Effects Of Microgravity On The Cell Cycle, Actin Skeleton And Proteome Of Physarum Polycephalum

Space environment has radiation rays, microgravity, vacuum and no changes of day and night. Many serious adverse physiological changes occur under the effect of microgravity, such as impaired immune system function bone deterioration, muscle loss, and losing Ca2+. Some researchers suggested that the changes of cell cycle under the effect of microgravity maybe associated with these diseases. In the search for underlying mechanisms and possible new countermeasures, we use the naturally synchronized Physarum polycephalum to study the effects of modeled microgravity on the cell cycle.In parallel, the cell cycle, actin skeleton and proteome were analysed in Physarum polycephalum cultured (1)in microgravity for 20h, (2)in microgravity for 40h, (3)in microgravity for 80h, (4)in microgravity for 40h and on the 1g ground for 72h, (5)in the 1g ground control. The comparison of the sample grown continuously in microgravity and the 1g ground control indicated that the duration of the G2 phases were lengthened about 20min, 2h and 2h in microgravity for 20h, 40h and 80h respectively. On the contrary, the transfer from microgravity for 40h to the 1g ground for 72h did not provoke any significant change in the duration of the G2 phase. Thus the effect of microgravity could be reversed by growing on the 1g ground. The differences observed in the duration of the G2 phases in above 5 groups could be due to the fact that Physarum polycephalum was subjected to the microgravity for different periods, which could show an effect of microgravity on the cell cycle.In addition, incubated in microgravity for 40h, forms and distribution of actin skeleton in G2 phase were unnormal; forms changed in some degree, actin skeleton became shorter, indisorder and in a chaos. But there are no changes in the other phases. And the method of two-dimensional electrophoresis (2-DE) was used to investigate the differences in proteome of Physarum polycephalum between microgravity for 40h and its control in the cell cycle with pI ranging from 3 to 10. We observed 208 spots in the 2-DE maps of control Physarum polycephalum and 245 spots in those of mutant Physarum polycephalum in S phase, 60 dots specially appeared in the mutant Physarum polycephalum; 200 spots in the 2-DE maps of control one and 231 spots in those of mutant one in G2 phase, 72 dots specially appeared in the mutant one; 188 spots in the 2-DE maps of control one and 231 spots in those of mutant one in prophase, 64 dots specially appeared in the mutant one; 192 spots in the 2-DE maps of control one and 220 spots in those of mutant one in metaphase, 47 dots specially appeared in the mutant one; 186 spots in the 2-DE maps of control one and 218 spots in those of mutant one in anaphase, 58 dots specially appeared in the mutant one; 196 spots in the 2-DE maps of control one and 225 spots in those of mutant one in telophase, 45 dots specially appeared in the mutant one. Our results show that microgravity can induce mutations in Physarum polycephalum at proteomic level.The study of the effect of microgravity on the cell cycle, actin skeleton and proteome of Physarum polycephalum is good to understand the mechanism of the microgravity of cell cycle and our study can supply some projects for the illness that induced by microgravity.