Figure 1.

Forkhead transcription factors are required for the induction of ste11⁺ mRNA and efficient mating. (A) wt (HM6), fkh2 (HM5657), fhl1 (HM4837), mei4 (HM50), fkh2 fhl1 (HM4887), fkh2 mei4 (HM5515), or fkh2 fhl1 mei4 (HM5544) cells were grown in EMM2 medium to a density of 1 × 10⁷ cells/ml, washed, and resuspended at a density of 2 × 10⁷ cells/ml in EMM2 medium lacking nitrogen. They were then cultured at 30°C and samples were collected at the indicated times for determination of mating frequency. Data are from representative experiments. (B) Total RNA was extracted from cells treated as in (A), and the abundance of ste11⁺ mRNA was examined by northern blot analysis. Ethidium bromide staining of rRNA is shown as a loading control. The ratios of intensities of ste11⁺ to rRNA signals were used to calculate the relative fold enrichment, shown below the rRNA. The samples from wt to fkh2, from fhl1 to mei4, from fkh2 mei4 to fkh2 fhl1 mei4 were from the same gel. All the samples were treated equally and the exposure time was the same. (C) Cells were transformed with pcL-ste11⁺ (ste11⁺), pAL-fkh2⁺ (fkh2⁺), or the empty vector pcL-X (Vec) and were cultured as in (A) for the determination of mating efficiency at 24 h after transfer to EMM2 medium without nitrogen. Data are from representative experiments.