The Experts below are selected from a list of 261 Experts worldwide ranked by ideXlab platform
Yoshinobu Mineyuki - One of the best experts on this subject based on the ideXlab platform.
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single microfilaments mediate the early steps of microtubule bundling during Preprophase Band formation in onion cotyledon epidermal cells
Molecular Biology of the Cell, 2016Co-Authors: Miyuki Takeuchi, Ichirou Karahara, Naoko Kajimura, Akio Takaoka, Kazuyoshi Murata, Kazuyo Misaki, Andrew L Staehelin, Shigenobu Yonemura, Yoshinobu MineyukiAbstract:The Preprophase Band (PPB) is a cytokinetic apparatus that determines the site of cell division in plants. It originates as a broad Band of microtubules (MTs) in G2 and narrows to demarcate the future division site during late prophase. Studies with fluorescent probes have shown that PPBs contain F-actin during early stages of their development but become actin depleted in late prophase. Although this suggests that actins contribute to the early stages of PPB formation, how actins contribute to PPB-MT organization remains unsolved. To address this question, we used electron tomography to investigate the spatial relationship between microfilaments (MFs) and MTs at different stages of PPB assembly in onion cotyledon epidermal cells. We demonstrate that the PPB actins observed by fluorescence microscopy correspond to short, single MFs. A majority of the MFs are bound to MTs, with a subset forming MT-MF-MT bridging structures. During the later stages of PPB assembly, the MF-mediated links between MTs are displaced by MT-MT linkers as the PPB MT arrays mature into tightly packed MT bundles. On the basis of these observations, we propose that the primary function of actins during PPB formation is to mediate the initial bundling of the PPB MTs.
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Preprophase Band formation and cortical division zone establishment rangap behaves differently from microtubules during their Band formation
Plant Signaling & Behavior, 2015Co-Authors: Takatoshi Yabuuchi, Tomonori Nakai, Seiji Sonobe, Daisuke Yamauchi, Yoshinobu MineyukiAbstract:Correct positioning of the division plane is a prerequisite for plant morphogenesis. The Preprophase Band (PPB) is a key intracellular structure of division site determination. PPB forms in G2 phase as a broad Band of microtubules (MTs) that narrows in prophase and specializes few-micrometer-wide cortical belt region, named the cortical division zone (CDZ), in late prophase. The PPB comprises several molecules, some of which act as MT Band organization and others remain in the CDZ marking the correct insertion of the cell plate in telophase. Ran GTPase-activating protein (RanGAP) is accumulated in the CDZ and forms a RanGAP Band in prophase. However, little is known about when and how RanGAPs gather in the CDZ, and especially with regard to their relationships to MT Band formation. Here, we examined the spatial and temporal distribution of RanGAPs and MTs in the Preprophase of onion root tip cells using confocal laser scanning microscopy and showed that the RanGAP Band appeared in mid-prophase as the width of MT Band was reduced to nearly 7 µm. Treatments with cytoskeletal inhibitors for 15 min caused thinning or broadening of the MT Band but had little effects on RanGAP Band in mid-prophase and most of late prophase cells. Detailed image analyses of the spatial distribution of RanGAP Band and MT Band showed that the RanGAP Band positioned slightly beneath the MT Band in mid-prophase. These results raise a possibility that RanGAP behaves differently from MTs during their Band formation.
