Fig. 5. Mug27 is required for FSM development. (A) The formation of the FSM in mug27⁺ (SOP091w) and mug27 (SOP095) cells during spore formation was visualized by examining the behavior of GFP-Psy1. Graphs show that the frequency of abnormal FSM growth in mug27⁺, mug27-3HA (SOP101), mug27 and mug27(KD)-3HA (SOP100) cells 20 hours after meiosis was increased. Typical images are shown in the right-hand panels. Abnormal localization of GFP-Psy1 to the cell cortex in a mug27 cell is indicated by the arrowheads. (B) Time-lapse images of the GFP-Psy1 and Meu14-GFP proteins in mug27⁺ (SOP091w; i) and mug27 (SOP095; ii) cells undergoing FSM formation at 28°C. These images show a subset of the GFP images that were captured every 2 minutes. The time in minutes, with 0 minutes being the time at which FSM formation begins, is indicated at the bottom of each photograph. Scale bars: 10 µm. (C,D) Comparison of the time taken for the FSM to form in mug27⁺ and mug27 cells. (C) Graph shows the time taken for the cells to proceed from metaphase II to closure of the Meu14 ring (n=50 for each cell type); (D) graph shows the duration of the two FSM-formation phases depicted in the upper panel of D. The FSM-formation process was divided into two phases as follows: phase I, from the initiation of FSM formation to the time at which the diameter of the Meu14-GFP ring is maximal; phase II, the time at which the large Meu14-GFP ring begins to reduce in size until FSM formation is complete. The depictions indicate how GFP-Psy1 and Meu14-GFP move during FSM formation in S. pombe. (E) Comparison between mug27⁺ and mug27 cells of the maximum diameter of the Meu14 ring. The maximum diameter of Meu14 was measured by MetaMorph software (n=84 for each cell type).