Cytokinesis, the partitioning of the cytoplasm following nuclear division, requires extensive coordination between membrane trafficking and cytoskeletal dynamics. In plants, the onset of cytokinesis is characterized b...Cytokinesis, the partitioning of the cytoplasm following nuclear division, requires extensive coordination between membrane trafficking and cytoskeletal dynamics. In plants, the onset of cytokinesis is characterized by the assembly of a bipolar microtubule array, the phragmoplast, and of a transient membrane compartment, the cell plate. Little is known about the coordination between membrane deposition at the cell plate and the dynamics of phragmoplast microtubules. In this study, we monitor the localization dynamics of microtubule and membrane markers throughout cytokinesis. Our spatiotemporal resolution is consistent with the general view that microtubule dynamics drive membrane movements. Nonetheless, we provide evidence for active sorting at the cell plate and show that this is, at least in part, mediated by the TRAPPII tethering complex. We also characterize phragmoplast microtubule organization and cell plate formation in a suite of cytokinesis-defective mutants. Of four mutant lines with defects in phragmoplast microtubule organization, only morl microtubule-associated mutants exhibited aberrant cell plates. Conversely, the mutants with the strongest impairment in phragmoplast microtubule reorganization are keule alleles, which have a primary defect in membrane fusion. Our findings identify the SEC1/Munc18 protein KEULE as a central regulatory node in the coordination of membrane and microtubule dynamics during plant cytokinesis.展开更多
The phragmoplast,a structure crucial for the completion of cytokinesis in plant cells,is composed of antiparallel microtubules(MTs)and actin filaments(AFs).However,how the parallel structure of phragmoplast MTs and AF...The phragmoplast,a structure crucial for the completion of cytokinesis in plant cells,is composed of antiparallel microtubules(MTs)and actin filaments(AFs).However,how the parallel structure of phragmoplast MTs and AFs is maintained,especially during centrifugal phragmoplast expansion,remains elusive.Here,we analyzed a new Arabidopsis thaliana MT and AF crosslinking protein(AtMAC).When AtMAC was deleted,the phragmoplast showed disintegrity during centrifugal expansion,and the resulting phragmoplast fragmentation led to incomplete cell plates.Overexpression of AtMAC increased the resistance of phragmoplasts to depolymerization and caused the formation of additional phragmoplasts during cytokinesis.Biochemical experiments showed that AtMAC crosslinked MTs and AFs in vitro,and the truncated AtMAC protein,N-CC1,was the key domain controlling the ability of AtMAC.Further analysis showed that N-CC1(51–154)is the key domain for binding MTs,and N-CC1(51–125)for binding AFs.In conclusion,AtMAC is the novel MT and AF crosslinking protein found to be involved in regulation of phragmoplast organization during centrifugal phragmoplast expansion,which is required for complete cytokinesis.展开更多
The phragmoplast is a special apparatus that functions in establishing a cell plate in dividing plant cells. It is known that microfilaments (MFs) are involved in constituting phragmoplast structure, but the dynamic d...The phragmoplast is a special apparatus that functions in establishing a cell plate in dividing plant cells. It is known that microfilaments (MFs) are involved in constituting phragmoplast structure, but the dynamic distribution and role of phragmoplast MFs are far from being understood. In this study, the precise structure and dynamics of MFs during the initiation and the late lateral expansion of the phragmoplast were observed by using a tobacco BY-2 cell line stably expressing the microfilament reporter construct GFP-fABD2. Three-dimensional imaging showed that the phragmoplast MFs were initiated by two populations of MFs emerging between the reconstituting daughter nuclei at anaphase, which migrated to the mid-zone and gave rise to two layers of microfilament arrays. FM4-64 stained vesicles accumulated and fused with the cell plate between the two populations of MFs. The two layers of microfilament arrays of phragmoplast with ends overlapped always surrounded the centrifugally expanding cell plate. Partial disruption of MFs at metaphase by low concentration of latrunculin B resulted in the inhibition of the cell plate consolidation and the blockage of cell plate lateral expansion, whereas high concentration of latrunculin B restrained the progression of the cell cycle. Treating the cell after the initiation of phragmoplast led to the cease of the expansion of the cell plate. Our observations provide new insights into the precise structure and dynamics of phragmoplast MFs during cytokinesis and suggest that dynamic phragmoplast MFs are important in cell plate formation.展开更多
