FIG. 1.

Cells of a dmc1/dmc1 rad17/rad17 strain and cells of a dmc1/dmc1 strain overexpressing NDT80 enter the meiotic divisions and express middle sporulation-specific genes. (A) Comparison of the efficiency of entry into the meiotic divisions by wild-type cells, dmc1/dmc1 rad17/rad17 cells, dmc1/dmc1 cells containing the high-copy plasmid pNDT80-426 (see Materials and Methods), and dmc1/dmc1 cells containing the vector pRS426. Cells that had been incubated in sporulation medium for the indicated times were fixed, stained with DAPI, and examined by fluorescence microscopy. Cells that appeared binucleate, trinucleate, or tetranucleate were scored as having completed meiosis I (MI). The data presented are representative of at least two trials per strain. (B) Sporulation-specific gene expression in wild-type cells (lanes 1 to 4), dmc1/dmc1 cells containing the pRS426 vector (lanes 5 to 8), dmc1/dmc1 cells containing the high-copy pNDT80-426 plasmid (lanes 9 to 12), and dmc1/dmc1 rad17/rad17 cells (lanes 13 to 16). This Northern filter contained RNA extracted from the indicated strains during vegetative growth (0 h), or 6, 8, or 10 h after transfer to sporulation medium, as noted above the top panel. The filter was hybridized sequentially with radioactively labeled probes specific for NDT80, SMK1, CLB1, SPS1, SPS4, SPS100, and the loading control, pC4 (see Materials and Methods).