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Azuma T, Pánek T, Tice AK, Kayama M, Kobayashi M, Miyashita H, Suzaki T, Yabuki A, Brown MW, Kamikawa R. An enigmatic stramenopile sheds light on early evolution in Ochrophyta plastid organellogenesis. Mol Biol Evol 2022; 39:6555011. [PMID: 35348760 PMCID: PMC9004409 DOI: 10.1093/molbev/msac065] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Ochrophyta is an algal group belonging to the Stramenopiles and comprises diverse lineages of algae which contribute significantly to the oceanic ecosystems as primary producers. However, early evolution of the plastid organelle in Ochrophyta is not fully understood. In this study, we provide a well-supported tree of the Stramenopiles inferred by the large-scale phylogenomic analysis that unveils the eukaryvorous (nonphotosynthetic) protist Actinophrys sol (Actinophryidae) is closely related to Ochrophyta. We used genomic and transcriptomic data generated from A. sol to detect molecular traits of its plastid and we found no evidence of plastid genome and plastid-mediated biosynthesis, consistent with previous ultrastructural studies that did not identify any plastids in Actinophryidae. Moreover, our phylogenetic analyses of particular biosynthetic pathways provide no evidence of a current and past plastid in A. sol. However, we found more than a dozen organellar aminoacyl-tRNA synthases (aaRSs) that are of algal origin. Close relationships between aaRS from A. sol and their ochrophyte homologs document gene transfer of algal genes that happened before the divergence of Actinophryidae and Ochrophyta lineages. We further showed experimentally that organellar aaRSs of A. sol are targeted exclusively to mitochondria, although organellar aaRSs in Ochrophyta are dually targeted to mitochondria and plastids. Together, our findings suggested that the last common ancestor of Actinophryidae and Ochrophyta had not yet completed the establishment of host–plastid partnership as seen in the current Ochrophyta species, but acquired at least certain nuclear-encoded genes for the plastid functions.
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Affiliation(s)
- Tomonori Azuma
- Graduate School of Human and Environmental Studies, Kyoto University, Yoshida nihonmatsu cho, Sakyo ku, Kyoto, Kyoto, Japan
| | - Tomáš Pánek
- Department of Zoology, Faculty of Science, Charles University, Prague, Czech Republic.,Department of Biological Sciences, Mississippi State University, Mississippi State, MS, USA
| | - Alexander K Tice
- Department of Biological Sciences, Mississippi State University, Mississippi State, MS, USA
| | - Motoki Kayama
- Graduate School of Human and Environmental Studies, Kyoto University, Yoshida nihonmatsu cho, Sakyo ku, Kyoto, Kyoto, Japan
| | | | - Hideaki Miyashita
- Graduate School of Human and Environmental Studies, Kyoto University, Yoshida nihonmatsu cho, Sakyo ku, Kyoto, Kyoto, Japan
| | | | - Akinori Yabuki
- Japan Agency for Marine-Earth Science and Technology, Japan
| | - Matthew W Brown
- Department of Biological Sciences, Mississippi State University, Mississippi State, MS, USA
| | - Ryoma Kamikawa
- Graduate School of Agriculture, Kyoto University, Kitashirakawa oiwake cho, Sakyo ku, Kyoto, Kyoto, Japan
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Ikeda R, Kurokawa M, Murai M, Saito N, Ando M. Immunocytochemical Analysis of α-Tubulin Distribution Before and After Rapid Axopodial Contraction in the Centrohelid Raphidocystis contractilis. ACTA PROTOZOOL 2020. [DOI: 10.4467/16890027ap.20.001.12157] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
The centrohelid Raphidocystis contractilis is a heliozoan that has many radiating axopodia, each containing a bundle of microtubules. Although the rapid contraction of the axopodia at nearly a video rate (30 frames/s) is induced by mechanical stimuli, the mechanism underlying this phenomenon in R. contractilis has not yet been elucidated. In the present study, we described for the first time an adequate immunocytochemical fixation procedure for R. contractilis and the cellular distribution of α-tubulin before and after rapid axopodial contraction. We developed a flow-through chamber equipped with a micro-syringe pump that allowed the test solution to be injected at a flow rate below the threshold required to induce rapid axopodial contraction. Next, we used this injection method for evaluating the effects of different combinations of two fixatives (paraformaldehyde or glutaraldehyde) and two buffers (phosphate buffer or PHEM) on the morphological structure of the axopodia. A low concentration of glutaraldehyde in PHEM was identified as an adequate fixative for immunocytochemistry. The distribution of α-tubulin