Charophytic algae and land plants together make up a monophyletic group, streptophytes, which represents one of the main lineages of multicellular eukaryotes and has contributed greatly to the change of the environmen...Charophytic algae and land plants together make up a monophyletic group, streptophytes, which represents one of the main lineages of multicellular eukaryotes and has contributed greatly to the change of the environment on earth in the Phanerozoic Eon. Significant progress has been made to understand phylogenetic relationships among members of this group by phylogenetic studies of morphological and molecular data over the last twenty-five years. Mesostigma viride is now regarded as among the earliest diverging unicellular organisms in streptophytes. Characeae are the sister group to land plants. Liverworts represent the first diverging lineage of land plants. Hornworts and lycophytes are extant representatives of bryophytes and vascular plants, respectively, when early land plants changed from gametophyte to sporophyte as the dominant generation in the life cycle. Equisetum, Psilotaceae, and ferns constitute the monophyletic group of monilophytes, which are sister to seed plants. Gnetales are related to conifers, not to angiosperms as previously thought. Amborella, Nymphaeales, Hydatellaceae, Illiciales, Trimeniaceae, and Austrobaileya represent the earliest diverging lineages of extant angiosperms. These phylogenetic results, together with recent progress on elucidating genetic and developmental aspects of the plant life cycle, multicellularity, and gravitropism, will facilitate evolutionary developmental studies of these key traits, which will help us to gain mechanistic understanding on how plants adapted to environmental challenges when they colonized the land during one of the major transitions in evolution of life.展开更多
The detyrosination/retyrosination cycle is the most common post-translational modification of α-tubulin.Removal of the conserved C-terminal tyrosine of α-tubulin by a still elusive tubulin tyrosine carboxypeptidase,...The detyrosination/retyrosination cycle is the most common post-translational modification of α-tubulin.Removal of the conserved C-terminal tyrosine of α-tubulin by a still elusive tubulin tyrosine carboxypeptidase, and religation of this tyrosine by a tubulin tyrosine ligase(TTL), are probably common to all eukaryotes. Interestingly, for plants, the only candidates qualifying as potential TTL homologs are the tubulin tyrosine ligase-like 12 proteins. To get insight into the biological functions of these potential TTL homologs, we cloned the rice TTL-like 12 protein(Os TTLL12)andgeneratedoverexpression Os TTLL12-RFP lines in both rice and tobacco BY-2 cells. We found, unexpectedly, that overexpression of this Os TTLL12-RFP increased the relative abundance of detyrosinated α-tubulin in both coleoptile and seminal root, correlated with more stable microtubules. This was independent of the respective orientation of cortical microtubule, and followed by correspondingly changing growth of coleoptiles and seminal roots. A perturbed organization of phragmoplast microtubules and disoriented cell walls were further characteristics of this phenotype. Thus, the elevated tubulin detyrosination in consequence of Os TTLL12 overexpression affects structural and dynamic features of microtubules, followed by changes in the axiality of cell plate deposition and, consequently, plant growth.展开更多
In eukaryotic cells, the course of the cell cycle depends on correct cytoskeleton arrangement. The cell cycle consists of several phases, and in each of them the cytoskeleton has a unique structure and set of characte...In eukaryotic cells, the course of the cell cycle depends on correct cytoskeleton arrangement. The cell cycle consists of several phases, and in each of them the cytoskeleton has a unique structure and set of characteristics. The dynamics of the cytoskeleton together with its binding proteins greatly contribute to progression of the cell cycle. Here, we mainly review recent research on the dynamic distribution of the actin cytoskeleton and actin-binding proteins, and the mechanisms by which they affect the progression of the plant cell cycle.展开更多
