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Melogno I, Takatani S, Llanos P, Goncalves C, Kodera C, Martin M, Lionnet C, Uyttewaal M, Pastuglia M, Trehin C, Bouchez D, Dumais J, Hamant O. A transient radial cortical microtubule array primes cell division in Arabidopsis. Proc Natl Acad Sci U S A 2024; 121:e2320470121. [PMID: 38990951 PMCID: PMC11260093 DOI: 10.1073/pnas.2320470121] [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: 11/21/2023] [Accepted: 05/23/2024] [Indexed: 07/13/2024] Open
Abstract
Although the formation of new walls during plant cell division tends to follow maximal tensile stress direction, analyses of individual cells over time reveal a much more variable behavior. The origin of such variability as well as the exact role of interphasic microtubule behavior before cell division have remained mysterious so far. To approach this question, we took advantage of the Arabidopsis stem, where the tensile stress pattern is both highly anisotropic and stable. Although cortical microtubules (CMTs) generally align with maximal tensile stress, we detected a specific time window, ca. 3 h before cell division, where cells form a radial pattern of CMTs. This microtubule array organization preceded preprophase band (PPB) formation, a transient CMT array predicting the position of the future division plane. It was observed under different growth conditions and was not related to cell geometry or polar auxin transport. Interestingly, this cortical radial pattern correlated with the well-documented increase of cytoplasmic microtubule accumulation before cell division. This radial organization was prolonged in cells of the trm678 mutant, where CMTs are unable to form a PPB. Whereas division plane orientation in trm678 is noisier, we found that cell division symmetry was in contrast less variable between daughter cells. We propose that this "radial step" reflects a trade-off in robustness for two essential cell division attributes: symmetry and orientation. This involves a "reset" stage in G2, where an increased cytoplasmic microtubule accumulation transiently disrupts CMT alignment with tissue stress.
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Affiliation(s)
- Isaty Melogno
- Laboratoire de Reproduction et Développement des Plantes, Université de Lyon, Ecole Normale Supérieure de Lyon, Université Claude Bernard Lyon 1, Institut national de recherche pour l’agriculture, l’alimentation et l’environnement (INRAE), CNRS, 69364Lyon Cedex 07, France
| | - Shogo Takatani
- Laboratoire de Reproduction et Développement des Plantes, Université de Lyon, Ecole Normale Supérieure de Lyon, Université Claude Bernard Lyon 1, Institut national de recherche pour l’agriculture, l’alimentation et l’environnement (INRAE), CNRS, 69364Lyon Cedex 07, France
- Department of Biological Science, Graduate School of Science, Nagoya University, Nagoya464-8602, Japan
| | - Paula Llanos
- Faculty of Engineering and Sciences, Universidad Adolfo Ibáñez, Viña del Mar2520000, Chile
| | - Coralie Goncalves
- Université Paris-Saclay, INRAE, AgroParisTech, Institute Jean-Pierre Bourgin for Plant Sciences (IJPB), Versailles78000, France
| | - Chie Kodera
- Université Paris-Saclay, INRAE, AgroParisTech, Institute Jean-Pierre Bourgin for Plant Sciences (IJPB), Versailles78000, France
| | - Marjolaine Martin
- Laboratoire de Reproduction et Développement des Plantes, Université de Lyon, Ecole Normale Supérieure de Lyon, Université Claude Bernard Lyon 1, Institut national de recherche pour l’agriculture, l’alimentation et l’environnement (INRAE), CNRS, 69364Lyon Cedex 07, France
| | - Claire Lionnet
- Laboratoire de Reproduction et Développement des Plantes, Université de Lyon, Ecole Normale Supérieure de Lyon, Université Claude Bernard Lyon 1, Institut national de recherche pour l’agriculture, l’alimentation et l’environnement (INRAE), CNRS, 69364Lyon Cedex 07, France
| | - Magalie Uyttewaal
- Université Paris-Saclay, INRAE, AgroParisTech, Institute Jean-Pierre Bourgin for Plant Sciences (IJPB), Versailles78000, France
| | - Martine Pastuglia
- Université Paris-Saclay, INRAE, AgroParisTech, Institute Jean-Pierre Bourgin for Plant Sciences (IJPB), Versailles78000, France
| | - Christophe Trehin
- Laboratoire de Reproduction et Développement des Plantes, Université de Lyon, Ecole Normale Supérieure de Lyon, Université Claude Bernard Lyon 1, Institut national de recherche pour l’agriculture, l’alimentation et l’environnement (INRAE), CNRS, 69364Lyon Cedex 07, France
| | - David Bouchez
- Université Paris-Saclay, INRAE, AgroParisTech, Institute Jean-Pierre Bourgin for Plant Sciences (IJPB), Versailles78000, France
| | - Jacques Dumais
- Faculty of Engineering and Sciences, Universidad Adolfo Ibáñez, Viña del Mar2520000, Chile
| | - Olivier Hamant
- Laboratoire de Reproduction et Développement des Plantes, Université de Lyon, Ecole Normale Supérieure de Lyon, Université Claude Bernard Lyon 1, Institut national de recherche pour l’agriculture, l’alimentation et l’environnement (INRAE), CNRS, 69364Lyon Cedex 07, France
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2
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Saltini M, Deinum EE. Microtubule simulations in plant biology: A field coming to maturity. CURRENT OPINION IN PLANT BIOLOGY 2024; 81:102596. [PMID: 38981324 DOI: 10.1016/j.pbi.2024.102596] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/15/2024] [Revised: 05/24/2024] [Accepted: 06/10/2024] [Indexed: 07/11/2024]
Abstract
The plant cortical microtubule array is an important determinant of cell wall structure and, therefore, plant morphology and physiology. The array consists of dynamic microtubules interacting through frequent collisions. Since the discovery by Dixit and Cyr (2004) that the outcome of such collisions depends on the collision angle, computer simulations have been indispensable in studying array behaviour. Over the last decade, the available simulation tools have drastically improved: multiple high-quality simulation platforms exist with specific strengths and applications. Here, we review how these platforms differ on the critical aspects of microtubule nucleation, flexibility, and local orienting cues; and how such differences affect array behaviour. Building upon concepts and control parameters from theoretical models of collective microtubule behaviour, we conclude that all these factors matter in the debate about what is most important for orienting the array: local cues like mechanical stresses or global cues deriving from the cell geometry.
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Affiliation(s)
- Marco Saltini
- Mathematical & Statistical Methods (Biometris), Plant Science Group, Wageningen University, 6708 PB Wageningen, the Netherlands
| | - Eva E Deinum
- Mathematical & Statistical Methods (Biometris), Plant Science Group, Wageningen University, 6708 PB Wageningen, the Netherlands.
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Mukherjee A, Andrés Jeske Y, Becam I, Taïeb A, Brooks P, Aouad J, Monguillon C, Conduit PT. γ-TuRCs and the augmin complex are required for the development of highly branched dendritic arbors in Drosophila. J Cell Sci 2024; 137:jcs261534. [PMID: 38606636 PMCID: PMC11128279 DOI: 10.1242/jcs.261534] [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: 08/04/2023] [Accepted: 04/05/2024] [Indexed: 04/13/2024] Open
Abstract
Microtubules are nucleated by γ-tubulin ring complexes (γ-TuRCs) and are essential for neuronal development. Nevertheless, γ-TuRC depletion has been reported to perturb only higher-order branching in elaborated Drosophila larval class IV dendritic arborization (da) neurons. This relatively mild phenotype has been attributed to defects in microtubule nucleation from Golgi outposts, yet most Golgi outposts lack associated γ-TuRCs. By analyzing dendritic arbor regrowth in pupae, we show that γ-TuRCs are also required for the growth and branching of primary and secondary dendrites, as well as for higher-order branching. Moreover, we identify the augmin complex (hereafter augmin), which recruits γ-TuRCs to the sides of pre-existing microtubules, as being required predominantly for higher-order branching. Augmin strongly promotes the anterograde growth of microtubules in terminal dendrites and thus terminal dendrite stability. Consistent with a specific role in higher-order branching, we find that augmin is expressed less strongly and is largely dispensable in larval class I da neurons, which exhibit few higher-order dendrites. Thus, γ-TuRCs are essential for various aspects of complex dendritic arbor development, and they appear to function in higher-order branching via the augmin pathway, which promotes the elaboration of dendritic arbors to help define neuronal morphology.
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Affiliation(s)
- Amrita Mukherjee
- Department of Zoology, University of Cambridge, Downing Street, Cambridge CB2 3EJ, UK
- MRC Toxicology Unit, Gleeson Building, Tennis Court Road, Cambridge CB2 1QR, UK
| | - Yaiza Andrés Jeske
- Department of Zoology, University of Cambridge, Downing Street, Cambridge CB2 3EJ, UK
| | - Isabelle Becam
- Université Paris Cité, CNRS, Institut Jacques Monod, F-75013 Paris, France
| | - Anaelle Taïeb
- Université Paris Cité, CNRS, Institut Jacques Monod, F-75013 Paris, France
| | - Paul Brooks
- Department of Zoology, University of Cambridge, Downing Street, Cambridge CB2 3EJ, UK
| | - Joanna Aouad
- Université Paris Cité, CNRS, Institut Jacques Monod, F-75013 Paris, France
| | | | - Paul T. Conduit
- Department of Zoology, University of Cambridge, Downing Street, Cambridge CB2 3EJ, UK
- Université Paris Cité, CNRS, Institut Jacques Monod, F-75013 Paris, France
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4
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Schmidt-Marcec S, Parish A, Smertenko T, Hickey M, Piette BMAG, Smertenko A. The microtubule-nucleating factor MACERATOR tethers AUGMIN7 to microtubules and governs phragmoplast architecture. THE PLANT CELL 2024; 36:1072-1097. [PMID: 38079222 PMCID: PMC11181950 DOI: 10.1093/plcell/koad304] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/05/2023] [Accepted: 11/08/2023] [Indexed: 04/02/2024]
Abstract
The plant cytokinetic microtubule array, called the phragmoplast, exhibits higher microtubule dynamics in its center (midzone) than at the periphery (distal zone). This behavior is known as the axial asymmetry. Despite being a major characteristic of the phragmoplast, little is known about regulators of this phenomenon. Here we address the role of microtubule nucleation in axial asymmetry by characterizing MACERATOR (MACET) proteins in Arabidopsis thaliana and Nicotiana benthamiana with a combination of genetic, biochemical, and live-cell imaging assays, using photo-convertible microtubule probes, and modeling. MACET paralogs accumulate at the shrinking microtubule ends and decrease the tubulin OFF rate. Loss of MACET4 and MACET5 function abrogates axial asymmetry by suppressing microtubule dynamicity in the midzone. MACET4 also narrows the microtubule nucleation angle at the phragmoplast leading edge and functions as a microtubule tethering factor for AUGMIN COMPLEX SUBUNIT 7 (AUG7). The macet4 macet5 double mutant shows diminished clustering of AUG7 in the phragmoplast distal zone. Knockout of AUG7 does not affect MACET4 localization, axial asymmetry, or microtubule nucleation angle, but increases phragmoplast length and slows down phragmoplast expansion. The mce4-1 mce5 aug7-1 triple knockout is not viable. Experimental data and modeling demonstrate that microtubule nucleation factors regulate phragmoplast architecture and axial asymmetry directly by generating new microtubules and indirectly by modulating the abundance of free tubulin.
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Affiliation(s)
- Sharol Schmidt-Marcec
- Institute of Biological Chemistry, Washington State University, Pullman, Washington 99164, USA
| | - Alyssa Parish
- Institute of Biological Chemistry, Washington State University, Pullman, Washington 99164, USA
| | - Tetyana Smertenko
- Institute of Biological Chemistry, Washington State University, Pullman, Washington 99164, USA
| | - Matthew Hickey
- Institute of Biological Chemistry, Washington State University, Pullman, Washington 99164, USA
| | | | - Andrei Smertenko
- Institute of Biological Chemistry, Washington State University, Pullman, Washington 99164, USA
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5
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Higa T, Kijima ST, Sasaki T, Takatani S, Asano R, Kondo Y, Wakazaki M, Sato M, Toyooka K, Demura T, Fukuda H, Oda Y. Microtubule-associated phase separation of MIDD1 tunes cell wall spacing in xylem vessels in Arabidopsis thaliana. NATURE PLANTS 2024; 10:100-117. [PMID: 38172572 DOI: 10.1038/s41477-023-01593-9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/05/2022] [Accepted: 11/14/2023] [Indexed: 01/05/2024]
Abstract
Properly patterned cell walls specify cellular functions in plants. Differentiating protoxylem and metaxylem vessel cells exhibit thick secondary cell walls in striped and pitted patterns, respectively. Cortical microtubules are arranged in distinct patterns to direct cell wall deposition. The scaffold protein MIDD1 promotes microtubule depletion by interacting with ROP GTPases and KINESIN-13A in metaxylem vessels. Here we show that the phase separation of MIDD1 fine-tunes cell wall spacing in protoxylem vessels in Arabidopsis thaliana. Compared with wild-type, midd1 mutants exhibited narrower gaps and smaller pits in the secondary cell walls of protoxylem and metaxylem vessel cells, respectively. Live imaging of ectopically induced protoxylem vessels revealed that MIDD1 forms condensations along the depolymerizing microtubules, which in turn caused massive catastrophe of microtubules. The MIDD1 condensates exhibited rapid turnover and were susceptible to 1,6-hexanediol. Loss of ROP abolished the condensation of MIDD1 and resulted in narrow cell wall gaps in protoxylem vessels. These results suggest that the microtubule-associated phase separation of MIDD1 facilitates microtubule arrangement to regulate the size of gaps in secondary cell walls. This study reveals a new biological role of phase separation in the fine-tuning of cell wall patterning.
