Mitotic cell cycle control in Physarum

摘要: High resolution flow-cytometric studies of isolated macroplasmodial nuclei the myxomycete. Physarum polycephalum provide definite evidence for persistence natural synchrony at mitosis throughout entire cell cycle, i.e. completely synchronous DNA replication and traverse G2. Even if within a given macroplasmodium belong to two distinct genome size classes (mixoploidy), they cycle in strict synchrony. This cannot be explained by current models regulation division based solely upon nuclear and/or nuclear/cytoplasm ratios. Constitutional content variation was apparent among all tested strains, loss late-replicating, presumably AT-rich accounts this variation. A constant duration S phase is maintained, irrespective content, via differential slowdown rates during 2nd 3rd hours replication. frequently described extension into G2 could not substantiated. Interference with protein synthesis provides first brief "G1 phase" equivalent 3-4 min asynchronous microplasmodial cultures, temporally assigns synthesis-dependent "transition point" completion initiation 5 prior actual which have passed point time addition cycloheximide replicate 5% their before become arrested. These findings strong experimental support transition concept control, additionally are commensurate some form replicon-set hypothesis Physarum.