Figure 3

Expression of the PA incompatibility domain at low-levels in yeast results in aberrant phenotypes. A) