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1.
Kunitoshi Yamanaka Teru Ogura Kazuyoshi Murata Toshinobu Suzaki Hironori Niki Sota Hiraga 《FEMS microbiology letters》1994,116(1):61-66
Abstract The smbA gene of Escherichia coli is essential for cell proliferation. The smbA2 mutant shows cold-sensitive colony formation at 22°C. A novel morphological phenotype, formation of a translucent segment at midcell or at a cell pole, was observed by phase-contrastt microscopy at a high frequency in the smbA2 mutant cells incubated in L medium lacking NaCl at 22°C, but not observed in L medium containing 1% NaCl or 20% sucrose at the same temperature. No translucent segment was observed in the wild-type cells in any of the media used. Electron microscopic observation revealed that the translucent segments resulted from the enlargement of a periplasmic space by separation of the inner membrane from the peptidoglycan layer and the outer membrane. 相似文献
2.
Plasma membrane-cell wall connections: Roles in mitosis and cytokinesis revealed by plasmolysis ofTradescantia virginiana leaf epidermal cells 总被引:3,自引:0,他引:3
Ann L. Cleary 《Protoplasma》2001,215(1-4):21-34
Summary
Tradescantia virginiana leaf epidermal cells were plasmolysed by sequential treatment with 0.8 M and 0.3 M sucrose. Plasmolysis revealed adhesion of the plasma membrane to the cell wall at sites coinciding with cytoskeletal arrays involved in the polarisation of cells undergoing asymmetric divisions — cortical actin patch — and in the establishment and maintenance of the division site —preprophase band of microtubules and filamentous (F) actin. The majority of cells retained adhesions at the actin patch throughout mitosis. However, only approximately 13% of cells formed or retained attachments at the site of the preprophase band. After the breakdown of the nuclear envelope, plasmolysis had a dramatic effect on spindle orientation, cell plate formation, and the plane of cytokinesis. Spindles were rotated at abnormal angles including tilted into the plane of the epidermis. Cell plates formed but were quickly replaced by vacuole-like intercellular compartments containing no Tinopal-stainable cell wall material. This compartment usually opened to the apoplast at one side, and cytokinesis was completed by the furrow extending across the protoplast. This atypical cytokinesis was facilitated by a phragmoplast containing microtubules and F-actin. Progression of the furrow was unaffected by 25 g of cytochalasin B per ml but inhibited by 10 M oryzalin. Phragmoplasts were contorted and misguided and cytokinesis prolonged, indicating severe disruption to the guidance mechanisms controlling phragmoplast expansion. These results are discussed in terms of cytoskeleton-plasma membrane-cell wall connections that could be important to the localisation of plasma membrane molecules defining the cortical division site and hence providing positional information to the cytokinetic apparatus, and/or for providing an anchor for cytoplasmic F-actin necessary to generate tension on the phragmoplast and facilitate its directed, planar expansion.Abbreviations ADZ
actin-depleted zone
- DIC
differential interference contrast
- GMC
guard mother cell
- MT
microtubule
- PPB
preprophase band
- SMC
subsidiary mother cell
Dedicated to Professor Brian E. S. Gunning on the occasion of his 65th birthday 相似文献
3.
Summary. Eleutherococcus senticosus zygotic embryos were pretreated with 1.0 M mannitol or sucrose for 3–24 h. This pretreatment resulted in a high frequency
of somatic-embryo formation on hormone-free medium. All the somatic embryos developed directly and independently from single
epidermal cells on the surface of zygotic embryos after plasmolyzing pretreatment. Scanning electron microscopic observation
revealed that the epidermal cells of hypocotyls rapidly became irregular and showed a random orientation before somatic-embryo
development commenced. At the same time, the epidermal cells in the untreated control remained regular. Callose concentration
determined by fluorometric analysis increased sharply in E. senticosus zygotic embryos after plasmolyzing pretreatment but remained low in the untreated control. Aniline blue fluorescent staining
of callose showed that the plasmolyzing pretreatment of zygotic embryos resulted in heavy accumulation of callose between
the plasma membrane and cell walls. On the basis of these results, we suggest that plasmolyzing pretreatment of zygotic embryos
induces the accumulation of callose, and the interruption of cell-to-cell communication imposed by this might stimulate the
reprogramming of epidermal cells into embryogenically competent cells and finally induce somatic-embryo development from single
cells.
