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Hashimoto T. A ring for all: γ-tubulin-containing nucleation complexes in acentrosomal plant microtubule arrays. CURRENT OPINION IN PLANT BIOLOGY 2013; 16:698-703. [PMID: 24075308 DOI: 10.1016/j.pbi.2013.09.002] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/20/2013] [Revised: 08/24/2013] [Accepted: 09/04/2013] [Indexed: 06/02/2023]
Abstract
The construction of dynamic polar microtubules from 13 protofilaments consisting of α-tubulin and β-tubulin heterodimers requires a preformed nucleation seed that specifies subcellular localization and timing of microtubule polymerization in vivo. An evolutionarily conserved γ-tubulin-containing ring complex is recruited to the lateral wall of preexisting microtubules or outer nuclear membranes in plant cells, and is then activated as a template for new microtubules of defined geometry. Specific regulators are thought to target/activate the ring complex to nucleate nascent microtubules in distinct polymerization patterns, as seen in interphase and mitotic arrays. The augmin complex, which was initially identified in metazoan cells, recruits the ring complex to plant mitotic microtubules, where new polymers are abundantly generated at shallow angles.
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Affiliation(s)
- Takashi Hashimoto
- Nara Institute of Science and Technology, Graduate School of Biological Sciences, Japan.
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52
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Cheng Y, Wang Q, Li Z, Cui J, Hu S, Zhao H, Chen M. Cytological and comparative proteomic analyses on male sterility in Brassica napus L. induced by the chemical hybridization agent monosulphuron ester sodium. PLoS One 2013; 8:e80191. [PMID: 24244648 PMCID: PMC3828188 DOI: 10.1371/journal.pone.0080191] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/13/2013] [Accepted: 09/30/2013] [Indexed: 01/18/2023] Open
Abstract
Male sterility induced by a chemical hybridization agent (CHA) is an important tool for utilizing crop heterosis. Monosulphuron ester sodium (MES), a new acetolactate synthase-inhibitor herbicide belonging to the sulphonylurea family, has been developed as an effective CHA to induce male sterility in rapeseed (Brassica napus L.). To understand MES-induced male sterility in rapeseed better, comparative cytological and proteomic analyses were conducted in this study. Cytological analysis indicated that defective tapetal cells and abnormal microspores were gradually generated in the developing anthers of MES-treated plants at various development stages, resulting in unviable microspores and male sterility. A total of 141 differentially expressed proteins between the MES-treated and control plants were revealed, and 131 of them were further identified by MALDI-TOF/TOF MS. Most of these proteins decreased in abundance in tissues of MES-treated rapeseed plants, and only a few increased. Notably, some proteins were absent or induced in developing anthers after MES treatment. These proteins were involved in several processes that may be crucial for tapetum and microspore development. Down-regulation of these proteins may disrupt the coordination of developmental and metabolic processes, resulting in defective tapetum and abnormal microspores that lead to male sterility in MES-treated plants. Accordingly, a simple model of CHA-MES-induced male sterility in rapeseed was established. This study is the first cytological and dynamic proteomic investigation on CHA-MES-induced male sterility in rapeseed, and the results provide new insights into the molecular events of male sterility.
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Affiliation(s)
- Yufeng Cheng
- State Key Laboratory of Crop Stress Biology in Arid Areas, Northwest A&F University, Yangling, Shaanxi, P. R. China
- College of Life Sciences, Northwest A&F University, Yangling, Shaanxi, P. R. China
| | - Qian Wang
- State Key Laboratory of Crop Stress Biology in Arid Areas, Northwest A&F University, Yangling, Shaanxi, P. R. China
- College of Life Sciences, Northwest A&F University, Yangling, Shaanxi, P. R. China
| | - Zhanjie Li
- State Key Laboratory of Crop Stress Biology in Arid Areas, Northwest A&F University, Yangling, Shaanxi, P. R. China
- College of Life Sciences, Northwest A&F University, Yangling, Shaanxi, P. R. China
| | - Jianmin Cui
- State Key Laboratory of Crop Stress Biology in Arid Areas, Northwest A&F University, Yangling, Shaanxi, P. R. China
- College of Agronomy, Northwest A&F University, Yangling, Shaanxi, P. R. China
| | - Shengwu Hu
- State Key Laboratory of Crop Stress Biology in Arid Areas, Northwest A&F University, Yangling, Shaanxi, P. R. China
- College of Agronomy, Northwest A&F University, Yangling, Shaanxi, P. R. China
- * E-mail: (SH); (HZ)
| | - Huixian Zhao
- State Key Laboratory of Crop Stress Biology in Arid Areas, Northwest A&F University, Yangling, Shaanxi, P. R. China
- College of Life Sciences, Northwest A&F University, Yangling, Shaanxi, P. R. China
- * E-mail: (SH); (HZ)
| | - Mingshun Chen
- USDA-ARS and Department of Entomology, Kansas State University, Manhattan, Kansas, United States of America
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53
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Pihan GA. Centrosome dysfunction contributes to chromosome instability, chromoanagenesis, and genome reprograming in cancer. Front Oncol 2013; 3:277. [PMID: 24282781 PMCID: PMC3824400 DOI: 10.3389/fonc.2013.00277] [Citation(s) in RCA: 100] [Impact Index Per Article: 9.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/29/2013] [Accepted: 10/28/2013] [Indexed: 12/19/2022] Open
Abstract
The unique ability of centrosomes to nucleate and organize microtubules makes them unrivaled conductors of important interphase processes, such as intracellular payload traffic, cell polarity, cell locomotion, and organization of the immunologic synapse. But it is in mitosis that centrosomes loom large, for they orchestrate, with clockmaker's precision, the assembly and functioning of the mitotic spindle, ensuring the equal partitioning of the replicated genome into daughter cells. Centrosome dysfunction is inextricably linked to aneuploidy and chromosome instability, both hallmarks of cancer cells. Several aspects of centrosome function in normal and cancer cells have been molecularly characterized during the last two decades, greatly enhancing our mechanistic understanding of this tiny organelle. Whether centrosome defects alone can cause cancer, remains unanswered. Until recently, the aggregate of the evidence had suggested that centrosome dysfunction, by deregulating the fidelity of chromosome segregation, promotes and accelerates the characteristic Darwinian evolution of the cancer genome enabled by increased mutational load and/or decreased DNA repair. Very recent experimental work has shown that missegregated chromosomes resulting from centrosome dysfunction may experience extensive DNA damage, suggesting additional dimensions to the role of centrosomes in cancer. Centrosome dysfunction is particularly prevalent in tumors in which the genome has undergone extensive structural rearrangements and chromosome domain reshuffling. Ongoing gene reshuffling reprograms the genome for continuous growth, survival, and evasion of the immune system. Manipulation of molecular networks controlling centrosome function may soon become a viable target for specific therapeutic intervention in cancer, particularly since normal cells, which lack centrosome alterations, may be spared the toxicity of such therapies.
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Affiliation(s)
- German A Pihan
- Department of Pathology and Laboratory Medicine, Beth Israel Deaconess Medical Center, Harvard Medical School , Boston, MA , USA
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54
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Kumar S, Jordan MC, Datla R, Cloutier S. The LuWD40-1 gene encoding WD repeat protein regulates growth and pollen viability in flax (Linum Usitatissimum L.). PLoS One 2013; 8:e69124. [PMID: 23935935 PMCID: PMC3728291 DOI: 10.1371/journal.pone.0069124] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/11/2013] [Accepted: 06/11/2013] [Indexed: 01/22/2023] Open
Abstract
As a crop, flax holds significant commercial value for its omega-3 rich oilseeds and stem fibres. Canada is the largest producer of linseed but there exists scope for significant yield improvements. Implementation of mechanisms such as male sterility can permit the development of hybrids to assist in achieving this goal. Temperature sensitive male sterility has been reported in flax but the leakiness of this system in field conditions limits the production of quality hybrid seeds. Here, we characterized a 2,588 bp transcript differentially expressed in male sterile lines of flax. The twelve intron gene predicted to encode a 368 amino acid protein has five WD40 repeats which, in silico, form a propeller structure with putative nucleic acid and histone binding capabilities. The LuWD40-1 protein localized to the nucleus and its expression increased during the transition and continued through the vegetative stages (seed, etiolated seedling, stem) while the transcript levels declined during reproductive development (ovary, anthers) and embryonic morphogenesis of male fertile plants. Knockout lines for LuWD40-1 in flax failed to develop shoots while overexpression lines showed delayed growth phenotype and were male sterile. The non-viable flowers failed to open and the pollen grains from these flowers were empty. Three independent transgenic lines overexpressing the LuWD40-1 gene had ∼80% non-viable pollen, reduced branching, delayed flowering and maturity compared to male fertile genotypes. The present study provides new insights into a male sterility mechanism present in flax.
