The Experts below are selected from a list of 315 Experts worldwide ranked by ideXlab platform
Bo Liu - One of the best experts on this subject based on the ideXlab platform.
-
Role of the BUB3 protein in Phragmoplast microtubule reorganization during cytokinesis.
Nature plants, 2018Co-Authors: Hongchang Zhang, Yuh-ru Julie Lee, Xingguang Deng, Baojuan Sun, Sonny Lee Van, Zhensheng Kang, Honghui Lin, Bo LiuAbstract:The evolutionarily conserved WD40 protein budding uninhibited by benzimidazole 3 (BUB3) is known for its function in spindle assembly checkpoint control. In the model plant Arabidopsis thaliana, nearly identical BUB3;1 and BUB3;2 proteins decorated the Phragmoplast midline through interaction with the microtubule-associated protein MAP65-3 during cytokinesis. BUB3;1 and BUB3;2 interacted with the carboxy-terminal segment of MAP65-3 (but not MAP65-1), which harbours its microtubule-binding domain for its post-mitotic localization. Reciprocally, BUB3;1 and BUB3;2 also regulated MAP65-3 localization in the Phragmoplast by enhancing its microtubule association. In the bub3;1 bub3;2 double mutant, MAP65-3 localization was often dissipated away from the Phragmoplast midline and abolished upon treatment of low doses of the cytokinesis inhibitory drug caffeine that were tolerated by the control plant. The Phragmoplast microtubule array exhibited uncoordinated expansion pattern in the double mutant cells as the Phragmoplast edge reached the parental plasma membrane at different times in different areas. Upon caffeine treatment, Phragmoplast expansion was halted as if the microtubule array was frozen. As a result, cytokinesis was abolished due to failed cell plate assembly. Our findings have uncovered a novel function of the plant BUB3 in MAP65-3-dependent microtubule reorganization during cytokinesis.
-
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.
-
Arabidopsis MAP65‐4 plays a role in Phragmoplast microtubule organization and marks the cortical cell division site
The 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.
-
The rise and fall of the Phragmoplast microtubule array.
Current opinion in plant biology, 2013Co-Authors: Yuh-ru Julie Lee, Bo LiuAbstract:The cytokinetic apparatus, the Phragmoplast, contains a bipolar microtubule (MT) framework that has the MT plus ends concentrated at or near the division site. This anti-parallel MT array provides tracks for the transport of Golgi-derived vesicles toward the plus ends so that materials enclosed are subsequently deposited at the division site. Here we will discuss a proposed model of the centrifugal expansion of the Phragmoplast that takes place concomitantly with the assembly of the cell plate, the ultimate product of vesicle fusion. The expansion is a result of continuous MT assembly at the Phragmoplast periphery while the MTs toward the center of the Phragmoplast are disassembled. These events are the result of MT-dependent MT polymerization, bundling of anti-parallel MTs coming from opposite sides of the division plane that occurs selectively at the Phragmoplast periphery, positioning of the plus ends of cross-linked MTs at or near the division site by establishing a minimal MT-overlapping zone, and debundling of anti-parallel MTs that is triggered by phosphorylation of MT-associated proteins. The debundled MTs are disassembled at last by factors including the MT severing enzyme katanin.