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Affiliation(s)
- Takeshi Higa
- Department of Gene Function and Phenomics, National Institute of Genetics, Mishima, Japan
- Department of Life Sciences, Graduate School of Arts and Sciences, The University of Tokyo, Meguro, Japan
| | - Saku T Kijima
- Department of Biological Science, Graduate School of Science, Nagoya University, Nagoya, Japan
- Plant Gene Regulation Research Group, Bioproduction Research Institute, National Institute of Advanced Industrial Science and Technology (AIST), Ibaraki, Japan
| | - Takema Sasaki
- Department of Biological Science, Graduate School of Science, Nagoya University, Nagoya, Japan
| | - Shogo Takatani
- Department of Biological Science, Graduate School of Science, Nagoya University, Nagoya, Japan
| | - Ryosuke Asano
- Department of Biological Science, Graduate School of Science, Nagoya University, Nagoya, Japan
| | - Yohei Kondo
- Quantitative Biology Research Group, Exploratory Research Center on Life and Living Systems (ExCELLS), National Institutes of Natural Sciences, Okazaki, Japan
- Division of Quantitative Biology, National Institute for Basic Biology, National Institutes of Natural Sciences, Okazaki, Japan
- Department of Basic Biology, School of Life Science, SOKENDAI (The Graduate University for Advanced Studies), Okazaki, Japan
| | - Mayumi Wakazaki
- RIKEN Center for Sustainable Resource Science, Yokohama, Japan
| | - Mayuko Sato
- RIKEN Center for Sustainable Resource Science, Yokohama, Japan
| | | | - Taku Demura
- Center for Digital Green-innovation, Nara Institute of Science and Technology, Ikoma, Japan
- Graduate School of Science and Technology, Nara Institute of Science and Technology, Ikoma, Japan
| | - Hiroo Fukuda
- Department of Bioscience and Biotechnology, Faculty of Bioenvironmental Sciences, Kyoto University of Advanced Science, Kameoka, Japan
- Akita Prefectural University, Akita, Japan
| | - Yoshihisa Oda
- Department of Biological Science, Graduate School of Science, Nagoya University, Nagoya, Japan.
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6
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Tian TYY, Macdonald CB, Cytrynbaum EN. A Stochastic Model of Cortical Microtubule Anchoring and Mechanics Provides Regulatory Control of Microtubule Shape. Bull Math Biol 2023; 85:103. [PMID: 37725222 DOI: 10.1007/s11538-023-01211-x] [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: 10/03/2022] [Accepted: 09/01/2023] [Indexed: 09/21/2023]
Abstract
The organization of cortical microtubule arrays play an important role in the development of plant cells. Until recently, the direct mechanical influence of cell geometry on the constrained microtubule (MT) trajectories have been largely ignored in computational models. Modelling MTs as thin elastic rods constrained on a surface, a previous study examined the deflection of MTs using a fixed number of segments and uniform segment lengths between MT anchors. It is known that the resulting MT curves converge to geodesics as the anchor spacing approaches zero. In the case of long MTs on a cylinder, buckling has been found for transverse trajectories. There is a clear interplay between two factors in the problem of deflection: curvature of the membrane and the lengths of MT segments. Here, we examine the latter in detail, in the backdrop of a circular cylinder. In reality, the number of segments are not predetermined and their lengths are not uniform. We present a minimal, realistic model treating the anchor spacing as a stochastic process and examine the net effect on deflection. We find that, by tuning the ratio of growth speed to anchoring rate, it is possible to mitigate MT deflection and even prevent buckling for lengths significantly larger than the previously-derived critical buckling length. We suggest that this mediation of deflection by anchoring might provide cells with a means of preventing arrays from deflecting away from the transverse orientation.
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Affiliation(s)
- Tim Y Y Tian
- Mathematics, University of British Columbia, 1984 Mathematics Rd, Vancouver, BC, V6T 1Z2, Canada.
| | - Colin B Macdonald
- Mathematics, University of British Columbia, 1984 Mathematics Rd, Vancouver, BC, V6T 1Z2, Canada
| | - Eric N Cytrynbaum
- Mathematics, University of British Columbia, 1984 Mathematics Rd, Vancouver, BC, V6T 1Z2, Canada
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7
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Li J, Szymanski DB, Kim T. Probing stress-regulated ordering of the plant cortical microtubule array via a computational approach. BMC PLANT BIOLOGY 2023; 23:308. [PMID: 37291489 DOI: 10.1186/s12870-023-04252-5] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Subscribe] [Scholar Register] [Received: 11/30/2022] [Accepted: 04/27/2023] [Indexed: 06/10/2023]
Abstract
BACKGROUND Morphological properties of tissues and organs rely on cell growth. The growth of plant cells is determined by properties of a tough outer cell wall that deforms anisotropically in response to high turgor pressure. Cortical microtubules bias the mechanical anisotropy of a cell wall by affecting the trajectories of cellulose synthases in the wall that polymerize cellulose microfibrils. The microtubule cytoskeleton is often oriented in one direction at cellular length-scales to regulate growth direction, but the means by which cellular-scale microtubule patterns emerge has not been well understood. Correlations between the microtubule orientation and tensile forces in the cell wall have often been observed. However, the plausibility of stress as a determining factor for microtubule patterning has not been directly evaluated to date. RESULTS Here, we simulated how different attributes of tensile forces in the cell wall can orient and pattern the microtubule array in the cortex. We implemented a discrete model with transient microtubule behaviors influenced by local mechanical stress in order to probe the mechanisms of stress-dependent patterning. Specifically, we varied the sensitivity of four types of dynamic behaviors observed on the plus end of microtubules - growth, shrinkage, catastrophe, and rescue - to local stress. Then, we evaluated the extent and rate of microtubule alignments in a two-dimensional computational domain that reflects the structural organization of the cortical array in plant cells. CONCLUSION Our modeling approaches reproduced microtubule patterns observed in simple cell types and demonstrated that a spatial variation in the magnitude and anisotropy of stress can mediate mechanical feedback between the wall and of the cortical microtubule array.
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Affiliation(s)
- Jing Li
- Weldon School of Biomedical Engineering, Purdue University, 206 S Martin Jischke Dr, West Lafayette, IN, 47907, USA
| | - Daniel B Szymanski
- Botany and Plant Pathology, Biological Sciences, Purdue University, 915 West State Street, West Lafayette, IN, 47907, USA.
| | - Taeyoon Kim
- Weldon School of Biomedical Engineering, Purdue University, 206 S Martin Jischke Dr, West Lafayette, IN, 47907, USA.
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8
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Travis SM, Mahon BP, Huang W, Ma M, Rale MJ, Kraus J, Taylor DJ, Zhang R, Petry S. Integrated model of the vertebrate augmin complex. Nat Commun 2023; 14:2072. [PMID: 37055408 PMCID: PMC10102177 DOI: 10.1038/s41467-023-37519-4] [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: 09/26/2022] [Accepted: 03/17/2023] [Indexed: 04/15/2023] Open
Abstract
Accurate segregation of chromosomes is required to maintain genome integrity during cell division. This feat is accomplished by the microtubule-based spindle. To build a spindle rapidly and with high fidelity, cells take advantage of branching microtubule nucleation, which rapidly amplifies microtubules during cell division. Branching microtubule nucleation relies on the hetero-octameric augmin complex, but lack of structure information about augmin has hindered understanding how it promotes branching. In this work, we combine cryo-electron microscopy, protein structural prediction, and visualization of fused bulky tags via negative stain electron microscopy to identify the location and orientation of each subunit within the augmin structure. Evolutionary analysis shows that augmin's structure is highly conserved across eukaryotes, and that augmin contains a previously unidentified microtubule binding site. Thus, our findings provide insight into the mechanism of branching microtubule nucleation.
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Affiliation(s)
- Sophie M Travis
- Department of Molecular Biology, Princeton University, Princeton, NJ, USA
| | - Brian P Mahon
- Department of Molecular Biology, Princeton University, Princeton, NJ, USA
- Department of Structural Biology, Bristol Myers Squibb, Princeton, NJ, USA
| | - Wei Huang
- Department of Pharmacology, Case Western Reserve University, Cleveland, OH, USA
| | - Meisheng Ma
- Department of Biochemistry and Molecular Biophysics, Washington University in St. Louis, School of Medicine, St. Louis, MO, USA
- Department of Histology and Embryology, School of Basic Medicine, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, Hubei, China
| | - Michael J Rale
- Department of Molecular Biology, Princeton University, Princeton, NJ, USA
- Department of Cell Biology, Harvard Medical School, Boston, MA, USA
| | - Jodi Kraus
- Department of Molecular Biology, Princeton University, Princeton, NJ, USA
| | - Derek J Taylor
- Department of Pharmacology, Case Western Reserve University, Cleveland, OH, USA
| | - Rui Zhang
- Department of Biochemistry and Molecular Biophysics, Washington University in St. Louis, School of Medicine, St. Louis, MO, USA.
| | - Sabine Petry
- Department of Molecular Biology, Princeton University, Princeton, NJ, USA.
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9
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Domozych DS, Bagdan K. The cell biology of charophytes: Exploring the past and models for the future. PLANT PHYSIOLOGY 2022; 190:1588-1608. [PMID: 35993883 PMCID: PMC9614468 DOI: 10.1093/plphys/kiac390] [Citation(s) in RCA: 10] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 05/09/2022] [Accepted: 07/26/2022] [Indexed: 06/15/2023]
Abstract
Charophytes (Streptophyta) represent a diverse assemblage of extant green algae that are the sister lineage to land plants. About 500-600+ million years ago, a charophyte progenitor successfully colonized land and subsequently gave rise to land plants. Charophytes have diverse but relatively simple body plans that make them highly attractive organisms for many areas of biological research. At the cellular level, many charophytes have been used for deciphering cytoskeletal networks and their dynamics, membrane trafficking, extracellular matrix secretion, and cell division mechanisms. Some charophytes live in challenging habitats and have become excellent models for elucidating the cellular and molecular effects of various abiotic stressors on plant cells. Recent sequencing of several charophyte genomes has also opened doors for the dissection of biosynthetic and signaling pathways. While we are only in an infancy stage of elucidating the cell biology of charophytes, the future application of novel analytical methodologies in charophyte studies that include a broader survey of inclusive taxa will enhance our understanding of plant evolution and cell dynamics.
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Affiliation(s)
| | - Kaylee Bagdan
- Department of Biology, Skidmore Microscopy Imaging Center, Skidmore College, Saratoga Springs, New York 12866, USA
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10
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Abstract
In contrast to well-studied fungal and animal cells, plant cells assemble bipolar spindles that exhibit a great deal of plasticity in the absence of structurally defined microtubule-organizing centers like the centrosome. While plants employ some evolutionarily conserved proteins to regulate spindle morphogenesis and remodeling, many essential spindle assembly factors found in vertebrates are either missing or not required for producing the plant bipolar microtubule array. Plants also produce proteins distantly related to their fungal and animal counterparts to regulate critical events such as the spindle assembly checkpoint. Plant spindle assembly initiates with microtubule nucleation on the nuclear envelope followed by bipolarization into the prophase spindle. After nuclear envelope breakdown, kinetochore fibers are assembled and unified into the spindle apparatus with convergent poles. Of note, compared to fungal and animal systems, relatively little is known about how plant cells remodel the spindle microtubule array during anaphase. Uncovering mitotic functions of novel proteins for spindle assembly in plants will illuminate both common and divergent mechanisms employed by different eukaryotic organisms to segregate genetic materials.
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Affiliation(s)
- Bo Liu
- Department of Plant Biology, University of California, Davis, California, USA; ,
| | - Yuh-Ru Julie Lee
- Department of Plant Biology, University of California, Davis, California, USA; ,
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11
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Kato S, Murakami M, Saika R, Soga K, Wakabayashi K, Hashimoto H, Yano S, Matsumoto S, Kasahara H, Kamada M, Shimazu T, Hashimoto T, Hoson T. Suppression of Cortical Microtubule Reorientation and Stimulation of Cell Elongation in Arabidopsis Hypocotyls under Microgravity Conditions in Space. PLANTS 2022; 11:plants11030465. [PMID: 35161447 PMCID: PMC8837939 DOI: 10.3390/plants11030465] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 01/17/2022] [Revised: 02/04/2022] [Accepted: 02/05/2022] [Indexed: 11/16/2022]
Abstract
How microgravity in space influences plant cell growth is an important issue for plant cell biology as well as space biology. We investigated the role of cortical microtubules in the stimulation of elongation growth in Arabidopsis (Arabidopsis thaliana) hypocotyls under microgravity conditions with the Resist Tubule space experiment. The epidermal cells in the lower half of the hypocotyls of wild-type Columbia were longer in microgravity than at on-orbit 1 g, which precipitated an increase in the entire hypocotyl length. In the apical region, cortical microtubules adjacent to the outer tangential wall were predominantly transverse to the long axis of the cell, whereas longitudinal microtubules were predominant in the basal region. In the 9th to 12th epidermal cells (1 to 3 mm) from the tip, where the modification of microtubule orientation from transverse to longitudinal directions (reorientation) occurred, cells with transverse microtubules increased, whereas those with longitudinal microtubules decreased in microgravity, and the average angle with respect to the transverse cell axis decreased, indicating that the reorientation was suppressed in microgravity. The expression of tubulin genes was suppressed in microgravity. These results suggest that under microgravity conditions, the expression of genes related to microtubule formation was downregulated, which may cause the suppression of microtubule reorientation from transverse to longitudinal directions, thereby stimulating cell elongation in Arabidopsis hypocotyls.
