Spindle and kinetochore morphology of Dictyostelium Discoideum

Abstract

The metaphase spindle of haploid Dictyostelium discoideum (n = 7) is 2µm long. It consists of some 20 microtubules which seem continuous between the spindle pole bodies and there are about 20 chromosomal microtubules at each end of the spindle. During anaphase the central spindle elongates and the chromosomal microtubules shorten. The spindle length and structure at this stage suggests that lengthening is caused by elongation as well as parallel sliding of the nonchromosoreal microtubules. The nuclear envelope remains mostly intact during mitosis, and nuclear separation through medial constriction takes place when the spindle is 6 µm long. Cytokinesis occurs when the spindle is 10 µm long. At that time the kinetochores double in size. During interphase, the spindle pole body separates from the nucleus to a distance of 0.7 µm, and it returns at the onset of the next prophase when it becomes functionally double, thereby starting the formation of a central spindle. When comparing mitosis in the cellular slime molds Polysphondylium violaceum and D. discoideum, several similarities and some differences are apparent. © 1976, Rockefeller University Press., All rights reserved.