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  • 1
    Electronic Resource
    Electronic Resource
    Palo Alto, Calif. : Annual Reviews
    Annual Review of Plant Physiology and Plant Molecular Biology 54 (2003), S. 431-454 
    ISSN: 1040-2519
    Source: Annual Reviews Electronic Back Volume Collection 1932-2001ff
    Topics: Biology
    Notes: Abstract Transfer cells are plant cells with secondary wall ingrowths. These cells are ubiquitous, occurring in all plant taxonomic groups and in algae and fungi. Transfer cells form from differentiated cells across developmental windows and in response to stress. They are considered to play a central role in nutrient distribution by facilitating high rates of transport at bottlenecks for apo-/symplasmic solute exchange. These properties are conferred by their unique structural features-an invaginated secondary wall ensheathed by an amplified area of plasma membrane enriched in a suite of solute transporters. Recent development of transfer cell experimental systems, combined with technologies to image the three-dimensional structure of wall ingrowths, is allowing identification of inductive and regulatory signals, discovery of sequential processes involved in their differentiation, and a search for transfer cell identity genes. A model of key events in differentiation of a transfer cell is presented to highlight areas for future investigation.
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Planta 188 (1992), S. 54-61 
    ISSN: 1432-2048
    Keywords: Actin ; Chara (protein kinase) ; Cytoplasmic streaming ; Myosin ; Protein kinase (calcium dependent)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Cytoplasmic streaming in the characean algae is inhibited by micromolar rises in the level of cytosolic free Ca2+, but both the mechanism of action and the molecular components involved in this process are unknown. We have used monoclonal antibodies against soybean Ca2+-dependent protein kinase (CDPK), a kinase that is activated by micromolar Ca2+ and co-localizes with actin filaments in higher-plant cells (Putnam-Evans et al., 1989, Cell Motil. Cytoskel. 12, 12–22) to identify and localize its characean homologue. Immunoblot analysis revealed that CDPK in Chara corralina Klein ex. Wild shares the same relative molecular mass (51–55 kDa) as the kinase purified from soybean, and after electrophoresis in denaturing gels is capable of phosphorylating histone III-S in a Ca2+-dependent manner. Immunofluorescence microscopy localized CDPK in Chara to the subcortical actin bundles and the surface of small organelles and other membrane components of the streaming endoplasm. The endoplasmic sites carrying CDPK were extracted from internodal cells by vacuolar perfusion with 1 mM ATP or 10−4 M Ca2+. Both the localization of CDPK and its extraction from internodal cells by perfusion with ATP or high Ca2+ are properties similar to that reported for the heavy chain of myosin in Chara (Grolig et al., 1988, Eur. J. Cell Biol. 47, 22–31). Based on its endoplasmic location and inferred enzymatic properties, we suggest that CDPK may be a putative element of the signal-transduction pathway that mediates the rapid Ca2+-induced inhibition of streaming that occurs in the characean algae.
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Planta 188 (1992), S. 54-61 
    ISSN: 1432-2048
    Keywords: Actin ; Chara (protein kinase) ; Cytoplasmic streaming ; Myosin ; Protein kinase (calcium dependent)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Cytoplasmic streaming in the characean algae is inhibited by micromolar rises in the level of cytosolic free Ca2+, but both the mechanism of action and the molecular components involved in this process are unknown. We have used monoclonal antibodies against soybean Ca2+-dependent protein kinase (CDPK), a kinase that is activated by micromolar Ca2+ and co-localizes with actin filaments in higher-plant cells (Putnam-Evans et al., 1989, Cell Motil. Cytoskel.12, 12–22) to identify and localize its characean homologue. Immunoblot analysis revealed that CDPK inChara corralina Klein ex. Wild shares the same relative molecular mass (51–55 kDa) as the kinase purified from soybean, and after electrophoresis in denaturing gels is capable of phosphorylating histone III-S in a Ca2+-dependent manner. Immunofluorescence microscopy localized CDPK inChara to the subcortical actin bundles and the surface of small organelles and other membrane components of the streaming endoplasm. The endoplasmic sites carrying CDPK were extracted from internodal cells by vacuolar perfusion with 1 mM ATP or 10−4 M Ca2+. Both the localization of CDPK and its extraction from internodal cells by perfusion with ATP or high Ca2+ are properties similar to that reported for the heavy chain of myosin inChara (Grolig et al., 1988, Eur. J. Cell Biol.47, 22–31). Based on its endoplasmic location and inferred enzymatic properties, we suggest that CDPK may be a putative element of the signal-transduction pathway that mediates the rapid Ca2+-induced inhibition of streaming that occurs in the characean algae.