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the Preprophase Band is a localized center of clathrin mediated endocytosis in late prophase cells of the onion cotyledon epidermis
Plant Journal, 2009Co-Authors: Ichirou Karahara, Kazuyo Misaki, Shigenobu Yonemura, Yoshinobu Mineyuki, Jinsuke Suda, Hiroshi Tahara, Etsuo Yokota, Teruo Shimmen, Lucas Andrew StaehelinAbstract:*† ‡ § Summary The Preprophase Band (PPB) marks the site on the plant cell cortex where the cell plate will fuse during the final stage of cytokinesis. Recent studies have shown that several cytoskeletal proteins are depleted at the PPB site, but the processes that bring about these changes are still unknown. We have investigated the membrane systems associated with the PPB regions of epidermal cells of onion cotyledons by means of serial thin sections and electron tomograms. In contrast with specimens preserved by chemical fixatives, our highpressure frozen cells demonstrated the presence of large numbers of clathrin-coated pits and vesicles in the PPB regions. The vesicles were of two types: clathrin-coated and structurally related, non-coated vesicles. Quantitative analysis of the data revealed that the number of clathrin-coated pits and vesicles is higher in the PPB regions than outside of these regions. Immunofluorescent microscopy using anti-plant clathrin-antibody confirmed this result. In contrast, no differences in secretory activities were observed. We postulate that the removal of membrane proteins by endocytosis plays a role in the formation of PPB ‘memory’ structures.
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loosening of a Preprophase Band of microtubules in onion allium cepa l root tip cells by kinase inhibitors
Cell Structure and Function, 1999Co-Authors: Akiko Nogami, Yoshinobu MineyukiAbstract:Effects of kinase inhibitors on the Preprophase Band of microtubules in onion (Allium cepa L.) root tip cells were examined. Bundled microtubules in Preprophase Bands were dispersed on the cell cortex when onion seedlings were incubated with 2.5-5.0 mM 6-dimethylaminopurine. Fifteen min was enough for the bundled microtubules to disappear. Although many Preprophase Bands remained when the seedlings were incubated with 60 microM staurosporin, these Preprophase Band microtubules were loosened and the width of the Band became broad. These results sugget that some kinases are involved in the microtubule bundling in the Preprophase Band development.
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the Preprophase Band of microtubules its function as a cytokinetic apparatus in higher plants
International Review of Cytology-a Survey of Cell Biology, 1999Co-Authors: Yoshinobu MineyukiAbstract:Features, development, and functions of Preprophase Bands (PPBs) of microtubules (MTs) are reviewed. The PPB is an array of cortical MTs in higher plants that appears in G 2 and prophase and predicts where the cell plate will be inserted (the division site). Experimental obliteration of the PPB causes misplacement of cell plate insertion, suggesting that the PPB is a determinant of the ultimate division site. Its development contains two elementary processes: Broad PPB formation first fixes the axis of division polarity in the cell, and PPB narrowing then defines the precise division site. The PPB disappears at the prophase/prometaphase transition stage, but it leaves information in some yet unidentified form at the division site. This information assists correct insertion of cell plates and maturation of new cell walls after cytokinesis. Several kinds of molecules are reported to occur in PPBs, but their roles are not yet understood. Actin and cyclin-dependent kinase homologs are suggested to be involved in the Band narrowing MT, which is essential for PPBs to mature at the division site. Other possible functions of the PPB, such as premitotic nuclear positioning and prophase spindle orientation, are also reviewed.
B Galatis - One of the best experts on this subject based on the ideXlab platform.
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de esterified homogalacturonan enrichment of the cell wall region adjoining the Preprophase cortical cytoplasmic zone in some protodermal cell types of three land plants
International Journal of Molecular Sciences, 2019Co-Authors: E Giannoutsou, B Galatis, P ApostolakosAbstract:The distribution of highly de-esterified homogalacturonans (HGs) in dividing protodermal cells of the monocotyledon Zea mays, the dicotyledon Vigna sinensis, and the fern Asplenium nidus was investigated in order to examine whether the cell wall region adjoining the Preprophase Band (PPB) is locally diversified. Application of immunofluorescence revealed that de-esterified HGs were accumulated selectively in the cell wall adjacent to the PPB in: (a) symmetrically dividing cells of stomatal rows of Z. mays, (b) the asymmetrically dividing protodermal cells of Z. mays, (c) the symmetrically dividing guard cell mother cells (GMCs) of Z. mays and V. sinensis, and (d) the symmetrically dividing protodermal cells of A. nidus. A common feature of the above cell types is that the cell division plane is defined by extrinsic cues. The presented data suggest that the PPB cortical zone-plasmalemma and the adjacent cell wall region function in a coordinated fashion in the determination/accomplishment of the cell division plane, behaving as a continuum. The de-esterified HGs, among other possible functions, might be involved in the perception and the transduction of the extrinsic cues determining cell division plane in the examined cells.