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Affiliation(s)
- Shiho Kato
- Department of Biology, Graduate School of Science, Osaka City University, Osaka 558-8585, Japan; (S.K.); (M.M.); (R.S.); (K.S.); (K.W.)
| | - Mana Murakami
- Department of Biology, Graduate School of Science, Osaka City University, Osaka 558-8585, Japan; (S.K.); (M.M.); (R.S.); (K.S.); (K.W.)
| | - Ryo Saika
- Department of Biology, Graduate School of Science, Osaka City University, Osaka 558-8585, Japan; (S.K.); (M.M.); (R.S.); (K.S.); (K.W.)
| | - Kouichi Soga
- Department of Biology, Graduate School of Science, Osaka City University, Osaka 558-8585, Japan; (S.K.); (M.M.); (R.S.); (K.S.); (K.W.)
| | - Kazuyuki Wakabayashi
- Department of Biology, Graduate School of Science, Osaka City University, Osaka 558-8585, Japan; (S.K.); (M.M.); (R.S.); (K.S.); (K.W.)
| | - Hirofumi Hashimoto
- Institute of Space and Astronautical Science, Japan Aerospace Exploration Agency, Sagamihara 252-5210, Japan;
| | - Sachiko Yano
- Japan Aerospace Exploration Agency, Tsukuba 305-8505, Japan;
| | - Shohei Matsumoto
- Japan Manned Space Systems, Tokyo 100-0004, Japan; (S.M.); (H.K.)
| | - Haruo Kasahara
- Japan Manned Space Systems, Tokyo 100-0004, Japan; (S.M.); (H.K.)
| | | | | | - Takashi Hashimoto
- Division of Biological Science, Nara Institute of Science and Technology, Ikoma 630-0192, Japan;
| | - Takayuki Hoson
- Department of Biology, Graduate School of Science, Osaka City University, Osaka 558-8585, Japan; (S.K.); (M.M.); (R.S.); (K.S.); (K.W.)
- Correspondence:
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12
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Gu Y, Rasmussen CG. Cell biology of primary cell wall synthesis in plants. THE PLANT CELL 2022; 34:103-128. [PMID: 34613413 PMCID: PMC8774047 DOI: 10.1093/plcell/koab249] [Citation(s) in RCA: 27] [Impact Index Per Article: 13.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/28/2021] [Accepted: 10/01/2021] [Indexed: 05/07/2023]
Abstract
Building a complex structure such as the cell wall, with many individual parts that need to be assembled correctly from distinct sources within the cell, is a well-orchestrated process. Additional complexity is required to mediate dynamic responses to environmental and developmental cues. Enzymes, sugars, and other cell wall components are constantly and actively transported to and from the plasma membrane during diffuse growth. Cell wall components are transported in vesicles on cytoskeletal tracks composed of microtubules and actin filaments. Many of these components, and additional proteins, vesicles, and lipids are trafficked to and from the cell plate during cytokinesis. In this review, we first discuss how the cytoskeleton is initially organized to add new cell wall material or to build a new cell wall, focusing on similarities during these processes. Next, we discuss how polysaccharides and enzymes that build the cell wall are trafficked to the correct location by motor proteins and through other interactions with the cytoskeleton. Finally, we discuss some of the special features of newly formed cell walls generated during cytokinesis.
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Affiliation(s)
- Ying Gu
- Department of Biochemistry and Molecular Biology, Pennsylvania State University, University Park, Pennsylvania 16802
| | - Carolyn G Rasmussen
- Department of Botany and Plant Sciences, Center for Plant Cell Biology, University of California, Riverside, California 92521
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13
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Nakamura M, Yagi N, Hashimoto T. Finding a right place to cut: How katanin is targeted to cellular severing sites. QUANTITATIVE PLANT BIOLOGY 2022; 3:e8. [PMID: 37077970 PMCID: PMC10095862 DOI: 10.1017/qpb.2022.2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 12/20/2021] [Revised: 01/24/2022] [Accepted: 01/24/2022] [Indexed: 05/03/2023]
Abstract
Microtubule severing by katanin plays key roles in generating various array patterns of dynamic microtubules, while also responding to developmental and environmental stimuli. Quantitative imaging and molecular genetic analyses have uncovered that dysfunction of microtubule severing in plant cells leads to defects in anisotropic growth, division and other cell processes. Katanin is targeted to several subcellular severing sites. Intersections of two crossing cortical microtubules attract katanin, possibly by using local lattice deformation as a landmark. Cortical microtubule nucleation sites on preexisting microtubules are targeted for katanin-mediated severing. An evolutionary conserved microtubule anchoring complex not only stabilises the nucleated site, but also subsequently recruits katanin for timely release of a daughter microtubule. During cytokinesis, phragmoplast microtubules are severed at distal zones by katanin, which is tethered there by plant-specific microtubule-associated proteins. Recruitment and activation of katanin are essential for maintenance and reorganisation of plant microtubule arrays.
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Affiliation(s)
- Masayoshi Nakamura
- Institute of Transformative Bio-Molecules (WPI-ITbM), Nagoya University, Nagoya, Japan
- Authors for correspondence: M. Nakamura and T. Hashimoto, E-mail: ,
| | - Noriyoshi Yagi
- Institute of Transformative Bio-Molecules (WPI-ITbM), Nagoya University, Nagoya, Japan
| | - Takashi Hashimoto
- Division of Biological Sciences, Nara Institute of Science and Technology, Ikoma, Japan
- Authors for correspondence: M. Nakamura and T. Hashimoto, E-mail: ,
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14
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Non-centrosomal Microtubule Organization in Plant Cells. THE CENTROSOME AND ITS FUNCTIONS AND DYSFUNCTIONS 2022; 235:105-111. [DOI: 10.1007/978-3-031-20848-5_10] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
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15
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Lucas JR. Appearance of microtubules at the cytokinesis to interphase transition in Arabidopsis thaliana. Cytoskeleton (Hoboken) 2021; 78:361-371. [PMID: 34569724 DOI: 10.1002/cm.21689] [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: 01/10/2021] [Revised: 09/19/2021] [Accepted: 09/20/2021] [Indexed: 11/06/2022]
Abstract
Microtubule arrays drastically reorganize during the cell cycle to facilitate specific events. Many cells contain a centrosome that dictates the assembly and organization of microtubule arrays. However, plant cells and many others do not contain centrosomes or discrete microtubule organizing centers. In plants, microtubules nucleate and polymerize from gamma-tubulin-containing complexes in the interphase cell cortex. During plant cell division, microtubules nucleate near nuclei to form the mitotic spindle and plant-specific phragmoplast required for cytokinesis. Therefore, during the plant cell cycle, microtubule nucleation shifts from cell cortex to the perinuclear region. While it is unclear how this shift occurs, previous studies observed microtubules that appeared to extend from nuclei into the cortex as cells transitioned into interphase in small cells. These data led to the hypothesis that microtubule nucleation complexes move from the nuclear surface to the cortex at the transition from cytokinesis into interphase. Here we document GFP labeled microtubules in living plant cells during the transition from cytokinesis to interphase. We observed apparent groups of microtubules spanning between the nucleus and cell cortex in large, vacuolated epidermal leaf cells. We also observed microtubules in the cell cortex that appeared separate from perinuclear-associated microtubules. While these cortical microtubules were not always seen, when present they were apparent before cytokinesis was complete and/or before nuclear-associated microtubules were obvious. These data add to and deepen the knowledge of microtubule reorganization at this cell cycle transition.
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Affiliation(s)
- Jessica R Lucas
- Department of Biology, University of Wisconsin-Oshkosh, Oshkosh, Wisconsin, USA
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16
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Chen S, Alhassen W, Vakil Monfared R, Vachirakorntong B, Nauli SM, Baldi P, Alachkar A. Dynamic Changes of Brain Cilia Transcriptomes across the Human Lifespan. Int J Mol Sci 2021; 22:10387. [PMID: 34638726 PMCID: PMC8509004 DOI: 10.3390/ijms221910387] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/04/2021] [Revised: 09/23/2021] [Accepted: 09/24/2021] [Indexed: 12/27/2022] Open
Abstract
Almost all brain cells contain primary cilia, antennae-like microtubule sensory organelles, on their surface, which play critical roles in brain functions. During neurodevelopmental stages, cilia are essential for brain formation and maturation. In the adult brain, cilia play vital roles as signaling hubs that receive and transduce various signals and regulate cell-to-cell communications. These distinct roles suggest that cilia functions, and probably structures, change throughout the human lifespan. To further understand the age-dependent changes in cilia roles, we identified and analyzed age-dependent patterns of expression of cilia's structural and functional components across the human lifespan. We acquired cilia transcriptomic data for 16 brain regions from the BrainSpan Atlas and analyzed the age-dependent expression patterns using a linear regression model by calculating the regression coefficient. We found that 67% of cilia transcripts were differentially expressed genes with age (DEGAs) in at least one brain region. The age-dependent expression was region-specific, with the highest and lowest numbers of DEGAs expressed in the ventrolateral prefrontal cortex and hippocampus, respectively. The majority of cilia DEGAs displayed upregulation with age in most of the brain regions. The transcripts encoding cilia basal body components formed the majority of cilia DEGAs, and adjacent cerebral cortices exhibited large overlapping pairs of cilia DEGAs. Most remarkably, specific α/β-tubulin subunits (TUBA1A, TUBB2A, and TUBB2B) and SNAP-25 exhibited the highest rates of downregulation and upregulation, respectively, across age in almost all brain regions. α/β-tubulins and SNAP-25 expressions are known to be dysregulated in age-related neurodevelopmental and neurodegenerative disorders. Our results support a role for the high dynamics of cilia structural and functional components across the lifespan in the normal physiology of brain circuits. Furthermore, they suggest a crucial role for cilia signaling in the pathophysiological mechanisms of age-related psychiatric/neurological disorders.
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Affiliation(s)
- Siwei Chen
- Department of Computer Science, School of Information and Computer Sciences, University of California-Irvine, Irvine, CA 92617, USA; (S.C.); (P.B.)
- Institute for Genomics and Bioinformatics, School of Information and Computer Sciences, University of California-Irvine, Irvine, CA 92617, USA
| | - Wedad Alhassen
- Department of Pharmaceutical Sciences, School of Pharmacy, University of California-Irvine, Irvine, CA 92617, USA; (W.A.); (R.V.M.); (B.V.)
| | - Roudabeh Vakil Monfared
- Department of Pharmaceutical Sciences, School of Pharmacy, University of California-Irvine, Irvine, CA 92617, USA; (W.A.); (R.V.M.); (B.V.)
| | - Benjamin Vachirakorntong
- Department of Pharmaceutical Sciences, School of Pharmacy, University of California-Irvine, Irvine, CA 92617, USA; (W.A.); (R.V.M.); (B.V.)
| | - Surya M. Nauli
- Department of Biomedical and Pharmaceutical Sciences, School of Pharmacy, Chapman University Rinker Health Science Campus, Irvine, CA 92618, USA;
| | - Pierre Baldi
- Department of Computer Science, School of Information and Computer Sciences, University of California-Irvine, Irvine, CA 92617, USA; (S.C.); (P.B.)
- Institute for Genomics and Bioinformatics, School of Information and Computer Sciences, University of California-Irvine, Irvine, CA 92617, USA
| | - Amal Alachkar
- Institute for Genomics and Bioinformatics, School of Information and Computer Sciences, University of California-Irvine, Irvine, CA 92617, USA
- Department of Pharmaceutical Sciences, School of Pharmacy, University of California-Irvine, Irvine, CA 92617, USA; (W.A.); (R.V.M.); (B.V.)
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17
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An anchoring complex recruits katanin for microtubule severing at the plant cortical nucleation sites. Nat Commun 2021; 12:3687. [PMID: 34140499 PMCID: PMC8211667 DOI: 10.1038/s41467-021-24067-y] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/04/2020] [Accepted: 05/25/2021] [Indexed: 02/05/2023] Open
Abstract
Microtubules are severed by katanin at distinct cellular locations to facilitate reorientation or amplification of dynamic microtubule arrays, but katanin targeting mechanisms are poorly understood. Here we show that a centrosomal microtubule-anchoring complex is used to recruit katanin in acentrosomal plant cells. The conserved protein complex of Msd1 (also known as SSX2IP) and Wdr8 is localized at microtubule nucleation sites along the microtubule lattice in interphase Arabidopsis cells. Katanin is recruited to these sites for efficient release of newly formed daughter microtubules. Our cell biological and genetic studies demonstrate that Msd1-Wdr8 acts as a specific katanin recruitment factor to cortical nucleation sites (but not to microtubule crossover sites) and stabilizes the association of daughter microtubule minus ends to their nucleation sites until they become severed by katanin. Molecular coupling of sequential anchoring and severing events by the evolutionarily conserved complex renders microtubule release under tight control of katanin activity.