-
Arabidopsis Microtubule-Associated Protein MAP65-3 Cross-Links Antiparallel Microtubules toward Their Plus Ends in the Phragmoplast via Its Distinct C-Terminal Microtubule Binding Domain
The Plant cell, 2012Co-Authors: Yuh-ru Julie Lee, Lindsay D. Kiyama, Savithramma P. Dinesh-kumar, Bo LiuAbstract:Plant cytokinesis is brought about by the Phragmoplast, which contains an antiparallel microtubule (MT) array. The MT-associated protein MAP65-3 acts as an MT-bundling factor that specifically cross-links antiparallel MTs near their plus ends. MAP65 family proteins contain an N-terminal dimerization domain and C-terminal MT interaction domain. Compared with other MAP65 isoforms, MAP65-3 contains an extended C terminus. A MT binding site was discovered in the region between amino acids 496 and 588 and found to be essential for the organization of Phragmoplast MTs. The frequent cytokinetic failure caused by loss of MAP65-3 was not rescued by ectopic expression of MAP65-1 under the control of the MAP65-3 promoter, indicating nonoverlapping functions between the two isoforms. In the presence of MAP65-3, however, ectopic MAP65-1 appeared in the Phragmoplast midline. We show that MAP65-1 could acquire the function of MAP65-3 when the C terminus of MAP65-3, which contains the MT binding site, was grafted to it. Our results also show that MAP65-1 and MAP65-3 may share redundant functions in MT stabilization. Such a stabilization effect was likely brought about by MT binding and bundling. We conclude that MAP65-3 contains a distinct C-terminal MT binding site with a specific role in cross-linking antiparallel MTs toward their plus ends in the Phragmoplast.
Yuh-ru Julie Lee - One of the best experts on this subject based on the ideXlab platform.
-
Role of the BUB3 protein in Phragmoplast microtubule reorganization during cytokinesis.
Nature plants, 2018Co-Authors: Hongchang Zhang, Yuh-ru Julie Lee, Xingguang Deng, Baojuan Sun, Sonny Lee Van, Zhensheng Kang, Honghui Lin, Bo LiuAbstract:The evolutionarily conserved WD40 protein budding uninhibited by benzimidazole 3 (BUB3) is known for its function in spindle assembly checkpoint control. In the model plant Arabidopsis thaliana, nearly identical BUB3;1 and BUB3;2 proteins decorated the Phragmoplast midline through interaction with the microtubule-associated protein MAP65-3 during cytokinesis. BUB3;1 and BUB3;2 interacted with the carboxy-terminal segment of MAP65-3 (but not MAP65-1), which harbours its microtubule-binding domain for its post-mitotic localization. Reciprocally, BUB3;1 and BUB3;2 also regulated MAP65-3 localization in the Phragmoplast by enhancing its microtubule association. In the bub3;1 bub3;2 double mutant, MAP65-3 localization was often dissipated away from the Phragmoplast midline and abolished upon treatment of low doses of the cytokinesis inhibitory drug caffeine that were tolerated by the control plant. The Phragmoplast microtubule array exhibited uncoordinated expansion pattern in the double mutant cells as the Phragmoplast edge reached the parental plasma membrane at different times in different areas. Upon caffeine treatment, Phragmoplast expansion was halted as if the microtubule array was frozen. As a result, cytokinesis was abolished due to failed cell plate assembly. Our findings have uncovered a novel function of the plant BUB3 in MAP65-3-dependent microtubule reorganization during cytokinesis.
-
The rise and fall of the Phragmoplast microtubule array.
Current opinion in plant biology, 2013Co-Authors: Yuh-ru Julie Lee, Bo LiuAbstract:The cytokinetic apparatus, the Phragmoplast, contains a bipolar microtubule (MT) framework that has the MT plus ends concentrated at or near the division site. This anti-parallel MT array provides tracks for the transport of Golgi-derived vesicles toward the plus ends so that materials enclosed are subsequently deposited at the division site. Here we will discuss a proposed model of the centrifugal expansion of the Phragmoplast that takes place concomitantly with the assembly of the cell plate, the ultimate product of vesicle fusion. The expansion is a result of continuous MT assembly at the Phragmoplast periphery while the MTs toward the center of the Phragmoplast are disassembled. These events are the result of MT-dependent MT polymerization, bundling of anti-parallel MTs coming from opposite sides of the division plane that occurs selectively at the Phragmoplast periphery, positioning of the plus ends of cross-linked MTs at or near the division site by establishing a minimal MT-overlapping zone, and debundling of anti-parallel MTs that is triggered by phosphorylation of MT-associated proteins. The debundled MTs are disassembled at last by factors including the MT severing enzyme katanin.