before and after rapid axopodial contraction was examined using immunocytochemistry and confocal laser scanning fluorescence microscopy. Positive signals were initially detected along the extended axopodia from the tips to the bases and were distributed in a non-uniform manner within the axopodia. Conversely, after the induction of a rapid axopodial contraction, these positive signals accumulated in the peripheral region of the cell. These results indicated that axopodial microtubules disassemble into fragments and/ or tubulin subunits during rapid axopodial contraction. Therefore, we hypothesize that the mechanism of extremely rapid axopodial contraction accompanied by cytoskeletal microtubule degradati
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Arikawa M, Saito A, Omura G, Khan SMMK, Suetomo Y, Kakuta S, Suzaki T. Ca2+-dependent in vitro contractility of a precipitate isolated from an extract of the heliozoonActinophrys sol. ACTA ACUST UNITED AC 2006; 63:57-65. [PMID: 16362955 DOI: 10.1002/cm.20106] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Contraction of axopodia in actinophrid heliozoons (protozoa) is induced by a unique contractile structure, the "contractile tubules structure (CTS)". We have previously shown that a cell homogenate of the heliozoon Actinophrys sol yields a precipitate on addition of Ca2+ that is mainly composed of filamentous structures morphologically identical to the CTS. In this study, to further characterize the nature of the CTS in vitro, biochemical and physiological properties of the precipitate were examined. SDS-PAGE analysis showed that the Ca2+-induced precipitate was composed of many proteins, and that no proteins in the precipitate showed any detectable changes in electrophoretic mobility on addition of Ca2+. Addition of extraneous proteins such as bovine serum albumin to the cell homogenate resulted in cosedimentation of the proteins with the Ca2+-induced precipitate, suggesting that the CTS has a high affinity for other proteins that are not related to precipitate formation. Appearance and disappearance of the precipitate were repeatedly induced by alternating addition of Ca2+ and EGTA, and its protein composition remained unchanged even after repeated cycles. When adhered to a glass surface, the precipitate showed Ca2+-dependent contractility with a threshold of 10-100 nM, and this contractility was not inhibited by colchicine or cytochalasin B. The precipitate repeatedly contracted and relaxed with successive addition and removal of Ca2+, indicating that the contraction was controlled by Ca2+ alone with no need for any other energy supply. From our characterization of the precipitate, we concluded that its Ca2+-dependent formation and contraction are associated with the unique contractile organelle, the "contractile tubules structure".
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Affiliation(s)
- Mikihiko Arikawa
- Department of Biological Sciences, Faculty of Science, Nara Women's University, Nara 630-8506, Japan.
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Arikawa M, Saito A, Omura G, Mostafa Kamal Khan SM, Suetomo Y, Kakuta S, Suzaki T. Ca2+-dependent nuclear contraction in the heliozoon Actinophrys sol. Cell Calcium 2005; 38:447-55. [PMID: 16099499 DOI: 10.1016/j.ceca.2005.06.034] [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] [Received: 05/10/2005] [Revised: 06/25/2005] [Accepted: 06/27/2005] [Indexed: 11/26/2022]
Abstract
Ca2+-dependent contractility was found to exist in the nucleus of the heliozoon protozoan Actinophrys sol. Upon addition of Ca2+ ([Ca2+]free = 2.0 x 10(-3) M), diameters of isolated and detergent-extracted nuclei became reduced from 16.5+/-1.7 microm to 11.0+/-1.3 microm. The threshold level of [Ca2+]free for the nuclear contraction was 2.9 x 10(-7) M. The nuclear contraction was not induced by Mg2+, and was not inhibited by colchicine or cytochalasin B. Contracted nuclei became expanded when Ca2+ was removed by EGTA; thus cycles of contraction and expansion could be repeated many times by alternating addition of Ca2+ and EGTA. The Ca2+-dependent nuclear contractility remained even after high salt treatment, suggesting a possible involvement of nucleoskeletal components in the nuclear contraction. Electron microscopy showed that, in the relaxed state, filamentous structures were observed to spread in the nucleus to form a network. After addition of Ca2+, they became aggregated and constructed a mass of thicker filaments, followed by re-distribution of the filaments spread around inside of the nucleus when Ca2+ was removed. These results suggest that the nuclear contraction is induced by Ca2+-dependent transformation of the filamentous structures in the nucleus.