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18
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Ferreira LT, Maiato H. Prometaphase. Semin Cell Dev Biol 2021; 117:52-61. [PMID: 34127384 DOI: 10.1016/j.semcdb.2021.06.004] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2021] [Revised: 05/31/2021] [Accepted: 06/02/2021] [Indexed: 11/28/2022]
Abstract
The establishment of a metaphase plate in which all chromosomes are attached to mitotic spindle microtubules and aligned at the cell equator is required for faithful chromosome segregation in metazoans. The achievement of this configuration relies on the precise coordination between several concurrent mechanisms that start upon nuclear envelope breakdown, mediate chromosome capture at their kinetochores during mitotic spindle assembly and culminate with the congression of all chromosomes to the spindle equator. This period is called 'prometaphase'. Because the nature of chromosome capture by mitotic spindle microtubules is error prone, the cell is provided of error correction mechanisms that sense and correct most erroneous kinetochore-microtubule attachments before committing to separate sister chromatids in anaphase. In this review, aimed for newcomers in the field, more than providing an exhaustive mechanistic coverage of each and every concurrent mechanism taking place during prometaphase, we provide an integrative overview of these processes that ultimately promote the subsequent faithful segregation of chromosomes during mitosis.
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Affiliation(s)
- Luísa T Ferreira
- Chromosome Instability & Dynamics Group, i3S - Instituto de Investigação e Inovação em Saúde, Universidade do Porto, Rua Alfredo Allen 208, 4200-135 Porto, Portugal; Instituto de Biologia Molecular e Celular, Universidade do Porto, Rua Alfredo Allen 208, 4200-135 Porto, Portugal
| | - Helder Maiato
- Chromosome Instability & Dynamics Group, i3S - Instituto de Investigação e Inovação em Saúde, Universidade do Porto, Rua Alfredo Allen 208, 4200-135 Porto, Portugal; Instituto de Biologia Molecular e Celular, Universidade do Porto, Rua Alfredo Allen 208, 4200-135 Porto, Portugal; Cell Division Group, Experimental Biology Unit, Department of Biomedicine, Faculdade de Medicina, Universidade do Porto, Alameda Prof. Hernâni Monteiro, 4200-319 Porto, Portugal.
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19
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Mani N, Wijeratne SS, Subramanian R. Micron-scale geometrical features of microtubules as regulators of microtubule organization. eLife 2021; 10:e63880. [PMID: 34114950 PMCID: PMC8195601 DOI: 10.7554/elife.63880] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/12/2020] [Accepted: 06/02/2021] [Indexed: 12/20/2022] Open
Abstract
The organization of micron-sized, multi-microtubule arrays from individual microtubules is essential for diverse cellular functions. The microtubule polymer is largely viewed as a passive building block during the organization process. An exception is the 'tubulin code' where alterations to tubulin at the amino acid level can influence the activity of microtubule-associated proteins. Recent studies reveal that micron-scale geometrical features of individual microtubules and polymer networks, such as microtubule length, overlap length, contact angle, and lattice defects, can also regulate the activity of microtubule-associated proteins and modulate polymer dynamics. We discuss how the interplay between such geometrical properties of the microtubule lattice and the activity of associated proteins direct multiple aspects of array organization, from microtubule nucleation and coalignment to specification of array dimensions and remodeling of dynamic networks. The mechanisms reviewed here highlight micron-sized features of microtubules as critical parameters to be routinely investigated in the study of microtubule self-organization.
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Affiliation(s)
- Nandini Mani
- Department of Molecular Biology, Massachusetts General HospitalBostonUnited States
- Department of Genetics, Harvard Medical SchoolBostonUnited States
| | - Sithara S Wijeratne
- Department of Molecular Biology, Massachusetts General HospitalBostonUnited States
- Department of Genetics, Harvard Medical SchoolBostonUnited States
| | - Radhika Subramanian
- Department of Molecular Biology, Massachusetts General HospitalBostonUnited States
- Department of Genetics, Harvard Medical SchoolBostonUnited States
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20
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Saltini M, Mulder BM. A plausible mechanism for longitudinal lock-in of the plant cortical microtubule array after light-induced reorientation. QUANTITATIVE PLANT BIOLOGY 2021; 2:e9. [PMID: 37077209 PMCID: PMC10095967 DOI: 10.1017/qpb.2021.9] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 01/22/2021] [Revised: 03/30/2021] [Accepted: 04/21/2021] [Indexed: 05/03/2023]
Abstract
The light-induced reorientation of the cortical microtubule array in dark-grown Arabidopsis thaliana hypocotyl cells is a striking example of the dynamical plasticity of the microtubule cytoskeleton. A consensus model, based on katanin-mediated severing at microtubule crossovers, has been developed that successfully describes the onset of the observed switch between a transverse and longitudinal array orientation. However, we currently lack an understanding of why the newly populated longitudinal array direction remains stable for longer times and re-equilibration effects would tend to drive the system back to a mixed orientation state. Using both simulations and analytical calculations, we show that the assumption of a small orientation-dependent shift in microtubule dynamics is sufficient to explain the long-term lock-in of the longitudinal array orientation. Furthermore, we show that the natural alternative hypothesis that there is a selective advantage in severing longitudinal microtubules, is neither necessary nor sufficient to achieve cortical array reorientation, but is able to accelerate this process significantly.
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Affiliation(s)
- Marco Saltini
- Department of Ecology and Genetics, Animal Ecology, Uppsala University, Uppsala, Sweden
- Author for correspondence: M. Saltini, E-mail:
| | - Bela M. Mulder
- Living Matter Department, AMOLF, Amsterdam, The Netherlands
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21
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Abstract
The latent left–right asymmetry (chirality) of vascular plants is best witnessed as a helical elongation of cylindrical organs in climbing plants. Interestingly, helical handedness is usually fixed in given species, suggesting genetic control of chirality. Arabidopsis thaliana, a small mustard plant, normally does not twist but can be mutated to exhibit helical growth in elongating organs. Genetic, molecular and cell biological analyses of these twisting mutants are providing mechanistic insights into the left–right handedness as well as how potential organ skewing is suppressed in most plants. Growth direction of elongating plant cells is determined by alignment of cellulose microfibrils in cell walls, which is guided by cortical microtubules localized just beneath the plasma membrane. Mutations in tubulins and regulators of microtubule assembly or organization give rise to helical arrangements of cortical microtubule arrays in Arabidopsis cells and cause helical growth of fixed handedness in axial organs such as roots and stems. Whether tubulins are assembled into a microtubule composed of straight or tilted protofilaments might determine straight or twisting growth. Mechanistic understanding of helical plant growth will provide a paradigm for connecting protein filament structure to cellular organization.
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22
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Jacobs B, Molenaar J, Deinum EE. Robust banded protoxylem pattern formation through microtubule-based directional ROP diffusion restriction. J Theor Biol 2020; 502:110351. [PMID: 32505828 DOI: 10.1016/j.jtbi.2020.110351] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/14/2019] [Revised: 04/07/2020] [Accepted: 05/27/2020] [Indexed: 12/28/2022]
Abstract
In plant vascular tissue development, different cell wall patterns are formed, offering different mechanical properties optimised for different growth stages. Critical in these patterning processes are Rho of Plants (ROP) proteins, a class of evolutionarily conserved small GTPase proteins responsible for local membrane domain formation in many organisms. While te spotted metaxylem pattern can easily be understood as a result of a Turing-style reaction-diffusion mechanism, it remains an open question how the consistent orientation of evenly spaced bands and spirals as found in protoxylem is achieved. We hypothesise that this orientation results from an interaction between ROPs and an array of transversely oriented cortical microtubules that acts as a directional diffusion barrier. Here, we explore this hypothesis using partial differential equation models with anisotropic ROP diffusion and show that a horizontal microtubule array acting as a vertical diffusion barrier to active ROP can yield a horizontally banded ROP pattern. We then study the underlying mechanism in more detail, finding that it can only orient curved pattern features but not straight lines. This implies that, once formed, banded and spiral patterns cannot be reoriented by this mechanism. Finally, we observe that ROPs and microtubules together only form ultimately static patterns if the interaction is implemented with sufficient biological realism.
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Affiliation(s)
- Bas Jacobs
- Biometris, Department for Mathematical and Statistical Methods, Wageningen University, Wageningen, The Netherlands
| | - Jaap Molenaar
- Biometris, Department for Mathematical and Statistical Methods, Wageningen University, Wageningen, The Netherlands
| | - Eva E Deinum
- Biometris, Department for Mathematical and Statistical Methods, Wageningen University, Wageningen, The Netherlands.
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23
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A Pushing Mechanism for Microtubule Aster Positioning in a Large Cell Type. Cell Rep 2020; 33:108213. [DOI: 10.1016/j.celrep.2020.108213] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/06/2019] [Revised: 01/12/2020] [Accepted: 09/10/2020] [Indexed: 12/15/2022] Open
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24
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Zupa E, Liu P, Würtz M, Schiebel E, Pfeffer S. The structure of the γ-TuRC: a 25-years-old molecular puzzle. Curr Opin Struct Biol 2020; 66:15-21. [PMID: 33002806 DOI: 10.1016/j.sbi.2020.08.008] [Citation(s) in RCA: 19] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2020] [Revised: 08/26/2020] [Accepted: 08/28/2020] [Indexed: 10/23/2022]
Abstract
The nucleation of microtubules from αβ-tubulin dimers is an essential cellular process dependent on γ-tubulin complexes. Mechanistic understanding of the nucleation reaction was hampered by the lack of γ-tubulin complex structures at sufficiently high resolution. The recent technical developments in cryo-electron microscopy have allowed resolving the vertebrate γ-tubulin ring complex (γ-TuRC) structure at near-atomic resolution. These studies clarified the arrangement and stoichiometry of gamma-tubulin complex proteins in the γ-TuRC, characterized the surprisingly versatile integration of the small proteins MZT1/2 into the complex, and identified actin as an integral component of the γ-TuRC. In this review, we summarize the structural insights into the molecular architecture, the assembly pathway, and the regulation of the microtubule nucleation reaction.
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Affiliation(s)
- Erik Zupa
- Zentrum für Molekulare Biologie der Universität Heidelberg, DKFZ-ZMBH Allianz, Im Neuenheimer Feld 282, 69120 Heidelberg, Germany
| | - Peng Liu
- Zentrum für Molekulare Biologie der Universität Heidelberg, DKFZ-ZMBH Allianz, Im Neuenheimer Feld 282, 69120 Heidelberg, Germany
| | - Martin Würtz
- Zentrum für Molekulare Biologie der Universität Heidelberg, DKFZ-ZMBH Allianz, Im Neuenheimer Feld 282, 69120 Heidelberg, Germany
| | - Elmar Schiebel
- Zentrum für Molekulare Biologie der Universität Heidelberg, DKFZ-ZMBH Allianz, Im Neuenheimer Feld 282, 69120 Heidelberg, Germany.
| | - Stefan Pfeffer
- Zentrum für Molekulare Biologie der Universität Heidelberg, DKFZ-ZMBH Allianz, Im Neuenheimer Feld 282, 69120 Heidelberg, Germany.
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25
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Fernández-Jiménez N, Pradillo M. The role of the nuclear envelope in the regulation of chromatin dynamics during cell division. JOURNAL OF EXPERIMENTAL BOTANY 2020; 71:5148-5159. [PMID: 32589712 DOI: 10.1093/jxb/eraa299] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/22/2020] [Accepted: 06/18/2020] [Indexed: 06/11/2023]
Abstract
The nuclear envelope delineates the eukaryotic cell nucleus. The membrane system of the nuclear envelope consists of an outer nuclear membrane and an inner nuclear membrane separated by a perinuclear space. It serves as more than just a static barrier, since it regulates the communication between the nucleoplasm and the cytoplasm and provides the anchoring points where chromatin is attached. Fewer nuclear envelope proteins have been identified in plants in comparison with animals and yeasts. Here, we review the current state of knowledge of the nuclear envelope in plants, focusing on its role as a chromatin organizer and regulator of gene expression, as well as on the modifications that it undergoes to be efficiently disassembled and reassembled with each cell division. Advances in knowledge concerning the mitotic role of some nuclear envelope constituents are also presented. In addition, we summarize recent progress on the contribution of the nuclear envelope elements to telomere tethering and chromosome dynamics during the meiotic division in different plant species.