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polarized endoplasmic reticulum aggregations in the establishing division plane of protodermal cells of the fern asplenium nidus
Protoplasma, 2015Co-Authors: E Giannoutsou, P Apostolakos, P Sotiriou, B GalatisAbstract:The determination of the division plane in protodermal cells of the fern Asplenium nidus occurs during interphase with the formation of the phragmosome, the organization of which is controlled by the actomyosin system. Usually, the phragmosomes between adjacent cells were oriented on the same plane. In the phragmosomal cortical cytoplasm, an interphase microtubule (MT) ring was formed and large quantities of endoplasmic reticulum (ER) membranes were gathered, forming an interphase U-like ER bundle. During Preprophase/prophase, the interphase MT ring and the U-like ER bundle were transformed into a MT and an ER Preprophase Band (PPB), respectively. Parts of the ER-PPB were maintained during mitosis. Furthermore, the plasmalemma as well as the nuclear envelope displayed local polarization on the phragmosome plane, while the cytoplasm between them was occupied by distinct ER aggregations. These consistent findings suggest that Α. nidus protodermal cells constitute a unique system in which three elements of the endomembrane system (ER, plasmalemma, and nuclear envelope) show specific characteristics in the establishing division plane. Our experimental data support that the organization of the U-like ER bundle is controlled on a cellular level by the actomyosin system and intercellularly by factors emitted from the leaf apex. The possible role of the above endomembrane system elements on the mechanism that coordinates the determination of the division plane between adjacent cells in protodermal tissue of A. nidus is discussed.
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formation of an endoplasmic reticulum ring associated with acetylated microtubules in the angiosperm Preprophase Band
Cytoskeleton, 2012Co-Authors: E Giannoutsou, B Galatis, Michael Zachariadis, P ApostolakosAbstract:We investigated the organization of the cortical endoplasmic reticulum (ER) in prophase cells of the angiosperms Zea mays, Triticum turgidum, and Vigna sinensis. In both symmetrically and asymmetrically dividing protodermal leaf cells, cortical ER was enriched in the Preprophase Band and colocalized there with microtubules, forming a ring-like structure (ER ring). In contrast, ER ring was absent from prophase root-tip cells of the same plants, suggesting that ER ring formation in the Preprophase Band is organ specific. Immunolabeling of the protodermal leaf cells revealed the presence of acetylated microtubules, which are more stable than the nonacetylated ones. In contrast, neither this post-translational modification of tubulin nor an accumulation of ER in the Preprophase Band was detected in root-tip cells. Experimentally delaying the maturation/disassembly of the microtubule ring of the Preprophase Band by taxol or cyclopiazonic acid treatment led to the appearance of ER ring and acetylated microtubules in the Preprophase Band. Together, our data show that in dividing cells of angiosperms, an ER ring associated with acetylated microtubules forms in the Preprophase Band. © 2012 Wiley Periodicals, Inc
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disturbance of reactive oxygen species homeostasis induces atypical tubulin polymer formation and affects mitosis in root tip cells of triticum turgidum and arabidopsis thaliana
Cytoskeleton, 2012Co-Authors: Pantelis Livanos, B Galatis, Hartmut Quader, P ApostolakosAbstract:In this study, the effects of disturbance of the reactive oxygen species (ROS) homeostasis on the organization of tubulin cytoskeleton in interphase and mitotic root-tip cells of Triticum turgidum and Arabidopsis thaliana were investigated. Reduced ROS levels were obtained by treatment with diphenylene iodonium (DPI) and N-acetyl-cysteine, whereas menadione was applied to achieve ROS overproduction. Both increased and low ROS levels induced: (a) Macrotubule formation in cells with low ROS levels and tubulin paracrystals under oxidative stress. The protein MAP65-1 was detected in treated cells, exhibiting a conformation comparable to that of the atypical tubulin polymers. (b) Disappearance of microtubules (MTs). (c) Inhibition of Preprophase Band formation. (d) Delay of the nuclear envelope breakdown at prometaphase. (e) Prevention of perinuclear tubulin polymer assembly in prophase cells. (f) Loss of bipolarity of prophase, metaphase and anaphase spindles. Interestingly, examination of the A. thaliana rhd2/At respiratory burst oxidase homolog C (rbohc) NADPH oxidase mutant, lacking RHD2/AtRBOHC, gave comparable results. Similarly to DPI, the decreased ROS levels in rhd2 root-tip cells, interfered with MT organization and induced macrotubule assembly. These data indicate, for first time in plants, that ROS are definitely implicated in: (a) mechanisms controlling the assembly/disassembly of interphase, Preprophase and mitotic MT systems and (b) mitotic spindle function. The probable mechanisms, by which ROS affect these processes, are discussed.
