FIGURE 4:

Pheromone sensitivity and pheromone production in germinating spores. Spores of strains YJM451 and YJM1399 were isolated from tetrads and germinated in the presence of 2 μM α-factor (A) or 100 nM α-factor (B). (C) Two isolated spores from DLY20288. The top-right spore (presumed MATα) shows expression of the Mfα1 reporter following germination, whereas the bottom-left spore (presumed MATa) does not. (D) Spores from DLY20922 and DLY21020 (containing the Mfα1 reporter integrated into YJM451 and YJM1399) were isolated from tetrads and imaged during germination. Expression of the Mfα1 reporter was determined just before bud emergence (see Materials and Methods). (E) Spores from DLY22729 (a lab strain in the YEF background) carrying the Mfα1 reporter were treated as in D, and expression was determined just before bud emergence during the first cell cycle, the second cell cycle, and the first cell cycle of the daughter. The second cell cycle and the daughter signals were each significantly higher than the first cell cycle (t test, p < 0.002). (F) Spores from DLY18930 carrying the TEF1 reporter were treated as in E. (G) Spores from the indicated wild strains carrying the Mfα1 reporter were treated as in D (note that data in D are also included in G). (H) Correlation between the percentage of spores that bud following germination (from Figure 2D) and the averaged Mfα1 reporter expression (from G; Pearson’s correlation, R² = 0.74, p < 0.01).