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Affiliation(s)
- Nadia Fernández-Jiménez
- Departamento de Genética, Fisiología y Microbiología, Facultad de Ciencias Biológicas, Universidad Complutense de Madrid, Madrid, Spain
| | - Mónica Pradillo
- Departamento de Genética, Fisiología y Microbiología, Facultad de Ciencias Biológicas, Universidad Complutense de Madrid, Madrid, Spain
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26
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Zhou R, Liu H, Ju T, Dixit R. Quantifying the polymerization dynamics of plant cortical microtubules using kymograph analysis. Methods Cell Biol 2020; 160:281-293. [PMID: 32896322 DOI: 10.1016/bs.mcb.2020.04.006] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
The plant cortical microtubule array is a dynamic structure that confers cell shape and enables plants to alter their growth and development in response to internal and external cues. Cells use a variety of microtubule regulatory proteins to spatially and temporally modulate the intrinsic polymerization dynamics of cortical microtubules to arrange them into specific configurations and to reshape arrays to adapt to changing conditions. To obtain mechanistic insight into how particular microtubule regulatory proteins mediate the dynamic (re)structuring of cortical microtubule arrays, we need to measure their effect on the dynamics of cortical microtubules. In this chapter, we describe new ImageJ plugins to generate kymographs from time-lapse images and to analyze them to measure the parameters that quantitatively describe cortical microtubule dynamics.
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Affiliation(s)
- Rudy Zhou
- Department of Computer Science and Engineering, Washington University in St. Louis, St. Louis, MO, United States; Department of Biology and Center for Engineering Mechanobiology, Washington University in St. Louis, St. Louis, MO, United States
| | - Han Liu
- Department of Computer Science and Engineering, Washington University in St. Louis, St. Louis, MO, United States; Department of Biology and Center for Engineering Mechanobiology, Washington University in St. Louis, St. Louis, MO, United States
| | - Tao Ju
- Department of Computer Science and Engineering, Washington University in St. Louis, St. Louis, MO, United States.
| | - Ram Dixit
- Department of Biology and Center for Engineering Mechanobiology, Washington University in St. Louis, St. Louis, MO, United States.
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27
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Wieczorek M, Urnavicius L, Ti SC, Molloy KR, Chait BT, Kapoor TM. Asymmetric Molecular Architecture of the Human γ-Tubulin Ring Complex. Cell 2020; 180:165-175.e16. [PMID: 31862189 PMCID: PMC7027161 DOI: 10.1016/j.cell.2019.12.007] [Citation(s) in RCA: 82] [Impact Index Per Article: 20.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/28/2019] [Revised: 11/21/2019] [Accepted: 12/07/2019] [Indexed: 10/25/2022]
Abstract
The γ-tubulin ring complex (γ-TuRC) is an essential regulator of centrosomal and acentrosomal microtubule formation, yet its structure is not known. Here, we present a cryo-EM reconstruction of the native human γ-TuRC at ∼3.8 Å resolution, revealing an asymmetric, cone-shaped structure. Pseudo-atomic models indicate that GCP4, GCP5, and GCP6 form distinct Y-shaped assemblies that structurally mimic GCP2/GCP3 subcomplexes distal to the γ-TuRC "seam." We also identify an unanticipated structural bridge that includes an actin-like protein and spans the γ-TuRC lumen. Despite its asymmetric architecture, the γ-TuRC arranges γ-tubulins into a helical geometry poised to nucleate microtubules. Diversity in the γ-TuRC subunits introduces large (>100,000 Å2) surfaces in the complex that allow for interactions with different regulatory factors. The observed compositional complexity of the γ-TuRC could self-regulate its assembly into a cone-shaped structure to control microtubule formation across diverse contexts, e.g., within biological condensates or alongside existing filaments.
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Affiliation(s)
- Michal Wieczorek
- Laboratory of Chemistry and Cell Biology, The Rockefeller University, 1230 York Avenue, New York, NY 10065, USA
| | - Linas Urnavicius
- Laboratory of Chemistry and Cell Biology, The Rockefeller University, 1230 York Avenue, New York, NY 10065, USA; Laboratory of Cell Biology, The Rockefeller University, 1230 York Avenue, New York, NY 10065, USA
| | - Shih-Chieh Ti
- Laboratory of Chemistry and Cell Biology, The Rockefeller University, 1230 York Avenue, New York, NY 10065, USA
| | - Kelly R Molloy
- Laboratory of Mass Spectrometry and Gaseous Ion Chemistry, The Rockefeller University, 1230 York Avenue, New York, NY 10065, USA
| | - Brian T Chait
- Laboratory of Mass Spectrometry and Gaseous Ion Chemistry, The Rockefeller University, 1230 York Avenue, New York, NY 10065, USA
| | - Tarun M Kapoor
- Laboratory of Chemistry and Cell Biology, The Rockefeller University, 1230 York Avenue, New York, NY 10065, USA.
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28
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Gao X, Schmid M, Zhang Y, Fukuda S, Takeshita N, Fischer R. The spindle pole body of Aspergillus nidulans is asymmetrical and contains changing numbers of γ-tubulin complexes. J Cell Sci 2019; 132:jcs.234799. [PMID: 31740532 DOI: 10.1242/jcs.234799] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/28/2019] [Accepted: 10/28/2019] [Indexed: 12/14/2022] Open
Abstract
Centrosomes are important microtubule-organizing centers (MTOCs) in animal cells. In addition, non-centrosomal MTOCs (ncMTOCs) are found in many cell types. Their composition and structure are only poorly understood. Here, we analyzed nuclear MTOCs (spindle-pole bodies, SPBs) and septal MTOCs in Aspergillus nidulans They both contain γ-tubulin along with members of the family of γ-tubulin complex proteins (GCPs). Our data suggest that SPBs consist of γ-tubulin small complexes (γ-TuSCs) at the outer plaque, and larger γ-tubulin ring complexes (γ-TuRC) at the inner plaque. We show that the MztA protein, an ortholog of the human MOZART protein (also known as MZT1), interacted with the inner plaque receptor PcpA (the homolog of fission yeast Pcp1) at SPBs, while no interaction nor colocalization was detected between MztA and the outer plaque receptor ApsB (fission yeast Mto1). Septal MTOCs consist of γ-TuRCs including MztA but are anchored through AspB and Spa18 (fission yeast Mto2). MztA is not essential for viability, although abnormal spindles were observed frequently in cells lacking MztA. Quantitative PALM imaging revealed unexpected dynamics of the protein composition of SPBs, with changing numbers of γ-tubulin complexes over time during interphase and constant numbers during mitosis.This article has an associated First Person interview with the first author of the paper.
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Affiliation(s)
- Xiaolei Gao
- Karlsruhe Institute of Technology (KIT) - South Campus, Institute for Applied Biosciences, Dept. of Microbiology, Fritz-Haber-Weg 4, D-76131 Karlsruhe, Germany
| | - Marjorie Schmid
- Karlsruhe Institute of Technology (KIT) - South Campus, Institute for Applied Biosciences, Dept. of Microbiology, Fritz-Haber-Weg 4, D-76131 Karlsruhe, Germany
| | - Ying Zhang
- Karlsruhe Institute of Technology (KIT) - South Campus, Institute for Applied Biosciences, Dept. of Microbiology, Fritz-Haber-Weg 4, D-76131 Karlsruhe, Germany
| | - Sayumi Fukuda
- Tsukuba University, Faculty of Life and Environmental Sciences, Tsukuba 305-8572, Japan
| | - Norio Takeshita
- Tsukuba University, Faculty of Life and Environmental Sciences, Tsukuba 305-8572, Japan
| | - Reinhard Fischer
- Karlsruhe Institute of Technology (KIT) - South Campus, Institute for Applied Biosciences, Dept. of Microbiology, Fritz-Haber-Weg 4, D-76131 Karlsruhe, Germany
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29
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Verma V, Maresca TJ. Direct observation of branching MT nucleation in living animal cells. J Cell Biol 2019; 218:2829-2840. [PMID: 31340987 PMCID: PMC6719462 DOI: 10.1083/jcb.201904114] [Citation(s) in RCA: 23] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/18/2019] [Revised: 06/07/2019] [Accepted: 07/01/2019] [Indexed: 02/07/2023] Open
Abstract
Branching microtubule nucleation by its molecular mediators has never been directly observed in animal cells. By imaging augmin, γ-TuRC, and microtubules with high spatiotemporal resolution, Verma and Maresca quantitatively define the sequential steps of augmin-mediated branching microtubule nucleation in dividing Drosophila cells. Centrosome-mediated microtubule (MT) nucleation has been well characterized; however, numerous noncentrosomal MT nucleation mechanisms exist. The branching MT nucleation pathway envisages that the γ-tubulin ring complex (γ-TuRC) is recruited to MTs by the augmin complex to initiate nucleation of new MTs. While the pathway is well conserved at a molecular and functional level, branching MT nucleation by core constituents has never been directly observed in animal cells. Here, multicolor TIRF microscopy was applied to visualize and quantitatively define the entire process of branching MT nucleation in dividing Drosophila cells during anaphase. The steps of a stereotypical branching nucleation event entailed augmin binding to a mother MT and recruitment of γ-TuRC after 15 s, followed by nucleation 16 s later of a daughter MT at a 36° branch angle. Daughters typically remained attached throughout their ∼40-s lifetime unless the mother depolymerized past the branch point. Assembly of branched MT arrays, which did not require Drosophila TPX2, enhanced localized RhoA activation during cytokinesis.
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Affiliation(s)
- Vikash Verma
- Biology Department, University of Massachusetts, Amherst, MA
| | - Thomas J Maresca
- Biology Department, University of Massachusetts, Amherst, MA .,Molecular and Cellular Biology Graduate Program, University of Massachusetts, Amherst, MA
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30
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Prelogović M, Winters L, Milas A, Tolić IM, Pavin N. Pivot-and-bond model explains microtubule bundle formation. Phys Rev E 2019; 100:012403. [PMID: 31499770 DOI: 10.1103/physreve.100.012403] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/18/2017] [Indexed: 06/10/2023]
Abstract
During mitosis, microtubules form a spindle, which is responsible for proper segregation of the genetic material. A common structural element in a mitotic spindle is a parallel bundle, consisting of two or more microtubules growing from the same origin and held together by cross-linking proteins. An interesting question is what are the physical principles underlying the formation and stability of such microtubule bundles. Here we show, by introducing the pivot-and-bond model, that random angular movement of microtubules around the spindle pole and forces exerted by cross-linking proteins can explain the formation of microtubule bundles as observed in our experiments. The model predicts that stable parallel bundles can form in the presence of either passive crosslinkers or plus-end directed motors, but not minus-end directed motors. In the cases where bundles form, the time needed for their formation depends mainly on the concentration of cross-linking proteins and the angular diffusion of the microtubule. In conclusion, the angular motion drives the alignment of microtubules, which in turn allows the cross-linking proteins to connect the microtubules into a stable bundle.
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Affiliation(s)
- Marcel Prelogović
- Department of Physics, Faculty of Science, University of Zagreb, Bijenička cesta 32, 10000 Zagreb, Croatia
| | - Lora Winters
- Max Planck Institute of Molecular Cell Biology and Genetics, Pfotenhauerstr. 108, 01307 Dresden, Germany
| | - Ana Milas
- Division of Molecular Biology, Ruđer Bošković Institute, Bijenička cesta 54, 10000 Zagreb, Croatia
| | - Iva M Tolić
- Max Planck Institute of Molecular Cell Biology and Genetics, Pfotenhauerstr. 108, 01307 Dresden, Germany
- Division of Molecular Biology, Ruđer Bošković Institute, Bijenička cesta 54, 10000 Zagreb, Croatia
| | - Nenad Pavin
- Department of Physics, Faculty of Science, University of Zagreb, Bijenička cesta 32, 10000 Zagreb, Croatia
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31
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Tian J, Kong Z. The role of the augmin complex in establishing microtubule arrays. JOURNAL OF EXPERIMENTAL BOTANY 2019; 70:3035-3041. [PMID: 30882862 DOI: 10.1093/jxb/erz123] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/25/2019] [Accepted: 03/11/2019] [Indexed: 05/14/2023]
Abstract
Microtubule-dependent microtubule nucleation occurs on the lateral surface of pre-existing microtubules and provides a highly efficient means of amplifying their populations and reorganizing their architectures. The γ‑tubulin ring complex serves as the template to initiate nascent microtubule polymerization. Augmin, a hetero-octameric protein complex, acts as a recruiting factor to target the γ‑tubulin ring complex to pre-existing microtubules and trigger new microtubule growth. Although microtubule-dependent microtubule nucleation has been extensively studied in both animal and plant cells, it remains unclear how the augmin complex assembles in plant cells, especially in cell-cycle-specific and cell-type-specific manners, and how its spatial structure orchestrates the nucleation geometry. In this review, we summarize the advances in knowledge of augmin-dependent microtubule nucleation and the regulation of its geometry, and highlight recent findings and emerging questions concerning the role of the augmin complex in establishing microtubule arrays and the cell-cycle-specific composition of augmin in plant cells.