-
Arabidopsis Microtubule-Associated Protein MAP65-3 Cross-Links Antiparallel Microtubules toward Their Plus Ends in the Phragmoplast via Its Distinct C-Terminal Microtubule Binding Domain
The Plant cell, 2012Co-Authors: Yuh-ru Julie Lee, Lindsay D. Kiyama, Savithramma P. Dinesh-kumar, Bo LiuAbstract:Plant cytokinesis is brought about by the Phragmoplast, which contains an antiparallel microtubule (MT) array. The MT-associated protein MAP65-3 acts as an MT-bundling factor that specifically cross-links antiparallel MTs near their plus ends. MAP65 family proteins contain an N-terminal dimerization domain and C-terminal MT interaction domain. Compared with other MAP65 isoforms, MAP65-3 contains an extended C terminus. A MT binding site was discovered in the region between amino acids 496 and 588 and found to be essential for the organization of Phragmoplast MTs. The frequent cytokinetic failure caused by loss of MAP65-3 was not rescued by ectopic expression of MAP65-1 under the control of the MAP65-3 promoter, indicating nonoverlapping functions between the two isoforms. In the presence of MAP65-3, however, ectopic MAP65-1 appeared in the Phragmoplast midline. We show that MAP65-1 could acquire the function of MAP65-3 when the C terminus of MAP65-3, which contains the MT binding site, was grafted to it. Our results also show that MAP65-1 and MAP65-3 may share redundant functions in MT stabilization. Such a stabilization effect was likely brought about by MT binding and bundling. We conclude that MAP65-3 contains a distinct C-terminal MT binding site with a specific role in cross-linking antiparallel MTs toward their plus ends in the Phragmoplast.
-
Characterization of the Arabidopsis Augmin Complex Uncovers Its Critical Function in the Assembly of the Acentrosomal Spindle and Phragmoplast Microtubule Arrays
The Plant cell, 2012Co-Authors: Takashi Hotta, Zhaosheng Kong, Cui Jing Tracy Zeng, Tetsuya Horio, Sophia Fong, Trang Vuong, Yuh-ru Julie Lee, Bo LiuAbstract:Plant cells assemble the bipolar spindle and Phragmoplast microtubule (MT) arrays in the absence of the centrosome structure. Our recent findings in Arabidopsis thaliana indicated that AUGMIN subunit3 (AUG3), a homolog of animal dim γ-tubulin 3, plays a critical role in γ-tubulin–dependent MT nucleation and amplification during mitosis. Here, we report the isolation of the entire plant augmin complex that contains eight subunits. Among them, AUG1 to AUG6 share low sequence similarity with their animal counterparts, but AUG7 and AUG8 share homology only with proteins of plant origin. Genetic analyses indicate that the AUG1, AUG2, AUG4, and AUG5 genes are essential, as stable mutations in these genes could only be transmitted to heterozygous plants. The sterile aug7-1 homozygous mutant in which AUG7 expression is significantly reduced exhibited pleiotropic phenotypes of seriously retarded vegetative and reproductive growth. The aug7-1 mutation caused delocalization of γ-tubulin in the mitotic spindle and Phragmoplast. Consequently, spindles were abnormally elongated, and their poles failed to converge, as MTs were splayed to discrete positions rendering deformed arrays. In addition, the mutant Phragmoplasts often had disorganized MT bundles with uneven edges. We conclude that assembly of MT arrays during plant mitosis depends on the augmin complex, which includes two plant-specific subunits.
-
Interaction of Antiparallel Microtubules in the Phragmoplast Is Mediated by the Microtubule-Associated Protein MAP65-3 in Arabidopsis
The Plant cell, 2011Co-Authors: Takashi Hotta, Yuh-ru Julie Lee, Fengli Guo, Robert W. Roberson, Bo LiuAbstract: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.
Michiko Sasabe - One of the best experts on this subject based on the ideXlab platform.
