Fig. 3. Cdc25p localisation and stability are altered in flp1 mutant fission yeast cells. (A) Asynchronous exponentially growing cultures of myc₁₂-cdc25 (reference control) and flp1 myc₁₂-cdc25, otherwise isogenic strains, were processed for indirect immunofluorescence microscopy using anti-Myc antibodies. Nuclei were stained with DAPI. Approximate phase of the cell division cycle is indicated. Cells at different stages of the cell cycle were scored to quantify the defect observed in proper Cdc25p localisation as compared with the reference control (myc₁₂-cdc25 cells). (B) Equal numbers of cells from asynchronous cultures of two different strains (myc₁₂-cdc25 GFP-atb2⁺ and flp1 myc₁₂-cdc25) were mixed and processed for indirect immunofluorescence microscopy using anti-Myc antibodies, DAPI and GFP-Atb2 (the latter to distinguish flp1⁺ wild-type from flp1 mutant). flp1 mutant cells are indicated by white arrowheads in the photomicrographs. Scale bars: 10 µm. Note that GFP-Atb2p-positive cells contain less Myc-Cdc25p (as judge by the relative intensity of anti-Myc staining). (C) Ten-fold dilution of the indicated strains from log-phase cultures at 25°C were inoculated in YES Petri dishes and incubated for 48 hours at the indicated temperatures.