title: The control of mitosis in Physarum polycephalum: the effect of delaying mitosis and evidence for the operation of the control mechanism in the absence of growth.
abstract: Possible mechanisms coordinating the control of mitosis and DNA synthesis with growth were experimentally tested in Physarum polycephalum by the response of plasmodia to 2 different kinds of perturbation of the DNA:mass ratio. Mitosis and DNA synthesis were delayed without stopping growth either by the use of fluorodeoxyuridine (FUdR) or puromycin, in both cases the delayed mitosis was followed by a single shortened intermitotic period, as predicted by all the mechanisms considered and substantiating a basic assumption made that the time of mitosis is homeostatically controlled to maintain a constant DNA:mass ratio. When more than 50% of the DNA was destroyed by ultraviolet irradiation 2 consecutive mitoses could occur even when growth was completely stopped by starvation. This result can only be accounted for by 2 of the 5 models considered, a finding which agrees with the results of previous experiments which were also consistent with only these 2 mechanisms.
mesh_terms: D004247:DNA / Q000096:biosynthesis; D005467:Floxuridine / Q000494:pharmacology; D008938:Mitosis / Q000187:drug effects; D008954:Models, Biological; D009235:Myxomycetes / Q000502:physiology*; D010804:Physarum / Q000254:growth & development / Q000378:metabolism / Q000502:physiology*; D011691:Puromycin / Q000494:pharmacology
chemical_list: D005467:Floxuridine; D011691:Puromycin; D004247:DNA