Correspondence and reprints: Division of Forest Resources, College of Forest Sciences, Kangwon National University, Chunchon
200-701, Republic of Korea. 相似文献
4.
Cotyledon explants of Panax ginseng zygotic embryos directly produced somatic embryos on Murashige and Skoog medium without growth regulators. Somatic embryos were formed only near the proximal excised region of cotyledons. Multiple and/or single embryos were formed and the frequency of these formations differed according to the degree of maturity of the zygotic embryos used as the explant source. When cotyledon explants pre-plasmolysed (1.0 M sucrose for 24 h), the frequency of single embryo formation was enhanced regardless of cotyledon maturity. In addition, the distribution pattern of somatic embryos changed markedly because the embryos were formed over the whole surface of the cotyledons. Histological observation revealed that plasmolyzing pretreatment broke the plasmodesmatal connection between cells and when the embryogenic cell divisions commenced, plasmodesmatal strands were hardly observed except for newly formed cell walls. This indicates that the enhanced single embryo formation over the entire surfaces of cotyledon explants might be the result of an interruption of cell–cell interaction by plasmolyzing pretreatment. 相似文献
5.
Y. L. Nandadeva C. G. Lupi C. S. Meyer P. S. Devi I. Potrykus R. Bilang 《Plant cell reports》1999,18(6):500-504
Microprojectile-mediated transient and integrative transformation frequencies in rice (Oryza sativa cv. Taipei 309) embryogenic suspension cells were studied as a function of various parameters. Mannitol at concentrations
of 0.5 and 0.6 m was best for osmotic preconditioning of the cells for transient, but not for integrative transformation, for which sucrose
yielded the best and most reliable results. Denaturation of the transforming plasmid DNA prior to bombardment improved transient
and integrative transformation frequencies two to three fold. Delivery of double-stranded plasmids in linear form had no effect
on transient transformation when compared to supercoiled plasmid DNA, but led to an overall two fold increase in integrative
transformation frequency. This shows that optimized protocols for generating transgenic plants should not be based exclusively
on transient gene expression assays.
Received: 29 September 1997 / Revision received: 27 February 1998 / Accepted: 2 April 1998 相似文献
6.
A plasmolytic cycle: The fate of cytoskeletal elements 总被引:4,自引:0,他引:4
Summary In most plant cells, transfer to hypertonic solutions causes osmotic loss of water from the vacuole and detachment of the living protoplast from the cell wall (plasmolysis). This process is reversible and after removal of the plasmolytic solution, protoplasts can re-expand to their original size (deplasmolysis). We have investigated this phenomenon with special reference to cytoskeletal elements in onion inner epidermal cells. The main processes of plasmolysis seem to be membrane dependent because destabilization of cytoskeletal elements had only minor effects on plasmolysis speed and form. In most cells, the array of cortical microtubules is similar to that found in nonplasmolyzed states except that longitudinal patterns seen in some control cells were never observed in plasmolyzed protoplasts of onion inner epidermis. As soon as deplasmolysis starts, cortical microtubules become disrupted and only slowly regenerate to form an oblique array, similar to most nontreated cells. Actin microfilaments responded rapidly to the plasmolysis-induced deformation of the protoplast and adapted to its new form without marked changes in organization and structure. Both actin microfilaments and microtubules can be present in Hechtian strands, which, in plasmolyzed cells, connect the cell wall to the protoplast. Anticytoskeletal drugs did not affect the formation of Hechtian strands.Abbreviations DIC
differential interference contrast
- DiOC6(3)
3,3-dihexyloxacarbocyanine iodide
Dedicated to Professor Walter Gustav Url on the occasion of his 70th birthday 相似文献
7.
Summary In mesophyll cells of the aquatic angiospermVallisneria gigantea Graebner, the endoplasm streams rotationally along the cell walls normal to the leaf surface in situ. Bundles of microfilaments
anchored in the ectoplasm serve as tracks for the cytoplasmic streaming. In single mesophyll cells isolated by enzymatic digestion,
hypertonic treatment induces abnormal streaming concomitant with plasmolysis, specifically at one or both of the shorter sides
of an approximate rectangle. The disorderly arrangement of microfilaments in such cells has been confirmed by fluorescence
microscopy of cells stained with FITC-phalloidin. While inhibitors of proteases added to the enzyme solution used for isolation
of cells suppress the disturbance of rotational streaming, exogenously applied protease promotes it. The results suggest that
bundles of microfilaments in the ectoplasm are stabilized by protease-sensitive factor(s) in the presence of the cell wall. 相似文献
8.