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Affiliation(s)
- Santosh Kumar
- Department of Plant Science, University of Manitoba, Winnipeg, Manitoba, Canada
- Cereal Research Centre, Agriculture and Agri-Food Canada, Winnipeg, Manitoba, Canada
| | - Mark C. Jordan
- Cereal Research Centre, Agriculture and Agri-Food Canada, Winnipeg, Manitoba, Canada
| | - Raju Datla
- National Research Council, Saskatoon, Saskatchewan, Canada
| | - Sylvie Cloutier
- Department of Plant Science, University of Manitoba, Winnipeg, Manitoba, Canada
- Cereal Research Centre, Agriculture and Agri-Food Canada, Winnipeg, Manitoba, Canada
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55
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Masoud K, Herzog E, Chabouté ME, Schmit AC. Microtubule nucleation and establishment of the mitotic spindle in vascular plant cells. THE PLANT JOURNAL : FOR CELL AND MOLECULAR BIOLOGY 2013; 75:245-257. [PMID: 23521421 DOI: 10.1111/tpj.12179] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/08/2012] [Revised: 02/25/2013] [Accepted: 03/12/2013] [Indexed: 06/01/2023]
Abstract
The microtubular cytoskeleton plays a major role in cellular organization and proliferation. The first step in construction of a microtubule is microtubule nucleation. Individual microtubules then participate in organization of more complex microtubule arrays. A strong body of evidence suggests that the underlying molecular mechanisms involve protein complexes that are conserved among eukaryotes. However, plant cell specificities, mainly characterized by the presence of a cell wall and the absence of centrosomes, must be taken into account to understand their mitotic processes. The goal of this review is to summarize and discuss current knowledge regarding the mechanisms involved in plant spindle assembly during early mitotic events. The functions of the proteins currently characterized at microtubule nucleation sites and involved in spindle assembly are considered during cell-cycle progression from G2 phase to metaphase.
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Affiliation(s)
- Kinda Masoud
- Institut de Biologie Moléculaire des Plantes, Laboratoire Propre du Centre National de la Recherche Scientifique (UPR 2357) Conventionné avec l'Université de Strasbourg, 12 rue du Général Zimmer, 67084 Strasbourg, France
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56
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Fishel EA, Dixit R. Role of nucleation in cortical microtubule array organization: variations on a theme. THE PLANT JOURNAL : FOR CELL AND MOLECULAR BIOLOGY 2013; 75:270-7. [PMID: 23464654 DOI: 10.1111/tpj.12166] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/06/2012] [Revised: 02/17/2013] [Accepted: 03/01/2013] [Indexed: 05/10/2023]
Abstract
The interphase cortical microtubules (CMTs) of plant cells form strikingly ordered arrays in the absence of a dedicated microtubule-organizing center. Considerable research effort has focused on activities such as bundling and severing that occur after CMT nucleation and are thought to be important for generating and maintaining ordered arrays. In this review, we focus on how nucleation affects CMT array organization. The bulk of CMTs are initiated from γ-tubulin-containing nucleation complexes localized to the lateral walls of pre-existing CMTs. These CMTs grow either at an acute angle or parallel to the pre-existing CMT. Although the impact of microtubule-dependent nucleation is not fully understood, recent genetic, live-cell imaging and computer simulation studies have demonstrated that the location, timing and geometry of CMT nucleation have a considerable impact on the organization and orientation of the CMT array. These nucleation properties are defined by the composition, position and dynamics of γ-tubulin-containing nucleation complexes, which represent control points for the cell to regulate CMT array organization.
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Affiliation(s)
- Erica A Fishel
- Biology Department, Washington University in St Louis, One Brookings Drive, CB 1137, St Louis, MO 63130, USA
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57
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McMichael CM, Bednarek SY. Cytoskeletal and membrane dynamics during higher plant cytokinesis. THE NEW PHYTOLOGIST 2013; 197:1039-1057. [PMID: 23343343 DOI: 10.1111/nph.12122] [Citation(s) in RCA: 65] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/07/2012] [Accepted: 12/02/2012] [Indexed: 05/08/2023]
Abstract
Following mitosis, cytoplasm, organelles and genetic material are partitioned into daughter cells through the process of cytokinesis. In somatic cells of higher plants, two cytoskeletal arrays, the preprophase band and the phragmoplast, facilitate the positioning and de novo assembly of the plant-specific cytokinetic organelle, the cell plate, which develops across the division plane and fuses with the parental plasma membrane to yield distinct new cells. The coordination of cytoskeletal and membrane dynamics required to initiate, assemble and shape the cell plate as it grows toward the mother cell cortex is dependent upon a large array of proteins, including molecular motors, membrane tethering, fusion and restructuring factors and biosynthetic, structural and regulatory elements. This review focuses on the temporal and molecular requirements of cytokinesis in somatic cells of higher plants gleaned from recent studies using cell biology, genetics, pharmacology and biochemistry.
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Affiliation(s)
- Colleen M McMichael
- Department of Biochemistry, University of Wisconsin-Madison, 433 Babcock Dr, Madison, WI, 53713, USA
| | - Sebastian Y Bednarek
- Department of Biochemistry, University of Wisconsin-Madison, 433 Babcock Dr, Madison, WI, 53713, USA
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58
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Remy MH, Merdes A, Gregory-Pauron L. Assembly of Gamma-Tubulin Ring Complexes. PROGRESS IN MOLECULAR BIOLOGY AND TRANSLATIONAL SCIENCE 2013; 117:511-30. [DOI: 10.1016/b978-0-12-386931-9.00019-2] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/17/2023]
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59
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Murata T, Sano T, Sasabe M, Nonaka S, Higashiyama T, Hasezawa S, Machida Y, Hasebe M. Mechanism of microtubule array expansion in the cytokinetic phragmoplast. Nat Commun 2013; 4:1967. [PMID: 23770826 PMCID: PMC3709505 DOI: 10.1038/ncomms2967] [Citation(s) in RCA: 79] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/08/2012] [Accepted: 05/02/2013] [Indexed: 12/18/2022] Open
Abstract
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.
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Affiliation(s)
- Takashi Murata
- Division of Evolutionary Biology, National Institute for Basic Biology, Okazaki 444-8585, Japan.
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60
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Nakamura M, Yagi N, Kato T, Fujita S, Kawashima N, Ehrhardt DW, Hashimoto T. Arabidopsis GCP3-interacting protein 1/MOZART 1 is an integral component of the γ-tubulin-containing microtubule nucleating complex. THE PLANT JOURNAL : FOR CELL AND MOLECULAR BIOLOGY 2012; 71:216-25. [PMID: 22404201 DOI: 10.1111/j.1365-313x.2012.04988.x] [Citation(s) in RCA: 59] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/08/2023]
Abstract
Microtubules in eukaryotic cells are nucleated from ring-shaped complexes that contain γ-tubulin and a family of homologous γ-tubulin complex proteins (GCPs), but the subunit composition of the complexes can vary among fungi, animals and plants. Arabidopsis GCP3-interacting protein 1 (GIP1), a small protein with no homology to the GCP family, interacts with GCP3 in vitro, and is a plant homolog of vertebrate mitotic-spindle organizing protein associated with a ring of γ-tubulin 1 (MOZART1), a recently identified component of the γ-tubulin complex in human cell lines. In this study, we characterized two closely related Arabidopsis GIP1s: GIP1a and GIP1b. Single mutants of gip1a and gip1b were indistinguishable from wild-type plants, but their double mutant was embryonic lethal, and showed impaired development of male gametophytes. Functional fusions of GIP1a with green fluorescent protein (GFP) were used to purify GIP1a-containing complexes from Arabidopsis plants, which contained all the subunits (except NEDD1) previously identified in the Arabidopsis γ-tubulin complexes. GIP1a and GIP1b interacted specifically with Arabidopsis GCP3 in yeast. GFP-GIP1a labeled mitotic microtubule arrays in a pattern largely consistent with, but partly distinct from, the localization of the γ-tubulin complex containing GCP2 or GCP3 in planta. In interphase cortical arrays, the labeled complexes were preferentially recruited to existing microtubules, from which new microtubules were efficiently nucleated. However, in contrast to complexes labeled with tagged GCP2 or GCP3, their recruitment to cortical areas with no microtubules was rarely observed. These results indicate that GIP1/MOZART1 is an integral component of a subset of the Arabidopsis γ-tubulin complexes.
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Affiliation(s)
- Masayoshi Nakamura
- Graduate School of Biological Sciences, Nara Institute of Science and Technology, Ikoma, Nara 630-0192, Japan
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61
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Ho CMK, Lee YRJ, Kiyama LD, Dinesh-Kumar SP, Liu B. 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 2012; 24:2071-85. [PMID: 22570443 PMCID: PMC3442588 DOI: 10.1105/tpc.111.092569] [Citation(s) in RCA: 49] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/10/2011] [Revised: 04/11/2012] [Accepted: 04/23/2012] [Indexed: 05/19/2023]
Abstract
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.