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Affiliation(s)
- Mikihiko Arikawa
- Department of Biological Sciences, Faculty of Science, Nara Women's University, Kitauoyanishi-machi, Nara 630-8506, Japan.
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Hausmann K, Patterson DJ. Pseudopod formation and membrane production during prey capture by a heliozoon (feeding by Actinophrys, II). ACTA ACUST UNITED AC 2005. [DOI: 10.1002/cm.970020103] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
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6
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Khan SMMK, Arikawa M, Omura G, Suetomo Y, Kakuta S, Suzaki T. Axopodial Contraction in the Heliozoon Raphidiophrys contractilis Requires Extracellular Ca2+. Zoolog Sci 2003; 20:1367-72. [PMID: 14624035 DOI: 10.2108/zsj.20.1367] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
Axopodial contraction of the centrohelid heliozoon Raphidiophrys contractilis was induced by mechanical or electrical stimulation. For inducing contraction, extracellular Ca(2+) was required. The threshold level of extracellular Ca(2+) was between 10(-6)-10(-7) M. The speed of axopodial contraction was faster than 3.0 mm/sec. Re-elongation of axopodia started just after contraction, and its initial velocity was approximately 0.30 microm/sec. Electron microscopic observations were carried out using an improved fixative that contained 1 mg/ml ruthenium red and 15 microM Taxol. This fixative prevented artificial retraction of axopodia and resulted in better fixation. A bundle of hexagonally-arranged microtubules was observed in each axopodium, but no other filamentous structures were detected, suggesting that the contractile machinery of axopodia in R. contractilis may be different from that in actinophryid heliozoons in which Ca(2+)-dependent contractile filaments are employed for contraction.
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Arikawa M, Suzaki T. Reactivation of Ca2+-dependent cytoplasmic contraction in permeabilized cell models of the heliozoon Echinosphaerium akamae. CELL MOTILITY AND THE CYTOSKELETON 2002; 53:267-72. [PMID: 12378536 DOI: 10.1002/cm.10071] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Permeabilized cell models of the large heliozoon Echinosphaerium akamae were prepared by treatment with 100 mM EGTA or 1% Triton X-100. When > 10(-6) M Ca(2+) was added to the EGTA-permeabilized cells, axopodial cytoplasm became contracted and several swellings were formed along the axopodial length. Axonemal microtubules remained intact, while higher concentration of Ca(2+) (> 10(-4) M) induced microtubule disassembly and complete breakdown of the axopodia. In Triton-permeabilized cells, cytoplasmic contraction and relaxation of the cell body were induced repeatedly by successive addition and removal of Ca(2+). The contraction did not require ATP, and was not inhibited by cytochalasin B. Electron microscopy showed, in EGTA-permeabilized axopodia, contractile tubules became granulated by the addition of Ca(2+). From these observations, it is strongly suggested that Ca(2+)-dependent granulation of the contractile tubules is responsible for the axopodial contraction.
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Affiliation(s)
- Mikihiko Arikawa
- Department of Biology, Faculty of Sciences, Kobe University, Japan.
