspore embryogenesis of three genotypes of sweet pepper including "Inspiration F1," "Maratus F1," and "Magno F1" cultivars in a factorial design with three replications. Heat shock (32 °C for 7 days), applied to mannitol-starved anthers of "Inspiration F1," showed higher multinuclear microspore percent, number of multicellular structures, total embryos, cotyledonary embryos, and regenerants. In the second experiment, the effect of different concentrations of putrescine (0, 0.5, 1, 2, and 5 mg l-1) was evaluated on microspore embryogenesis of the three aforementioned cultivars of sweet pepper. The highest mean number of multicellular structures, cotyledonary embryos, and regenerants were achieved by applying 0.5-1 mg l-1 putrescine during the mannitol starvation and heat shock (32 °C) treatments of isolated microspore culture of "Inspiration F1" cultivar. Significant decrease in microspore embryogenesis efficiency was observed when high levels of putrescine (2 and 5 mg l-1) were used. Microspore embryogenesis was prevented completely at 5.0 mg l-1 putrescine. In the third experiment, the effect of different concentrations of ascorbic acid (0, 20, 50, 100, and 200 mg l-1) was investigated and the results showed that the application of ascorbic acid (20 and 50 mg l-1) during mannitol starvation and heat shock treatment (32 °C) caused remarkable improvement in the number of produced cotyledonary embryos and their regeneration ability compared to control treatment. However, the application of higher levels of ascorbic acid (100 and 200 mg l-1) inhibited microspore cell divisions and embryogenesis. In conclusion, the results indicated that both putrescine and ascorbic acid have significant effect on microspore embryogenesis efficiency of sweet pepper when they are used in appropriate concentrations.
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Affiliation(s)
- Ali Akbar Heidari-Zefreh
- Department of Horticultural Science, College of Agricultural Science and Natural Resources, Tehran Science and Research Branch, Islamic Azad University, Tehran, Iran
- Department of Tissue and Cell Culture, Agricultural Biotechnology Research Institute of Iran (ABRII), Agricultural Research, Education and Extension Organization (AREEO), Mahdasht Road, P. O. Box 31535-1897, Karaj, Iran
| | - Mehran E Shariatpanahi
- Department of Tissue and Cell Culture, Agricultural Biotechnology Research Institute of Iran (ABRII), Agricultural Research, Education and Extension Organization (AREEO), Mahdasht Road, P. O. Box 31535-1897, Karaj, Iran.
| | - Amir Mousavi
- Department of Molecular Plant Biotechnology, National Institute of Genetic Engineering and Biotechnology (NIGEB), Tehran, Iran
| | - Sepideh Kalatejari
- Department of Horticultural Science, College of Agricultural Science and Natural Resources, Tehran Science and Research Branch, Islamic Azad University, Tehran, Iran
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The remembrance of the things past: Conserved signalling pathways link protozoa to mammalian nervous system. Cell Calcium 2018; 73:25-39. [DOI: 10.1016/j.ceca.2018.04.001] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2018] [Revised: 04/01/2018] [Accepted: 04/01/2018] [Indexed: 12/13/2022]
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Rhiel E, Wöhlbrand L, Rabus R, Voget S. Candidates of trichocyst matrix proteins of the dinoflagellate Oxyrrhis marina. PROTOPLASMA 2018; 255:217-230. [PMID: 28779305 DOI: 10.1007/s00709-017-1148-2] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/21/2017] [Accepted: 07/18/2017] [Indexed: 06/07/2023]
Abstract
Trichocysts are a common cell organelle of ciliates and dinoflagellates. They are composed of trichocyst matrix proteins and have been intensely investigated and characterized in ciliates. Here, for the first time, data have been obtained for trichocyst matrix proteins of a dinoflagellate. A DELTA-BLAST search using 14 available and complete amino acid sequences of mature trichocyst matrix proteins of the ciliate Paramecium tetraurelia resulted in 16 hits for the dinoflagellate Oxyrrhis marina when the E values and bit values to be scored were <10-4 and >40. They code for proteins with acidic pI values and exceeded the precursors of the trichocyst matrix proteins of the ciliate approximately twofold in length. The values calculated for coverage, identity, and positives ranged from 76 to 100, 21.5 to 28.3, and 44.9 to 53.9%, respectively. Protein conformation predictions indicate coiled-coil domains which are a common feature of mature ciliate trichocyst matrix proteins. As often several EST sequences of O. marina matched with a queried mature trichocyst matrix protein of P. tetraurelia, a multigene family can be assumed for trichocyst proteins in this dinophyte, too. Trichocyst-enriched fractions of O. marina were isolated and subjected to sodium dodecyl sulfate polyacrylamide gel electrophoresis. When samples were incubated with loading buffer without a reducing agent, the banding pattern was mainly composed of three regions in the range of >90, 75-60, and 50-35 kDa, with each region consisting of four to five bands. Tryptic in gel digestion of proteins excised from these three gel regions followed by mass spectrometry confirmed that up to 14 of the 16 predicted proteins were present within the trichocyst-enriched fractions. When the samples were reduced with either ß-mercaptoethanol or dithiothreitol, the proteins of the three regions disappeared almost completely and proteins in the range of 27 to 15 kDa became the dominating bands. Up to 12 of the predicted proteins were detected within these bands.
