Summary
We found a new type of morphogenesis in the plasmodia of the true slime moldPhysarum polycephalum: The plasmodium broke temporarily into pieces with uniform size at low temperatures. This fragmentation took place sharply around 5 h after the organism was transferred to low temperatures, and, unlike dormant spherulation, the fragments coalesced to recover the large plasmodium in about 15 h. Each fragment contained about 8 nuclei. The volume of the fragments remained constant under slight compression, but was halved under strong compression. The fragmentation showed a sharp temperature transition. The transition temperature was constant at 16 °C when plasmodia had been cultured above 16 °C, and decreased gradually as the culture temperature decreased below 16 °C. Both cycloheximide and actinomycin D inhibited the fragmentation in a dose-dependent manner, indicating that the transcription and protein synthesis took a part in the fragmentation. The tested strains with a high chemoreception sensitivity exhibited fragmentation similar to that of the strain with low sensitivity, but the transition temperature was lower. The biological significance of the fragmentation and its relationship with the other morphogenetic processes are discussed.
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Kakiuchi, Y., Ueda, T. Fragmentation of the plasmodium into equally sized pieces by low temperatures in the true slime moldPhysarum polycephalum: A new morphogenesis. Protoplasma 206, 131–136 (1999). https://doi.org/10.1007/BF01279259
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DOI: https://doi.org/10.1007/BF01279259