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Arikawa M, Saito A, Omura G, Mostafa Kamal Khan S, Kinoshita E, Suzaki T. Ca2+-dependent cytoplasmic contractility of the heliozoon Actinophrys sol. Eur J Protistol 2002. [DOI: 10.1078/0932-4739-00879] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
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9
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Kinoshita E, Shigenaka Y, Suzaki T. The ultrastructure of contractile tubules in the heliozoon Actinophrys sol and their possible involvement in rapid axopodial contraction. J Eukaryot Microbiol 2001; 48:519-26. [PMID: 11596916 DOI: 10.1111/j.1550-7408.2001.tb00187.x] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
We employed an improved fixation procedure for electron microscopy using ruthenium red, and found a bundle of contractile tubules inside the axopodia of the heliozoon Actinophrys sol. Upon food uptake, the tubules shorten and transform into a mass of small granules when rapid axopodial contraction occurs, suggesting that these structures are involved in the process of axopodial contraction. The relationship between transformation of the contractile tubules and accompanying disassembly of the axonemal microtubules was studied by examining the ultrastructure of the contractile tubules after disassembly of the microtubules was artificially induced by cold or colchicine treatment. Granulation of the contractile tubules was induced by cold but not by colchicine treatment. During recovery from cold treatment, granular forms of the contractile tubules became re-elongated and their initial tubular appearance was restored. These results suggest that the contractile tubules in heliozoon axopodia play a role in repetitive cytoplasmic contraction.
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Affiliation(s)
- E Kinoshita
- Department of Physiology, Faculty of Medicine, Hiroshima University, Japan
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PIERCE RICHARDW, COATS DWAYNE. The Feeding Ecology of Actinophrys sol (Sarcodina: Heliozoa) in Chesapeake Bay. J Eukaryot Microbiol 1999. [DOI: 10.1111/j.1550-7408.1999.tb06060.x] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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KINOSHITA EIJI, SUZAKI TOSHINOBU, SHIGENAKA YOSHINOBU, SUGIYAMA MASANORI. Ultrastructure and Rapid Axopodial Contraction of a Heliozoa, Raphidiophrys contractilis Sp. Nov. J Eukaryot Microbiol 1995. [DOI: 10.1111/j.1550-7408.1995.tb01581.x] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
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12
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Suzaki T, Ando M, Inai Y, Shigenaka Y. Structure and function of the cytoskeleton in heliozoa. Eur J Protistol 1994. [DOI: 10.1016/s0932-4739(11)80215-4] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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13
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Suzaki T, Ando M, Ishigame K, Shigenaka Y, Sugiyama M. Structure and function of the cytoskeleton in heliozoa: 2. Measurement of the force of rapid axopodial contraction in Echinosphaerium. Eur J Protistol 1992. [PMID: 23195343 DOI: 10.1016/s0932-4739(11)80007-6] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
The large heliozoan Echinosphaerium extends a number of needle-like axopodia by which it captures food organisms. Every axopodium contains a bundle of several hundreds of axonemal microtubules as a cytoskeletal element. When the tip of a poly-L-lysine-coated glass micro-needle came into contact with the distal part of an axopodium, a rapid axopodial contraction (2.6 mm/s) occurred with a concomitant bending of the needle toward the cell body. In this report, we measured the force of the axopodial contraction by utilizing the relation between force and bending displacement of the micro-needle, and examined a possibility that the axopodial contraction is ascribed to the axopodial tension (surface tension and/or cytoplasmic elasticity) that is developed as a result of microtubule degradation. The force of the axopodial contraction was estimated in the order of 10(-9) N. Treatment with 10 mM colchicine induced disassembly of the axopodial microtubules and a resulting slow retraction of the axopodia (0.1 μm/s) occurred. The force of the slow retraction was also measured by the same procedure to estimate the axopodial tension, and was in the order of 10(-11) N. It was thus demonstrated that the motive force for axopodial contraction cannot be explained as an axopodial tension generated as a result of disassembly of the microtubules.
