Fig. 5. Observation of SFA-GFP in dividing GFP8 cells. Living cells: the recording time of each picture is indicated (MESZ hours in large numbers; minutes — and in c-e, also seconds — in small numbers). (a,b) Two examples of cells prior to the first division. (c-e) Cells during the first division. (e) Phase contrast images of the cell documented in d showing the four pulsing contractile vacuoles (arrowheads). Arrowhead in c: moving dot of SFA-GFP. Arrowheads in d: #1, rapidly moving dot; #2, slowly moving dot; #3, dot appearing from the back of the cell. Bars, 5 µm (c,d), 4 µm (a,b). Methanol-fixed cells: (a,c) SFA-GFP and corresponding anti-SFA signals (b,d) showing that SFA-GFP is underrepresented in two of the fibers (arrowhead in b) and in dividing cells (arrowheads in c). The differences documented in a/b are characteristic for cells before division and indicate a rapid removal of SFA-GFP from the axisforming fibers (arrowheads in b) along the two-stranded roots. Bars, 2 µm (a,b), 10 µm (c,d).