title: Interaction of antiparallel microtubules in the phragmoplast is mediated by the microtubule-associated protein MAP65-3 in Arabidopsis.
abstract: In plant cells, microtubules (MTs) in the cytokinetic apparatus phragmoplast exhibit an antiparallel array and transport Golgi-derived vesicles toward MT plus ends located at or near the division site. By transmission electron microscopy, we observed that certain antiparallel phragmoplast MTs overlapped and were bridged by electron-dense materials in Arabidopsis thaliana. Robust MT polymerization, reported by fluorescently tagged End Binding1c (EB1c), took place in the phragmoplast midline. The engagement of antiparallel MTs in the central spindle and phragmoplast was largely abolished in mutant cells lacking the MT-associated protein, MAP65-3. We found that endogenous MAP65-3 was selectively detected on the middle segments of the central spindle MTs at late anaphase. When MTs exhibited a bipolar appearance with their plus ends placed in the middle, MAP65-3 exclusively decorated the phragmoplast midline. A bacterially expressed MAP65-3 protein was able to establish the interdigitation of MTs in vitro. MAP65-3 interacted with antiparallel microtubules before motor Kinesin-12 did during the establishment of the phragmoplast MT array. Thus, MAP65-3 selectively cross-linked interdigitating MTs (IMTs) to allow antiparallel MTs to be closely engaged in the phragmoplast. Although the presence of IMTs was not essential for vesicle trafficking, they were required for the phragmoplast-specific motors Kinesin-12 and Phragmoplast-Associated Kinesin-Related Protein2 to interact with MT plus ends. In conclusion, we suggest that the phragmoplast contains IMTs and highly dynamic noninterdigitating MTs, which work in concert to bring about cytokinesis in plant cells.
authors.affiliation: Department of Plant Biology, University of California, Davis, CA 95616, USA.
authors.forename: Chin-Min Kimmy
authors.initials: CM
authors.lastname: Ho
authors.forename: Takashi
authors.initials: T
authors.lastname: Hotta
authors.forename: Fengli
authors.initials: F
authors.lastname: Guo
authors.forename: Robert W
authors.initials: RW
authors.lastname: Roberson
authors.forename: Yuh-Ru Julie
authors.initials: YR
authors.lastname: Lee
authors.forename: Bo
authors.initials: B
authors.lastname: Liu
mesh_terms: D000818:Animals; D017360:Arabidopsis / Q000235:genetics / Q000502:physiology* / Q000648:ultrastructure; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism*; D048749:Cytokinesis / Q000502:physiology*; D004926:Escherichia coli / Q000235:genetics / Q000378:metabolism; D018506:Gene Expression Regulation, Plant; D016547:Kinesins / Q000235:genetics / Q000378:metabolism; D051379:Mice; D008868:Microtubule Proteins / Q000378:metabolism; D008869:Microtubule-Associated Proteins / Q000235:genetics / Q000378:metabolism*; D008870:Microtubules / Q000502:physiology* / Q000648:ultrastructure; D009154:Mutation; D018515:Plant Leaves / Q000235:genetics / Q000502:physiology / Q000648:ultrastructure; D018517:Plant Roots / Q000235:genetics / Q000502:physiology / Q000648:ultrastructure; D030821:Plants, Genetically Modified; D021381:Protein Transport; D011817:Rabbits; D011993:Recombinant Fusion Proteins; D036226:Seedlings / Q000235:genetics / Q000502:physiology / Q000648:ultrastructure; D008941:Spindle Apparatus / Q000502:physiology
chemical_list: D029681:Arabidopsis Proteins; C445071:At4g14330 protein, Arabidopsis; C576219:MAP65-3 protein, Arabidopsis; D008868:Microtubule Proteins; D008869:Microtubule-Associated Proteins; D011993:Recombinant Fusion Proteins; D016547:Kinesins