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  • 1
    Electronic Resource
    Electronic Resource
    Cell specific expression of three genes involved in plasma membrane sucrose transport in developingVicia faba seed (1997)
    Springer
    Protoplasma 197 (1997), S. 160-173 
    Details
    ISSN: 1615-6102
    Keywords: Gene expression ; Plasma membrane transport ; Seed ; Sucrose efflux/influx ; Transfer cells ; Vicia faba
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary In developing seeds ofVicia faba, transfer cells line the inner surface of the seed coat and the juxtaposed epidermal surface of the cotyledons. Circumstantial evidence, derived from anatomical and physiological studies, indicates that these cells are the likely sites of sucrose efflux to, and influx from, the seed apoplasm, respectively. In this study, expression of an H+/sucrose symporter-gene was found to be localised to the epidermal-transfer cell complexes of the cotyledons. The sucrose binding protein (SBP) gene was expressed in these cells as well as in the thin-walled parenchyma transfer cells of the seed coat. SBP was immunolocalised exclusively to the plasma membranes located in the wall ingrowth regions of the transfer cells. In addition, a plasma membrane H+-ATPase was most abundant in the wall ingrowth regions with decreasing levels of expression at increasing distance from the transfer cell layers. The observed co-localisation of high densities of a plasma membrane H+-ATPase and sucrose transport proteins to the wall ingrowths of the seed coat and cotyledon transfer cells provides strong evidence that these regions are the principal sites of facilitated membrane transport of sucrose to and from the seed apoplasm.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01288025
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    Paper (German National Licenses)
    Fulltext
  • 2
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    ECA1 complements yeast mutants defective in Ca2+ pumps and encodes an endoplasmic reticulum-type Ca2+-ATPase in Arabidopsis thaliana (1997)
    National Academy of Sciences
    Details
    Publication Date: 1997-08-05
    Print ISSN: 0027-8424
    Electronic ISSN: 1091-6490
    Topics: Biology , Medicine , Natural Sciences in General
    Published by National Academy of Sciences
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  • 3
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    Bubbles rising in line: why is the first approximation so bad? (1997)
    Cambridge University Press
    Details
    Publication Date: 1997-11-25
    Description: An analytical theory is given for the viscous wake behind a spherical bubble rising steadily in a pure liquid at high Reynolds number, and for that wake's effect on the motion of a second bubble rising underneath the first. Previous theoretical work on this subject consists of just two papers: a first approximation ignoring wake vorticity diffusion between the bubbles, and a full numerical solution avoiding simplifying approximations (apart from that of spherical shape of the bubbles). A second approximation is now found; it removes much of the discrepancy between the first approximation and the full solution. The leading-order calculation of wake vorticity diffusion uses a transformation of the independent variables which appears to be new. Experimental work to date has disagreed with all the theoretical work, but it addresses a somewhat different problem: a line of many bubbles.
    Print ISSN: 0022-1120
    Electronic ISSN: 1469-7645
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Published by Cambridge University Press
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  • 4
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    The axisymmetric Prandtl-Batchelor eddy behind a circular disc in a uniform stream (1998)
    Cambridge University Press
    Details
    Publication Date: 1998-12-25
    Description: Analytical support is given to Fornberg's numerical evidence that the steady axially symmetric flow of a uniform stream past a bluff body has a wake eddy which tends towards a large Hill's spherical vortex as the Reynolds number tends to infinity. The viscous boundary layer around the eddy resembles that around a liquid drop rising in a liquid, especially if the body is a circular disc, so that the boundary layer on it does not separate. This makes it possible to show that if the first-order perturbation of the eddy shape from a sphere is small then the eddy diameter is of order R1/5 times the disc diameter, where R is the Reynolds number based on the disc diameter. Previous authors had suggested R1/3 and 1n R, but they appear to have made unjustified assumptions.
    Print ISSN: 0022-1120
    Electronic ISSN: 1469-7645
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Published by Cambridge University Press
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  • 5
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    A novel chloride channel in Vicia faba guard cell vacuoles activated by the serine/threonine kinase, CDPK. (1996)
    EMBO Press
    Details
    Publication Date: 1996-12-01
    Print ISSN: 0261-4189
    Electronic ISSN: 1460-2075
    Topics: Biology , Medicine
    Published by EMBO Press on behalf of European Molecular Biology Organization.
