title: Antibody against phosphorylated proteins (MPM-2) recognizes mitotic microtubules in endosperm cells of higher plant Haemanthus.
abstract: In diverse cell types, monoclonal antibody MPM-2 recognizes a class of phosphorylated proteins related to microtubule organizing centers and abundant during mitosis. We have used this antibody in an attempt to identify the spatial and temporal localization of putative microtubule organizing centers in endosperm cells of the higher plant Haemanthus. Our results show that MPM-2 recognized epitope is present in interphase cells and enriched in mitotic cells. In interphase the antibody usually stains cytoplasmic granules. During the interphase-prophase transition immunoreactive material appears in the nucleus, at the nuclear envelope, and in association with microtubules. Concomitantly, we observed an increase of immunoreactivity of the cytoplasm. During mitosis the phosphorproteins recognized by MPM-2 are detected in the cytoplasm, in association with microtubules of the spindle, the phragmoplast, and in the newly-formed cell plate. After completion of mitosis, only the cell plate and cytoplasmic granules are MPM-2 positive. Extraction of the cells with Triton X-100 prior to fixation removes staining of the cytoplasm by MPM-2. The detergent resistant immunoreactive material remains associated with surrounding the nucleus microtubules of the prophase spindle, the core of kinetochore fibers, and the phragmoplast. In the phragmoplast, however, segments of microtubules which are distal to the cell plate are depleted of MPM-2. These data demonstrate that microtubule arrays of endosperm cells are phosphorylated during mitosis. Thus, similar to animal cells, interphase and mitotic microtubules of higher plants have different properties. Additionally, the localization of detergent resistant MPM-2 antigen points to the difference in microtubule nucleation/organization between higher plant and animal cells.
authors.affiliation: Biology Faculty, Moscow State University, Russia.
authors.forename: E A
authors.initials: EA
authors.lastname: Smirnova
authors.forename: D L
authors.initials: DL
authors.lastname: Cox
authors.forename: A S
authors.initials: AS
authors.lastname: Bajer
mesh_terms: D000911:Antibodies, Monoclonal; D000918:Antibody Specificity; D002457:Cell Extracts / Q000276:immunology; D018385:Centrosome / Q000737:chemistry*; D005455:Fluorescent Antibody Technique; D008870:Microtubules / Q000737:chemistry* / Q000276:immunology; D008938:Mitosis / Q000502:physiology; D017830:Octoxynol; D010750:Phosphoproteins / Q000032:analysis*; D010940:Plant Proteins / Q000032:analysis* / Q000276:immunology; D008941:Spindle Apparatus / Q000737:chemistry*
chemical_list: D000911:Antibodies, Monoclonal; D002457:Cell Extracts; D010750:Phosphoproteins; D010940:Plant Proteins; D017830:Octoxynol