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    Plant molecular biology 36 (1998), S. 23-31 
    ISSN: 1573-5028
    Keywords: actin-binding protein ; Arabidopsis thaliana ; cytoskeleton ; fimbrin-like ; molecular cloning
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Fimbrin is a 68–70 kDa actin-bundling protein in animal cells and lower eukaryotes that participates in diverse morphogenetic processes by cross-linking actin filaments into bundles. Here we report the cloning by degenerate polymerase chain reaction (PCR) of ATFIM1, a 2.3 kb cDNA from Arabidopsis thaliana that codes for a novel 76 kDa fimbrin-like polypeptide (AtFim1). The predicted sequence of AtFim1 shares ca. 40% identity with non-plant fimbrins and contains two tandem repeats, each possessing a 27 amino acid region identified as a putative actin-binding domain in fimbrins and in a larger family of actin cross-linking proteins. Preceding the tandem repeats at the amino terminus of AtFim1 is a single-EF-hand-like domain with moderate homology to calmodulin-like calcium-binding proteins. AtFim1 differs from non-plant fimbrins, however, in that it contains an extended carboxy-terminal tail of ca. 65 amino acids. ATFIM1 is encoded by a single gene, although sequencing of two partial fimbrin-like expressed sequence tag (EST) clones indicates that Arabidopsis contains at least two fimbrin-like proteins. Northern blot analysis and reverse-transcription PCR (RT-PCR) demonstrated that ATFIM1 is expressed in all major organs examined (roots, leaves, stems, flowers and siliques). This is the first report of the cloning of a full length plant gene that encodes a putative actin filament-bundling protein.
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  • 5
    ISSN: 1573-5028
    Keywords: gene expression ; heterologous expression ; H+/hexose symporter ; Lycopersicon esculentum ; quantitative PCR ; Saccharomyces cerevisiae
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract A full-length (LeHT2) and two partial (LeHT1 and LeHT3) cDNA clones, encoding hexose transporters, were isolated from tomato (Lycopersicon esculentum) fruit and flower cDNA libraries. Southern blot analysis confirmed the presence of a gene family of hexose transporters in tomato consisting of at least three members. The full-length cDNA (LeHT2) encodes a protein of 523 amino acids, with a calculated molecular mass of 57.6 kDa. The predicted protein has 12 putative membrane-spanning domains and belongs to the Major Facilitator Superfamily of membrane carriers. The three clones encode polypeptides that are homologous to other plant monosaccharide transporters and contain conserved amino acid motifs characteristic of this superfamily. Expression of the three genes in different organs of tomato was investigated by quantitative PCR. LeHT1 and LeHT3 are expressed predominantly in sink tissues, with both genes showing highest expression in young fruit and root tips. LeHT2 is expressed at relatively high levels in source leaves and certain sink tissues such as flowers. LeHT2 was functionally expressed in a hexose transport-deficient mutant (RE700A) of Saccharomyces cerevisiae. LeHT2-dependent transport of glucose in RE700A exhibited properties consistent with the operation of an energy-coupled transporter and probably a H+/hexose symporter. The K m of the symporter for glucose is 45 μM.
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  • 6
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Cell Motility and the Cytoskeleton 15 (1990), S. 76-87 
    ISSN: 0886-1544
    Keywords: antiactin ; cytochalasin B ; plant cytoskeleton ; tubulin ; oryzalin ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Following our recent description [McCurdy et al.: Protoplasma. 147:204-206, 1988] of arrays of transverse cortical microfilaments (MFs) in preprophase roottip cells of wheat (Triticum aestivum L. cv. Kite), we have performed double label immunofluorescence microscopy to correlate the formation of these arrays with the known rearrangement of cortical microtubules (MTs) that occurs during preprophase. At early preprophase, indicated by a broad (i.e., young) preprophase band (PPB) of MTs, actin MFs are transverse only in the central region of the cell cortex. By late preprophase, however, cells that possess a mature (i.e., narrow) PPB of MTs have arrays of transverse MFs that occupy the entire cortical surface of the cell. Thus, apart from the PPB zone, the transverse MFs in these arrays do not colocalize with transverse cortical MTs. Depolymerization of MTs using the herbicide oryzalin does not effect the arrays of cortical MFs; however, experiments using cytochalasin B in combination with oryzalin indicate that cellular MTs are necessary for the formation of the arrays of transverse cortical MFs. The arrays of cortical MFs disintegrate during prophase into short fragments of random, filamentous actin. This situation persists until the completion of cytokinesis. The absence of MFs during mitosis in densely-cytoplasmic meristematic cells of wheat root tips indicates that filamentous actin may not have a universal function in plant cell division. The possible function of the arrays of cortical MFs in preprophase cells is discussed.
