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A purified cellular extract accelerates the cell cycle in Physarum polycephalum
U Hobohm1, A Hildebrandt, L Rensing
1Dept. Biology, University of Bremen, West Germany.
Abstract:
Plasmodia of the myxomycete Physarum polycephalum (strain Cl) were collected at different times during the cell cycle and extracts were prepared from homogenates using a buffer optimized for microinjection into plasmodial veins. These extracts were injected into plasmodia during the first 3 h of the cell cycle. The time of the following mitosis was monitored and compared with that of the buffer-injected controls. Extracts of plasmodia homogenized 45 min before late telophase accelerated the onset of mitosis in the injected plasmodium up to 70 min, i.e., an advance of 10-14% compared to the 8- to 10-h cell cycle duration of the controls. The accelerating activity vanished completely after heating, freezing, or protease digestion, thus indicating the peptide nature of the active agent. Purification of the active compound by means of gel filtration revealed a molecular mass of about 2500 Da. The active portion of the extract was further fractionated by HPLC and the activity determined in a single peak.
Insights
Researchers discovered a peptide in Physarum polycephalum that significantly accelerates mitosis. This finding offers insights into cell cycle regulation in this model organism.
Area of Science:
- Cell Biology
- Mycology
- Biochemistry
Background:
- Physarum polycephalum is a widely studied acellular slime mold.
- Understanding cell cycle regulation is crucial in developmental biology.
Purpose of the Study:
- To identify factors within Physarum polycephalum that influence cell cycle progression.
- To investigate the potential of these factors to accelerate mitosis.
Main Methods:
- Preparation of extracts from Physarum polycephalum plasmodia at specific cell cycle stages.
- Microinjection of extracts into plasmodial veins.
- Monitoring and comparison of mitosis onset in injected versus control plasmodia.
- Biochemical assays including heat, freezing, protease digestion, gel filtration, and HPLC for purification and characterization.
Main Results:
- Extracts from late telophase significantly accelerated mitosis by 10-14% (up to 70 min advance).
- The accelerating activity was abolished by heat, freezing, and protease digestion, indicating a peptide nature.
- Gel filtration suggested a molecular mass of approximately 2500 Da for the active compound.
- HPLC purification isolated the active agent into a single peak.
Conclusions:
- A peptide factor present in Physarum polycephalum accelerates the onset of mitosis.
- This peptide plays a role in regulating the cell cycle in this organism.
- The findings contribute to the understanding of molecular mechanisms governing cell division.