Summary. Successful cryopreservation of plant shoot tips is dependent upon effective desiccation through osmotic or physical processes.
Microscopy techniques were used to determine the extent of cellular damage and plasmolysis that occurs in peppermint (Mentha × piperita) shoot tips during the process of cryopreservation, using the cryoprotectant plant vitrification solution 2 (PVS2) (30% glycerol,
15% dimethyl sulfoxide, 15% ethylene glycol, 0.4 M sucrose) prior to liquid-nitrogen exposure. The meristem cells were the
smallest and least plasmolyzed cell type of the shoot tips, while the large, older leaf and lower cortex cells were the most
damaged. When treated with cryoprotectant solutions, meristem cells exhibited concave plasmolysis, suggesting that this cell
type has a highly viscous protoplasm, and protoplasts have many cell wall attachment sites. Shoot tip cells were most severely
plasmolyzed after PVS2 treatment, liquid-nitrogen exposure, and warming in 1.2 M sucrose. Successful recovery may be dependent
upon surviving the plasmolytic conditions induced by warming and diluting treated shoot tips in 1.2 M sucrose solutions. In
peppermint shoot tips, clumps of young meristem or young leaf cells survive the cryopreservation process and regenerate plants
containing many shoots. Cryoprotective treatments that favor survival of small, meristematic cells and young leaf cells are
most likely to produce high survival rates after liquid-nitrogen exposure.
Correspondence and reprints: National Center for Genetic Resources Preservation, U.S. Department of Agriculture, 1111 S. Mason
Street, Fort Collins, CO 80521, U.S.A. 相似文献
9.
Delivery of plasmid DNA into intact plant cells by electroporation of plasmolyzed cells 总被引:7,自引:0,他引:7
This report describes the delivery of plasmid DNA containing either the β-glucuronidase (GUS) or the green fluorescent protein (GFP) reporter gene into intact plant cells of bamboo callus, lilium
scales, and Nicotiana benthamiana suspension culture cells. By first plasmolyzing the tissues or cells with 0.4 m sucrose in the presence of plasmid DNA, electroporation effectively delivers plasmid DNA into the intact plant cells. Transient
expression of the GUS gene, as revealed by histochemical assays, showed the presence of blue-staining areas in the electroporated
tissues. A short exposure of cells to 2% DMSO (dimethyl sulfoxide) prior to plasmolysis elevated the level of transient GUS
activity. When plasmid DNA containing a synthetic GFP gene was used, a strong green fluorescence was observed in N. benthamiana suspension culture cells that were subjected to plasmolysis and electroporation. These results suggest that plasmolysis brings
the plasmid DNA into the void space that is in close vicinity to the plasmalemma, allowing electroporation to efficiently
deliver the plasmid DNA into intact plant cells.
Received: 15 June 1998 / Revision received: 18 August 1998 / Accepted: 28 August 1998 相似文献
10.
Summary. Plant protoplasts are embedded within surrounding cell walls and the cell wall–plasma membrane–cytoskeleton (WMC) structural
continuum seems to be crucial for the proper functioning of plant cells. We have utilised the protoplast preparation methodology
to study the organisation and the putative components of the WMC continuum. Application of an osmotic agent evoked plasmolysis
of the Zea mays root apex cells which appeared to be cell type- and growth stage-specific. Simultaneous use of wall polysaccharide-digesting
enzymes selectively severed linkages between the components of the WMC continuum which changed the plasmolytic patterns in
various cell types. This was followed by a reorganisation of filamentous actin aimed to reinforce protoplast boundaries and
maintain the functioning of intercellular contact sites, especially at the cross walls. Particularly strong effects were evoked
by pectin-degrading enzymes. Such treatments demonstrated directly the differentiated composition of various wall domains
surrounding individual cells with the pectin-enriched cross walls (synapses), and the cellulose-hemicellulose network dominating
the side walls. The same wall-degrading enzymes were used for in vitro digestion of isolated Lupinus albus cell walls followed by the extraction of wall proteins. Selective release of proteins suggested the importance of wall polysaccharide–protein
interactions in the maintenance of the functioning and mechanical stability of root cell walls.
Correspondence and reprints: Department of Molecular and Cellular Biology, Adam Mickiewicz University, Międzychodzka 5, 60-371
Poznań, Poland. 相似文献