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Affiliation(s)
- T Suzaki
- Laboratories of Cell Biology, Faculty of Integrated Arts and Sciences, Hiroshima University, Hiroshima, Japan
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14
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15
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Ando M, Shigenaka Y. Structure and function of the cytoskeleton in heliozoa: I. Mechanism of rapid axopodial contraction inEchinosphaerium. ACTA ACUST UNITED AC 1989. [DOI: 10.1002/cm.970140214] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
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Febvre-Chevalier C, Febvre J. Motility mechanisms in the actinopods (Protozoa): A review with particular attention to axopodial contraction/extension, and movement of nonactin filament systems. ACTA ACUST UNITED AC 1986. [DOI: 10.1002/cm.970060219] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
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17
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Grain J. The cytoskeleton in protists: nature, structure, and functions. INTERNATIONAL REVIEW OF CYTOLOGY 1986; 104:153-249. [PMID: 3531064 DOI: 10.1016/s0074-7696(08)61926-9] [Citation(s) in RCA: 67] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
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18
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Tucker JB. Spatial organization of microtubule-organizing centers and microtubules. J Biophys Biochem Cytol 1984; 99:55s-62s. [PMID: 6746731 PMCID: PMC2275597 DOI: 10.1083/jcb.99.1.55s] [Citation(s) in RCA: 54] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023] Open
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19
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Brugerolle G, Mignot JP. The cell characters of two Helioflagellates related to the Centrohelidian lineage:Dimorpha andTetradimorpha. ACTA ACUST UNITED AC 1984. [DOI: 10.1007/bf00927179] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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MATSUOKA TATSUOMI, SHIGENAKA YOSHINOBU. LOCALIZATION OF CALCIUM DURING AXOPODIAL CONTRACTION IN HELIOZOAN, ECHINOSPHAERIUM AKAMAE . Biomed Res 1984. [DOI: 10.2220/biomedres.5.425] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Affiliation(s)
- TATSUOMI MATSUOKA
- Zoological Institute, Faculty of Science, Faculty of Integrated Arts and Sciences, Hiroshima University
| | - YOSHINOBU SHIGENAKA
- Department of Information and Behavior Sciences, Faculty of Integrated Arts and Sciences, Hiroshima University
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Hausmann K, Linnenbach M, Patterson DJ. The effects of taxol on microtubular arrays: in vivo effects on heliozoan axonemes. JOURNAL OF ULTRASTRUCTURE RESEARCH 1983; 82:212-20. [PMID: 6131145 DOI: 10.1016/s0022-5320(83)90054-0] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/18/2023]
Abstract
The effects of the antitumor drug taxol on the microtubular axonemes of the heliozoon Actinophrys sol have been investigated. The drug induces polymerization of microtubules as shown by a large increase in the length and number of microtubular arrays. The interaction between microtubules and microtubule-associated proteins is also affected, with the result that the normal geometric patterning within the microtubular arrays is disturbed. This is due to the loss or inactivation of long intermicrotubule links. As a result, arms lose their rigidity. Because the drug stabilizes polymerized microtubules, C-shaped profiles and other signs of poor microtubule preservation are absent in taxol-treated cells.
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22
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Little M, Ludueña RF, Keenan R, Asnes CF. Tubulin evolution: two major types of alpha-tubulin. J Mol Evol 1982; 19:80-6. [PMID: 6761444 DOI: 10.1007/bf02100226] [Citation(s) in RCA: 31] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
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23
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Bernstam VA, Gray RH, Bernstein IA. Effect of microtubule-disrupting drugs on protein and RNA synthesis in Physarum polycephalum amoebae. Arch Microbiol 1980; 128:34-40. [PMID: 7192968 DOI: 10.1007/bf00422302] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023]
Abstract
The effects of the microtubule-disrupting drugs, colchicine, vinblastine, podophyllotoxin, griseofulvin, and lumicolchicine (10(-5) M), on protein and RNA synthesis were studied in Physarum polycephalum amoebae in culture. All, except lumicolchicine, were found to simultaneously reduce the rate of protein synthesis and stimulate RNA synthesis. These results parallel the effects seen in cells exposed to heat shock. Treatment of cells with a microfilament-disrupting drug, cytochalasin B (10 micrograms/ml in ethanol), resulted in a reduced rate of protein synthesis after 2 h compared to a similar effect by vinblastine in 5--15 min. A morphological abnormality, microtubule paracrystals, were seen associated with centrioles in vinblastine-treated cells in which protein synthesis had been reduced by 50%. Vinblastine and podophyllotoxin were shown to interfere with the recovery of protein synthesis after inhibition by low or elevated temperatures. The possible role of microtubules in regulating the translational response of a cell to an external environmental stimulus is discussed.