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Affiliation(s)
| | | | | | | | - Bo Liu
- Address correspondence to
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62
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Hotta T, Kong Z, Ho CMK, Zeng CJT, Horio T, Fong S, Vuong T, Lee YRJ, Liu B. Characterization of the Arabidopsis augmin complex uncovers its critical function in the assembly of the acentrosomal spindle and phragmoplast microtubule arrays. THE PLANT CELL 2012; 24:1494-509. [PMID: 22505726 PMCID: PMC3398559 DOI: 10.1105/tpc.112.096610] [Citation(s) in RCA: 49] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/06/2012] [Revised: 03/10/2012] [Accepted: 03/20/2012] [Indexed: 05/19/2023]
Abstract
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.
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Affiliation(s)
- Takashi Hotta
- Department of Plant Biology, University of California, Davis, California 95616
| | - Zhaosheng Kong
- Department of Plant Biology, University of California, Davis, California 95616
| | - Chin-Min Kimmy Ho
- Department of Plant Biology, University of California, Davis, California 95616
| | - Cui Jing Tracy Zeng
- Department of Plant Biology, University of California, Davis, California 95616
| | - Tetsuya Horio
- Department of Molecular Biosciences, University of Kansas, Lawrence, Kansas 66045
| | - Sophia Fong
- Department of Plant Biology, University of California, Davis, California 95616
| | - Trang Vuong
- Department of Plant Biology, University of California, Davis, California 95616
| | - Yuh-Ru Julie Lee
- Department of Plant Biology, University of California, Davis, California 95616
| | - Bo Liu
- Department of Plant Biology, University of California, Davis, California 95616
- Address correspondence to
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63
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Janski N, Masoud K, Batzenschlager M, Herzog E, Evrard JL, Houlné G, Bourge M, Chabouté ME, Schmit AC. The GCP3-interacting proteins GIP1 and GIP2 are required for γ-tubulin complex protein localization, spindle integrity, and chromosomal stability. THE PLANT CELL 2012; 24:1171-87. [PMID: 22427335 PMCID: PMC3336128 DOI: 10.1105/tpc.111.094904] [Citation(s) in RCA: 58] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/16/2011] [Revised: 02/03/2012] [Accepted: 02/27/2012] [Indexed: 05/18/2023]
Abstract
Microtubules (MTs) are crucial for both the establishment of cellular polarity and the progression of all mitotic phases leading to karyokinesis and cytokinesis. MT organization and spindle formation rely on the activity of γ-tubulin and associated proteins throughout the cell cycle. To date, the molecular mechanisms modulating γ-tubulin complex location remain largely unknown. In this work, two Arabidopsis thaliana proteins interacting with gamma-tubulin complex protein3 (GCP3), GCP3-interacting protein1 (GIP1) and GIP2, have been characterized. Both GIP genes are ubiquitously expressed in all tissues analyzed. Immunolocalization studies combined with the expression of GIP-green fluorescent protein fusions have shown that GIPs colocalize with γ-tubulin, GCP3, and/or GCP4 and reorganize from the nucleus to the prospindle and the preprophase band in late G2. After nuclear envelope breakdown, they localize on spindle and phragmoplast MTs and on the reforming nuclear envelope of daughter cells. The gip1 gip2 double mutants exhibit severe growth defects and sterility. At the cellular level, they are characterized by MT misorganization and abnormal spindle polarity, resulting in ploidy defects. Altogether, our data show that during mitosis GIPs play a role in γ-tubulin complex localization, spindle stability and chromosomal segregation.
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Affiliation(s)
- Natacha Janski
- Institut de Biologie Moléculaire des Plantes, Centre National de la Recherche Scientifique, Unité Propre de Recherche 2357, Conventionné avec l’Université de Strasbourg, 67084 Strasbourg, France
| | - Kinda Masoud
- Institut de Biologie Moléculaire des Plantes, Centre National de la Recherche Scientifique, Unité Propre de Recherche 2357, Conventionné avec l’Université de Strasbourg, 67084 Strasbourg, France
| | - Morgane Batzenschlager
- Institut de Biologie Moléculaire des Plantes, Centre National de la Recherche Scientifique, Unité Propre de Recherche 2357, Conventionné avec l’Université de Strasbourg, 67084 Strasbourg, France
| | - Etienne Herzog
- Institut de Biologie Moléculaire des Plantes, Centre National de la Recherche Scientifique, Unité Propre de Recherche 2357, Conventionné avec l’Université de Strasbourg, 67084 Strasbourg, France
| | - Jean-Luc Evrard
- Institut de Biologie Moléculaire des Plantes, Centre National de la Recherche Scientifique, Unité Propre de Recherche 2357, Conventionné avec l’Université de Strasbourg, 67084 Strasbourg, France
| | - Guy Houlné
- Institut de Biologie Moléculaire des Plantes, Centre National de la Recherche Scientifique, Unité Propre de Recherche 2357, Conventionné avec l’Université de Strasbourg, 67084 Strasbourg, France
| | - Mickael Bourge
- Laboratoire Dynamique de la Compartimentation Cellulaire, Institut des Sciences du Végétal, Centre National de la Recherche Scientifique, Unité Propre de Recherche 2355/Institut Fédératif de Recherche 87, Centre de Recherche de Gif (Fédération de Recherche du Centre National de la Recherche Scientifique 115), 91198 Gif-sur-Yvette cedex, France
| | - Marie-Edith Chabouté
- Institut de Biologie Moléculaire des Plantes, Centre National de la Recherche Scientifique, Unité Propre de Recherche 2357, Conventionné avec l’Université de Strasbourg, 67084 Strasbourg, France
| | - Anne-Catherine Schmit
- Institut de Biologie Moléculaire des Plantes, Centre National de la Recherche Scientifique, Unité Propre de Recherche 2357, Conventionné avec l’Université de Strasbourg, 67084 Strasbourg, France
- Address correspondence to
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64
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Kirik A, Ehrhardt DW, Kirik V. TONNEAU2/FASS regulates the geometry of microtubule nucleation and cortical array organization in interphase Arabidopsis cells. THE PLANT CELL 2012; 24:1158-70. [PMID: 22395485 PMCID: PMC3336111 DOI: 10.1105/tpc.111.094367] [Citation(s) in RCA: 53] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/01/2011] [Revised: 02/06/2012] [Accepted: 02/20/2012] [Indexed: 05/19/2023]
Abstract
Organization of microtubules into ordered arrays involves spatial and temporal regulation of microtubule nucleation. Here, we show that acentrosomal microtubule nucleation in plant cells involves a previously unknown regulatory step that determines the geometry of microtubule nucleation. Dynamic imaging of interphase cortical microtubules revealed that the ratio of branching to in-bundle microtubule nucleation on cortical microtubules is regulated by the Arabidopsis thaliana B'' subunit of protein phosphatase 2A, which is encoded by the TONNEAU2/FASS (TON2) gene. The probability of nucleation from γ-tubulin complexes localized at the cell cortex was not affected by a loss of TON2 function, suggesting a specific role of TON2 in regulating the nucleation geometry. Both loss of TON2 function and ectopic targeting of TON2 to the plasma membrane resulted in defects in cell shape, suggesting the importance of TON2-mediated regulation of the microtubule cytoskeleton in cell morphogenesis. Loss of TON2 function also resulted in an inability for cortical arrays to reorient in response to light stimulus, suggesting an essential role for TON2 and microtubule branching nucleation in reorganization of microtubule arrays. Our data establish TON2 as a regulator of interphase microtubule nucleation and provide experimental evidence for a novel regulatory step in the process of microtubule-dependent nucleation.
