Fig. 2. mfr1+ is expressed exclusively during meiosis. Cells of the diploid strain Sp966 were presynchronized in G1 by nitrogen starvation for 14 hours at 25°C. Nitrogen was added and the culture was incubated at 34°C to inactivate the pat1-114 temperature-sensitive protein kinase. (A) Northern and western blots showing mfr1+ mRNA and protein levels. Cdc13 and cdc2 protein levels are shown. Exp, mitotic exponentially growing cells before nitrogen starvation. (B) FACS analysis. Pre-meiotic S-phase occurred between 2 and 3 hours. Cells with 1C DNA content observed after 6.5 hours correspond to haploid spores that are released when cells are sonicated before flow cytometry. (C) Percentage of cells with 1, 2 and 4 nuclei and percentage of asci. Meiosis I occurred between 4 and 5 hours, meiosis II between 5 and 6 hours and sporulation after 7.5 hours.