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Mesland DA, Hoffman JL, Caligor E, Goodenough UW. Flagellar tip activation stimulated by membrane adhesions in Chlamydomonas gametes. J Biophys Biochem Cytol 1980; 84:599-617. [PMID: 7358792 PMCID: PMC2110563 DOI: 10.1083/jcb.84.3.599] [Citation(s) in RCA: 106] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023] Open
Abstract
Membrane adhesions between the flagella of mating-type "plus" and "minus" gametes of Chlamydomonas reinhardi are shown to stimulate a rapid change in the ultrastructure of the flagellar tips, designated as flagellar tip activation (FTA). A dense substance, termed fibrous tip material (FTM), accumulates between the flagellar membrane and the nine single A microtubules of the tip. The A microtubules then elongate, growing into the distal region of the tip, increasing tip length by 30%. This study describes FTA kinetics during normal and mutant matings, presents experiments designed to probe its role in the mating reaction, and offers the following conclusions: (a) FTA is elicited by agents that cross-link flagellar membrane components (including natural sexual agglutinins, antiflagellar antisera, and concanavalin A) but not by flagellar adherence to polylysine-coated films. (b) FTA is reversed by flagellar disadhesion. (c) Gametes can undergo repeated cycles of FTA during successive rounds of adhesion/disadhesion. (d) FTA, flagellar tipping, and sexual signaling are simultaneously blocked by colchicine and by vinblastine, suggesting that tubulinlike molecules, perhaps exposed at the membrane surface, are involved in all three responses. (e) FTA is not blocked by short exposure to chymotrypsin, by cytochalasins B and D, nor by concanavalin A, even though all block cell fusion; the response is therefore autonomous and experimentally dissociable from later stages in the mating reaction. (f) Under no experimental conditions is mating-structure activation observed to occur unless FTA also occurs. This study concludes that FTA is a necessary event in the sexual signaling sequence, and presents a testable working model for its mechanism.
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Bergstrom-Porter B, Shelton E. Effect of uncouplers of oxidative phosphorylation on microtubule location and surface structure in murine mast cells. Anat Rec (Hoboken) 1979; 195:375-86. [PMID: 507398 DOI: 10.1002/ar.1091950210] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
"Uncouplers" of oxidative phosphorylation (sodium azide, DNP, and oligomycin) alter the location of microtubules within murine mast cells. Both cytoplasmic microtubules, perpendicular to the plasma membrane within cell surface folds, and intranuclear microtubules were observed. In addition, one or more dense plaque-like structures adjacent the plasma membrane in mast cells appeared following incubation in the antimetabolities. Intranuclear microtubules and cytoplasmic microtubules within the cell surface ridges disappeared in azide-treated mast cells that were reincubated or "recovered" in PBS. However, both these structures remained in oligomycin- and DNP-treated murine mast cells following reincubation.
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26
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Spiegelman BM, Lopata MA, Kirschner MW. Multiple sites for the initiation of microtubule assembly in mammalian cells. Cell 1979; 16:239-52. [PMID: 455434 DOI: 10.1016/0092-8674(79)90002-3] [Citation(s) in RCA: 84] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
The pattern of microtubule regrowth in mammalian fibroblast and epithelial cells has been examined by immunofluorescence of cytoskeletal preparations with antibody to tubulin. After reversal of treatment with colcemid, vinblastine or low temperature, microtubules appear to grow simultaneously from several distinct initiation sites located within 5 microns of the nucleus of mouse and human fibroblasts. Each site initiates the growth of 10-30 microtubules. More than 70% of the mouse fibroblasts have between 5 and 10 initiation sites with an average of 8. The human fibroblasts have an average of 5 sites per cell. The average number and numerical distribution of sites per fibroblast cell are not affected by time of exposure to colcemid or the concentration of colcemid applied to the cells. Multiple microtubule initiation sites are also observed during the process of microtubule depolymerization. In addition to growth from these complex initiation sites, microtubules appear to grow singly from the perinuclear region of human fibroblasts. The regrowth of individual microtubules from the perinuclear growth is especially prominent in epithelial cell lines from rat kangaroo and pig. These epithelial lines have only a single complex initiation site per cell. Two classes of complex initiation sites can be distinguished in microtubule regrowth experiments in human and mouse fibroblasts after exposure to griseofulvin. Microtubules first grow extensively from a single distinct site, which has approximately 20 microtubules growing from it and may be the centriole or centriolar pair. Subsequently, microtubules regrow from other perinuclear complex initiation sites. It thus appears that at least three distinct classes of initiation sites can be observed in mammalian cells: primary sites, which regrow microtubules first after griseofulvin treatment; secondary sites, which are distinct perinuclear sites and recover from griseofulvin treatment more slowly than the primary sites; and tertiary sites or sites of growth of single microtubules, also located near the cell nucleus.