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Affiliation(s)
- Angela Kirik
- School of Biological Sciences, Illinois State University, Normal, Illinois 61790
| | - David W. Ehrhardt
- Department of Plant Biology, Carnegie Institution for Science, Stanford, California 94305
| | - Viktor Kirik
- School of Biological Sciences, Illinois State University, Normal, Illinois 61790
- Address correspondence to
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Sequence characterization and expression pattern of BcMF21, a novel gene related to pollen development in Brassica campestris ssp. chinensis. Mol Biol Rep 2012; 39:7319-26. [PMID: 22311045 DOI: 10.1007/s11033-012-1563-6] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/10/2011] [Accepted: 01/25/2012] [Indexed: 01/11/2023]
Abstract
In this report a full length cDNA, Brassica campestris Male Fertile 21 (BcMF21) was successfully isolated from one of the cDNA-amplified fragment length polymorphism (cDNA-AFLP) transcript-derived fragments (TDFs), BBP10, that was found down-regulated in the flower buds of sterile plants in Brassica campestris L. ssp. chinensis Makino genic male sterile (GMS) AB line system (Bcajh 97-01A/B). BcMF21 protein structure analysis showed a signal peptide at the N-terminus; two protein kinase C phosphorylation sites, five N-myristoylation sites and one casein kinase II phosphorylation site. The promoter region of BcMF21, a 779 bp upstream of ATG was isolated by thermal asymmetric interlaced-PCR (TAIL-PCR). Bioinformatics analysis revealed that the promoter of BcMF21 contained several classical cis-acting elements and three pollen specific elements. Transient expression analysis showed that the promoter could drive green fluorescence protein (GFP) expression. Quantitative reverse transcript-PCR analysis revealed that BcMF21 was specifically expressed in flower buds. The transcript level of BcMF21 was much lower in the sterile flower buds than in the fertile flower buds in 'Bcajh 97-01A/B' system. In situ hybridization further showed that BcMF21 was only expressed in the tetrads and the microspores at the tetrad stage and the uninucleate stage. In addition, phylogenetic analysis demonstrated that the BcMF21 was relative conserved within family Crucifereae and might be originated from the ancestor diploid B. campestris within genus Brassica according to the Triangle of U theory.
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66
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Teixidó-Travesa N, Roig J, Lüders J. The where, when and how of microtubule nucleation – one ring to rule them all. J Cell Sci 2012; 125:4445-56. [DOI: 10.1242/jcs.106971] [Citation(s) in RCA: 131] [Impact Index Per Article: 10.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
The function of microtubules depends on their arrangement into highly ordered arrays. Spatio-temporal control over the formation of new microtubules and regulation of their properties are central to the organization of these arrays. The nucleation of new microtubules requires γ-tubulin, an essential protein that assembles into multi-subunit complexes and is found in all eukaryotic organisms. However, the way in which γ-tubulin complexes are regulated and how this affects nucleation and, potentially, microtubule behavior, is poorly understood. γ-tubulin has been found in complexes of various sizes but several lines of evidence suggest that only large, ring-shaped complexes function as efficient microtubule nucleators. Human γ-tubulin ring complexes (γTuRCs) are composed of γ-tubulin and the γ-tubulin complex components (GCPs) 2, 3, 4, 5 and 6, which are members of a conserved protein family. Recent work has identified additional unrelated γTuRC subunits, as well as a large number of more transient γTuRC interactors. In this Commentary, we discuss the regulation of γTuRC-dependent microtubule nucleation as a key mechanism of microtubule organization. Specifically, we focus on the regulatory roles of the γTuRC subunits and interactors and present an overview of other mechanisms that regulate γTuRC-dependent microtubule nucleation and organization.
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67
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Drevensek S, Goussot M, Duroc Y, Christodoulidou A, Steyaert S, Schaefer E, Duvernois E, Grandjean O, Vantard M, Bouchez D, Pastuglia M. The Arabidopsis TRM1-TON1 interaction reveals a recruitment network common to plant cortical microtubule arrays and eukaryotic centrosomes. THE PLANT CELL 2012; 24:178-91. [PMID: 22286137 PMCID: PMC3289559 DOI: 10.1105/tpc.111.089748] [Citation(s) in RCA: 90] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/01/2011] [Revised: 11/29/2011] [Accepted: 01/03/2012] [Indexed: 05/19/2023]
Abstract
Land plant cells assemble microtubule arrays without a conspicuous microtubule organizing center like a centrosome. In Arabidopsis thaliana, the TONNEAU1 (TON1) proteins, which share similarity with FOP, a human centrosomal protein, are essential for microtubule organization at the cortex. We have identified a novel superfamily of 34 proteins conserved in land plants, the TON1 Recruiting Motif (TRM) proteins, which share six short conserved motifs, including a TON1-interacting motif present in all TRMs. An archetypal member of this family, TRM1, is a microtubule-associated protein that localizes to cortical microtubules and binds microtubules in vitro. Not all TRM proteins can bind microtubules, suggesting a diversity of functions for this family. In addition, we show that TRM1 interacts in vivo with TON1 and is able to target TON1 to cortical microtubules via its C-terminal TON1 interaction motif. Interestingly, three motifs of TRMs are found in CAP350, a human centrosomal protein interacting with FOP, and the C-terminal M2 motif of CAP350 is responsible for FOP recruitment at the centrosome. Moreover, we found that TON1 can interact with the human CAP350 M2 motif in yeast. Taken together, our results suggest conservation of eukaryotic centrosomal components in plant cells.
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Affiliation(s)
- Stéphanie Drevensek
- Institut Jean-Pierre Bourgin, Unité Mixte de Recherche 1318, Institut National de la Recherche Agronomique–AgroParisTech, Institut National de la Recherche Agronomique, Centre de Versailles, F-78000 Versailles, France
| | - Magali Goussot
- Institut Jean-Pierre Bourgin, Unité Mixte de Recherche 1318, Institut National de la Recherche Agronomique–AgroParisTech, Institut National de la Recherche Agronomique, Centre de Versailles, F-78000 Versailles, France
| | - Yann Duroc
- Institut Jean-Pierre Bourgin, Unité Mixte de Recherche 1318, Institut National de la Recherche Agronomique–AgroParisTech, Institut National de la Recherche Agronomique, Centre de Versailles, F-78000 Versailles, France
| | - Anna Christodoulidou
- Institut Jean-Pierre Bourgin, Unité Mixte de Recherche 1318, Institut National de la Recherche Agronomique–AgroParisTech, Institut National de la Recherche Agronomique, Centre de Versailles, F-78000 Versailles, France
| | - Sylvie Steyaert
- Institut Jean-Pierre Bourgin, Unité Mixte de Recherche 1318, Institut National de la Recherche Agronomique–AgroParisTech, Institut National de la Recherche Agronomique, Centre de Versailles, F-78000 Versailles, France
| | - Estelle Schaefer
- Institut Jean-Pierre Bourgin, Unité Mixte de Recherche 1318, Institut National de la Recherche Agronomique–AgroParisTech, Institut National de la Recherche Agronomique, Centre de Versailles, F-78000 Versailles, France
| | - Evelyne Duvernois
- Institut Jean-Pierre Bourgin, Unité Mixte de Recherche 1318, Institut National de la Recherche Agronomique–AgroParisTech, Institut National de la Recherche Agronomique, Centre de Versailles, F-78000 Versailles, France
| | - Olivier Grandjean
- Institut Jean-Pierre Bourgin, Unité Mixte de Recherche 1318, Institut National de la Recherche Agronomique–AgroParisTech, Institut National de la Recherche Agronomique, Centre de Versailles, F-78000 Versailles, France
| | - Marylin Vantard
- Institut de Recherches en Technologies et Sciences pour le Vivant, Commissariat à l’Energie Atomique/Centre National de la Recherche Scientifique/Institut National de la Recherche Agronomique/Université Joseph Fourier, 38054 Grenoble, France
| | - David Bouchez
- Institut Jean-Pierre Bourgin, Unité Mixte de Recherche 1318, Institut National de la Recherche Agronomique–AgroParisTech, Institut National de la Recherche Agronomique, Centre de Versailles, F-78000 Versailles, France
- Address correspondence to
| | - Martine Pastuglia
- Institut Jean-Pierre Bourgin, Unité Mixte de Recherche 1318, Institut National de la Recherche Agronomique–AgroParisTech, Institut National de la Recherche Agronomique, Centre de Versailles, F-78000 Versailles, France
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Banora MY, Rodiuc N, Baldacci-Cresp F, Smertenko A, Bleve-Zacheo T, Mellilo MT, Karimi M, Hilson P, Evrard JL, Favery B, Engler G, Abad P, de Almeida Engler J. Feeding cells induced by phytoparasitic nematodes require γ-tubulin ring complex for microtubule reorganization. PLoS Pathog 2011; 7:e1002343. [PMID: 22144887 PMCID: PMC3228788 DOI: 10.1371/journal.ppat.1002343] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2011] [Accepted: 09/15/2011] [Indexed: 01/05/2023] Open
Abstract
Reorganization of the microtubule network is important for the fast isodiametric expansion of giant-feeding cells induced by root-knot nematodes. The efficiency of microtubule reorganization depends on the nucleation of new microtubules, their elongation rate and activity of microtubule severing factors. New microtubules in plants are nucleated by cytoplasmic or microtubule-bound γ-tubulin ring complexes. Here we investigate the requirement of γ-tubulin complexes for giant feeding cells development using the interaction between Arabidopsis and Meloidogyne spp. as a model system. Immunocytochemical analyses demonstrate that γ-tubulin localizes to both cortical cytoplasm and mitotic microtubule arrays of the giant cells where it can associate with microtubules. The transcripts of two Arabidopsis γ-tubulin (TUBG1 and TUBG2) and two γ-tubulin complex proteins genes (GCP3 and GCP4) are upregulated in galls. Electron microscopy demonstrates association of GCP3 and γ-tubulin as part of a complex in the cytoplasm of giant cells. Knockout of either or both γ-tubulin genes results in the gene dose-dependent alteration of the morphology of feeding site and failure of nematode life cycle completion. We conclude that the γ-tubulin complex is essential for the control of microtubular network remodelling in the course of initiation and development of giant-feeding cells, and for the successful reproduction of nematodes in their plant hosts.
