Figure 6.

DGK expression suppresses the inositol auxotrophy associated with Δsac1 strains. (A) The indicated yeast strains were streaked for isolation on solid uracil-deficient minimal medium that either contained inositol (+Inositol) or was inositol free (−Inositol). Plates were incubated at 26°C for 72 h. Wild-type and Δsac1 strains were CTY182 and CTY244, respectively. Episomal DGK expression plasmids and cognate vector-only controls are designated YEpDGK and YEpURA3, respectively. (B) Mutations that block PtdCho biosynthesis by the CDP-choline pathway suppress the inositol auxotrophy of Δsac1 strains. Yeast strains with the indicated genotypes were streaked for isolation on solid minimal defined medium that was either supplemented with inositol (+Inositol) or was inositol-free (−Inositol). Plates were incubated at 26°C for 72 h and scored for growth. Wild-type and Δsac1 strains were CTY182 and CTY244, respectively. The Δcki1 and Δopi3 derivatives were generated by transformation of yeast cells with the appropriate disruption constructs and confimed by genomic Southern analysis. In these experiments, heavy inocula of the Δsac1 and Δsac1, Δopi3 strains were streaked onto the −Inositol plates to illustrate the tightness of the inositol auxotrophy.