-
Actin Filament Disruption Alters Phragmoplast Microtubule Dynamics during the Initial Phase of Plant Cytokinesis
Plant & cell physiology, 2020Co-Authors: Keisho Maeda, Michiko Sasabe, Seiichiro Hasezawa, Yasunori Machida, Shigeru Hanamata, Takumi HigakiAbstract:Plant growth and development relies on the accurate positioning of the cell plate between dividing cells during cytokinesis. The cell plate is synthetized by a specialized structure called the Phragmoplast, which contains bipolar microtubules that polymerize to form a framework with the plus ends at or near the division site. This allows the transport of Golgi-derived vesicles toward the plus ends to form and expand the cell plate. Actin filaments play important roles in cell plate expansion and guidance in plant cytokinesis at the late phase, but whether they are involved at the early phase is unknown. To investigate this further, we disrupted the actin filaments in cell cycle-synchronized tobacco BY-2 cells with latrunculin B (LatB), an actin polymerization inhibitor. We observed the cells under a transmission electron microscope or a spinning-disk confocal laser scanning microscope. We found that disruption of actin filaments by LatB caused the membrane vesicles at the equatorial plane of the cell plate to be dispersed rather than form clusters as they did in the untreated cells. The midzone constriction of Phragmoplast microtubules also was perturbed in LatB-treated cells. The live cell imaging and kymograph analysis showed that disruption of actin filaments also changed the accumulation timing of NACK1 kinesin, which plays a crucial role in cell plate expansion. This suggests that there are two functionally different types of microtubules in the Phragmoplast. Together, our results show that actin filaments regulate Phragmoplast microtubules at the initial phase of plant cytokinesis.
-
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.
-
Arabidopsis MAP65‐4 plays a role in Phragmoplast microtubule organization and marks the cortical cell division site
The 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.
-
Mechanism of microtubule array expansion in the cytokinetic Phragmoplast
Nature communications, 2013Co-Authors: Takashi Murata, Michiko Sasabe, Seiichiro Hasezawa, Yasunori Machida, Toshio Sano, Shigenori Nonaka, Tetsuya Higashiyama, Mitsuyasu HasebeAbstract:In land plants, the cell plate partitions the daughter cells at cytokinesis. The cell plate initially forms between daughter nuclei and expands centrifugally until reaching the plasma membrane. The centrifugal development of the cell plate is driven by the centrifugal expansion of the Phragmoplast microtubule array, but the molecular mechanism underlying this expansion is unknown. Here, we show that the Phragmoplast array comprises stable microtubule bundles and dynamic microtubules. We find that the dynamic microtubules are nucleated by γ-tubulin on stable bundles. The dynamic microtubules elongate at the plus ends and form new bundles preferentially at the leading edge of the Phragmoplast. At the same time, they are moved away from the cell plate, maintaining a restricted distribution of minus ends. We propose that cycles of attachment of γ-tubulin complexes onto the microtubule bundles, microtubule nucleation and bundling, accompanied by minus-end-directed motility, drive the centrifugal development of the Phragmoplast.
-
Regulation of organization and function of microtubules by the mitogen‐activated protein kinase cascade during plant cytokinesis
Cytoskeleton (Hoboken N.J.), 2012Co-Authors: Michiko Sasabe, Yasunori MachidaAbstract:Cytokinesis in eukaryotes involves specific arrays of microtubules (MTs), which are known as the central spindle in animals, the anaphase spindle in yeasts, and the Phragmoplast in plants. In plants, a mitogen-activated protein kinase (MAPK) cascade stimulates the turnover of Phragmoplast MTs, which allows the expansion of the Phragmoplast that is essential for cytokinesis including the formation of cell plates. A prerequisite for activation of this cascade is the interaction between mitotic kinesin NACK1 in tobacco (HINKEL in Arabidopsis) and MAPK kinase kinase NPK1 (ANP1, 2, 3 in Arabidopsis). Other members of this cascade are NQK1 MAPK kinase and NRK1/NTF6 MAPK in tobacco and the respective orthologs in Arabidopsis. All the components in the pathway (designated the NACK-PQR pathway) concentrate at the midzone of the Phragmoplast in plant cells during cytokinesis. Downstream MAPKs in both plant species phosphorylate microtubule-associated protein 65 (MAP65). Interestingly, activities of components in the NACK-PQR pathway are downregulated by depolymerization of MTs. In the present review, we summarize current views on the mechanisms involved in activating the kinase cascade, a role of MAP65 phosphorylation by MAPK during cytokinesis, and the feedback mechanism for regulating inactivation of the kinase cascade.