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Affiliation(s)
- Mohamed Youssef Banora
- Unité Mixte de Recherches Interactions Biotiques et Santé Végétale, INRA-CNRS-UNS, Sophia Antipolis, France
| | - Natalia Rodiuc
- Unité Mixte de Recherches Interactions Biotiques et Santé Végétale, INRA-CNRS-UNS, Sophia Antipolis, France
| | - Fabien Baldacci-Cresp
- Unité Mixte de Recherches Interactions Biotiques et Santé Végétale, INRA-CNRS-UNS, Sophia Antipolis, France
| | - Andrei Smertenko
- School of Biological and Biomedical Sciences, Durham University, Durham, United Kingdom
| | | | | | - Mansour Karimi
- Department of Plant Systems Biology, Flanders Institute for Biotechnology, Ghent, Belgium
| | - Pierre Hilson
- Department of Plant Systems Biology, Flanders Institute for Biotechnology, Ghent, Belgium
| | - Jean-Luc Evrard
- Institut de Biologie Moléculaire des Plantes, CNRS, Strasbourg, France
| | - Bruno Favery
- Unité Mixte de Recherches Interactions Biotiques et Santé Végétale, INRA-CNRS-UNS, Sophia Antipolis, France
| | - Gilbert Engler
- Unité Mixte de Recherches Interactions Biotiques et Santé Végétale, INRA-CNRS-UNS, Sophia Antipolis, France
| | - Pierre Abad
- Unité Mixte de Recherches Interactions Biotiques et Santé Végétale, INRA-CNRS-UNS, Sophia Antipolis, France
| | - Janice de Almeida Engler
- Unité Mixte de Recherches Interactions Biotiques et Santé Végétale, INRA-CNRS-UNS, Sophia Antipolis, France
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Smertenko AP, Piette B, Hussey PJ. The origin of phragmoplast asymmetry. Curr Biol 2011; 21:1924-30. [PMID: 22079114 DOI: 10.1016/j.cub.2011.10.012] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/11/2011] [Revised: 09/09/2011] [Accepted: 10/06/2011] [Indexed: 11/27/2022]
Abstract
The phragmoplast coordinates cytokinesis in plants [1]. It directs vesicles to the midzone, the site where they coalesce to form the new cell plate. Failure in phragmoplast function results in aborted or incomplete cytokinesis leading to embryo lethality, morphological defects, or multinucleate cells [2, 3]. The asymmetry of vesicular traffic is regulated by microtubules [1, 4, 5, 6], and the current model suggests that this asymmetry is established and maintained through treadmilling of parallel microtubules. However, we have analyzed the behavior of microtubules in the phragmoplast using live-cell imaging coupled with mathematical modeling and dynamic simulations and report that microtubules initiate randomly in the phragmoplast and that the majority exhibit dynamic instability with higher turnover rates nearer to the midzone. The directional transport of vesicles is possible because the majority of the microtubules polymerize toward the midzone. Here, we propose the first inclusive model where microtubule dynamics and phragmoplast asymmetry are consistent with the localization and activity of proteins known to regulate microtubule assembly and disassembly.
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Affiliation(s)
- Andrei P Smertenko
- School of Biological and Biomedical Sciences, Durham University, Durham DH1 3LE, UK
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Khan GA, Declerck M, Sorin C, Hartmann C, Crespi M, Lelandais-Brière C. MicroRNAs as regulators of root development and architecture. PLANT MOLECULAR BIOLOGY 2011; 77:47-58. [PMID: 21607657 DOI: 10.1007/s11103-011-9793-x] [Citation(s) in RCA: 79] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/28/2010] [Accepted: 05/09/2011] [Indexed: 05/18/2023]
Abstract
MicroRNAs (miRNAs) are post-transcriptional regulators of growth and development in both plants and animals. In plants, roots play essential roles in their anchorage to the soil as well as in nutrient and water uptake. In this review, we present recent advances made in the identification of miRNAs involved in embryonic root development, radial patterning, vascular tissue differentiation and formation of lateral organs (i.e., lateral and adventitious roots and symbiotic nitrogen-fixing nodules in legumes). Certain mi/siRNAs target members of the Auxin Response Factors family involved in auxin homeostasis and signalling and participate in complex regulatory loops at several crucial stages of root development. Other miRNAs target and restrict the action of various transcription factors that control root-related processes in several species. Finally, because abiotic stresses, which include nutrient or water deficiencies, generally modulate root growth and branching, we summarise the action of certain miRNAs in response to these stresses that may be involved in the adaptation of the root system architecture to the soil environment.
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Affiliation(s)
- Ghazanfar A Khan
- Institut des Sciences du Végétal, Centre National de la Recherche Scientifique (C.N.R.S.), 91198 Gif-sur-Yvette Cedex, France
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71
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Kimmy Ho CM, Hotta T, Kong Z, Tracy Zeng CJ, Sun J, Julie Lee YR, Liu B. Augmin plays a critical role in organizing the spindle and phragmoplast microtubule arrays in Arabidopsis. THE PLANT CELL 2011; 23:2606-18. [PMID: 21750235 PMCID: PMC3226208 DOI: 10.1105/tpc.111.086892] [Citation(s) in RCA: 45] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/28/2011] [Revised: 06/12/2011] [Accepted: 06/28/2011] [Indexed: 05/19/2023]
Abstract
In higher plant cells, microtubules (MTs) are nucleated and organized in a centrosome-independent manner. It is unclear whether augmin-dependent mechanisms underlie spindle MT organization in plant cells as they do in animal cells. When AUGMIN subunit3 (AUG3), which encodes a homolog of animal dim γ-tubulin 3/human augmin-like complex, subunit 3, was disrupted in Arabidopsis thaliana, gametogenesis frequently failed due to defects in cell division. Compared with the control microspores, which formed bipolar spindles at the cell periphery, the mutant cells often formed peripheral half spindles that only attached to condensed chromosomes or formed elongated spindles with unfocused interior poles. In addition, defective cells exhibited disorganized phragmoplast MT arrays, which caused aborted cytokinesis. The resulting pollen grains were either shrunken or contained two nuclei in an undivided cytoplasm. AUG3 was localized along MTs in the spindle and phragmoplast, and its signal was pronounced in anaphase spindle poles. An AUG3-green fluorescent protein fusion exhibited a dynamic distribution pattern, similar to that of the γ-tubulin complex protein2. When AUG3 was enriched from seedlings by affinity chromatography, AUG1 was detected by immunoblotting, suggesting an augmin-like complex was present in vivo. We conclude that augmin plays a critical role in MT organization during plant cell division.
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Affiliation(s)
- Chin-Min Kimmy Ho
- Department of Plant Biology, University of California, Davis, California 95616
| | - Takashi Hotta
- Department of Plant Biology, University of California, Davis, California 95616
| | - Zhaosheng Kong
- Department of Plant Biology, University of California, Davis, California 95616
| | - Cui Jing Tracy Zeng
- Department of Plant Biology, University of California, Davis, California 95616
| | - Jie Sun
- Department of Plant Biology, University of California, Davis, California 95616
- College of Agriculture, Shihezi University, Shihezi, Xinjiang 832003, China
| | - Yuh-Ru Julie Lee
- Department of Plant Biology, University of California, Davis, California 95616
| | - Bo Liu
- Department of Plant Biology, University of California, Davis, California 95616
- Address correspondence to
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Oh SA, Twell D, Park SK. SIDECAR POLLEN suggests a plant-specific regulatory network underlying asymmetric microspore division in Arabidopsis. PLANT SIGNALING & BEHAVIOR 2011; 6:416-9. [PMID: 21364317 PMCID: PMC3142426 DOI: 10.4161/psb.6.3.14385] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/05/2010] [Accepted: 12/06/2010] [Indexed: 05/19/2023]
Abstract
Asymmetric cell division is a universal strategy to generate diverse cell types necessary for patterning and proliferation of all eukaryotes. The development of haploid male gametophytes (pollen grains) in flowering plants is a remarkable example in which division asymmetry governs the functional specialization and germline differentiation essential for double fertilization. The male gametophyte is patterned via two mitotic divisions resulting in three highly differentiated daughter cells at maturity, a vegetative cell and two sperm cells. The first asymmetric division segregates a unique male germ cell from an undetermined haploid microspore and is executed in an elaborate sequence of cellular events. However the molecular mechanisms governing the division asymmetry in microspores are poorly understood. Recently we studied the phenotype of sidecar pollen (scp) mutants in detail, and demonstrated a requirement of SCP for both the correct timing and orientation of microspore division. SCP is a microspore-specific member of the LOB/AS2 domain family (LBD27/ASL29) showing that a plant-specific regulator plays a key role in oriented division of polarized microspores. Identification of SCP will serve as a new platform to further explore the largely unknown molecular networks regulating division asymmetry in microspores that establishes the male germline in flowering plants.
