Knockout of DAG kinase leads to more droplets and a bypass in Pah1p function. (A) Knockout of DGK1 increases droplet number independent of TAG. The indicated strains were grown in SD, and lipid droplets were stained with BODIPY. Images incorporate brightfield channel. Arrows illustrate pearls-on-a-string phenotype. Bar, 5 µm. (B) Droplet number increases in dgk1Δ even in the absence of TAG. The inset illustrates the enzymes that catalyze PA-DAG interconversions; the source for the other PA phosphatase activity is unknown. Droplets were counted in at least three random fields, ∼20 cells per field; mean ± SEM is shown. *, P < 0.05; ***, P < 0.0001. (C) Comparison of DAG and PA levels of wild type (WT) and dgk1Δ, showing an increase in DAG and decrease in PA in the mutant. Error bars are SEM based on measurements from three independent experiments. (D) Histogram showing the percentage of cells with pearls-on-a-string lipid droplet phenotype; mean ± SEM (**, P < 0.001) based on three random fields (at least 20 cells per field) from three independent experiments.