Fig 4. Phenotypic characterization of ATG18 and FAB1 alleles.

A) Hemizygous diploid Δatg18 cells showed different sporulation patterns. After 48 hours on 1% K-acetate, the counted asci were expressed as a percentage of total cells. B) Effect of nitrogen starvation on cell viability of the Δatg18 strains. The hybrid WE (Nat ^R)/WA (Hyg ^R) (●), WA (Nat ^R)/WE (Hyg ^R) (▲), WE/ATG18 ^WA (○), and WA/ATG18 ^WE (Δ) strains were grown until the mid-log phase in SD and then moved to SD-N. Aliquots were collected and plated on YPD at the indicated times. The scale of viability (%) indicates the percentage of viable cells for the different strains against the time in starvation medium. Values are the mean of triplicate measurements, and the standard deviation was less than 15%. C) FAB1 ^WA and ATG18 ^WE rescue cells from ionic-hyperosmotic stress at 37°C. Serial dilutions of heterozygous and hemizygous strain cells were plated on YPD medium, YPD medium containing 1 M NaCl, and 1 M sorbitol and grown at the indicated temperatures. D) Hemizygous cells show vacuole fragmentation and vacuole acidification deficiency. Each pair of image columns show phase microscopy of the same field, which shows cells stained with FM4-64 to visualize vacuole membrane, pH vacuolar dye cell blue Arg-CMAC, and the differential interference contrast (DIC) images.