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Covisualization by computation optical-sectioning microscopy of integrin and associated proteins at the cell membrane of living onion protoplasts (1996)

Gens, J. Scott ; Reuzeau, Christophe ; Doolittle, Keith W. ; [et al.]

Springer

Protoplasma 194 (1996), S. 215-230

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ISSN: 1615-6102

Keywords: Adhesion sites ; Allium cepa ; Wide-field computational optical-sectioning microscopy ; Fibronectin antibodies ; Integrin ; Vitronectin antibodies

Source: Springer Online Journal Archives 1860-2000

Topics: Biology

Notes: Summary Using higher-resolution wide-field computational optical-sectioning fluorescence microscopy, the distribution of antigens recognized by antibodies against animal β1 integrin, fibronectin, and vitronectin has been visualized at the outer surface of enzymatically protoplasted onion epidermis cells and in depectinated cell wall fragments. On the protplast all three antigens are colocalized in an array of small spots, as seen in raw images, in Gaussian filtered images, and in images restored by two different algorithms. Fibronectin and vitronectin but not β1 integrin antigenicities colocalize as puncta in comparably prepared and processed images of the wall fragments. Several control visualizations suggest considerable specificity of antibody recognition. Affinity purification of onion cell extract with the same anti-integrin used for visualization has yielded protein that separates in SDS-PAGE into two bands of about 105–110 and 115–125 kDa. These bands are again recognized by the visualizationi antibody, which was raised against the extracellular domain of chicken β1 integrin, and are also reconized by an antibody against the intracellular domain of chicken β1 integrin. Because β1 integrin is a key protein in numerous animal adhesion sites, it appears that the punctate distribution of this protein in the cell membranes of onion epidermis represents the adhesion sites long known to occur in cells of this tissue. Because vitronectin and fibronectin are matrix proteins that bind to integrin in animals, the punctate occurrence of antigenically similar proteins both in the wall (matrix) and on enzymatically prepared protoplasts reinforces the concept that onion cells have adhesion sites with some similarity to certain kinds of adhesioni sites in animals.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1007/BF01882029

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Molecular characterization of a new type of receptor-like kinase (wlrk) gene family in wheat (1998)

Feuillet, Catherine ; Reuzeau, Christophe ; Kjellbom, Per ; [et al.]

Springer

Plant molecular biology 37 (1998), S. 943-953

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ISSN: 1573-5028

Keywords: barley ; kinase ; leaf rust ; receptor-like kinase ; resistance ; wheat

Source: Springer Online Journal Archives 1860-2000

Topics: Biology

Notes: Abstract In plants, several types of receptor-like kinases (RLK) have been isolated and characterized based on the sequence of their extracellular domains. Some of these RLKs have been demonstrated to be involved in plant development or in the reaction to environmental signals. Here, we describe a RLK gene family in wheat (wlrk, wheat leaf rust kinase) with a new type of extracellular domain. A member of this new gene family has previously been shown to cosegregate with the leaf rust resistance gene Lr10. The diversity of the wlrk gene family was studied by cloning the extracellular domain of different members of the family. Sequence comparisons demonstrated that the extracellular domain consists of three very conserved regions interrupted by three variable regions. Linkage analysis indicated that the wlrk genes are specifically located on chromosome group 1 in wheat and on the corresponding chromosomes of other members of the Triticeae family. The wlrk genes are constitutively expressed in the aerial parts of the plant whereas no expression was detected in roots. Protein immunoblots demonstrated that the WLRK protein coded by the Lrk10 gene is an intrinsic plasma membrane protein. This is consistent with the hypothesis that WLRK proteins are receptor protein kinases localized to the cell surface. In addition, we present preliminary evidence that other disease resistance loci in wheat contain genes which are related to wlrk.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1023/A:1006062016593

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Covisualization in living onion cells of putative integrin, putative spectrin, actin, putative intermediate filaments, and other proteins at the cell membrane and in an endomembrane sheath (1997)

Reuzeau, Christophe ; Doolittle, Keith W. ; McNally, James G. ; [et al.]

Springer

Protoplasma 199 (1997), S. 173-197

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ISSN: 1615-6102

Keywords: Actin ; Adhesion sites ; Allium cepa ; Endomembrane system ; Integrin ; Spectrin

Source: Springer Online Journal Archives 1860-2000

Topics: Biology

Notes: Summary Covisualizations with wide-field computational opticalsectioning microscopy of living epidermal cells of the onion bulb scale have evidenced two major new cellular features. First, a sheath of cytoskeletal elements clads the endomembrane system. Similar elements clad the inner faces of punctate plasmalemmal sites interpreted as plasmalemmal control centers. One component of the endomembrane sheath and plasmalemmal control center cladding is antigenicity-recognized by two injected antibodies against animal spectrin. Immunoblots of separated epidermal protein also showed bands recognized by these antibodies. Injected phalloidin identified F-actin with the same cellular distribution pattern, as did antibodies against intermediate-filament protein and other cytoskeletal elements known from animal cells. Injection of general protein stains demonstrated the abundance of endomembrane sheath protein. Second, the endomembrane system, like the plasmalemmal puncta, contains antigen recognized by an anti-β1 integrin injected into the cytoplasm. Previously, immunoblots of separated epidermal protein were shown to have a major band recognized both by this antibody prepared against a peptide representing the cytosolic region of β1 integrin and an antibody against the matrix region of β1 integrin. The latter antibody also identified puncta at the external face of protoplasts. It is proposed that integrin and associated transmembrane proteins secure the endomembrane sheath and transmit signals between it and the lumen or matrix of the endoplasmic reticulum and organellar matrices. This function is comparable to that proposed for such transmembrane linkers in the plasmalemmal control centers, which also appear to bind cytoskeleton and a host of related molecules and transmit signals between them and the wall matrix. It is at the plasmalemmal control centers that the endoplasmic reticulum, a major component of the endomembrane system, attaches to the plasma membrane.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1007/BF01294505

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The endomembrane sheath: a key structure for understanding the plant cell? (1997)

Reuzeau, Christophe ; McNally, James G. ; Pickard, Barbara G.

Springer

Protoplasma 200 (1997), S. 1-9

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ISSN: 1615-6102

Keywords: Actin ; Adhesion sites ; Channeling ; Cytoplasmic streaming ; Endomembrane system ; Integrin

Source: Springer Online Journal Archives 1860-2000

Topics: Biology

Notes: Summary Recent evidence suggests that integrin is abundant in endomembranes of plant cells, and the endomembranes are clad by a sheath of cytoskeleton including F-actin. A role for endomembrane integrin and the endomembrane sheath is proposed: this system might orchestrate metabolic regulation by providing and modulating loci for channelling, and might accelerate channeling as needed by dragging the endoplasmic reticulum (ER) and organelles through the cytoplasm. To accomplish this “streaming”, F-actin might lever against the rest of the endomembrane sheath and the ER might also lever against adhesion sites (i.e., plasmodesmata and plasmalemmal control centers). As an important agent in the control of cellular activities, according to this model, the endomembrane sheath would play a major part in responses to diverse signals and stresses, and under extreme stress cell survival would depend on the ability of the system to maintain enough integrity to direct critical syntheses and degradations.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1007/BF01280729

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