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  • 6
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    Activation of a Ca(2+)-dependent protein kinase involves intramolecular binding of a calmodulin-like regulatory domain (1996)
    In:  Other Sources
    Details
    Publication Date: 2011-08-24
    Description: Ca(2+)-dependent protein kinases (CDPKs) are regulated by a C-terminal calmodulin-like domain (CaM-LD). The CaM-LD is connected to the kinase by a short junction sequence which contains a pseudosubstrate autoinhibitor. To understand how the CaM-LD regulates a CDPK, a recombinant CDPK (isoform CPK-1 from Arabidopsis, accession no. L14771) was made as a fusion protein in Escherichia coli. We show here that a truncated CDPK lacking a CaM-LD (e.g. mutant delta NC-26H) can be activated by exogenous calmodulin or an isolated CaM-LD (Kact approximately 2 microM). We propose that Ca2+ activation of a CDPK normally occurs through intramolecular binding of the CaM-LD to the junction. When the junction and CaM-LD are made as two separate polypeptides, the CaM-LD can bind the junction in a Ca(2+)-dependent fashion with a dissociation constant (KD) of 6 x 10(-6) M, as determined by kinetic binding analyses. When the junction and CaM-LD are tethered in a single polypeptide (e.g. in protein JC-1), their ability to engage in bimolecular binding is suppressed (e.g. the tethered CaM-LD cannot bind a separate junction). A mutation which disrupts the putative CaM-LD binding sequence (e.g. substitution LRV-1444 to DLPG) appears to block intramolecular binding, as indicated by the restored ability of a tethered CaM-LD to engage in bimolecular binding. This mutation, in the context of a full-length enzyme (mutant KJM46H), appears to block Ca2+ activation. Thus, a disruption of intramolecular binding correlates with a disruption of the Ca2+ activation mechanism. CDPKs provide the first example of a member of the calmodulin superfamily where a target binding sequence is located within the same polypeptide.
    Keywords: Life Sciences (General)
    Type: Biochemistry (ISSN 0006-2960); Volume 35; 40; 13222-30
    Format: text
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  • 7
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    A novel calmodulin-regulated Ca2+-ATPase (ACA2) from Arabidopsis with an N-terminal autoinhibitory domain (1998)
    In:  Other Sources
    Details
    Publication Date: 2011-08-24
    Description: To study transporters involved in regulating intracellular Ca2+, we isolated a full-length cDNA encoding a Ca2+-ATPase from a model plant, Arabidopsis, and named it ACA2 (Arabidopsis Ca2+-ATPase, isoform 2). ACA2p is most similar to a "plasma membrane-type" Ca2+-ATPase, but is smaller (110 kDa), contains a unique N-terminal domain, and is missing a long C-terminal calmodulin-binding regulatory domain. In addition, ACA2p is localized to an endomembrane system and not the plasma membrane, as shown by aqueous-two phase fractionation of microsomal membranes. ACA2p was expressed in yeast as both a full-length protein (ACA2-1p) and an N-terminal truncation mutant (ACA2-2p; Delta residues 2-80). Only the truncation mutant restored the growth on Ca2+-depleted medium of a yeast mutant defective in both endogenous Ca2+ pumps, PMR1 and PMC1. Although basal Ca2+-ATPase activity of the full-length protein was low, it was stimulated 5-fold by calmodulin (50% activation around 30 nM). In contrast, the truncated pump was fully active and insensitive to calmodulin. A calmodulin-binding sequence was identified within the first 36 residues of the N-terminal domain, as shown by calmodulin gel overlays on fusion proteins. Thus, ACA2 encodes a novel calmodulin-regulated Ca2+-ATPase distinguished by a unique N-terminal regulatory domain and a non-plasma membrane localization.
