Recognition of Mitosis

Mohberg, Joyce

doi:10.1016/b978-0-12-049602-0.50020-2

Cited by 5 publications

(9 citation statements)

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“…The patches were reminiscent of the patchwork‐like structure of reconstituting nuclei in early S phase seen by phase contrast illumination (e.g. [29]). In the case of staining with high amounts of the dye–polymalate conjugate, the nuclei were evenly stained.…”

Section: Resultsmentioning

confidence: 93%

“…At low probe concentrations, however, the fluorescence intensity was distributed in patches, and these did not coincide with the intensity of the DAPI‐stained DNA. In the plasmodium, the early S phase immediately follows mitosis and coincides with the phase of nuclear reconstitution [29]. The fluorescent patchwork could correspond to the existence of the reported higher order complexes of polymalate and nuclear proteins [9,10].…”

Section: Discussionmentioning

confidence: 99%

“…The fluorescent patchwork could correspond to the existence of the reported higher order complexes of polymalate and nuclear proteins [9,10]. The bright spots are indicative of the reconstituting nucleolus [29], reflecting complexes of polymalate with nucleolus‐specific proteins, such as the basic fibrillarin‐like protein B‐36 [32]. The high degree of staining in the early S phase correlates with the reported massive incorporation of 14 C‐polymalate into nuclei during feeding of plasmodia with d ‐[ 14 C]glucose [13].…”

Section: Discussionmentioning

confidence: 99%

“…[28]. In control experiments, the progress of the mitotic cycle was followed by the phase contrast technique of Mohberg [29]. For staining, the ultra‐thin plasmodia were overlayed with culture medium containing 10 mg·mL −1 of fluorescence‐labeled polymalate or fluorescent dye alone (control) at the times 10, 30 and 40 min (in S phase), and 200 min (in G 2 phase) after mitosis.…”

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confidence: 99%

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Localization of fluorescence‐labeled poly(malic acid) to the nuclei of the plasmodium of Physarum polycephalum

Karl¹,

Gasselmaier²,

Krieg

et al. 2003

European Journal of Biochemistry

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The nuclei in the plasmodium of Physarum polycephalum, as of other myxomycetes, contain high amounts of polymalate, which has been proposed to function as a scaffold for the carriage and storage of several DNA-binding proteins [Angerer, B. and Holler, E. (1995) Biochemistry 34, 14741-14751]. By delivering fluorescence-labeled polymalate into a growing plasmodium by injection, we observed microscopic staining of nuclei in agreement with the proposed function. The fluorescence intensity was highest during the reconstruction phase of the nuclei. To examine whether the delivery was under the control of polymalatase or related proteins [Karl, M. & Holler, E. (1998) Eur. J. Biochem. 251, 405-412], the cellular distribution of these proteins was also examined by staining with antibodies against polymalatase. Double-stained plasmodia revealed a fluorescent halo around each fluorescent nucleus during the reconsititution. Fluorescent nuclei were not observed when the hydroxyl terminus of polymalate, known to be essential for the binding of polymalatase, was blocked by labeling with fluorescein-5-isothiocyanate. By immune precipitation, it was shown that polymalate and polymalatase or related proteins were in the precipitate. It is concluded that polymalate is delivered to the surface of nuclei in the complex with polymalatase or related proteins. The complex dissociates, and polymalate translocates into the nucleus, while polymalatase or related proteins remain at the surface.Keywords: Physarum polycephalum; plasmodium; polymalic acid; polymalatase; reconstituting nuclei.Physarum polycephalum is a well characterized member of the plasmodial slime molds (myxomycetes) that typically have a life cycle involving haploid (spores, amoebae) and diploid (plasmodia) cell forms [1]. Together with the cellular slime mold Dictyostelium discoideum and other Mycetozoa, P. polycephalum has been placed among the multicellular eukaryotes on the basis of molecular phylogenetic criteria [2]. The plasmodium undergoes mitosis without cytokinesis and usually develops into a multinuclear giant cell (macroplasmodium). This can contain billions of nuclei (e.g. 10 9 nuclei for a cell having a diameter of 14 cm), which divide synchronously within 3-4 min in an 8-9 h cycle. P. polycephalum, especially the plasmodium, has been chosen as a model to study biological and biochemical questions concerning differentiation and cell cycle [3,4].Considering the synchronous timing of cellular events and the giant dimension of a plasmodium, an appropriate device is necessary to achieve at any given moment an even distribution of molecular constituents. A characteristic oscillating protoplasma streaming [1] probably accounts for the travelling of material along the veins over a certain distance, although the mechanistic details are not known. To achieve a coordinated delivery of equilocally functioning proteins, molecular vehicles would have the advantage of stockpiling and carrying a number of different molecules jointly to defined loci, for example, nuclear p...

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Section: Resultsmentioning

confidence: 93%

Section: Discussionmentioning

confidence: 99%