文摘Cytokinesis, the partitioning of the cytoplasm following nuclear division, requires extensive coordination between membrane trafficking and cytoskeletal dynamics. In plants, the onset of cytokinesis is characterized by the assembly of a bipolar microtubule array, the phragmoplast, and of a transient membrane compartment, the cell plate. Little is known about the coordination between membrane deposition at the cell plate and the dynamics of phragmoplast microtubules. In this study, we monitor the localization dynamics of microtubule and membrane markers throughout cytokinesis. Our spatiotemporal resolution is consistent with the general view that microtubule dynamics drive membrane movements. Nonetheless, we provide evidence for active sorting at the cell plate and show that this is, at least in part, mediated by the TRAPPII tethering complex. We also characterize phragmoplast microtubule organization and cell plate formation in a suite of cytokinesis-defective mutants. Of four mutant lines with defects in phragmoplast microtubule organization, only morl microtubule-associated mutants exhibited aberrant cell plates. Conversely, the mutants with the strongest impairment in phragmoplast microtubule reorganization are keule alleles, which have a primary defect in membrane fusion. Our findings identify the SEC1/Munc18 protein KEULE as a central regulatory node in the coordination of membrane and microtubule dynamics during plant cytokinesis.
基金supported by grants from the National Natural Science Foundation of China(92254303 and 32170335)to Haiyun Ren and(32200272)to Pingzhou Duthe start-up fund of Beijing Normal University at Zhuhai(310432102)to Pingzhou Du。
文摘The phragmoplast,a structure crucial for the completion of cytokinesis in plant cells,is composed of antiparallel microtubules(MTs)and actin filaments(AFs).However,how the parallel structure of phragmoplast MTs and AFs is maintained,especially during centrifugal phragmoplast expansion,remains elusive.Here,we analyzed a new Arabidopsis thaliana MT and AF crosslinking protein(AtMAC).When AtMAC was deleted,the phragmoplast showed disintegrity during centrifugal expansion,and the resulting phragmoplast fragmentation led to incomplete cell plates.Overexpression of AtMAC increased the resistance of phragmoplasts to depolymerization and caused the formation of additional phragmoplasts during cytokinesis.Biochemical experiments showed that AtMAC crosslinked MTs and AFs in vitro,and the truncated AtMAC protein,N-CC1,was the key domain controlling the ability of AtMAC.Further analysis showed that N-CC1(51–154)is the key domain for binding MTs,and N-CC1(51–125)for binding AFs.In conclusion,AtMAC is the novel MT and AF crosslinking protein found to be involved in regulation of phragmoplast organization during centrifugal phragmoplast expansion,which is required for complete cytokinesis.
基金Supported by National Natural Science Foundation of China(Grant Nos.30630005,30470176)National Key Basic Research and Development Program of China(Grant Nos.2006CB100100,2007CB108700)
文摘The phragmoplast is a special apparatus that functions in establishing a cell plate in dividing plant cells. It is known that microfilaments (MFs) are involved in constituting phragmoplast structure, but the dynamic distribution and role of phragmoplast MFs are far from being understood. In this study, the precise structure and dynamics of MFs during the initiation and the late lateral expansion of the phragmoplast were observed by using a tobacco BY-2 cell line stably expressing the microfilament reporter construct GFP-fABD2. Three-dimensional imaging showed that the phragmoplast MFs were initiated by two populations of MFs emerging between the reconstituting daughter nuclei at anaphase, which migrated to the mid-zone and gave rise to two layers of microfilament arrays. FM4-64 stained vesicles accumulated and fused with the cell plate between the two populations of MFs. The two layers of microfilament arrays of phragmoplast with ends overlapped always surrounded the centrifugally expanding cell plate. Partial disruption of MFs at metaphase by low concentration of latrunculin B resulted in the inhibition of the cell plate consolidation and the blockage of cell plate lateral expansion, whereas high concentration of latrunculin B restrained the progression of the cell cycle. Treating the cell after the initiation of phragmoplast led to the cease of the expansion of the cell plate. Our observations provide new insights into the precise structure and dynamics of phragmoplast MFs during cytokinesis and suggest that dynamic phragmoplast MFs are important in cell plate formation.
