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Replication of nucleolus-associated DNA during "G2 phase" in Physarum polycephalum

E Guttes, S Guttes

    The Journal of Cell Biology
    |November 1, 1969
    PubMed

    Insights

    Physarum polycephalum DNA replication peaks after mitosis. Some large nuclei show continuous DNA synthesis throughout interphase, differing from typical Physarum cell cycles.

    Area of Science:

    • Cell Biology
    • Molecular Biology
    • Mycology

    Background:

    • The slime mold Physarum polycephalum exhibits a unique cell cycle with a distinct period of rapid nuclear DNA replication following mitosis.
    • Understanding the temporal regulation of DNA replication in eukaryotes is crucial for comprehending cell proliferation and genome stability.

    Purpose of the Study:

    • To investigate the kinetics and localization of DNA replication during the intermitotic period in Physarum polycephalum.
    • To characterize nuclei exhibiting unusual DNA synthesis patterns during interphase.

    Main Methods:

    • Radioautography using thymidine-3H incorporation to track DNA synthesis.
    • Microscopic analysis of nuclear morphology and nucleolar organization in Physarum polycephalum.

    Main Results:

    • The majority of nuclear DNA replication in Physarum polycephalum occurs in a short window immediately after mitosis.
    • Low-level thymidine-3H incorporation was observed in the nucleolar region throughout interphase.
    • A subpopulation of exceptionally large nuclei displayed high rates of extranucleolar DNA synthesis continuously during interphase, often with multiple, small nucleoli.

    Conclusions:

    • Physarum polycephalum exhibits a tightly regulated, predominantly post-mitotic DNA replication phase.
    • The presence of large nuclei with continuous DNA synthesis suggests alternative replication strategies or cell cycle variations within the Physarum population.

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