FIG. 4.

PKA regulatory subunit Pkr1 regulates melanin, capsule, and mating and functions downstream of the Gα protein Gpa1. (A) Melanin production in the wild-type, gpa1, pkr1, pkr1 gpa1, and pkr1 pka1 strains was assessed on Niger seed agar following incubation at 37°C for 2 days. (B) Phenoloxidase activity in glucose-starved wild-type, gpa1, pka1, pka1+PKA1, pkr1, and pkr1 gpa1 strains was determined by measuring the oxidation of the diphenolic substrate ABTS (1 U of activity = 0.01 A₄₂₀ absorbance units in 30 min). The values shown are the average of duplicate samples. (C) The wild-type, gpa1, pkr1, pkr1 gpa1, and pkr1 pka1 strains were grown in low-iron media (LIM plus EDDHA), and the capsule was visualized with India ink and photographed (final magnification, ×324). The packed volumes of these cells are shown in Fig. 1B. (D) Wild-type, gpa1, pkr1, pkr1 gpa1, and pkr1 pka1 strains were cocultured with serotype D MATa cells on V8 agar for 14 days at 24°C and photographed (final magnification, ×32.4).