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cytoskeletal asymmetry in zea mays subsidiary cell mother cells a monopolar prophase microtubule half spindle anchors the nucleus to its polar position
Cytoskeleton, 2006Co-Authors: Emmanuel Panteris, P Apostolakos, B GalatisAbstract:Double labeling of microtubules and actin filaments revealed that in prophase subsidiary mother cells of Zea mays a monopolar prophase microtubule \halfspindle" is formed, which lines the nuclear hemisphere distal to the inducing guard mother cell. The nuclear hemisphere proximal to the guard mother cell is lined by an F-actin cap, consisting of a cortical F-actin patch and actin filaments originating from it. The microtubules of the \half-spindle" decline from the nuclear surface and terminate to the Preprophase microtubule Band. After disintegration of the latter, a bipolar metaphase spindle is organized. The polar F-actin cap persists during mitosis and early cytokinesis, extending to the chromosomes and the subsidiary cell daughter nucleus. In oryzalin treated subsidiary mother cells the prophase nuclei move away from the polar site. Cytochalasin B and latrunculin-B block the polar migration of subsidiary mother cell nuclei, but do not affect those already settled to the polar position. The prophase nuclei of latrunculin-B treated subsidiary mother cells are globally surrounded by microtubules, while the division plane of latrunculin-B treated subsidiary mother cells is misaligned. The prophase nuclei of brick 1 mutant Zea mays subsidiary mother cells without Factin patch are also globally surrounded by microtubules. The presented data show that the prophase microtubule \half-spindle"-Preprophase Band complex anchors the subsidiary mother cell nucleus to the polar cell site, while the polar Factin cap stabilizes the one metaphase spindle pole proximal to the inducing guard mother cell. Cell Motil. Cytoskeleton 2006. ' 2006 Wiley-Liss, Inc.
Masamitsu Wada - One of the best experts on this subject based on the ideXlab platform.
