Figure 4.—

Guanine reverts the pleiotropic phenotype of the gua1–G388D mutant. (A) Reversion of the Slg⁻ phenotype of gua1–G388D by guanine. Strains Hm458 (gua1–G388D) and H117 (GUA1) were streaked for single colonies on minimally supplemented SD plates (right), and on SD plates containing 130 μm guanine (+G, left) that were incubated for 3 days at the indicated temperatures. (B) Reversion of the Gcd phenotype by guanine requires the integrity of the salvage pathway. Strains H117 (GUA1) and Hm535 (GUA1 Δhpt1), and transformants of Hm458 (gua1–G388D) and Hm534 (gua1–G388D Δhpt1) with scGUA1 (pDI3) or with empty vector (pRS426), were replica printed to 10 mm 3AT plates (top) and to 3AT plates containing 130 μm guanine (+G, bottom) that were incubated for 4 days at 28°. (C) Growth phenotypes of the five strains used to obtain WCE for HPLC assays (Table 3 and materials and methods). Cells of the five strains with the relevant genotypes indicated were streaked for single colonies on minimally supplemented SD plates and incubated for 8 days at 25°.