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Affiliation(s)
- Juan Tian
- State Key Laboratory of Plant Genomics, Institute of Microbiology, Chinese Academy of Sciences, Beijing, China
| | - Zhaosheng Kong
- State Key Laboratory of Plant Genomics, Institute of Microbiology, Chinese Academy of Sciences, Beijing, China
- University of Chinese Academy of Sciences, Beijing, China
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32
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Lee YRJ, Liu B. Microtubule nucleation for the assembly of acentrosomal microtubule arrays in plant cells. THE NEW PHYTOLOGIST 2019; 222:1705-1718. [PMID: 30681146 DOI: 10.1111/nph.15705] [Citation(s) in RCA: 32] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/03/2018] [Accepted: 01/07/2019] [Indexed: 05/15/2023]
Abstract
Contents Summary I. Introduction II. MT arrays in plant cells III. γ-Tubulin and MT nucleation IV. MT nucleation sites or flexible MTOCs in plant cells V. MT-dependent MT nucleation VI. Generating new MTs for spindle assembly VII. Generation of MTs for phragmoplast expansion during cytokinesis VIII. MT generation for the cortical MT array IX. MT nucleation: looking forward Acknowledgements References SUMMARY: Cytoskeletal microtubules (MTs) have a multitude of functions including intracellular distribution of molecules and organelles, cell morphogenesis, as well as segregation of the genetic material and separation of the cytoplasm during cell division among eukaryotic organisms. In response to internal and external cues, eukaryotic cells remodel their MT network in a regulated manner in order to assemble physiologically important arrays for cell growth, cell proliferation, or for cells to cope with biotic or abiotic stresses. Nucleation of new MTs is a critical step for MT remodeling. Although many key factors contributing to MT nucleation and organization are well conserved in different kingdoms, the centrosome, representing the most prominent microtubule organizing centers (MTOCs), disappeared during plant evolution as angiosperms lack the structure. Instead, flexible MTOCs may emerge on the plasma membrane, the nuclear envelope, and even organelles depending on types of cells and organisms and/or physiological conditions. MT-dependent MT nucleation is particularly noticeable in plant cells because it accounts for the primary source of MT generation for assembling spindle, phragmoplast, and cortical arrays when the γ-tubulin ring complex is anchored and activated by the augmin complex. It is intriguing what proteins are associated with plant-specific MTOCs and how plant cells activate or inactivate MT nucleation activities in spatiotemporally regulated manners.
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Affiliation(s)
- Yuh-Ru Julie Lee
- Department of Plant Biology, University of California, Davis, CA, 95616, USA
| | - Bo Liu
- Department of Plant Biology, University of California, Davis, CA, 95616, USA
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33
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Lindeboom JJ, Nakamura M, Saltini M, Hibbel A, Walia A, Ketelaar T, Emons AMC, Sedbrook JC, Kirik V, Mulder BM, Ehrhardt DW. CLASP stabilization of plus ends created by severing promotes microtubule creation and reorientation. J Cell Biol 2019; 218:190-205. [PMID: 30377221 PMCID: PMC6314540 DOI: 10.1083/jcb.201805047] [Citation(s) in RCA: 32] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2018] [Revised: 09/04/2018] [Accepted: 10/17/2018] [Indexed: 12/23/2022] Open
Abstract
Central to the building and reorganizing cytoskeletal arrays is creation of new polymers. Although nucleation has been the major focus of study for microtubule generation, severing has been proposed as an alternative mechanism to create new polymers, a mechanism recently shown to drive the reorientation of cortical arrays of higher plants in response to blue light perception. Severing produces new plus ends behind the stabilizing GTP-cap. An important and unanswered question is how these ends are stabilized in vivo to promote net microtubule generation. Here we identify the conserved protein CLASP as a potent stabilizer of new plus ends created by katanin severing in plant cells. Clasp mutants are defective in cortical array reorientation. In these mutants, both rescue of shrinking plus ends and the stabilization of plus ends immediately after severing are reduced. Computational modeling reveals that it is the specific stabilization of severed ends that best explains CLASP's function in promoting microtubule amplification by severing and array reorientation.
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Affiliation(s)
- Jelmer J Lindeboom
- Department of Plant Biology, Carnegie Institution for Science, Stanford, CA
- Laboratory of Cell Biology, Wageningen University, Wageningen, Netherlands
| | - Masayoshi Nakamura
- Department of Plant Biology, Carnegie Institution for Science, Stanford, CA
- Institute of Transformative Bio-Molecules, Nagoya University, Nagoya, Japan
| | | | - Anneke Hibbel
- Laboratory of Cell Biology, Wageningen University, Wageningen, Netherlands
| | - Ankit Walia
- Department of Plant Biology, Carnegie Institution for Science, Stanford, CA
- Sainsbury Laboratory, University of Cambridge, Cambridge, UK
| | - Tijs Ketelaar
- Laboratory of Cell Biology, Wageningen University, Wageningen, Netherlands
| | - Anne Mie C Emons
- Laboratory of Cell Biology, Wageningen University, Wageningen, Netherlands
- Institute AMOLF, Amsterdam, Netherlands
| | - John C Sedbrook
- School of Biological Sciences, Illinois State University, Normal, IL
| | - Viktor Kirik
- School of Biological Sciences, Illinois State University, Normal, IL
| | - Bela M Mulder
- Laboratory of Cell Biology, Wageningen University, Wageningen, Netherlands
- Institute AMOLF, Amsterdam, Netherlands
| | - David W Ehrhardt
- Department of Plant Biology, Carnegie Institution for Science, Stanford, CA
- Department of Biology, Stanford University, Stanford, CA
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34
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Li J, Kim T, Szymanski DB. Multi-scale regulation of cell branching: Modeling morphogenesis. Dev Biol 2018; 451:40-52. [PMID: 30529250 DOI: 10.1016/j.ydbio.2018.12.004] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/15/2018] [Revised: 11/29/2018] [Accepted: 12/03/2018] [Indexed: 01/05/2023]
Abstract
Plant growth and development are driven by extended phases of irreversible cell expansion generating cells that increase in volume from 10- to 100-fold. Some specialized cell types define cortical sites that reinitiate polarized growth and generate branched cell morphology. This structural specialization of individual cells has a major importance for plant adaptation to diverse environments and practical importance in agricultural contexts. The patterns of cell shape are defined by highly integrated cytoskeletal and cell wall systems. Microtubules and actin filaments locally define the material properties of a tough outer cell wall to generate complex shapes. Forward genetics, powerful live cell imaging experiments, and computational modeling have provided insights into understanding of mechanisms of cell shape control. In particular, finite element modeling of the cell wall provides a new way to discover which cell wall heterogeneities generate complex cell shapes, and how cell shape and cell wall stress can feedback on the cytoskeleton to maintain growth patterns. This review focuses on cytoskeleton-dependent cell wall patterning during cell branching, and how combinations of multi-scale imaging experiments and computational modeling are being used to unravel systems-level control of morphogenesis.
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Affiliation(s)
- Jing Li
- Weldon School of Biomedical Engineering, Purdue University, West Lafayette, IN 47907, United States
| | - Taeyoon Kim
- Weldon School of Biomedical Engineering, Purdue University, West Lafayette, IN 47907, United States
| | - Daniel B Szymanski
- Department of Botany and Plant Pathology, Purdue University, West Lafayette, IN 47907, United States; Department of Biological Sciences, Purdue University, West Lafayette, IN 47907, United States; Department of Agronomy, Purdue University, West Lafayette, IN 47907, United States.
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35
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Yi P, Goshima G. Microtubule nucleation and organization without centrosomes. CURRENT OPINION IN PLANT BIOLOGY 2018; 46:1-7. [PMID: 29981930 DOI: 10.1016/j.pbi.2018.06.004] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/30/2018] [Revised: 06/11/2018] [Accepted: 06/15/2018] [Indexed: 06/08/2023]
Abstract
Centrosomes play various critical roles in animal cells such as microtubule nucleation and stabilization, mitotic spindle morphogenesis, and spindle orientation. Land plants have lost centrosomes and yet must execute many of these functions. Recent studies have revealed the crucial roles played by morphologically distinct cytoplasmic microtubule-organizing centers (MTOCs) in initiating spindle bipolarity and maintaining spindle orientation robustness. These MTOCs resemble centrosomes in many aspects, implying an evolutionary divergence of MT-organizing structures in plants. However, their functions rely on conserved nucleation and amplification mechanisms, indicating a similarity in MT network establishment between animals and plants. Moreover, recent characterization of a plant-specific MT minus-end tracking protein suggests that plants have developed functionally equivalent modules to stabilize and organize MTs at minus ends. These findings support the theory that plants overcome centrosome loss by utilizing modified but substantially conserved mechanisms to organize MT networks.
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Affiliation(s)
- Peishan Yi
- Division of Biological Science, Graduate School of Science, Nagoya University, Furo-cho, Chikusa-ku, Nagoya 464-8602, Japan.
| | - Gohta Goshima
- Division of Biological Science, Graduate School of Science, Nagoya University, Furo-cho, Chikusa-ku, Nagoya 464-8602, Japan.
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36
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McNally FJ, Roll-Mecak A. Microtubule-severing enzymes: From cellular functions to molecular mechanism. J Cell Biol 2018; 217:4057-4069. [PMID: 30373906 PMCID: PMC6279391 DOI: 10.1083/jcb.201612104] [Citation(s) in RCA: 106] [Impact Index Per Article: 17.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/12/2018] [Revised: 08/13/2018] [Accepted: 10/04/2018] [Indexed: 12/24/2022] Open
Abstract
McNally and Roll-Mecak review the molecular mechanism of microtubule-severing enzymes and their diverse roles in processes ranging from cell division to ciliogensis and morphogenesis. Microtubule-severing enzymes generate internal breaks in microtubules. They are conserved in eukaryotes from ciliates to mammals, and their function is important in diverse cellular processes ranging from cilia biogenesis to cell division, phototropism, and neurogenesis. Their mutation leads to neurodegenerative and neurodevelopmental disorders in humans. All three known microtubule-severing enzymes, katanin, spastin, and fidgetin, are members of the meiotic subfamily of AAA ATPases that also includes VPS4, which disassembles ESCRTIII polymers. Despite their conservation and importance to cell physiology, the cellular and molecular mechanisms of action of microtubule-severing enzymes are not well understood. Here we review a subset of cellular processes that require microtubule-severing enzymes as well as recent advances in understanding their structure, biophysical mechanism, and regulation.
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Affiliation(s)
- Francis J McNally
- Department of Molecular and Cellular Biology, University of California, Davis, Davis, CA
| | - Antonina Roll-Mecak
- Cell Biology and Biophysics Unit, Porter Neuroscience Research Center, National Institute of Neurological Disorders and Stroke, Bethesda, MD .,Biochemistry and Biophysics Center, National Heart, Lung and Blood Institute, Bethesda, MD
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37
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Direct induction of microtubule branching by microtubule nucleation factor SSNA1. Nat Cell Biol 2018; 20:1172-1180. [PMID: 30250060 PMCID: PMC6330057 DOI: 10.1038/s41556-018-0199-8] [Citation(s) in RCA: 34] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/19/2017] [Accepted: 08/20/2018] [Indexed: 12/22/2022]
Abstract
Microtubules are central elements of the eukaryotic cytoskeleton that often function as part of branched networks. Current models for branching include nucleation of new microtubules from severed microtubule seeds or from gamma-tubulin recruited to the side of a pre-existing microtubule. Here, we found that microtubules can be directly remodeled into branched structures by the microtubule-remodeling factor SSNA1 (or also NA14/DIP13). The branching activity of SSNA1 relies on its ability to self-assemble into fibrils in a head-to-tail fashion. SSNA1 fibrils guide protofilaments of a microtubule to split apart to form daughter microtubules. We further found that SSNA1 localizes at axon branching sites and has a key role in neuronal development. SSNA1 mutants that abolish microtubule branching in vitro also fail to promote axon development and branching when overexpressed in neurons. We have therefore, discovered a mechanism for microtubule-branching and implicated its role in neuronal development.
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38
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Tolić IM. Mitotic spindle: kinetochore fibers hold on tight to interpolar bundles. EUROPEAN BIOPHYSICS JOURNAL : EBJ 2018; 47:191-203. [PMID: 28725997 PMCID: PMC5845649 DOI: 10.1007/s00249-017-1244-4] [Citation(s) in RCA: 33] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 03/29/2017] [Revised: 06/30/2017] [Accepted: 07/02/2017] [Indexed: 12/24/2022]
Abstract
When a cell starts to divide, it forms a spindle, a micro-machine made of microtubules, which separates the duplicated chromosomes. The attachment of microtubules to chromosomes is mediated by kinetochores, protein complexes on the chromosome. Spindle microtubules can be divided into three major classes: kinetochore microtubules, which form k-fibers ending at the kinetochore; interpolar microtubules, which extend from the opposite sides of the spindle and interact in the middle; and astral microtubules, which extend towards the cell cortex. Recent work in human cells has shown a close relationship between interpolar and kinetochore microtubules, where interpolar bundles are attached laterally to kinetochore fibers almost all along their length, acting as a bridge between sister k-fibers. Most of the interpolar bundles are attached to a pair of sister kinetochore fibers and vice versa. Thus, the spindle is made of modules consisting of a pair of sister kinetochore fibers and a bundle of interpolar microtubules that connects them. These interpolar bundles, termed bridging fibers, balance the forces acting at kinetochores and support the rounded shape of the spindle during metaphase. This review discusses the structure, function, and formation of kinetochore fibers and interpolar bundles, with an emphasis on how they interact. Their connections have an impact on the force balance in the spindle and on chromosome movement during mitosis because the forces in interpolar bundles are transmitted to kinetochore fibers and hence to kinetochores through these connections.