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Re-Formation of the Preprophase Band After Cold-Induced Depolymerization of Microtubules in Adiantwn Protonemata
2016Co-Authors: Takashi Murata, Masamitsu WadaAbstract:Re-formation of the Preprophase Band (PPB) of microtubules (MTs) after cold-induced depolymerization of MTs was investigated in protonemal cells of the fern, Adiantum capillus-veneris L. When protonemata with a PPB were chilled at 0°C, MTs of the PPB depolymerized within 5 min leaving only a few fragments of MTs, and all such fragments were disrupted within 2 h after the onset of cold treatment. When cells were chilled for 5 min and then rewarmed at 25 °C, the transverse MTs of the PPB gradually increased in number in the region of the PPB and re-formation of the PPB was accomplished within 20 min. In contrast, when cells chilled for 2 h were rewarmed, randomly oriented MTs appeared initially and then a PPB with a low density of MTs became apparent. The PPB re-formed even when the nucleus and most of the endoplasm had been displaced from the region of the PPB by centrifugation (2,800 x^, 15 min). These results suggest that MTs of the PPB nucleate and are organized in the cortical cytoplasm during re-formation of the PPB after disruption. Key words: Adiantum capillus-veneris — Fern protonema — Low temperature — Microtubule assembly — Preprophase Band. Since the location of the PPB of MTs in higher plan
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cytoskeletal pattern changes during branch formation in a centrifuged adiantum protonema
Journal of Plant Research, 1998Co-Authors: Masamitsu Wada, Kazunari Nozue, Akeo KadotaAbstract:A protonemal branch was induced on a side wall of a fern filamentous protonema by cell centrifugation and subsequent polarized-red light irradiation as described in a previous paper (Wada 1995, J. Plant Res. 108: 501–509). Changes in microtubule (MT) and microfilament (MF) patters during the branch development were observed under fluorescence microscopy. A ring-like Band of cortical MTs (MT-ring) and MFs similar to a Preprophase Band or a subapical ring structure (Murataet al. 1987) appeared transiently at the future branching site before cell swelling, the first visible step of branch formation. At this stage, the nucleus was located far from the branching site and the MT-ring appeared to be connected to the nucleus by endoplasmic MFs as well as with endoplasmic MTs. The MT-ring disappeared when cell wall swelling occurred. When the cell wall swelling began, a fan-like pattern of cortical MTs emanating from the new growing tip was established and the MTs reached the opposite flank of the protonema. When a new branch started to elongate and the nucleus moved into the branch, a faint subapical ring of MTs appeared at the subapical part of the new branch. Strands of MTs and MFs emanating from the nuclear front end reached a part of the subapical ring.
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cell division in caffeine induced binucleate protonemal cells of adiantum ii formation of the Preprophase Band and cell division in centrifuged and non centrifuged cells
Journal of Plant Research, 1993Co-Authors: Takashi Murata, Masamitsu WadaAbstract:Organization of microtubules (MTs) in relation to the behavior of nuclei was examined in dividing binucleate cells ofAdiantum capillus-veneris L. To induce binucleate cells, caffeine, an inhibitor of formation of the cell plate, was applied at 4 mM to synchronously dividing protonemal cells during cytokinesis (Murata and Wada 1993). Formation of the Preprophase Band (PPB) during the next cell cycle was examined in non-centrifuged and centrifuged cells. The two nuclei were separated or associated with one another in both non-centrifuged and centrifuged cells, although the location of the nuclei in the cylindrical protonemal cells was different (Murata and Wada 1993). Irrespective of centrifugation, a single PPB was formed around the nuclei in cells with associated nuclei. Two PPBs were formed in cells with separated nuclei in centrifuged cells. Patterns of mitosis and cytokinesis varied, depending on the location of the PPB and the distribution of the nuclei. The role of the nucleus in formation of the PPB is discussed.
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cell cycle specific disruption of the Preprophase Band of microtubules in fern protonemata effects of displacement of the endoplasm by centrifugation
Journal of Cell Science, 1992Co-Authors: Takashi Murata, Masamitsu WadaAbstract:The Preprophase Band (PPB) of microtubules (MTs), which appears at the future site of cytokinesis prior to cell division in higher plant cells, disappears by metaphase. Recent studies have shown that displacement of the endoplasm from the PPB region by centrifugation delays the disappearance of the PPB. To study the role of the endoplasm in the cell cycle-specific disruption of the PPB, the filamentous protonemal cells of the fern Adiantum capilius-veneris L. were centrifuged twice so that the first centrifugation displaced the endoplasm from the site of the PPB and the second returned it to its original location. The endoplasm, including the nucleus of various stages of mitosis, could be returned by the second centrifugation to the original region of the PPB, which persists during mitosis in the centrifuged cells. When endoplasm with a prophase nucleus was returned to its original location, the PPB was not disrupted. When endoplasm with a prometa-phase telophase nucleus was similarly returned, the PPB was disrupted within 10 min of termination of centrifugation. In protonemal cells of Adiantum, a second PPB is often formed near the displaced nucleus after the first centrifugation. In cells in which the endoplasm was considered to have been returned to its original location at the prophase/prometaphase transition, the second PPB did not disappear even though the initial PPB was disrupted by the endoplasm. These results suggest that cell cycle-specific disruption of the PPB is regulated by some factor(s) in the endoplasm, which appears at prometaphase, i.e. the stage at which the PPB is disrupted in non-centrifuged cells.