Yasunori Machida - One of the best experts on this subject based on the ideXlab platform.
-
Actin Filament Disruption Alters Phragmoplast Microtubule Dynamics during the Initial Phase of Plant Cytokinesis
Plant & cell physiology, 2020Co-Authors: Keisho Maeda, Michiko Sasabe, Seiichiro Hasezawa, Yasunori Machida, Shigeru Hanamata, Takumi HigakiAbstract:Plant growth and development relies on the accurate positioning of the cell plate between dividing cells during cytokinesis. The cell plate is synthetized by a specialized structure called the Phragmoplast, which contains bipolar microtubules that polymerize to form a framework with the plus ends at or near the division site. This allows the transport of Golgi-derived vesicles toward the plus ends to form and expand the cell plate. Actin filaments play important roles in cell plate expansion and guidance in plant cytokinesis at the late phase, but whether they are involved at the early phase is unknown. To investigate this further, we disrupted the actin filaments in cell cycle-synchronized tobacco BY-2 cells with latrunculin B (LatB), an actin polymerization inhibitor. We observed the cells under a transmission electron microscope or a spinning-disk confocal laser scanning microscope. We found that disruption of actin filaments by LatB caused the membrane vesicles at the equatorial plane of the cell plate to be dispersed rather than form clusters as they did in the untreated cells. The midzone constriction of Phragmoplast microtubules also was perturbed in LatB-treated cells. The live cell imaging and kymograph analysis showed that disruption of actin filaments also changed the accumulation timing of NACK1 kinesin, which plays a crucial role in cell plate expansion. This suggests that there are two functionally different types of microtubules in the Phragmoplast. Together, our results show that actin filaments regulate Phragmoplast microtubules at the initial phase of plant cytokinesis.
-
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.
-
Arabidopsis MAP65‐4 plays a role in Phragmoplast microtubule organization and marks the cortical cell division site
The 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.
-
Mechanism of microtubule array expansion in the cytokinetic Phragmoplast
Nature communications, 2013Co-Authors: Takashi Murata, Michiko Sasabe, Seiichiro Hasezawa, Yasunori Machida, Toshio Sano, Shigenori Nonaka, Tetsuya Higashiyama, Mitsuyasu HasebeAbstract:In land plants, the cell plate partitions the daughter cells at cytokinesis. The cell plate initially forms between daughter nuclei and expands centrifugally until reaching the plasma membrane. The centrifugal development of the cell plate is driven by the centrifugal expansion of the Phragmoplast microtubule array, but the molecular mechanism underlying this expansion is unknown. Here, we show that the Phragmoplast array comprises stable microtubule bundles and dynamic microtubules. We find that the dynamic microtubules are nucleated by γ-tubulin on stable bundles. The dynamic microtubules elongate at the plus ends and form new bundles preferentially at the leading edge of the Phragmoplast. At the same time, they are moved away from the cell plate, maintaining a restricted distribution of minus ends. We propose that cycles of attachment of γ-tubulin complexes onto the microtubule bundles, microtubule nucleation and bundling, accompanied by minus-end-directed motility, drive the centrifugal development of the Phragmoplast.