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Affiliation(s)
- Sung Aeong Oh
- Division of Plant Biosciences; Kyungpook National University; Daegu, South Korea
| | - David Twell
- Department of Biology; University of Leicester; Leicester, UK
| | - Soon Ki Park
- Division of Plant Biosciences; Kyungpook National University; Daegu, South Korea
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74
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Liu B, Ho CMK, Lee YRJ. Microtubule Reorganization during Mitosis and Cytokinesis: Lessons Learned from Developing Microgametophytes in Arabidopsis Thaliana. FRONTIERS IN PLANT SCIENCE 2011; 2:27. [PMID: 22639587 PMCID: PMC3355579 DOI: 10.3389/fpls.2011.00027] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/30/2011] [Accepted: 06/21/2011] [Indexed: 05/13/2023]
Abstract
In angiosperms, mitosis and cytokinesis take place in the absence of structurally defined microtubule-organizing centers and the underlying mechanisms are largely unknown. In the spindle and phragmoplast, microtubule reorganization depends on microtubule-interacting factors like the γ-tubulin complex. Because of their critical functions in cell division, loss-of-function mutations in the corresponding genes are often homozygous or sporophytic lethal. However, a number of mutations like gem1, gcp2, and nedd1 can be maintained in heterozygous mutants in Arabidopsis thaliana. When mutant microspores produced by a heterozygous parent undergo pollen mitosis I, they are amenable for phenotypic characterization by fluorescence microscopy. The results would allow us to pinpoint at specific functions of particular proteins in microtubule reorganization that are characteristic to specific stages of mitosis and cytokinesis. Conclusions made in the developing microgametophytes can be extrapolated to somatic cells regarding mechanisms that regulate nuclear migration, spindle pole formation, phragmoplast assembly, and cell division plane determination.
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Affiliation(s)
- Bo Liu
- Department of Plant Biology, University of CaliforniaDavis, CA, USA
- *Correspondence: Bo Liu, Department of Plant Biology, University of California, 1 Shields Avenue, Davis, CA 95616, USA. e-mail:
| | | | - Yuh-Ru Julie Lee
- Department of Plant Biology, University of CaliforniaDavis, CA, USA
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75
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Oh SA, Park KS, Twell D, Park SK. The SIDECAR POLLEN gene encodes a microspore-specific LOB/AS2 domain protein required for the correct timing and orientation of asymmetric cell division. THE PLANT JOURNAL : FOR CELL AND MOLECULAR BIOLOGY 2010; 64:839-50. [PMID: 21105930 DOI: 10.1111/j.1365-313x.2010.04374.x] [Citation(s) in RCA: 46] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/10/2023]
Abstract
Cellular patterning and differentiation in plants depend on the balance of asymmetric and symmetric divisions. Patterning of the male gametophyte (pollen grains) in flowering plants requires asymmetric division of the microspore followed by a symmetric division of the germ cell to produce three highly differentiated cells: a single vegetative cell and two sperm cells. In Arabidopsis sidecar pollen (scp) mutants a proportion of microspores first divide symmetrically, and then go on to produce 'four-celled' pollen with an extra vegetative cell; however, details of the timing and origin of phenotypic defects in scp and the identity of the SCP gene have remained obscure. Comparative analysis of the original hypomorphic scp-1 allele and a T-DNA-induced null allele, scp-2, revealed that in the absence of SCP, microspores undergo normal nuclear positioning, but show delayed entry into mitosis, increased cell expansion and alterations in the orientation of nuclear division. We identified the SCP gene to encode a male gametophyte-specific LATERAL ORGAN BOUNDARIES DOMAIN/ASYMMETRIC LEAVES 2-like (LBD/ASL) protein that is expressed in microspore nuclei in a tightly regulated phase-specific manner. Therefore, our study demonstrates that the correct patterning of male gametophyte depends on the activity of a nuclear LBD/ASL family protein that is essential for the correct timing and orientation of asymmetric microspore division.
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Affiliation(s)
- Sung Aeong Oh
- Division of Plant Biosciences, Kyungpook National University, Daegu 702-701, South Korea
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76
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Wu XH, Chen RC, Gao Y, Wu YD. The effect of Asp-His-Ser/Thr-Trp tetrad on the thermostability of WD40-repeat proteins. Biochemistry 2010; 49:10237-45. [PMID: 20939513 DOI: 10.1021/bi101321y] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Abstract
We recently found that Asp-His-Ser/Thr-Trp hydrogen-bonded tetrads are widely and uniquely present in the WD40-repeat proteins. WDR5 protein is a seven WD40-repeat propeller with five such tetrads. To explore the effect of the tetrad on the structure and stability of WD40-repeat proteins, the wild-type WDR5 and its seven mutants involving the substitutions of tetrad residues have been isolated. The crystal structures of the wild-type WDR5 and its three WDR5 mutants have been determined by X-ray diffraction method. The mutations of the tetrad residues are found not to change the basic structural features. The denaturing profiles of the wild type and the seven mutants with the use of denaturant guanidine hydrochloride have been studied by circular dichroism spectroscopy to determine the folding free energies of these proteins. The folding free energies of the wild type and the S62A, S146A, S188A, D192E, W330F, W330Y, and D324E mutants are measured to be about -11.6, -2.7, -3.1, -2.9, -3.6, -7.1, -7.0, and -7.5 kcal/mol, respectively. These suggest that (1) the hydrogen bonds in these hydrogen bond networks are unusually strong; (2) each hydrogen-bonded tetrad provides over 12 kcal/mol stability to the protein; thus, the removal of any single tetrad would cause unfolding of the protein; (3) since there are five tetrads, the protein must be in a highly unstable state without the tetrads, which might be related to its biological functions.
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Affiliation(s)
- Xian-Hui Wu
- School of Chemical Biology and Biotechnology, Laboratory of Chemical Genomics, Shenzhen Graduate School of Peking University, Shenzhen 518055, China
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Drader T, Kleinhofs A. A synteny map and disease resistance gene comparison between barley and the model monocot Brachypodium distachyon. Genome 2010; 53:406-17. [PMID: 20616871 DOI: 10.1139/g10-014] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
Grass species have coevolved with current economically important crop pathogens over millions of years. During this time, speciation of current domestic crops has occurred, resulting in related yet divergent genomes. Here, we present a synteny map between the crop species Hordeum vulgare and the recently sequenced Brachypodium distachyon genome, focusing on regions known to harbor important barley disease resistance genes. The resistance genes have orthologous genes in Brachypodium that show conservation of the form and likely the function of the genes. The level of colinearity between the genomes is highly dependent on the region of interest and, at the DNA level or protein level, the gene of interest. The stem rust resistance gene Rpg1 has an ortholog with a high level of identity at the amino acid level, while the stem rust resistance gene Rpg5 has two orthologs with a high level of identity, one corresponding to the NBS-LRR domain and the other to the serine/threonine protein kinase domain, on different contigs. Interestingly, the predicted product of the Brachypodium Rpg1 ortholog contained a WD40 domain at the C-terminal end. The stem rust resistance gene rpg4 (actin depolymerizing factor 2) also has an ortholog with a high level of identity, in which one of the three residues indicated by allele sequencing in barley cultivars to be important in disease resistance is conserved. The syntenous region of the seedling spot blotch resistance locus, Rcs5, has a high level of colinearity that may prove useful in efforts to identify and clone this gene. A synteny map and orthologous resistance gene comparisons are presented.
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Affiliation(s)
- Tom Drader
- School of Molecular Biosciences, Washington State University, Pullman, WA 99164-7520, USA.