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Affiliation(s)
- Iva M Tolić
- Division of Molecular Biology, Ruđer Bošković Institute, Bijenička cesta 54, 10000, Zagreb, Croatia.
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39
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Abstract
The contribution of microtubule tip dynamics to the assembly and function of plant microtubule arrays remains poorly understood. Here, we report that the Arabidopsis SPIRAL2 (SPR2) protein modulates the dynamics of the acentrosomal cortical microtubule plus and minus ends in an opposing manner. Live imaging of a functional SPR2-mRuby fusion protein revealed that SPR2 shows both microtubule plus- and minus-end tracking activity in addition to localization at microtubule intersections and along the lattice. Analysis of microtubule dynamics showed that cortical microtubule plus ends rarely undergo catastrophe in the spr2-2 knockout mutant compared to wild-type. In contrast, cortical microtubule minus ends in spr2-2 depolymerized at a much faster rate than in wild-type. Destabilization of the minus ends in spr2-2 caused a significant decrease in the lifetime of microtubule crossovers, which dramatically reduced the microtubule-severing frequency and inhibited light-induced microtubule array reorientation. Using in vitro reconstitution experiments combined with single-molecule imaging, we found that recombinant SPR2-GFP intrinsically localizes to microtubule minus ends, where it binds stably and inhibits their dynamics. Together, our data establish SPR2 as a new type of microtubule tip regulator that governs the length and lifetime of microtubules.
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Affiliation(s)
- Yuanwei Fan
- Department of Biology and Center for Engineering Mechanobiology, Washington University in St. Louis, St. Louis, MO 63130, USA
| | - Graham M Burkart
- Department of Biology and Center for Engineering Mechanobiology, Washington University in St. Louis, St. Louis, MO 63130, USA
| | - Ram Dixit
- Department of Biology and Center for Engineering Mechanobiology, Washington University in St. Louis, St. Louis, MO 63130, USA.
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40
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Chakrabortty B, Blilou I, Scheres B, Mulder BM. A computational framework for cortical microtubule dynamics in realistically shaped plant cells. PLoS Comput Biol 2018; 14:e1005959. [PMID: 29394250 PMCID: PMC5812663 DOI: 10.1371/journal.pcbi.1005959] [Citation(s) in RCA: 33] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2017] [Revised: 02/14/2018] [Accepted: 01/05/2018] [Indexed: 01/07/2023] Open
Abstract
Plant morphogenesis is strongly dependent on the directional growth and the subsequent oriented division of individual cells. It has been shown that the plant cortical microtubule array plays a key role in controlling both these processes. This ordered structure emerges as the collective result of stochastic interactions between large numbers of dynamic microtubules. To elucidate this complex self-organization process a number of analytical and computational approaches to study the dynamics of cortical microtubules have been proposed. To date, however, these models have been restricted to two dimensional planes or geometrically simple surfaces in three dimensions, which strongly limits their applicability as plant cells display a wide variety of shapes. This limitation is even more acute, as both local as well as global geometrical features of cells are expected to influence the overall organization of the array. Here we describe a framework for efficiently simulating microtubule dynamics on triangulated approximations of arbitrary three dimensional surfaces. This allows the study of microtubule array organization on realistic cell surfaces obtained by segmentation of microscopic images. We validate the framework against expected or known results for the spherical and cubical geometry. We then use it to systematically study the individual contributions of global geometry, cell-edge induced catastrophes and cell-face induced stability to array organization in a cuboidal geometry. Finally, we apply our framework to analyze the highly non-trivial geometry of leaf pavement cells of Arabidopsis thaliana, Nicotiana benthamiana and Hedera helix. We show that our simulations can predict multiple features of the microtubule array structure in these cells, revealing, among others, strong constraints on the orientation of division planes.
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Affiliation(s)
- Bandan Chakrabortty
- Plant Developmental Biology, Wageningen University, Wageningen, The Netherlands
- Department of Living Matter, Institute AMOLF, Amsterdam, The Netherlands
| | - Ikram Blilou
- Laboratory of plant cell and developmental biology, King Abdullah University of Science and Technology, Thuwal, Kingdom of Saudi Arabia
| | - Ben Scheres
- Plant Developmental Biology, Wageningen University, Wageningen, The Netherlands
| | - Bela M. Mulder
- Department of Living Matter, Institute AMOLF, Amsterdam, The Netherlands
- Cell Biology, Wageningen University, Wageningen, The Netherlands
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41
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Yagi N, Matsunaga S, Hashimoto T. Insights into cortical microtubule nucleation and dynamics in Arabidopsis leaf cells. J Cell Sci 2018; 131:jcs.203778. [PMID: 28615412 DOI: 10.1242/jcs.203778] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2017] [Accepted: 06/12/2017] [Indexed: 12/16/2022] Open
Abstract
Plant microtubules (MTs) are nucleated from the γ-tubulin-containing ring complex (γTuRC). In cortical MT arrays of interphase plant cells, γTuRC is preferentially recruited to the lattice of preexisting MTs, where it initiates MT nucleation in either a branch- or bundle-forming manner, or dissociates without mediating nucleation. In this study, we analyzed how γTuRCs influence MT nucleation and dynamics in cotyledon pavement cells of Arabidopsis thaliana We found that γTuRC nucleated MTs at angles of ∼40° toward the plus-ends of existing MTs, or in predominantly antiparallel bundles. A small fraction of γTuRCs was motile and tracked MT ends. When γTuRCs decorated the depolymerizing MT end, they reduced the depolymerization rate. Non-nucleating γTuRCs associated with the MT lattice promoted MT regrowth after a depolymerization phase. These results suggest that γTuRCs not only nucleate MT growth but also regulate MT dynamics by stabilizing MT ends. On rare occasions, a non-MT-associated γTuRC was pushed in the direction of the MT minus-end, while nucleating a new MT, suggesting that the polymerizing plus-end is anchored to the plasma membrane.
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Affiliation(s)
- Noriyoshi Yagi
- Graduate School of Biological Sciences, Nara Institute of Science and Technology, 8916-5 Takayama, Ikoma, Nara 630-0192, Japan
| | - Sachihiro Matsunaga
- Department of Applied Biological Science, Faculty of Science and Technology, Tokyo University of Science, 2641 Yamazaki, Noda, Chiba 278-8510, Japan
| | - Takashi Hashimoto
- Graduate School of Biological Sciences, Nara Institute of Science and Technology, 8916-5 Takayama, Ikoma, Nara 630-0192, Japan
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42
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Nakamura M, Lindeboom JJ, Saltini M, Mulder BM, Ehrhardt DW. SPR2 protects minus ends to promote severing and reorientation of plant cortical microtubule arrays. J Cell Biol 2018; 217:915-927. [PMID: 29339437 PMCID: PMC5839793 DOI: 10.1083/jcb.201708130] [Citation(s) in RCA: 52] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/18/2017] [Revised: 11/01/2017] [Accepted: 12/04/2017] [Indexed: 01/05/2023] Open
Abstract
The cortical microtubule arrays of higher plants are organized without centrosomes and feature treadmilling polymers that are dynamic at both ends. The control of polymer end stability is fundamental for the assembly and organization of cytoskeletal arrays, yet relatively little is understood about how microtubule minus ends are controlled in acentrosomal microtubule arrays, and no factors have been identified that act at the treadmilling minus ends in higher plants. Here, we identify Arabidopsis thaliana SPIRAL2 (SPR2) as a protein that tracks minus ends and protects them against subunit loss. SPR2 function is required to facilitate the rapid reorientation of plant cortical arrays as stimulated by light perception, a process that is driven by microtubule severing to create a new population of microtubules. Quantitative live-cell imaging and computer simulations reveal that minus protection by SPR2 acts by an unexpected mechanism to promote the lifetime of potential SPR2 severing sites, increasing the likelihood of severing and thus the rapid amplification of the new microtubule array.
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Affiliation(s)
- Masayoshi Nakamura
- Department of Plant Biology, Carnegie Institution for Science, Stanford, CA
| | - Jelmer J Lindeboom
- Department of Plant Biology, Carnegie Institution for Science, Stanford, CA
| | | | - Bela M Mulder
- Institute AMOLF, Amsterdam, Netherlands.,Laboratory of Cell Biology, Wageningen University, Wageningen, Netherlands
| | - David W Ehrhardt
- Department of Plant Biology, Carnegie Institution for Science, Stanford, CA .,Department of Biology, Stanford University, Stanford, CA
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43
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Lopez RA, Mansouri K, Henry JS, D Flowers N, C Vaughn K, Renzaglia KS. Immunogold Localization of Molecular Constituents Associated with Basal Bodies, Flagella, and Extracellular Matrices in Male Gametes of Land Plants. Bio Protoc 2017; 7:e2599. [PMID: 34595276 DOI: 10.21769/bioprotoc.2599] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/21/2017] [Revised: 05/31/2017] [Accepted: 10/10/2017] [Indexed: 11/02/2022] Open
Abstract
Male gametes (spermatozoids) are the only motile cells produced during the life cycle of land plants. While absent from flowering and most cone-bearing plants, motile cells are found in less derived taxa, including bryophytes (mosses, liverworts and hornworts), pteridophytes (lycophytes and ferns) and some seed plants (Ginkgo and cycads). During development, these cells undergo profound changes that involve the production of a locomotory apparatus, unique microtubule (MT) arrays, and a series of special cell walls that are produced in sequence and are synchronized with cellular differentiation. Immunogold labeling in the transmission electron microscope (TEM) provides information on the exact location and potential function of macromolecules involved with this developmental process. Specifically, it is possible to localize epitopes to proteins that are associated with the cellular inclusions involved in MT production and function. Spermatogenesis in these plants is also ideal for examining the differential expression of carbohydrates and glycoproteins that comprise the extracellular matrixes associated with the dramatic architectural changes in gamete shape and locomotory apparatus development. Here we provide methodologies using monoclonal antibodies (MAbs) and immunogold labeling in the TEM to localize macromolecules that are integral to spermatozoid development.
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Affiliation(s)
- Renee A Lopez
- Department of Plant Biology, Southern Illinois University, Carbondale, IL, USA
| | | | - Jason S Henry
- Department of Plant Biology, Southern Illinois University, Carbondale, IL, USA
| | - Nicholas D Flowers
- Department of Plant Biology, Southern Illinois University, Carbondale, IL, USA
| | - Kevin C Vaughn
- Department of Plant Biology, Southern Illinois University, Carbondale, IL, USA.,Department of Cell Biology, Duke University, Durham, NC, USA
| | - Karen Sue Renzaglia
- Department of Plant Biology, Southern Illinois University, Carbondale, IL, USA
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44
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Zhang Q, Song P, Qu Y, Wang P, Jia Q, Guo L, Zhang C, Mao T, Yuan M, Wang X, Zhang W. Phospholipase Dδ negatively regulates plant thermotolerance by destabilizing cortical microtubules in Arabidopsis. PLANT, CELL & ENVIRONMENT 2017; 40:2220-2235. [PMID: 28710795 DOI: 10.1111/pce.13023] [Citation(s) in RCA: 30] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/01/2017] [Revised: 06/30/2017] [Accepted: 07/02/2017] [Indexed: 05/20/2023]
Abstract
The pattern of cortical microtubule arrays plays an important role in plant growth and adaptation in response to hormonal and environmental changes. Cortical microtubules are connected with the plasma membrane (PM); however, how the membrane affects cortical microtubule organization is not well understood. Here, we showed that phospholipase Dδ (PLDδ) was associated with the PM and co-localized with microtubules in cells. In vitro analysis revealed that PLDδ bound to microtubules, resulting in microtubule disorganization. Site-specific mutations that decreased PLDδ enzymatic activity impaired its effects on destabilizing microtubule organization. Heat shock transiently activated PLDδ, without any change of its PM localization, triggering microtubule dissociation from PM and depolymerization and seedling death in Arabidopsis, but these effects were alleviated in pldδ knockout mutants. Complementation of pldδ with wild-type PLDδ, but not mutated PLDδ, restored the phenotypes of microtubules and seedling survival to those of wild-type Arabidopsis. Thus, we conclude that the PM-associated PLDδ negatively regulates plant thermotolerance via destabilizing cortical microtubules, in an activity-dependent manner, rather than its subcellular translocation.