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Affiliation(s)
- Erhard Rhiel
- Planktology, ICBM, Carl von Ossietzky University Oldenburg, P.O.B. 2503, 26129, Oldenburg, Germany.
| | - Lars Wöhlbrand
- General and Molecular Microbiology, ICBM, Carl von Ossietzky University Oldenburg, P.O.B. 2503, 26129, Oldenburg, Germany
| | - Ralf Rabus
- General and Molecular Microbiology, ICBM, Carl von Ossietzky University Oldenburg, P.O.B. 2503, 26129, Oldenburg, Germany
| | - Sonja Voget
- Stabsstelle Sicherheitswesen/Umweltschutz, Georg-August University Göttingen, Grisebachstr. 8, 37077, Göttingen, Germany
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Buonanno F, Anesi A, Giuseppe GD, Guella G, Ortenzi C. Chemical Defense by Erythrolactones in the Euryhaline Ciliated Protist, Pseudokeronopsis erythrina. Zoolog Sci 2017; 34:42-51. [PMID: 28148211 DOI: 10.2108/zs160123] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
Pseudokeronopsis erythrina produces three new secondary metabolites, erythrolactones A2, B2 and C2, and their respective sulfate esters (A1, B1, C1), the structures of which have been recently elucidated on the basis of NMR spectroscopic data coupled to high resolution mass measurements (HR-MALDI-TOF). An analysis of the discharge of the protozoan pigment granules revealed that the non-sulfonated erythrolactones are exclusively stored in these cortical organelles, which are commonly used by a number of ciliates as chemical weapons in offense/defense interactions with prey and predators. We evaluated the toxic activity of pigment granule discharge on a panel of free-living ciliates and micro-invertebrates, and the activity of each single purified erythrolactone on three ciliate species. We also observed predator-prey interactions of P. erythrina with unicellular and multicellular predators. Experimental results confirm that only P. erythrina cells with discharged pigment granules were preferentially or exclusively hunted and eaten by at least some of its predators, whereas almost all intact (fully pigmented) cells remained alive. Our results indicate that erythrolactones are very effective as a chemical defense in P. erythrina.
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Affiliation(s)
- Federico Buonanno
- 1 Laboratory of Protistology and Biology Education, Department of ECHT, University of Macerata, Piazzale Bertelli, 1, 62100 Macerata, Italy
| | - Andrea Anesi
- 2 Bioorganic Chemistry Laboratory, Department of Physics, University of Trento, Via Sommarive 14, 38123 Povo (Trento), Italy
| | - Graziano Di Giuseppe
- 3 Department of Biology, University of Pisa, Via Alessandro Volta 4, 56126, Pisa, Italy
| | - Graziano Guella
- 2 Bioorganic Chemistry Laboratory, Department of Physics, University of Trento, Via Sommarive 14, 38123 Povo (Trento), Italy.,4 Biophysical Institute, CNR, Via alla Cascata 56/C, 38123 Povo (Trento), Italy
| | - Claudio Ortenzi
- 1 Laboratory of Protistology and Biology Education, Department of ECHT, University of Macerata, Piazzale Bertelli, 1, 62100 Macerata, Italy
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Song C, Murata K, Suzaki T. Intracellular symbiosis of algae with possible involvement of mitochondrial dynamics. Sci Rep 2017; 7:1221. [PMID: 28450706 PMCID: PMC5430747 DOI: 10.1038/s41598-017-01331-0] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/19/2016] [Accepted: 03/27/2017] [Indexed: 11/26/2022] Open
Abstract
Algal endosymbiosis is widely present among eukaryotes including many protists and metazoans. However, the mechanisms involved in their interactions between host and symbiont remain unclear. Here, we used electron microscopy and three-dimensional reconstruction analyses to examine the ultrastructural interactions between the symbiotic zoochlorella and the organelles in the host Paramecium bursaria, which is a model system of endosymbiosis. Although in chemically fixed samples the symbiotic algae show no direct structural interactions with the host organelles and the perialgal vacuole membrane (PVM), in cryofixed P. bursaria samples the intimate connections were identified between the host mitochondria and the symbiotic algae via the PVM. The PVM was closely apposed to the cell wall of the symbiotic algae and in some places it showed direct contacts to the host mitochondrial membrane and the cell wall of the symbiotic algae. Further, the PVM-associated mitochondria formed a mitochondrial network and were also connected to host ER. Our observations propose a new endosymbiotic systems between the host eukaryotes and the symbionts where the benefiting symbiosis is performed through intimate interactions and an active structural modification in the host organelles.
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Affiliation(s)
- Chihong Song
- Graduate School of Science, Kobe University, 1-1 Rokkodai, Nada, Kobe, 657-8501, Japan.
- National Institute for Physiological Sciences, 5-1 Higashiyama Myodaiji, Okazaki, Aichi, 444-8787, Japan.
| | - Kazuyoshi Murata
- National Institute for Physiological Sciences, 5-1 Higashiyama Myodaiji, Okazaki, Aichi, 444-8787, Japan
| | - Toshinobu Suzaki
- Graduate School of Science, Kobe University, 1-1 Rokkodai, Nada, Kobe, 657-8501, Japan.
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