Concerted Movement of Prestalk Cells in Migrating Slugs of Dictyostelium Revealed by the Localization of Myosin

Localization of myosin in slugs of the cellular slime mold Dictyostelium discoideum was investigated by an immunofluorescence technique. Myosin is thought to provide the molecular machinery for cellular movement. We found that myosin could be visualized as c-shaped fluorescence at the cortex of prestalk cells in a migrating slug, and that the open regions of all c-shaped fluorescence point in the direction of the slug's migration. We reported previously that the c-shaped fluorescence of myosin can be seen at the cortex of the tail region of actively locomoting cells at the unicellular stage (39, 41). These results suggest that prestalk cells move actively in the slug, and that their direction of movement, which can be identified from the polarity of c-shaped fluorescence, correspond with the direction of the slug's migration. The distribution of c-shaped fluorescence in slugs during migration, phototaxis and avoidance of ammonia strongly suggests that the slug's behavior is controlled by the concerted movement of prestalk cells.