Fig 3. Identification of genes acting upstream of the Pho80/Pho85/Pho81 kinase complex.

(A) A schematic diagram depicting the expected outcome of epistasis analysis depending on whether or not a mutant is defective in the signaling process upstream of Pho80/Pho85. Genes in red act upstream of Pho80/Pho85 and those in blue do not act upstream of Pho80/Pho85. (B) The PHO84 reporter levels of double mutants carrying the less induced hits and pho80DΔ in 50 μM P_i conditions. All 380 less induced hits were used to generate the double mutants. The PHO84 reporter levels of double mutants in (B) were normalized to that of pho80DΔ. A red dashed line in (B) indicates the maximum PHO84 reporter level of double mutants generated by one of the known downstream genes (pho80DΔ gcn5Δ). (C) The PHO84 reporter levels of double mutants carrying the less repressed hits and pho81Δ in 1 mM P_i conditions. All 243 less repressed hits were used to generate the double mutants. The PHO84 reporter levels of double mutants in (C) were normalized to that of pho81Δ. In (B) and (C), mutants in blue and red are defective in signaling process downstream and upstream of Pho80/Pho85, respectively. (D) A schematic diagram depicting adenine nucleotide metabolism. A gene in red is identified in this study and those in bold black are previously identified.