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  • 7
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Cell Motility and the Cytoskeleton 18 (1991), S. 107-112 
    ISSN: 0886-1544
    Keywords: cell division ; cytoskeleton ; root cell ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: A collaborative effort was initiated to resolve differences in two recent papers on the effects of cytochalasins in root cells. While both studies reported similar effects on interphase cells (i.e., replacement of microfilaments by many small specks and rods), Palevitz (Cell Motil. Cytoskeleton 9:283-298, 1988) maintained that cytochalasins B and D induce actin aggregation at the poles of dividing Allium root cells at a concentration of 10 μM with rhodamine phalloidin as a reporter probe, whereas McCurdy and Gunning (Cell Motil. Cytoskeleton 15:76-87, 1990) could not find these aggregates following antiactin immunocytochemistry in Triticum roots treated with CB at 50 μM. Employing identical methods and materials in the same laboratory, we found that CD induces polar actin aggregates in dividing cells of both species. However, the aggregates in Triticum are smaller and occur less frequently than those in Allium. A similar pattern is seen with CB.
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  • 8
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Cell Motility and the Cytoskeleton 22 (1992), S. 117-126 
    ISSN: 0886-1544
    Keywords: algae ; cell division ; cytokinesis ; mitosis ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: We have used two monoclonal antibodies to demonstrate the presence and localization of actin in interphase and mitotic vegetative cells of the green alga Chlamydomonas reinhardtii. Commercially available monoclonal antibodies raised against smooth muscle actin (Lessard: Cell Motil. Cytoskeleton 10:349-362, 1988; Lin: Proc. Natl. Acad. Sci. USA 78:2335-2339, 1981) identify Chlamydomonasactin as a ∼43,000-Mr protein by Western immunoblot procedures. In an earlier study, Detmers and coworkers (Cell Motil. 5:415-430, 1985) first identified Chlamydomonas actin using NBD-phallacidin and an antibody raised against Dictyostelium actin; they demonstrated that F-actin is localized in the fertilization tubule of mating gametes. Here, we show by immunofluorescence that vegetative Chlamydomonas cells have an array of actin that surrounds the nucleus in interphase cells and undergoes dramatic reorganization during mitosis and cytokinesis. This includes the following: reorganization of actin to the ante- rior of the cell during preprophase; the formation of a cruciate actin band in prophase; reorganization to a single anterior actin band in metaphase; rearrange- ment forming a focus of actin anterior to the metaphase plate; reextension of the actin band in anaphase; presence of actin in the forming cleavage furrow during telophase and cytokinesis; and finally reestablishment of the interphase actin array. The studies presented here do not allow us to discriminate between G and F-actin. None the less, our observations, demonstrating dynamic reorganization of actin during the cell cycle, suggest a role for actin that may include the movement of basal bodies toward the spindle poles in mitosis and the formation of the cleavage furrow during cytokinesis. © 1992 Wiley-Liss, Inc.
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  • 9
    ISSN: 1615-6102
    Keywords: Cytoskeleton ; Immunofluorescence microscopy ; Microtubules ; Transfer cells ; Vicia faba ; Cotyledons
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The epidermal transfer cells in developingVicia faba L. cotyledons are highly polarized. Extensive wall ingrowths occur on their outer periclinal walls and extend part way down both anticlinal walls. This ingrowth development serves to increase the surface area of the plasma membrane and thus maximize porter-dependent uptake of sugars from the seed apoplasm. In contrast, the inner periclinal walls of these transfer cells do not form wall ingrowths. We have commenced a study of the mechanisms responsible for establishing this polarity by first analysing the microtubule (MT) cytoskeleton in developing transfer cells. Thin sections of fixed cotyledons embedded in methacrylate resin were processed for immunofluorescence microscopy using monoclonal anti-β-tubulin and counterstained with Calcofluor White to visualize wall ingrowths. In epidermal cells of young cotyledons where wall ingrowths were yet to develop, MT labelling was detected around all cortical regions of the cell. However, in cells where wall ingrowths were clearly established, MT labelling was detected almost exclusively in cortical regions adjacent to the wall ingrowths. Little, if any, MT labelling was detected on the anticlinal or inner periclinal walls of these cells. This distribution of MTs was most prominent in cells with well developed wall ingrowths. In these cells, a subpopulation of MTs were also detected emanating from the subcortex and extending towards the wall ingrowth region. The possible role of MT distribution in establishing transfer cell polarity and wall ingrowth formation is discussed.
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  • 10
    ISSN: 1615-6102
    Keywords: Cortical actin ; Immunofluorescence ; Microfilaments ; Triticum
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Actin microfilaments in isolated root-tip cells from wheat (Triticum aestivum L. cv. Kite) were visualized by immunofluorescence microscopy using two different antiactin monoclonal antibodies. Cells in interphase contain predominantly subcortical bundles of microfilaments, as described in many cell types, but in preprophase and prophase cells, immunodetectable actin is organized solely in ordered arrays of cortical microfilaments that cover the entire surface of the cell, transverse on lateral faces, random on end walls. Intermediate stages with random and transverse microfilaments are also seen on lateral faces. The cell cycle stage-dependent transverse cortical microfilaments described here are previously unreported in higher plant cells.
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