SYNCHRONIZATION OF MITOSIS BY THE FUSION OF THE PLASMODIA OF <i>PHYSARUM POLYCEPHALUM </i>

Rusch, H. P.; Sachsenmaier, W.; Behrens, Kathryn; Gruter, Vera

doi:10.1083/jcb.31.1.204

Cited by 134 publications

(38 citation statements)

References 7 publications

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“…When plasmodia on different mitotic schedules are fused, the heterokaryon goes through a synchronous mitosis at an averaged time (20). One explanation for this result is that a mitogen accumulates and then triggers mitosis when it reaches a critical level (see ref.…”

Section: Copolymerization Of Periodic Polypeptides With Porcinementioning

confidence: 99%

Periodic synthesis of microtubular proteins in the cell cycle of Physarum.

Laffler¹,

Chen²,

Dove³

1981

Proc. Natl. Acad. Sci. U.S.A.

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Periodic polypeptide labeling over the naturally synchronous nuclear replication cycle of Physarum polycephalum was analyzed by fluorography of two-dimensional electropherograms. Two sets of polypeptides, denoted as P and Q, showed strong periodicity; they were maximally labeled just prior to mitosis. This periodicity was shown to reflect synthesis rather than turnover or recovery. Both P and Q copolymerized with porcine microtubular proteins and displayed electrophoretic properties similar to those of porcine tubulins. The significance of the periodic synthesis of these microtubular proteins is discussed as a possible component within the chain ofevents that establishes the high mitotic synchrony of Physarum syncytia. The replicative cell cycle of eukaryotes is marked by major cellular events such as entry into DNA synthesis (S phase) and progression through the stages of mitosis. Do these cellular events reflect molecular periodicities in protein synthesis?One can distinguish between division cycles that generate apparently equivalent daughter cells and those cycles that yield frankly distinct progeny. In the differentiative cell cycle ofCaulobacter crescentus, the generation of a new cell type, the swarmer, is accompanied by strong periodicities in the synthesis ofa number ofpolypeptides such as the flagellin needed for this new cell type (1).The situation for proliferative systems with equational division is less clear. Experimental analysis in these systems is complicated by the problem of distinguishing between a natural, endogenous periodicity and an artifactual one induced by the synchronization procedure (e.g., see ref.2). Two approaches have arisen to deal with this problem: (i) postsynchronization methods such as elutriation or mitotic detachment, to separate prelabeled cells into temporal classes; and (ii) natural synchrony in a syncytium large enough for biochemical analysis, such as that of the myxomycete Physarum polycephalum (see ref. 3).The first approach has been used to analyze the periodicity of labeling of polypeptides in Saccharomyces cerevisiae (4) and HeLa cells (5). Among the polypeptides that can be identified in two-dimensional electropherograms from Saccharomyces or from HeLa, the amplitude oflabeling never changes more than 3-fold.We have adopted the second approach, using Physarum. The extreme natural synchrony might permit detection of periodicities that would be obscured by a loss of resolution in postsynchronization methods.We report that Physarum polypeptides with properties of microtubular proteins are synthesized preferentially in the premitotic interval of the division cycle. The amplitude of the periodicity is at least 30-fold. MATERIALS AND METHODSCultures. The general culture methods have been described by Mittermayer et al. (6). Microplasmodia of strain CL (7) were grown in suspension culture in a simplified soy medium (SSM) adapted from a medium of E. Brewer and B. Prior (personal communication): per liter, 10 g of Difco BactoSoytone, 3 g of yeast extract, 9 g ...

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Section: Copolymerization Of Periodic Polypeptides With Porcinementioning

confidence: 99%

Periodic synthesis of microtubular proteins in the cell cycle of Physarum.

Laffler¹,

Chen²,

Dove³

1981

Proc. Natl. Acad. Sci. U.S.A.

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“…For demonstration of the presence or absence, during this short period, of factors which could initiate DNA synthesis in nuclei that have not undergone mitosis, it would have been necessary to use combinations of plasmodia in which the G2-phase nuclei entered the host plasmodia just prior to mitosis of the latter, without subsequently undergoing mitosis along with the nuclei of the host. Unfortunately, such a combination results in advanced mitosis of the G 2 -phase nuclei in synchrony with a somewhat delayed mitosis of the host nuclei (14,30).…”

Section: >99mentioning

confidence: 99%

REGULATION OF DNA REPLICATION IN THE NUCLEI OF THE SLIME MOLD PHYSARUM POLYCEPHALUM

Guttes

Güttes

1968

The Journal of Cell Biology

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Nuclei in G2 phase of the slime mold Physarum polycephalum, when transplanted, by plasmodial coalescence, into an S-phase plasmodium, failed to start another round of DNA synthesis. In the reciprocal combination, S-phase nuclei in a G2-phase host continued DNA synthesis for several hours without appreciable decrease in rate. It is suggested that the beginning of DNA replication is determined by an event, either during or shortly after mitosis, which renders the chromosomes structurally competent for DNA replication.

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“…Prominent 'veins' developed between the plasmodia and rapid transport of protoplasm occurred along these channels. A thorough mixing of the protoplasm of the two strains over a wide area was inferred from studies of plasmodia1 fusion by other workers (Miller, Anderson & Peterjohn, I 964; Rusch, Sachsenmaier, Behrens & Gruter, 1966;Kerr & Waxlax, 1968). For about 4 h the fused plasmodia did not show any abnormalities; up to this point fusion proceeded and a common system of veins was established, as also occurred when plasmodia of the same strain met.…”

Section: The Normal Course Of the Lethal Reactionmentioning

confidence: 99%

The Lethal Interaction Following Plasmodial Fusion between Two Strains of the Myxomycete Physarum polycephalum

Carlile¹

1972

Journal of General Microbiology

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A lethal reaction followed fusion between plasmodia of two strains ( 15 and 29) of the Myxomycete Physarum polycephalum on a solid medium. Dead areas were seen about 5 h after fusion and increased in size rapidly. Strain 29 was often wholly destroyed but strain 15 commonly survived and subsequently reinvaded the dead areas. Large plasmodia of 29 were destroyed by fusion with small plasmodia of 15, but large plasmodia of 15 survived fusion with small plasmodia of 29. The lethal reaction did not normally occur under conditions of suboptimal nutrition, but disappearance of strain 29 still took place. It is suggested that protoplasm of strain 15 can eliminate nuclei of strain 29, but that strain 29 has little or no ability to tolerate or eliminate nuclei of strain 15.

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SYNCHRONIZATION OF MITOSIS BY THE FUSION OF THE PLASMODIA OF PHYSARUM POLYCEPHALUM

Cited by 134 publications

References 7 publications

Periodic synthesis of microtubular proteins in the cell cycle of Physarum.

Periodic synthesis of microtubular proteins in the cell cycle of Physarum.

REGULATION OF DNA REPLICATION IN THE NUCLEI OF THE SLIME MOLD PHYSARUM POLYCEPHALUM

The Lethal Interaction Following Plasmodial Fusion between Two Strains of the Myxomycete Physarum polycephalum

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