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Affiliation(s)
- Qun Zhang
- College of Life Sciences, State Key Laboratory of Crop Genetics and Germplasm Enhancement, Nanjing Agricultural University, Nanjing, 210095, China
| | - Ping Song
- College of Life Sciences, State Key Laboratory of Crop Genetics and Germplasm Enhancement, Nanjing Agricultural University, Nanjing, 210095, China
| | - Yana Qu
- College of Life Sciences, State Key Laboratory of Crop Genetics and Germplasm Enhancement, Nanjing Agricultural University, Nanjing, 210095, China
| | - Peipei Wang
- College of Life Sciences, State Key Laboratory of Crop Genetics and Germplasm Enhancement, Nanjing Agricultural University, Nanjing, 210095, China
| | - Qianru Jia
- College of Life Sciences, State Key Laboratory of Crop Genetics and Germplasm Enhancement, Nanjing Agricultural University, Nanjing, 210095, China
| | - Liang Guo
- National Key Laboratory of Crop Genetic Improvement, Huazhong Agricultural University, Wuhan, 430070, China
| | - Chuanpeng Zhang
- College of Life Sciences, State Key Laboratory of Crop Genetics and Germplasm Enhancement, Nanjing Agricultural University, Nanjing, 210095, China
| | - Tonglin Mao
- College of Biology, China Agricultural University, Beijing, 100083, China
| | - Ming Yuan
- College of Biology, China Agricultural University, Beijing, 100083, China
| | - Xuemin Wang
- Department of Biology, University of Missouri, St Louis, MO, 63121, USA
- Donald Danforth Plant Science Center, St Louis, MO, 63132, USA
| | - Wenhua Zhang
- College of Life Sciences, State Key Laboratory of Crop Genetics and Germplasm Enhancement, Nanjing Agricultural University, Nanjing, 210095, China
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45
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Shevchenko GV. Putative gravisensors among microtubule associated proteins. Cell Biol Int 2017; 43:983-990. [PMID: 28656641 DOI: 10.1002/cbin.10811] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/08/2017] [Accepted: 06/24/2017] [Indexed: 12/27/2022]
Abstract
Despite of long period of investigation (over 100 years), still a lot of questions remain unclear about molecular mechanisms of plant graviperception. This requires designing new experiments and new approaches to be applied in gravitational biology. Investigation of plant cell reactions under clinorotation (plant disorientation in respect to gravity vector) is of significant importance to such type of research. Clinorotation is known to cause changes of cell polarity and exert mechanical stress in plant cells. Microtubular cytoskeleton is highly dynamic structure and it responds to both of these stresses. Due to turgor pressure and cell elongation, endogenous mechanical forces influence microtubule orientation in order to coordinate cell growth. Rearrangements of microtubules are regulated by numerous associated proteins which functional activity is not fully clear. In this review, we discuss how MT associated proteins regulate cortical MT arrays under mechanical stress and consider how these proteins may act as plant cell gravisensors. Investigation of microtubule associated proteins under clinorotation might shed the light on molecular mechanism of plant cytoskeleton arrangement and its involvement in initial reactions of cell graviperception.
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Affiliation(s)
- Galina V Shevchenko
- Institute of Botany, NAS Ukraine, Cell Biology Department, 2, Tereshchenkivska St., Kiev, 01004, Ukraine
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46
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Takatani S, Ozawa S, Yagi N, Hotta T, Hashimoto T, Takahashi Y, Takahashi T, Motose H. Directional cell expansion requires NIMA-related kinase 6 (NEK6)-mediated cortical microtubule destabilization. Sci Rep 2017; 7:7826. [PMID: 28798328 PMCID: PMC5552743 DOI: 10.1038/s41598-017-08453-5] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/05/2017] [Accepted: 07/12/2017] [Indexed: 11/09/2022] Open
Abstract
Plant cortical microtubules align perpendicular to the growth axis to determine the direction of cell growth. However, it remains unclear how plant cells form well-organized cortical microtubule arrays in the absence of a centrosome. In this study, we investigated the functions of Arabidopsis NIMA-related kinase 6 (NEK6), which regulates microtubule organization during anisotropic cell expansion. Quantitative analysis of hypocotyl cell growth in the nek6-1 mutant demonstrated that NEK6 suppresses ectopic outgrowth and promotes cell elongation in different regions of the hypocotyl. Loss of NEK6 function led to excessive microtubule waving and distortion, implying that NEK6 suppresses the aberrant cortical microtubules. Live cell imaging showed that NEK6 localizes to the microtubule lattice and to the shrinking plus and minus ends of microtubules. In agreement with this observation, the induced overexpression of NEK6 reduced and disorganized cortical microtubules and suppressed cell elongation. Furthermore, we identified five phosphorylation sites in β-tubulin that serve as substrates for NEK6 in vitro. Alanine substitution of the phosphorylation site Thr166 promoted incorporation of mutant β-tubulin into microtubules. Taken together, these results suggest that NEK6 promotes directional cell growth through phosphorylation of β-tubulin and the resulting destabilization of cortical microtubules.
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Affiliation(s)
- Shogo Takatani
- Department of Biological Science, Graduate School of Natural Science and Technology, Okayama University, 3-1-1 Tsushimanaka, Okayama, 700-8530, Japan
| | - Shinichiro Ozawa
- Department of Biological Science, Graduate School of Natural Science and Technology, Okayama University, 3-1-1 Tsushimanaka, Okayama, 700-8530, Japan.,Japan Science and Technology Agency, 4-1-8 Kawaguchi, Saitama, 332-0012, Japan
| | - Noriyoshi Yagi
- Graduate School of Biological Science, Nara Institute of Science and Technology, Ikoma, 630-0192, Japan.,Department of Applied Biological Science, Tokyo University of Science, Noda, Chiba, 278-8510, Japan
| | - Takashi Hotta
- Graduate School of Biological Science, Nara Institute of Science and Technology, Ikoma, 630-0192, Japan.,Department of Embryology, Carnegie Institution for Science, 3520 San Martin Drive, Baltimore, MD, 21218, USA
| | - Takashi Hashimoto
- Graduate School of Biological Science, Nara Institute of Science and Technology, Ikoma, 630-0192, Japan
| | - Yuichiro Takahashi
- Department of Biological Science, Graduate School of Natural Science and Technology, Okayama University, 3-1-1 Tsushimanaka, Okayama, 700-8530, Japan.,Japan Science and Technology Agency, 4-1-8 Kawaguchi, Saitama, 332-0012, Japan
| | - Taku Takahashi
- Department of Biological Science, Graduate School of Natural Science and Technology, Okayama University, 3-1-1 Tsushimanaka, Okayama, 700-8530, Japan
| | - Hiroyasu Motose
- Department of Biological Science, Graduate School of Natural Science and Technology, Okayama University, 3-1-1 Tsushimanaka, Okayama, 700-8530, Japan.
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47
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Sugiyama Y, Wakazaki M, Toyooka K, Fukuda H, Oda Y. A Novel Plasma Membrane-Anchored Protein Regulates Xylem Cell-Wall Deposition through Microtubule-Dependent Lateral Inhibition of Rho GTPase Domains. Curr Biol 2017; 27:2522-2528.e4. [PMID: 28803875 DOI: 10.1016/j.cub.2017.06.059] [Citation(s) in RCA: 67] [Impact Index Per Article: 9.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2017] [Revised: 05/29/2017] [Accepted: 06/22/2017] [Indexed: 11/29/2022]
Abstract
Spatial control of cell-wall deposition is essential for determining plant cell shape [1]. Rho-type GTPases, together with the cortical cytoskeleton, play central roles in regulating cell-wall patterning [2]. In metaxylem vessel cells, which are the major components of xylem tissues, active ROP11 Rho GTPases form oval plasma membrane domains that locally disrupt cortical microtubules, thereby directing the formation of oval pits in secondary cell walls [3-5]. However, the regulatory mechanism that determines the planar shape of active Rho of Plants (ROP) domains is still unknown. Here we show that IQD13 associates with cortical microtubules and the plasma membrane to laterally restrict the localization of ROP GTPase domains, thereby directing the formation of oval secondary cell-wall pits. Loss and overexpression of IQD13 led to the formation of abnormally round and narrow secondary cell-wall pits, respectively. Ectopically expressed IQD13 increased the presence of parallel cortical microtubules by promoting microtubule rescue. A reconstructive approach revealed that IQD13 confines the area of active ROP domains within the lattice of the cortical microtubules, causing narrow ROP domains to form. This activity required the interaction of IQD13 with the plasma membrane. These findings suggest that IQD13 positively regulates microtubule dynamics as well as their linkage to the plasma membrane, which synergistically confines the area of active ROP domains, leading to the formation of oval secondary cell-wall pits. This finding sheds light on the role of microtubule-plasma membrane linkage as a lateral fence that determines the planar shape of Rho GTPase domains.
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Affiliation(s)
- Yuki Sugiyama
- Department of Biological Sciences, Graduate School of Science, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033, Japan; Center for Frontier Research, National Institute of Genetics, 1111 Yata, Mishima, Shizuoka 411-8540, Japan
| | - Mayumi Wakazaki
- Mass Spectrometry and Microscopy Unit, Center for Sustainable Resource Science, RIKEN, 1-7-22 Suehiro, Tsurumi, Yokohama, Kanagawa 230-0045, Japan
| | - Kiminori Toyooka
- Mass Spectrometry and Microscopy Unit, Center for Sustainable Resource Science, RIKEN, 1-7-22 Suehiro, Tsurumi, Yokohama, Kanagawa 230-0045, Japan
| | - Hiroo Fukuda
- Department of Biological Sciences, Graduate School of Science, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033, Japan
| | - Yoshihisa Oda
- Center for Frontier Research, National Institute of Genetics, 1111 Yata, Mishima, Shizuoka 411-8540, Japan; Department of Genetics, SOKENDAI (The Graduate University for Advanced Studies), 1111 Yata, Mishima, Shizuoka 411-8540, Japan.
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48
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Sulimenko V, Hájková Z, Klebanovych A, Dráber P. Regulation of microtubule nucleation mediated by γ-tubulin complexes. PROTOPLASMA 2017; 254:1187-1199. [PMID: 28074286 DOI: 10.1007/s00709-016-1070-z] [Citation(s) in RCA: 33] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/14/2016] [Accepted: 12/22/2016] [Indexed: 05/18/2023]
Abstract
The microtubule cytoskeleton is critically important for spatio-temporal organization of eukaryotic cells. The nucleation of new microtubules is typically restricted to microtubule organizing centers (MTOCs) and requires γ-tubulin that assembles into multisubunit complexes of various sizes. γ-Tubulin ring complexes (TuRCs) are efficient microtubule nucleators and are associated with large number of targeting, activating and modulating proteins. γ-Tubulin-dependent nucleation of microtubules occurs both from canonical MTOCs, such as spindle pole bodies and centrosomes, and additional sites such as Golgi apparatus, nuclear envelope, plasma membrane-associated sites, chromatin and surface of pre-existing microtubules. Despite many advances in structure of γ-tubulin complexes and characterization of γTuRC interacting factors, regulatory mechanisms of microtubule nucleation are not fully understood. Here, we review recent work on the factors and regulatory mechanisms that are involved in centrosomal and non-centrosomal microtubule nucleation.
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Affiliation(s)
- Vadym Sulimenko
- Department of Biology of Cytoskeleton, Institute of Molecular Genetics, Academy of Sciences of the Czech Republic, Vídeňská 1083, 142 20, Prague 4, Czech Republic
| | - Zuzana Hájková
- Department of Biology of Cytoskeleton, Institute of Molecular Genetics, Academy of Sciences of the Czech Republic, Vídeňská 1083, 142 20, Prague 4, Czech Republic
| | - Anastasiya Klebanovych
- Department of Biology of Cytoskeleton, Institute of Molecular Genetics, Academy of Sciences of the Czech Republic, Vídeňská 1083, 142 20, Prague 4, Czech Republic
| | - Pavel Dráber
- Department of Biology of Cytoskeleton, Institute of Molecular Genetics, Academy of Sciences of the Czech Republic, Vídeňská 1083, 142 20, Prague 4, Czech Republic.
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49
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Kapoor TM. Metaphase Spindle Assembly. BIOLOGY 2017; 6:biology6010008. [PMID: 28165376 PMCID: PMC5372001 DOI: 10.3390/biology6010008] [Citation(s) in RCA: 30] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 10/03/2016] [Revised: 01/17/2017] [Accepted: 01/19/2017] [Indexed: 01/31/2023]
Abstract
A microtubule-based bipolar spindle is required for error-free chromosome segregation during cell division. In this review I discuss the molecular mechanisms required for the assembly of this dynamic micrometer-scale structure in animal cells.
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Affiliation(s)
- Tarun M Kapoor
- Laboratory of Chemistry and Cell Biology, the Rockefeller University, New York, NY 10065, USA.
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50
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Yamada M, Goshima G. Mitotic Spindle Assembly in Land Plants: Molecules and Mechanisms. BIOLOGY 2017; 6:biology6010006. [PMID: 28125061 PMCID: PMC5371999 DOI: 10.3390/biology6010006] [Citation(s) in RCA: 48] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 10/01/2016] [Revised: 11/29/2016] [Accepted: 01/08/2017] [Indexed: 11/16/2022]
Abstract
In textbooks, the mitotic spindles of plants are often described separately from those of animals. How do they differ at the molecular and mechanistic levels? In this chapter, we first outline the process of mitotic spindle assembly in animals and land plants. We next discuss the conservation of spindle assembly factors based on database searches. Searches of >100 animal spindle assembly factors showed that the genes involved in this process are well conserved in plants, with the exception of two major missing elements: centrosomal components and subunits/regulators of the cytoplasmic dynein complex. We then describe the spindle and phragmoplast assembly mechanisms based on the data obtained from robust gene loss-of-function analyses using RNA interference (RNAi) or mutant plants. Finally, we discuss future research prospects of plant spindles.
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Affiliation(s)
- Moé Yamada
- Graduate School of Science, Division of Biological Science, Nagoya University, Furo-cho, Chikusa-ku, Nagoya 464-8602, Japan.
| | - Gohta Goshima
- Graduate School of Science, Division of Biological Science, Nagoya University, Furo-cho, Chikusa-ku, Nagoya 464-8602, Japan.
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