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Abstract
Microtubular organization in the melanophores of the angelfish, Pterophyllum scalare, has been studied by serial thin sectioning. The course of microtubules has been followed in sets of transverse serial sections taken from the centrosphere and a segment of a cell process, respectively. Microtubules arise from a prominent zone in the cell center, the central apparatus, which is composed of numerous, small, electron-dense aggregates. the number of these loosely distributed densities is highest in the center of the centrosphere, but they may also be found at its periphery. Microtubules insert into, or becomes part of, the dense material, or at least start in its vicinity. Dense aggregates may be separated from centrioles by several micrometers rather than only being closely associated with these organelles. At some distance from the organizing zone, most of the microtubules gradually assume a cortical arrangement, i.e., take a course within about 100 nm of the limiting membrane. Serial sections were used to trace all microtubules within a 6mum-long segment of a cell process. 94 percent of the microtubules observed in this segment run its entire length; it is conceivable, therefore that a considerable number of microtubules extend between the initiating site in the centrosphere and the outermost cell region. A three-dimensional model of the 6mum-long segment reveals that, despite changes in the cell process outline, microtubules maintain a strictly cortical arrangement which gives the impression of a microtubule "palisade" lining the cortex of the cell process. The features of the microtubular apparatus of angelfish melanophores are discussed in relation to factors controlling microtubule initiation and distribution.
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Wolosewick JJ, Bryan JH. Ultrastructural characterization of the manchette microtubules in the seminiferous epithelium of the mouse. THE AMERICAN JOURNAL OF ANATOMY 1977; 150:301-31. [PMID: 920632 DOI: 10.1002/aja.1001500206] [Citation(s) in RCA: 34] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
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Hardham AR, Gunning BE. The length and disposition of cortical microtubules in plant cells fixed in glutaraldehyde-Osmium tetroxide. PLANTA 1977; 134:201-203. [PMID: 24419701 DOI: 10.1007/bf00384972] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/01/1976] [Accepted: 12/10/1976] [Indexed: 06/03/2023]
Abstract
Serial sectioning has been used to show that the majority of circumferential microtubules lying in the cortex of root tip cells are much shorter than the cell circumference. The significance of this observation is briefly discussed.
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Affiliation(s)
- A R Hardham
- Department of Developmental Biology, Research School of Biological Sciences, Australian National University, 2601, Canberra City, A.C.T., Australia
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Abstract
This study evidence for tension transmission by microtubules and desmosomes in the follicular epithelium during anisometric growth of certain insect eggs. Most insect oocytes, and the follicles which surround them, grow anisometrically as they assume shapes which approximate to those of long prolate spheroids. Surface growth is most rapid in directions which parallel the polar axis of an oocyte and slowest in circumferential directions at right angles to this axis. The longitudinal axes of microtubule bundles in follicle cells of the gall midge Heteropeza and the cockroach Periplaneta are oriented circumferentially with respect to the surfaces of developing eggs and at right angles to the polar axes of eggs. At cell boundaries, the tubules appear to be attached to spot desmosomes. It is suggested that microtubules and desmosomes form a mechanical continuum throughout a follicular epithelium which transmits tensile forces around the circumference of a growing egg. Follicular resistance to circumferential expansion may be largely responsible for defining the elongate form of insect eggs.
