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. 2002 Sep;22(18):6430–6440. doi: 10.1128/MCB.22.18.6430-6440.2002

FIG. 4.

FIG. 4.

Examination of the effect of deletion of SWE1 on dmc1-induced arrest. (A) Comparison of the efficiency of entry into the meiotic divisions in wild-type cells, dmc1/dmc1 cells, dmc1/dmc1 swe1/swe1 cells containing the pRS426 vector, dmc1/dmc1 swe1/swe1 cells containing the high-copy pNDT80-426 plasmid, and dmc1/dmc1 swe1/swe1 ndt80/ndt80 cells. Cells were taken during growth (0 h) or at the indicated times after transfer to sporulation medium, fixed, stained with DAPI, and examined by fluorescence microscopy. Completion of the meiosis I (MI) division was assessed as described in the legend for Fig. 1A. The data for wild-type cells, dmc1/dmc1 cells, and dmc1/dmc1 rad17/rad17 cells are the same as those presented in Fig. 2A. All data presented are representative of at least two trials per strain. (B to H) Deletion of SWE1 does not restore a wild-type level of middle gene expression to dmc1/dmc1 cells. A Northern filter was prepared with RNA purified from wild-type cells (lanes 1 to 4), dmc1/dmc1 cells (lanes 5 to 8), dmc1/dmc1 rad17/rad17 cells (lanes 9 to 12), dmc1/dmc1 swe1/swe1 cells containing the vector plasmid pRS426 (lanes 13 to 16) or the high-copy plasmid pNDT80-426 (lanes 17 to 20), and dmc1/dmc1 swe1/swe1 ndt80/ndt80 cells (lanes 21 to 24) harvested during vegetative growth (0 h) or at 6, 8, or 10 h after transfer to sporulation medium, as noted above the top panel (see Materials and Methods). The RNA used in the wild-type, dmc1/dmc1, and dmc1/dmc1 rad17/rad17 lanes was from the same preparations as those used for the experiment shown in Fig. 2B to H. The filter was hybridized sequentially with radioactively labeled probes specific for NDT80 (B), SMK1 (C), CLB1 (D), SPS1 (E), SPS4 (F), SPS100 (G), and the loading control, pC4 (H) (see Materials and Methods). (I to K) Initiation of spore morphogenesis in dmc1/dmc1 swe1/swe1 cells is dependent on NDT80. Cells of a dmc1/dmc1 swe1/swe1 strain (I and J) and of a dmc1/dmc1 swe1/swe1 ndt80/ndt80 strain (K) were fixed and prepared for examination by electron microscopy 24 h after transfer to sporulation medium (see Materials and Methods). (I) A representative field of dmc1/dmc1 swe1/swe1 cells shows no mature asci; some cells contain prospore-like compartments. (J) A higher-magnification micrograph showing a dmc1/dmc1 swe1/swe1 cell that contains immature and aberrant spore-like compartments. (K) A representative field of dmc1/dmc1 swe1/swe1 ndt80/ndt80 cells shows no asci or any cells that have initiated spore morphogenesis.