OBSERVATIONS ON POLARITY IN THE SLIME MOLD DICTYOSTELIUM DISCOIDEUM

¹ Princeton University

Experiments designed to give some insight into the nature of polarity were performed on the amoeboid slime mold Dictyostelium discoideum. The separate myxamoebae which stream together to form aggregations of myxamoebae show an external polarity and the resulting cell mass has a clear over-all antero-posteriority. In both cases it was shown that the internal parts do not reflect the external polarity. It is known from previous experiments that the aggregating myxamoebae orient in a concentration gradient of a chemical substance tentatively called acrasin, and that acrasin is found in later stages of development. By reversing the gradient of acrasin, separate myxamoebae did not back up but re-oriented towards the point of high concentration. However, it was shown by various experiments that the external acrasin gradient cannot always determine the direction of the polarity, for in the cell masses the polar movement occurs when there is no external gradient of acrasin, or in some cases away from the region of high acrasin emission. It was also shown that polarity can arise in spherical cell masses undergoing gentle shaking in liquid media.

This article has been cited by other articles:

				S. Hirose, T. Mayanagi, C. Pears, A. Amagai, W. F. Loomis, and Y. Maeda Transcriptional Switch of the dia1 and impA Promoter during the Growth/Differentiation Transition Eukaryot. Cell, August 1, 2005; 4(8): 1477 - 1482. [Abstract] [Full Text] [PDF]