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Schliwa M. The role of divalent cations in the regulation of microtubule assembly. In vivo studies on microtubules of the heliozoan axopodium using the ionophore A23187. J Cell Biol 1976; 70:527-40. [PMID: 821953 PMCID: PMC2109838 DOI: 10.1083/jcb.70.3.527] [Citation(s) in RCA: 87] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022] Open
Abstract
Low concentrations of calcium and magnesium ions have been shown to influence microtubule assembly in vitro. To test whether these cations also have an effect on microtubules in vivo, specimens of Actinosphaerium eichhorni were exposed to different concentrations of Ca++ and Mg++ and the divalent cation ionophore A23187. Experimental degradation and reformation of axopodia were studied by light and electron microscopy. In the presence of Ca++ and the ionophore axopodia gradually shorten, the rate of shortening depending on the concentrations of Ca++ and the ionophore used. Retraction of axopodia was observed with a concentration of Ca++ as low as 0.01 mM. After transfer to a Ca++-free solution containing EGTA, axopodia re-extend; the initial length is reached after about 2 h. Likewise, reformation of axopodia of cold-treated organisms is observed only in solutions of EGTA or Mg++, whereas it is completely inhibited in a Ca++ solution. Electron microscope studies demonstrate degradation of the axonemal microtubular array in organisms treated with Ca++ and A23187. No alteration was observed in organisms treated with Mg++ or EGTA plus ionophore. The results suggest that, in the presence of the ionophore, formation of axonemal microtubules can be regulated by varying the Ca++ concentration in the medium. Since A23187 tends to equilibrate the concentrations of divalent cations between external medium and cell interior, it is likely that microtubule formation invivo is influenced by micromolar concentrations of Ca++. These concentrations are low enough to be of physiological significance for a role in the regulation of microtubule assembly in vivo.
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Ockleford CD. Redundancy of washing in the preparation of biological specimens for transmission electron microscopy. J Microsc 1975; 105:193-203. [PMID: 814242 DOI: 10.1111/j.1365-2818.1975.tb04050.x] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
A marine unicellular organism, human trophoblast tissue and cultured trophoblast cells of human origin have been satisfactorily preserved for electron microscopy without resort to washing either before dehydration or between different stages of fixation. The time required to fix and dehydrate a specimen using this method is 55 min.
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Ockleford CD. Ultraviolet light microbeam irradiation of the microtubules in single heliozoan axopodia. Exp Cell Res 1975; 93:127-35. [PMID: 1140215 DOI: 10.1016/0014-4827(75)90431-0] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
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Tucker JB, Mackie JB. Configurational changes in helical microtubule frameworks in feeding tentacles of the suctorian ciliate Tokophyra. Tissue Cell 1975; 7:601-12. [PMID: 813328 DOI: 10.1016/0040-8166(75)90029-4] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
Microtubules at the tip of a resting (non-feeding) tentacle are arranged helically in two concentric tube-shaped arrays. The pitches of the helical paths followed by tubules in the two arrays differ. At the start of feeding these microtubules bend along their longitudinal axes and splay outwards and downwards away from the tentacle tip as it 'everts'. Tubules in the two arrays slide across each other as this occurs. Comparison of the fine structure of the tips of feeding and resting tentacles with a dynamic model of the microtubular framework indicates that movement of the tubules is not brought about by active sliding of the tubules against each other or by the action of contractile elements attached along the lengths of the tubules. The tips of microtubules forming the inner tube may be pulled downwards by contractile elements in the tentacular pellicle; these tubules apparently push those in the outer tube to their new position. The pattern of configurational changes in a tentacle tip at the start of feeding appears to be largely defined by the elastic resistance of the microtubules to bending, and the ways in which tubules are packed and linked together and attached to the pellicle.
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Roberts K. Cytoplasmic microtubules and their functions. PROGRESS IN BIOPHYSICS AND MOLECULAR BIOLOGY 1974; 28:371-420. [PMID: 4617250 DOI: 10.1016/0079-6107(74)90022-4] [Citation(s) in RCA: 57] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/11/2023]
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