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78
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Nakamura M, Ehrhardt DW, Hashimoto T. Microtubule and katanin-dependent dynamics of microtubule nucleation complexes in the acentrosomal Arabidopsis cortical array. Nat Cell Biol 2010; 12:1064-70. [DOI: 10.1038/ncb2110] [Citation(s) in RCA: 175] [Impact Index Per Article: 12.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2010] [Accepted: 09/09/2010] [Indexed: 12/21/2022]
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79
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Teixidó-Travesa N, Villén J, Lacasa C, Bertran MT, Archinti M, Gygi SP, Caelles C, Roig J, Lüders J. The gammaTuRC revisited: a comparative analysis of interphase and mitotic human gammaTuRC redefines the set of core components and identifies the novel subunit GCP8. Mol Biol Cell 2010; 21:3963-72. [PMID: 20861304 PMCID: PMC2982109 DOI: 10.1091/mbc.e10-05-0408] [Citation(s) in RCA: 81] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022] Open
Abstract
The γ-tubulin complex is a multi-subunit protein complex that nucleates microtubule polymerization. γ-Tubulin complexes are present in all eukaryotes, but size and subunit composition vary. In Drosophila, Xenopus, and humans large γ-tubulin ring complexes (γTuRCs) have been described, which have a characteristic open ring-shaped structure and are composed of a similar set of subunits, named γ-tubulin, GCPs 2-6, and GCP-WD in humans. Despite the identification of these proteins, γTuRC function and regulation remain poorly understood. Here we establish a new method for the purification of native human γTuRC. Using mass spectrometry of whole protein mixtures we compared the composition of γTuRCs from nonsynchronized and mitotic human cells. Based on our analysis we can define core subunits as well as more transient interactors such as the augmin complex, which associates specifically with mitotic γTuRCs. We also identified GCP8/MOZART2 as a novel core subunit that is present in both interphase and mitotic γTuRCs. GCP8 depletion does not affect γTuRC assembly but interferes with γTuRC recruitment and microtubule nucleation at interphase centrosomes without disrupting general centrosome structure. GCP8-depleted cells do not display any obvious mitotic defects, suggesting that GCP8 specifically affects the organization of the interphase microtubule network.
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Affiliation(s)
- Neus Teixidó-Travesa
- Cell and Developmental Biology Programme and Molecular Medicine Programme, Institute for Research in Biomedicine (IRB), Department of Biochemistry and Molecular Biology, Universitat de Barcelona, 08028 Barcelona, Spain
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80
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Abstract
The first haploid angiosperm, a dwarf form of cotton with half the normal chromosome complement, was discovered in 1920, and in the ninety years since then such plants have been identified in many other species. They can occur either spontaneously or can be induced by modified pollination methods in vivo, or by in vitro culture of immature male or female gametophytes. Haploids represent an immediate, one-stage route to homozygous diploids and thence to F(1) hybrid production. The commercial exploitation of heterosis in such F(1) hybrids leads to the development of hybrid seed companies and subsequently to the GM revolution in agriculture. This review describes the range of techniques available for the isolation or induction of haploids and discusses their value in a range of areas, from fundamental research on mutant isolation and transformation, through to applied aspects of quantitative genetics and plant breeding. It will also focus on how molecular methods have been used recently to explore some of the underlying aspects of this fascinating developmental phenomenon.
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Affiliation(s)
- Jim M Dunwell
- School of Biological Sciences, University of Reading, Whiteknights, Reading, UK.
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81
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Wu XH, Zhang H, Wu YD. Is Asp-His-Ser/Thr-Trp tetrad hydrogen-bond network important to WD40-repeat proteins: a statistical and theoretical study. Proteins 2010; 78:1186-94. [PMID: 19927323 DOI: 10.1002/prot.22638] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
WD40-repeat proteins are abundant and play important roles in forming protein complexes. The domain usually has seven WD40 repeats, which folds into a seven beta-sheet propeller with each beta-sheet in a four-strand structure. An analysis of 20 available WD40-repeat proteins in Protein Data Bank reveals that each protein has at least one Asp-His-Ser/Thr-Trp (D-H-S/T-W) hydrogen-bonded tetrad, and some proteins have up to six or seven such tetrads. The relative positions of the four residues in the tetrads are also found to be conserved. A sequence alignment analysis of 560 WD40-repeat protein sequences in human reveals very similar features, indicating that such tetrad may be a general feature of WD40-repeat proteins. We carried out density functional theory and found that these tetrads can lead to significant stabilization including hydrogen-bonding cooperativity. The hydrogen bond involving Trp is significant. These results lead us to propose that the tetrads may be critical to the stability and the mechanism of folding of these proteins.
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Affiliation(s)
- Xian-Hui Wu
- Laboratory of Chemical Genomics, Shenzhen Graduate School of Peking University, Shenzhen, China
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82
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Karlowski WM, Zielezinski A, Carrère J, Pontier D, Lagrange T, Cooke R. Genome-wide computational identification of WG/GW Argonaute-binding proteins in Arabidopsis. Nucleic Acids Res 2010; 38:4231-45. [PMID: 20338883 PMCID: PMC2910046 DOI: 10.1093/nar/gkq162] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
Domains in Arabidopsis proteins NRPE1 and SPT5-like, composed almost exclusively of repeated motifs in which only WG or GW sequences and an overall amino-acid preference are conserved, have been experimentally shown to bind multiple molecules of Argonaute (AGO) protein(s). Domain swapping between the WG/GW domains of NRPE1 and the human protein GW182 showed a conserved function. As classical sequence alignment methods are poorly-adapted to detect such weakly-conserved motifs, we have developed a tool to carry out a systematic analysis to identify genes potentially encoding AGO-binding GW/WG proteins. Here, we describe exhaustive analysis of the Arabidopsis genome for all regions potentially encoding proteins bearing WG/GW motifs and consider the possible role of some of them in AGO-dependent mechanisms. We identified 20 different candidate WG/GW genes, encoding proteins in which the predicted domains range from 92aa to 654aa. These mostly correspond to a limited number of families: RNA-binding proteins, transcription factors, glycine-rich proteins, translation initiation factors and known silencing-associated proteins such as SDE3. Recent studies have argued that the interaction between WG/GW-rich domains and AGO proteins is evolutionarily conserved. Here, we demonstrate by an in silico domain-swapping simulation between plant and mammalian WG/GW proteins that the biased amino-acid composition of the AGO-binding sites is conserved.
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Affiliation(s)
- Wojciech M Karlowski
- Bioinformatics Laboratory, Institute of Molecular Biology and Biotechnology, Adam Mickiewicz University, 61-614 Poznan, Poland.
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83
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Naya L, Khan GA, Sorin C, Hartmann C, Crespi M, Lelandais-Brière C. Cleavage of a non-conserved target by a specific miR156 isoform in root apexes of Medicago truncatula. PLANT SIGNALING & BEHAVIOR 2010; 5:328-31. [PMID: 20200496 PMCID: PMC2881292 DOI: 10.4161/psb.5.3.11190] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/12/2010] [Accepted: 01/12/2010] [Indexed: 05/24/2023]
Abstract
Micro RNAs (miRNAs) have emerged as an important class of gene expression regulators controlling development, growth and metabolism. These short RNA molecules are 20-24 nucleotides in length and act post-transcriptionally to regulate the cleavage or translation of specific mRNA targets. In the model legume Medicago truncatula, we have recently reported identification of 100 novel and 27 conserved miRNAs in root apexes and nodules. Statistical analysis on sequencing results revealed specific miRNA isoforms for the same family (up to 3 mismatches) showing contrasting expression patterns between these tissues. Here, we report the cleavage of a non-conserved target of miR156 in root apexes complementary to a differentially expressed miR156 isoform. This suggests that changes in the abundance of miRNA isoforms may have functional consequences on the post-transcriptional regulation of new mRNA targets in different organs.
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Affiliation(s)
- Loreto Naya
- Institut des Sciences du Végétal; Centre National de la Recherche Scientifique; Gif-sur-Yvette, France
| | - Ghazanfar Abbas Khan
- Institut des Sciences du Végétal; Centre National de la Recherche Scientifique; Gif-sur-Yvette, France
| | - Céline Sorin
- Institut des Sciences du Végétal; Centre National de la Recherche Scientifique; Gif-sur-Yvette, France
- Université Paris Diderot-Paris 7; Paris, France
| | - Caroline Hartmann
- Institut des Sciences du Végétal; Centre National de la Recherche Scientifique; Gif-sur-Yvette, France
- Université Paris Diderot-Paris 7; Paris, France
| | - Martin Crespi
- Institut des Sciences du Végétal; Centre National de la Recherche Scientifique; Gif-sur-Yvette, France
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84
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Manning JA, Lewis M, Koblar SA, Kumar S. An essential function for the centrosomal protein NEDD1 in zebrafish development. Cell Death Differ 2010; 17:1302-14. [PMID: 20150915 DOI: 10.1038/cdd.2010.12] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
The centrosome is the primary microtubule organising centre of the cell. It is composed of many proteins, some of which make up the core of the centrosome, whereas others are used for specific functions. Although the cellular roles of many centrosomal proteins are well defined, much less is known about their functions and the role of the centrosome in development. In this study we investigated the function of NEDD1, a critical component of the centrosome essential for microtubule nucleation, in zebrafish (Danio rerio) development. The zebrafish homologue of NEDD1 (zNEDD1) was cloned and found to have a similar localisation and function to mammalian NEDD1. We show that zNEDD1 is essential for survival, as a high level of knockdown was embryonic lethal. Partial knockdown of zNEDD1 caused abnormalities including an increase in mitotic and apoptotic cells. Pronounced phenotypic defects were seen in the brain, with a lack of defined brain structures, incomplete neural tube formation and a disorganisation of neurons. In addition, we show that a reduction in zNEDD1 resulted in the loss of gamma-tubulin at the centrosome. Our data thus demonstrate that zNEDD1 is critical for the recruitment of gamma-tubulin to the centrosome, and is essential for the proper development of zebrafish.