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Experimental obliteration of the Preprophase Band alters the site of cell division, cell plate orientation and phragmoplast expansion in Adiantum protonemata
Journal of Cell Science, 1991Co-Authors: Yoshinobu Mineyuki, Takashi Murata, Masamitsu WadaAbstract:the premitotic nuclear positioning is delayed markedly and irregularly oriented cell plates are frequently observed. Re-irradiation with red light also causes an increase in cells without Preprophase Bands (PPBs) at prophase and the irregular expansion of the phragmoplast at late telophase, while early phragmoplast microtubule (MT) organization takes place normally. These data suggest the indirect involvement of PPBs in the guidance of phragmoplast expansion.
Richard J Cyr - One of the best experts on this subject based on the ideXlab platform.
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an ungrouped plant kinesin accumulates at the Preprophase Band in a cell cycle dependent manner
Cytoskeleton, 2011Co-Authors: Jennelle L Malcos, Richard J CyrAbstract:Past phylogenic studies have identified a plant-specific, ungrouped family of kinesins in which the motor domain does not group to one of the fourteen recognized families. Members of this family contain an N-terminal motor domain, a C-terminal armadillo repeat domain and a conserved destruction box (D-BOX) motif. This domain architecture is unique to plants and to a subset of protists. Further characterization of one representative member from Arabidopsis, Arabidopsis thaliana KINESIN ungrouped clade, gene A (AtKINUa), was completed to ascertain its functional role in plants. Fluorescence confocal microscopy revealed an accumulation of ATKINUA:GFP at the Preprophase Band (PPB) in a cell cycle-dependent manner in Arabidopsis epidermal cells and tobacco BY-2 cells. Fluorescence accumulation was highest during prophase and decreased after nuclear envelope breakdown. A conserved D-BOX motif was identified through alignment of AtKINU homologous sequences. Mutagenesis work with D-BOX revealed that conserved residues were necessary for the observed degradation pattern of ATKINUA:GFP, as well as the targeted accumulation at the PPB. Overall results suggest that AtKINUa is necessary for normal plant growth and/or development and is likely involved with PPB organization through microtubule association and specific cell cycle regulation. The D-BOX motif may function to bridge microtubule organization with changes that occur during progression through mitosis and may represent a novel regulatory motif in plant microtubule motor proteins.
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mitotic spindle organization by the Preprophase Band
Molecular Plant, 2008Co-Authors: Christian J Ambrose, Richard J CyrAbstract:In higher plants, the Preprophase Band (PPB) of microtubules (MTs) forecasts the cell division site prior to mitosis and specifies the organization of MTs into a bipolar prophase spindle surrounding the nucleus. However, the mechanisms governing this PPB-dependent establishment of bipolarity are unclear. Here, we present evidence from live cell imaging studies that suggest a role for the MTs bridging the PPB and the prophase nucleus in mediating this function. Results from drug treatments, along with genetic evidence from null kinesin plants, suggest that these MTs contribute to the bipolarity, orientation, and position of the prophase spindle. Specifically, the absence of these bridge MTs is associated with lack of bipolarity, while non-uniform distributions of bridge MTs correlate with prophase spindle migration, deformation, and enhanced bipolarity toward the region of highest bridge MT density. This behavior does not require actomyosin-based forces, and is enhanced by suppressing MT dynamics with taxol. These observations occur during late prophase, and are coincident with the gradual closing of annular spindle poles. Based on these data, we describe a hypothetical mechanism for bridge MT-dependent organization of prophase spindles.