    Keywords: Life Sciences (General)
    Type: The Journal of biological chemistry (ISSN 0021-9258); Volume 273; 2; 1099-106
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  • 8
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    Cameleon calcium indicator reports cytoplasmic calcium dynamics in Arabidopsis guard cells (1999)
    In:  Other Sources
    Details
    Publication Date: 2011-08-24
    Description: Cytoplasmic free calcium ([Ca2+]cyt) acts as a stimulus-induced second messenger in plant cells and multiple signal transduction pathways regulate [Ca2+]cyt in stomatal guard cells. Measuring [Ca2+]cyt in guard cells has previously required loading of calcium-sensitive dyes using invasive and technically difficult micro-injection techniques. To circumvent these problems, we have constitutively expressed the pH-independent, green fluorescent protein-based calcium indicator yellow cameleon 2.1 in Arabidopsis thaliana (Miyawaki et al. 1999; Proc. Natl. Acad. Sci. USA 96, 2135-2140). This yellow cameleon calcium indicator was expressed in guard cells and accumulated predominantly in the cytoplasm. Fluorescence ratio imaging of yellow cameleon 2.1 allowed time-dependent measurements of [Ca2+]cyt in Arabidopsis guard cells. Application of extracellular calcium or the hormone abscisic acid (ABA) induced repetitive [Ca2+]cyt transients in guard cells. [Ca2+]cyt changes could be semi-quantitatively determined following correction of the calibration procedure for chloroplast autofluorescence. Extracellular calcium induced repetitive [Ca2+]cyt transients with peak values of up to approximately 1.5 microM, whereas ABA-induced [Ca2+]cyt transients had peak values up to approximately 0.6 microM. These values are similar to stimulus-induced [Ca2+]cyt changes previously reported in plant cells using ratiometric dyes or aequorin. In some guard cells perfused with low extracellular KCl concentrations, spontaneous calcium transients were observed. As yellow cameleon 2.1 was expressed in all guard cells, [Ca2+]cyt was measured independently in the two guard cells of single stomates for the first time. ABA-induced, calcium-induced or spontaneous [Ca2+]cyt increases were not necessarily synchronized in the two guard cells. Overall, these data demonstrate that that GFP-based cameleon calcium indicators are suitable to measure [Ca2+]cyt changes in guard cells and enable the pattern of [Ca2+]cyt dynamics to be measured with a high level of reproducibility in Arabidopsis cells. This technical advance in combination with cell biological and molecular genetic approaches will become an invaluable tool in the dissection of plant cell signal transduction pathways.
    Keywords: Life Sciences (General)
    Type: The Plant journal : for cell and molecular biology (ISSN 0960-7412); Volume 19; 6; 735-47
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  • 9
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    Identification of a calmodulin-regulated Ca2+-ATPase in the endoplasmic reticulum (1999)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: A unique subfamily of calmodulin-dependent Ca2+-ATPases was recently identified in plants. In contrast to the most closely related pumps in animals, plasma membrane-type Ca2+-ATPases, members of this new subfamily are distinguished by a calmodulin-regulated autoinhibitor located at the N-terminal instead of a C-terminal end. In addition, at least some isoforms appear to reside in non-plasma membrane locations. To begin delineating their functions, we investigated the subcellular localization of isoform ACA2p (Arabidopsis Ca2+-ATPase, isoform 2 protein) in Arabidopsis. Here we provide evidence that ACA2p resides in the endoplasmic reticulum (ER). In buoyant density sucrose gradients performed with and without Mg2+, ACA2p cofractionated with an ER membrane marker and a typical "ER-type" Ca2+-ATPase, ACA3p/ECA1p. To visualize its subcellular localization, ACA2p was tagged with a green fluorescence protein at its C terminus (ACA2-GFPp) and expressed in transgenic Arabidopsis. We collected fluorescence images from live root cells using confocal and computational optical-sectioning microscopy. ACA2-GFPp appeared as a fluorescent reticulum, consistent with an ER location. In addition, we observed strong fluorescence around the nuclei of mature epidermal cells, which is consistent with the hypothesis that ACA2p may also function in the nuclear envelope. An ER location makes ACA2p distinct from all other calmodulin-regulated pumps identified in plants or animals.
    Keywords: Life Sciences (General)
    Type: Plant physiology (ISSN 0032-0889); 119; 4; 1165-76
    Format: text
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