基金supported by the National Natural Science Foundation of China(31570246 and 32170279)the Fundamental Research Funds for the Central Universities(2572019CT03)。
文摘Charophytic algae and land plants together make up a monophyletic group, streptophytes, which represents one of the main lineages of multicellular eukaryotes and has contributed greatly to the change of the environment on earth in the Phanerozoic Eon. Significant progress has been made to understand phylogenetic relationships among members of this group by phylogenetic studies of morphological and molecular data over the last twenty-five years. Mesostigma viride is now regarded as among the earliest diverging unicellular organisms in streptophytes. Characeae are the sister group to land plants. Liverworts represent the first diverging lineage of land plants. Hornworts and lycophytes are extant representatives of bryophytes and vascular plants, respectively, when early land plants changed from gametophyte to sporophyte as the dominant generation in the life cycle. Equisetum, Psilotaceae, and ferns constitute the monophyletic group of monilophytes, which are sister to seed plants. Gnetales are related to conifers, not to angiosperms as previously thought. Amborella, Nymphaeales, Hydatellaceae, Illiciales, Trimeniaceae, and Austrobaileya represent the earliest diverging lineages of extant angiosperms. These phylogenetic results, together with recent progress on elucidating genetic and developmental aspects of the plant life cycle, multicellularity, and gravitropism, will facilitate evolutionary developmental studies of these key traits, which will help us to gain mechanistic understanding on how plants adapted to environmental challenges when they colonized the land during one of the major transitions in evolution of life.
基金This work was supported by a fellowship from the the Chinese Scholarship Council to Kunxi ZhangOpen access funding enabled and organized by Projekt DEAL。
文摘The detyrosination/retyrosination cycle is the most common post-translational modification of α-tubulin.Removal of the conserved C-terminal tyrosine of α-tubulin by a still elusive tubulin tyrosine carboxypeptidase, and religation of this tyrosine by a tubulin tyrosine ligase(TTL), are probably common to all eukaryotes. Interestingly, for plants, the only candidates qualifying as potential TTL homologs are the tubulin tyrosine ligase-like 12 proteins. To get insight into the biological functions of these potential TTL homologs, we cloned the rice TTL-like 12 protein(Os TTLL12)andgeneratedoverexpression Os TTLL12-RFP lines in both rice and tobacco BY-2 cells. We found, unexpectedly, that overexpression of this Os TTLL12-RFP increased the relative abundance of detyrosinated α-tubulin in both coleoptile and seminal root, correlated with more stable microtubules. This was independent of the respective orientation of cortical microtubule, and followed by correspondingly changing growth of coleoptiles and seminal roots. A perturbed organization of phragmoplast microtubules and disoriented cell walls were further characteristics of this phenotype. Thus, the elevated tubulin detyrosination in consequence of Os TTLL12 overexpression affects structural and dynamic features of microtubules, followed by changes in the axiality of cell plate deposition and, consequently, plant growth.
基金supported by the National Natural Science Foundation of China (30870211, 30970174)the National Basic Research Program of China (2007CB108700)the Chinese Transgenic Project (2009ZX08009-059B) to H. Ren
文摘In eukaryotic cells, the course of the cell cycle depends on correct cytoskeleton arrangement. The cell cycle consists of several phases, and in each of them the cytoskeleton has a unique structure and set of characteristics. The dynamics of the cytoskeleton together with its binding proteins greatly contribute to progression of the cell cycle. Here, we mainly review recent research on the dynamic distribution of the actin cytoskeleton and actin-binding proteins, and the mechanisms by which they affect the progression of the plant cell cycle.
