Fig. 8. Cru1 is required for the expression of the mfa1 gene. (A) Mixtures of the indicated strains were spotted on PD-charcoal plates and incubated for 48 hours at room temperature. Fuzziness was an indication of a successful mating. (B) Formation of conjugative tubes by autocrine cells. Cultures of the autocrine strain TAU3 growing in CMD at OD₆₀₀ of 0.2 were treated with 0.1 ng/ml of synthetic a1-mating pheromone for 8 hours, resulting in the induction of conjugation tubes. A similar treatment of the TAU3 cru1 derivate (TAU7) resulted in no response. Treatment of TAU3 cru1 with 1 µg/ml of synthetic pheromone induces the formation of hyphal extensions that resemble conjugation tubes. Bars, 10 µm. (C) Absence of mfa1 expression in Cru1-defective cells. Cultures of TAU3 and TAU7 cells were treated with 0.1 ng/ml of synthetic a1-mating pheromone and samples were obtained at the indicated times (in minutes). RNA was isolated and 10 µg of RNA was loaded per lane. The blot was probed with mfa1 and rRNA.