-
Regulation of organization and function of microtubules by the mitogen‐activated protein kinase cascade during plant cytokinesis
Cytoskeleton (Hoboken N.J.), 2012Co-Authors: Michiko Sasabe, Yasunori MachidaAbstract:Cytokinesis in eukaryotes involves specific arrays of microtubules (MTs), which are known as the central spindle in animals, the anaphase spindle in yeasts, and the Phragmoplast in plants. In plants, a mitogen-activated protein kinase (MAPK) cascade stimulates the turnover of Phragmoplast MTs, which allows the expansion of the Phragmoplast that is essential for cytokinesis including the formation of cell plates. A prerequisite for activation of this cascade is the interaction between mitotic kinesin NACK1 in tobacco (HINKEL in Arabidopsis) and MAPK kinase kinase NPK1 (ANP1, 2, 3 in Arabidopsis). Other members of this cascade are NQK1 MAPK kinase and NRK1/NTF6 MAPK in tobacco and the respective orthologs in Arabidopsis. All the components in the pathway (designated the NACK-PQR pathway) concentrate at the midzone of the Phragmoplast in plant cells during cytokinesis. Downstream MAPKs in both plant species phosphorylate microtubule-associated protein 65 (MAP65). Interestingly, activities of components in the NACK-PQR pathway are downregulated by depolymerization of MTs. In the present review, we summarize current views on the mechanisms involved in activating the kinase cascade, a role of MAP65 phosphorylation by MAPK during cytokinesis, and the feedback mechanism for regulating inactivation of the kinase cascade.
Ioannis-dimosthenis S. Adamakis - One of the best experts on this subject based on the ideXlab platform.
-
Cytokinesis in fra2 Arabidopsis thaliana p60-Katanin Mutant: Defects in Cell Plate/Daughter Wall Formation.
International journal of molecular sciences, 2021Co-Authors: Emmanuel Panteris, Anna Kouskouveli, Dimitris Pappas, Ioannis-dimosthenis S. AdamakisAbstract:Cytokinesis is accomplished in higher plants by the Phragmoplast, creating and conducting the cell plate to separate daughter nuclei by a new cell wall. The microtubule-severing enzyme p60-katanin plays an important role in the centrifugal expansion and timely disappearance of Phragmoplast microtubules. Consequently, aberrant structure and delayed expansion rate of the Phragmoplast have been reported to occur in p60-katanin mutants. Here, the consequences of p60-katanin malfunction in cell plate/daughter wall formation were investigated by transmission electron microscopy (TEM), in root cells of the fra2Arabidopsis thaliana loss-of-function mutant. In addition, deviations in the chemical composition of cell plate/new cell wall were identified by immunolabeling and confocal microscopy. It was found that, apart from defective Phragmoplast microtubule organization, cell plates/new cell walls also appeared faulty in structure, being unevenly thick and perforated by large gaps. In addition, demethylesterified homogalacturonans were prematurely present in fra2 cell plates, while callose content was significantly lower than in the wild type. Furthermore, KNOLLE syntaxin disappeared from newly formed cell walls in fra2 earlier than in the wild type. Taken together, these observations indicate that delayed cytokinesis, due to faulty Phragmoplast organization and expansion, results in a loss of synchronization between cell plate growth and its chemical maturation.
-
Cytokinesis in fra2 Arabidopsis thaliana p60-katanin Mutant: Defects in Cell Plate/Daughter Wall Formation
2021Co-Authors: Emmanuel Panteris, Anna Kouskouveli, Dimitris Pappas, Ioannis-dimosthenis S. AdamakisAbstract:Cytokinesis is accomplished in higher plants by the Phragmoplast, creating and conducting the cell plate, to separate daughter nuclei by a new cell wall. The microtubule-severing enzyme p60-katanin plays an important role in the centrifugal expansion and timely disappearance of Phragmoplast microtubules. Consequently, aberrant structure and delayed expansion rate of the Phragmoplast occur in p60-katanin mutants. Here, the consequences of p60-katanin malfunction in cell plate/daughter wall formation were investigated by transmission electron microscopy (TEM), while deviations in the chemical composition of cell plate/new cell wall were identified by immunolabeling and confocal microscopy, in root cells of the fra2 Arabidopsis thaliana mutant. It was found that, apart from defective Phragmoplast microtubule organization, cell plates/new cell walls appeared also faulty in structure, being unevenly thick and perforated by large gaps. In addition, demethylesterified homogalacturonans were prematurely present in fra2 cell plates, while callose content was significantly lower than in the wild-type. Furthermore, KNOLLE syntaxin disappeared from newly formed cell walls in fra2 earlier than in the wild-type. Taken together, these observations indicate that delayed cytokinesis, due to faulty Phragmoplast organization and expansion, results in a loss of synchronization between cell plate growth and its chemical maturation.