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spatio temporal relationship between nuclear envelope breakdown and Preprophase Band disappearance in cultured tobacco cells
Protoplasma, 2002Co-Authors: Ram Dixit, Richard J CyrAbstract:Cell division involves the coordinated progression of karyokinesis and cytokinesis, which is accomplished by communication between the nucleus and the cytoplasm. We have utilized green-fluorescent-protein technology to generate a line of tobacco 'Bright Yellow 2' (BY-2) cells labeled for both microtubules and the nuclear envelope. This cell line allowed us to use living cells to investigate the relationship between nuclear-envelope breakdown and Preprophase Band disappearance with high spatial and temporal resolution. Our observations demonstrate that nuclear-envelope breakdown always precedes Preprophase Band disappearance in BY-2 cells. In addition, the rate of Preprophase Band disappearance, and the attenuation of perinuclear microtubule fluorescence, correlates with the proximity of the nucleus to the Preprophase Band site. These results indicate the presence of communication between the nucleus and the Preprophase Band and suggest a causal relationship between nuclear-envelope breakdown and Preprophase Band disappearance.
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golgi secretion is not required for marking the Preprophase Band site in cultured tobacco cells
Plant Journal, 2002Co-Authors: Ram Dixit, Richard J CyrAbstract:The Preprophase Band predicts the future cell division site. However, the mechanism of how a transient Preprophase Band fulfils this function is unknown. We have investigated the possibility that Golgi secretion might be involved in marking the Preprophase Band site. Observations on living BY-2 cells labeled for microtubules and Golgi stacks indicated an increased Golgi stack frequency at the Preprophase Band site. However, inhibition of Golgi secretion by brefeldin A during Preprophase Band formation did not prevent accurate phragmoplast fusion, and subsequent cell plate formation, at the Preprophase Band site. The results show that Golgi secretion does not mark the Preprophase Band site and thus does not play an active role in determination of the cell division site.
Bo Liu - One of the best experts on this subject based on the ideXlab platform.
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the Preprophase Band associated kinesin 14 oskch2 is a processive minus end directed microtubule motor
Nature Communications, 2018Co-Authors: Kuofu Tseng, Bo Liu, Pan Wang, Yuhru Julie Lee, Joel Bowen, Allison M Gicking, Lijun Guo, Weihong QiuAbstract:In animals and fungi, cytoplasmic dynein is a processive minus-end-directed motor that plays dominant roles in various intracellular processes. In contrast, land plants lack cytoplasmic dynein but contain many minus-end-directed kinesin-14s. No plant kinesin-14 is known to produce processive motility as a homodimer. OsKCH2 is a plant-specific kinesin-14 with an N-terminal actin-binding domain and a central motor domain flanked by two predicted coiled-coils (CC1 and CC2). Here, we show that OsKCH2 specifically decorates Preprophase Band microtubules in vivo and transports actin filaments along microtubules in vitro. Importantly, OsKCH2 exhibits processive minus-end-directed motility on single microtubules as individual homodimers. We find that CC1, but not CC2, forms the coiled-coil to enable OsKCH2 dimerization. Instead, our results reveal that removing CC2 renders OsKCH2 a nonprocessive motor. Collectively, these results show that land plants have evolved unconventional kinesin-14 homodimers with inherent minus-end-directed processivity that may function to compensate for the loss of cytoplasmic dynein.
