A new collection of thermosensitive endocytosis mutants in the cellular slime mold Dictyostelium discoideum.

We used a photoactivatable fluid-phase marker to isolate a new collection of thermosensitive endocytosis mutants in the cellular slime mold Dictyostelium discoideum. All the strains were thermosensitive for growth on bacteria or axenic medium at 27 degrees C. Initial rates of endocytosis rapidly decreased upon incubation at the restrictive temperature, but surprisingly most of the strains showed a transient recovery of activity with prolonged exposure to 27 degrees C. Endocytosis and exocytosis activities were uncoupled for some of the cell lines at 27 degrees C whereas the others had to be shifted to 29 degrees C. Further molecular analysis of these mutants could lead to the discovery of new proteins involved in endocytosis and its regulation.