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Affiliation(s)
- J A Manning
- Department of Haematology, Centre for Cancer Biology, SA Pathology, Frome Rd, Adelaide, SA 5000, Australia
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85
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Ma W, Baumann C, Viveiros MM. NEDD1 is crucial for meiotic spindle stability and accurate chromosome segregation in mammalian oocytes. Dev Biol 2010; 339:439-50. [PMID: 20079731 DOI: 10.1016/j.ydbio.2010.01.009] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2009] [Revised: 01/04/2010] [Accepted: 01/05/2010] [Indexed: 10/20/2022]
Abstract
Defects in meiotic spindle structure contribute to chromosome segregation errors leading to genomic instability in oocytes and embryos upon fertilization. In this study, we analyzed the mechanisms that control spindle microtubule nucleation and stability in mammalian oocytes, and identified NEDD1/GCP-WD as a key regulator. NEDD1 specifically co-localizes with gamma-tubulin and pericentrin at microtubule-organizing centers (MTOCs) in mouse oocytes arrested at prophase-I. During metaphase-I and metaphase-II, the protein remains associated with MTOCs, in a pericentrin dependent manner. Notably, knockdown of Nedd1 transcripts using specific siRNAs resulted in a high incidence (65-70%) of metaphase-I arrest. The arrested oocytes were characterized by disrupted meiotic spindle structure, reduced microtubule density and significant chromosome misalignment. Detection of MAD2 at kinetochores indicated an absence of stable chromosome-microtubule attachment as well as activation of the spindle assembly checkpoint (SAC). Importantly, the disruption of meiotic spindle stability was associated with decreased gamma-tubulin at MTOCs in NEDD1-depleted oocytes, as well as a high frequency of chromosome non-disjunction errors leading to aneuploidy (50%) in the oocytes that did progress to metaphase-II. This study demonstrates that NEDD1 is an essential component of acentriolar oocyte MTOCs, which functions in the regulation of meiotic spindle stability. Moreover, it underscores that disruption of spindle stability in oocytes can lead to chromosomes segregation errors that are not fully resolved by SAC.
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Affiliation(s)
- Wei Ma
- Department of Animal Biology, Center for Animal Transgenesis and Germ Cell Research, School of Veterinary Medicine, University of Pennsylvania, PA 19384, USA
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86
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Buschmann H, Sambade A, Pesquet E, Calder G, Lloyd CW. Microtubule dynamics in plant cells. Methods Cell Biol 2010; 97:373-400. [PMID: 20719281 DOI: 10.1016/s0091-679x(10)97020-9] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023]
Abstract
This chapter describes some of the choices and unavoidable compromises to be made when studying microtubule dynamics in plant cells. The choice of species still depends very much on the ability to produce transgenic plants and most work has been done in the relatively small cells of Arabidopsis plants or in tobacco BY-2 suspension cells. Fluorescence-tagged microtubule proteins have been used to label entire microtubules, or their plus ends, but there are still few minus-end markers for these acentrosomal cells. Pragmatic decisions have to be made about probes, balancing the efficacy of microtubule labeling against a tendency to overstabilize and bundle the microtubules and even induce helical plant growth. A key limitation in visualizing plant microtubules is the ability to keep plants alive for long periods under the microscope and we describe a biochamber that allows for plant cell growth and development while allowing gas exchange and reducing evaporation. Another major difficulty is the limited fluorescence lifetime and we describe imaging strategies to reduce photobleaching in long-term imaging. We also discuss methods of measuring microtubule dynamics, with emphasis on the behavior of plant-specific microtubule arrays.
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Affiliation(s)
- Henrik Buschmann
- Department of Cell and Developmental Biology, John Innes Centre, Norwich NR47UH, United Kingdom
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87
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Kong Z, Hotta T, Lee YRJ, Horio T, Liu B. The {gamma}-tubulin complex protein GCP4 is required for organizing functional microtubule arrays in Arabidopsis thaliana. THE PLANT CELL 2010; 22:191-204. [PMID: 20118227 PMCID: PMC2828712 DOI: 10.1105/tpc.109.071191] [Citation(s) in RCA: 45] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/05/2009] [Revised: 12/19/2009] [Accepted: 01/13/2010] [Indexed: 05/18/2023]
Abstract
Microtubule (MT) nucleation and organization depend on the evolutionarily conserved protein gamma -tubulin, which forms a complex with GCP2-GCP6 (GCP for gamma -Tubulin Complex Protein). To date, it is still unclear how GCP4-GCP6 (the non-core GCPs) may be involved in acentrosomal MT nucleation in plant cells. We found that GCP4 was associated with gamma -tubulin in vivo in Arabidopsis thaliana. When GCP4 expression was repressed by an artificial microRNA, transgenic plants exhibited phenotypes of dwarfism and reduced organ size. In mitotic cells, it was observed that the gamma -tubulin signal associated with the mitotic spindle, and the phragmoplast was depleted when GCP4 was downregulated. Consequently, MTs failed to converge at unified spindle poles, and the bipolar phragmoplast MT array frequently had discrete bundles with extended minus ends, resulting in failed cytokinesis as reflected by cell wall stubs in leaf epidermal cells. In addition, cortical MTs in swollen guard cells and pavement cells of the leaf epidermis became hyperparallel and bundled, which was likely caused by frequent MT nucleation with shallow angles on the wall of extant MTs. Therefore, our results support the notion that GCP4 is an indispensable component for the function of gamma -tubulin in MT nucleation and organization in plant cells.
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Affiliation(s)
- Zhaosheng Kong
- Department of Plant Biology, University of California, Davis, California 95616
| | - Takashi Hotta
- Department of Plant Biology, University of California, Davis, California 95616
| | - Yuh-Ru Julie Lee
- Department of Plant Biology, University of California, Davis, California 95616
| | - Tetsuya Horio
- Department of Molecular Biosciences, University of Kansas, Lawrence, Kansas 66045
| | - Bo Liu
- Department of Plant Biology, University of California, Davis, California 95616
- Address correspondence to
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88
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Farquharson KL. On the origin of cortical microtubules. THE PLANT CELL 2009; 21:2193. [PMID: 19706793 PMCID: PMC2751960 DOI: 10.1105/tpc.109.210812] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/28/2023]
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89
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Chan J, Sambade A, Calder G, Lloyd C. Arabidopsis cortical microtubules are initiated along, as well as branching from, existing microtubules. THE PLANT CELL 2009; 21:2298-306. [PMID: 19706794 PMCID: PMC2751946 DOI: 10.1105/tpc.109.069716] [Citation(s) in RCA: 66] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/30/2009] [Revised: 08/05/2009] [Accepted: 08/13/2009] [Indexed: 05/18/2023]
Abstract
The principles by which cortical microtubules self-organize into a global template hold important implications for cell wall patterning. Microtubules move along bundles of microtubules, and neighboring bundles tend to form mobile domains that flow in a common direction. The bundles themselves move slowly and for longer than the individual microtubules, with domains describing slow rotary patterns. Despite this tendency for colinearity, microtubules have been seen to branch off extant microtubules at approximately 45 degrees . To examine this paradoxical behavior, we investigated whether some microtubules may be born on and grow along extant microtubule(s). The plus-end markers Arabidopsis thaliana end binding protein 1a, AtEB1a-GFP, and Arabidopsis SPIRAL1, SPR1-GFP, allowed microtubules of known polarity to be distinguished from underlying microtubules. This showed that the majority of microtubules do branch but in a direction heavily biased toward the plus end of the mother microtubule: few grow backward, consistent with the common polarity of domains. However, we also found that a significant proportion of emergent comets do follow the axes of extant microtubules, both at sites of apparent microtubule nucleation and at cross-over points. These phenomena help explain the persistence of bundles and counterbalance the tendency to branch.
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Affiliation(s)
- Jordi Chan
- Department of Cell and Developmental Biology, John Ines Centre, Colney, Norwich, NR4 7UH, United Kingdom.
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