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the Preprophase Band associated kinesin 14 oskch2 is a processive minus end directed microtubule motor
bioRxiv, 2017Co-Authors: Kuofu Tseng, Bo Liu, Pan Wang, Yuhru Julie Lee, Joel Bowen, Allison M Gicking, Lijun Guo, Weihong QiuAbstract:In animals and fungi, cytoplasmic dynein is a processive motor that plays dominant roles in various intracellular processes. In contrast, land plants lack cytoplasmic dynein but contain many minus-end-directed kinesin-14s. No plant kinesin-14 is known to produce processive motility as a homodimer. OsKCH2 is a plant-specific kinesin-14 with an N-terminal actin-binding domain and a central motor domain flanked by two predicted coiled-coils (CC1 and CC2). Here, we show that OsKCH2 specifically decorates Preprophase Band microtubules in vivo and transports actin filaments along microtubules in vitro. Importantly, OsKCH2 exhibits processive minus-end-directed motility on single microtubules as individual homodimers. We find that CC1 but not CC2 forms the coiled-coil for OsKCH2 dimerization. Instead, CC2 functions to enable OsKCH2 processivity by enhancing its binding to microtubules. Collectively, these results show that land plants have evolved unconventional kinesin-14 homodimers with inherent minus-end-directed processivity that may function to compensate for the loss of cytoplasmic dynein.
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arabidopsis map65 4 plays a role in phragmoplast microtubule organization and marks the cortical cell division site
New Phytologist, 2017Co-Authors: Baojuan Sun, Michiko Sasabe, Y.-r. Julie Lee, Yasunori Machida, Xingguang Deng, Honghui Lin, Bo LiuAbstract:The evolutionarily conserved MAP65 family proteins bundle anti-parallel microtubules (MTs). In Arabidopsis thaliana, mutations in the MAP65-3 gene lead to serious defects in MT organization in the phragmoplast and cause failures in cytokinesis. However, the functions of other ArabidopsisMAP65 isoforms are largely unknown. MAP65 functions were analyzed based on genetic interactions among different map65 mutations. Live-cell imaging and immunolocalization experiments revealed dynamic activities of two closely related MAP65 proteins in dividing cells. The map65-4 mutation caused synthetic lethality with map65-3 although map65-4 alone did not cause a noticeable phenotype. Furthermore, the introduction of an extra copy of the MAP65-4 gene significantly suppressed defects in cytokinesis and seedling growth caused by map65-3 because of restoring MT engagement in the spindle midzone. During mitosis, MAP65-4 first appeared at the Preprophase Band and persisted at the cortical division site afterwards. It was also concentrated on MTs in the spindle midzone and the phragmoplast. In the absence of MAP65-3, MAP65-4 exhibited greatly enhanced localization in the midzone of developing phragmoplast. Therefore, we have uncovered redundant but differential contributions of MAP65-3 and MAP65-4 to engaging and bundling anti-parallel MTs in the phragmoplast and disclosed a novel action of MAP65-4 at the cortical cell division site.
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a gamma tubulin related protein associated with the microtubule arrays of higher plants in a cell cycle dependent manner
Journal of Cell Science, 1993Co-Authors: Bo Liu, H C Joshi, J Marc, Barry A PalevitzAbstract:An antibody specific for a conserved gamma-tubulin peptide identifies a plant polypeptide of 58 kDa. gamma-Tubulin antibody affinity purified from this polypeptide recognizes the centrosome in mammalian cells. Using immunofluorescence microscopy, we determined the distribution of this gamma-tubulin-related polypeptide during the complex changes in microtubule arrays that occur throughout the plant cell cycle. We report a punctate association of gamma-tubulin-related polypeptide with the cortical microtubule array and the Preprophase Band. As cells enter prophase, gamma-tubulin-related polypeptide accumulates around the nucleus and forms a polar cap from which early spindle microtubules radiate. During metaphase and anaphase, gamma-tubulin-related polypeptide preferentially associates with kinetochore fibers and eventually accumulates at the poles. In telophase, localization occurs over the phragmoplast. gamma-Tubulin-related polypeptide appears to be excluded from the plus ends of microtubules at the metaphase plate and cell plate. Its distribution during the cell cycle may be significant in light of differences in the behavior and organization of plant microtubules. The identification of gamma-tubulin-related polypeptide could help characterize microtubule organizing centers in these organisms.