FIGURE 3.

The pattern of PI synthesis after reintroduction of inositol is reduced in mutant strains unable to mobilize or store TAG. Lipids in cultures of wild type, dga1Δlro1Δare1Δare2Δ, and tgl3Δtgl4Δtgl5Δ were labeled to steady state with [1-¹⁴C]acetate (1 μCi/ml) in I⁺C⁺ medium at 37 °C as described under “Experimental Procedures” for at least 7 generations and grown to mid-logarithmic phase and shifted to I⁻C⁺ medium at 37 °C for 180 min as described under “Experimental Procedures,” maintaining label at constant specific activity. At 180 min, inositol was reintroduced, and samples were taken at the time points depicted in the figure. Parallel cultures grown in the same fashion were treated with cerulenin at a final concentration of 10 μg/ml at 90 min after the shift to medium lacking inositol. Cells were allowed to grow for additional 90 min, and inositol was reintroduced. Samples were collected at 0, 5, 15, and 30 min after inositol addition. Lipids were extracted and analyzed as described under “Experimental Procedures”. Panel A, wild type. Panel B, dga1Δlro1Δare1Δare2Δ. Panel C, tgl3Δtgl4Δtgl5Δ. Panel D, wild type + cerulenin. Panel E, dga1Δlro1Δare1Δare2Δ + cerulenin. Panel F, tgl3Δtgl4Δtgl5Δ + cerulenin. The data represent the average of at least two independent experiments. Experimental error was less than 10% in all cases. Error bars are not shown for clarity of presentation. The lipids indicated are PI (solid squares) and PC (solid circles). ODU, optical density units.