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Two Kinesin-14A Motors Oligomerize to Drive Poleward Microtubule Convergence for Acentrosomal Spindle Morphogenesis in Arabidopsis thaliana

Plant cells form acentrosomal spindles with microtubules (MTs) converged toward two structurally undefined poles by employing MT minus end-directed Kinesin-14 motors. To date, it is unclear whether the convergent bipolar MT array assumes unified poles in plant spindles, and if so, how such a goal is...

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Autores principales: Hotta, Takashi, Lee, Yuh-Ru Julie, Higaki, Takumi, Hashimoto, Takashi, Liu, Bo
Formato: Online Artículo Texto
Lenguaje:English
Publicado: Frontiers Media S.A. 2022
Materias:
Acceso en línea:https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9380777/
https://www.ncbi.nlm.nih.gov/pubmed/35982853
http://dx.doi.org/10.3389/fcell.2022.949345
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author Hotta, Takashi
Lee, Yuh-Ru Julie
Higaki, Takumi
Hashimoto, Takashi
Liu, Bo
author_facet Hotta, Takashi
Lee, Yuh-Ru Julie
Higaki, Takumi
Hashimoto, Takashi
Liu, Bo
author_sort Hotta, Takashi
collection PubMed
description Plant cells form acentrosomal spindles with microtubules (MTs) converged toward two structurally undefined poles by employing MT minus end-directed Kinesin-14 motors. To date, it is unclear whether the convergent bipolar MT array assumes unified poles in plant spindles, and if so, how such a goal is achieved. Among six classes of Kinesin-14 motors in Arabidopsis thaliana, the Kinesin-14A motors ATK1 (KatA) and ATK5 share the essential function in spindle morphogenesis. To understand how the two functionally redundant Kinesin-14A motors contributed to the spindle assembly, we had ATK1-GFP and ATK5-GFP fusion proteins expressed in their corresponding null mutants and found that they were functionally comparable to their native forms. Although ATK1 was a nuclear protein and ATK5 cytoplasmic prior to nuclear envelop breakdown, at later mitotic stages, the two motors shared similar localization patterns of uniform association with both spindle and phragmoplast MTs. We found that ATK1 and ATK5 were rapidly concentrated toward unified polar foci when cells were under hyperosmotic conditions. Concomitantly, spindle poles became perfectly focused as if there were centrosome-like MT-organizing centers where ATK1 and ATK5 were highly enriched and at which kinetochore fibers pointed. The separation of ATK1/ATK5-highlighted MTs from those of kinetochore fibers suggested that the motors translocated interpolar MTs. Our protein purification and live-cell imaging results showed that ATK1 and ATK5 are associated with each other in vivo. The stress-induced spindle pole convergence was also accompanied by poleward accumulation of the MT nucleator γ-tubulin. These results led to the conclusion that the two Kinesin-14A motors formed oligomeric motor complexes that drove MT translocation toward the spindle pole to establish acentrosomal spindles with convergent poles.
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spelling pubmed-93807772022-08-17 Two Kinesin-14A Motors Oligomerize to Drive Poleward Microtubule Convergence for Acentrosomal Spindle Morphogenesis in Arabidopsis thaliana Hotta, Takashi Lee, Yuh-Ru Julie Higaki, Takumi Hashimoto, Takashi Liu, Bo Front Cell Dev Biol Cell and Developmental Biology Plant cells form acentrosomal spindles with microtubules (MTs) converged toward two structurally undefined poles by employing MT minus end-directed Kinesin-14 motors. To date, it is unclear whether the convergent bipolar MT array assumes unified poles in plant spindles, and if so, how such a goal is achieved. Among six classes of Kinesin-14 motors in Arabidopsis thaliana, the Kinesin-14A motors ATK1 (KatA) and ATK5 share the essential function in spindle morphogenesis. To understand how the two functionally redundant Kinesin-14A motors contributed to the spindle assembly, we had ATK1-GFP and ATK5-GFP fusion proteins expressed in their corresponding null mutants and found that they were functionally comparable to their native forms. Although ATK1 was a nuclear protein and ATK5 cytoplasmic prior to nuclear envelop breakdown, at later mitotic stages, the two motors shared similar localization patterns of uniform association with both spindle and phragmoplast MTs. We found that ATK1 and ATK5 were rapidly concentrated toward unified polar foci when cells were under hyperosmotic conditions. Concomitantly, spindle poles became perfectly focused as if there were centrosome-like MT-organizing centers where ATK1 and ATK5 were highly enriched and at which kinetochore fibers pointed. The separation of ATK1/ATK5-highlighted MTs from those of kinetochore fibers suggested that the motors translocated interpolar MTs. Our protein purification and live-cell imaging results showed that ATK1 and ATK5 are associated with each other in vivo. The stress-induced spindle pole convergence was also accompanied by poleward accumulation of the MT nucleator γ-tubulin. These results led to the conclusion that the two Kinesin-14A motors formed oligomeric motor complexes that drove MT translocation toward the spindle pole to establish acentrosomal spindles with convergent poles. Frontiers Media S.A. 2022-07-22 /pmc/articles/PMC9380777/ /pubmed/35982853 http://dx.doi.org/10.3389/fcell.2022.949345 Text en Copyright © 2022 Hotta, Lee, Higaki, Hashimoto and Liu. https://creativecommons.org/licenses/by/4.0/This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) and the copyright owner(s) are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.
spellingShingle Cell and Developmental Biology
Hotta, Takashi
Lee, Yuh-Ru Julie
Higaki, Takumi
Hashimoto, Takashi
Liu, Bo
Two Kinesin-14A Motors Oligomerize to Drive Poleward Microtubule Convergence for Acentrosomal Spindle Morphogenesis in Arabidopsis thaliana
title Two Kinesin-14A Motors Oligomerize to Drive Poleward Microtubule Convergence for Acentrosomal Spindle Morphogenesis in Arabidopsis thaliana
title_full Two Kinesin-14A Motors Oligomerize to Drive Poleward Microtubule Convergence for Acentrosomal Spindle Morphogenesis in Arabidopsis thaliana
title_fullStr Two Kinesin-14A Motors Oligomerize to Drive Poleward Microtubule Convergence for Acentrosomal Spindle Morphogenesis in Arabidopsis thaliana
title_full_unstemmed Two Kinesin-14A Motors Oligomerize to Drive Poleward Microtubule Convergence for Acentrosomal Spindle Morphogenesis in Arabidopsis thaliana
title_short Two Kinesin-14A Motors Oligomerize to Drive Poleward Microtubule Convergence for Acentrosomal Spindle Morphogenesis in Arabidopsis thaliana
title_sort two kinesin-14a motors oligomerize to drive poleward microtubule convergence for acentrosomal spindle morphogenesis in arabidopsis thaliana
topic Cell and Developmental Biology
url https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9380777/
https://www.ncbi.nlm.nih.gov/pubmed/35982853
http://dx.doi.org/10.3389/fcell.2022.949345
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