Fig. 2. Endocytosis in fission yeast passes from the cell membrane to the vacuole via intermediate prevacuolar compartments. (A) Vacuoles were prelabelled with CDCFDA and then exposed to FM4-64. After 15 minutes, FM4-64 labels prevacuolar compartments not stained with CDCFDA. (B) Quantification of the experiment in A. The number of CDCFDA-stained vacuoles (green line, V) remains constant throughout the experiment. The number of FM4-64-stained PVC initially rises but subsequently falls as fluorescence is transferred to the vacuolar membrane (red line, PVC). The number of FM4-64-labelled vacuoles (red line, V) increases with time. (C) The same experiment as in A but vacuoles were first fused by incubation in water for 60 minutes. (D) The number of CDCFDA-stained vacuoles (green line, V) remains constant through the experiment but the number of FM4-64-labelled PVC reaches a plateau as transfer to the vacuolar membrane is blocked (red line, PVC). Bar, 10 µm.