Cell cycle dependent distribution of a centrosomal antigen at the perinuclear MTOC or at the kinetochores of higher plant cells |
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Authors: | Anne-Catherine Schmit Virginie Stoppin Véronique Chevrier Didier Job Anne-Marie Lambert |
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Institution: | (1) Institut de Biologie Moléculaire des Plantes, Centre National de la Recherche Scientifique, UPR 406, Université Louis Pasteur, 12 rue du Général Zimmer, F-67084 Strasbourg-Cedex, France;(2) Départment de Biologie Moléculaire et Structurale, Laboratoire du Cytosquelette, INSERM U 366, Centre d'Etudes Nucléaires de Grenoble, 17 rue des Martyrs, F-38054 Grenoble-Cedex, France |
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Abstract: | Compelling evidence has been obtained in favour of the idea that the nuclear surface of higher plant cells is a microtubule-nucleating and/or organizing site (MTOC), in the absence of defined centrosomes. How these plant MTOC proteins are redistributed and function during the progression of the cell cycle remains entirely unknown. Using a monoclonal antibody (mAb 6C6) raised against isolated calf thymus centrosomes and showing apparent reaction with the plant nuclear surface, we followed the targeted antigen distribution during mitosis and meiosis of higher plants. Immunoblot analysis of protein fractions from Allium root meristematic cell extracts probed with mAb 6C6 reveals a polypeptide of an apparent Mr of 78000. In calf centrosome extracts, a polypeptide of comparable molecular mass is found in addition to a major antigen of Mr 180000 after mAb 6C6 immunoblotting. During mitotic initiation, the plant antigen is prominent on the periphery of the prophase nucleus. When the nuclear envelope breaks down, the antigen suddenly becomes associated with the centromere-kinetochores until late anaphase. In telophase, when the nuclear envelope is being reconstructed, it is no longer detected at the kinetochores but is solely associated again with the nuclear surface. This antigen displays a unique spatial and temporal distribution, which may reflect the pathway of plant protein(s) between the nuclear surface and the kinetochores under cell cycle control. So far, such processes have not been described in higher plant cells. These observations shed light on the putative activity of the plant kinetochore as a protein transporter. They also suggest that a plant centrosome-like antigen may have different cytoskeletal related functions depending on cell cycle regulated changes in its subcellular distribution.Abbreviations mAb
monoclonal antibody
- MSB
microtubule stabilizing buffer
- TBS
Tris buffered saline
- MTOC
microtubule organizing centre |
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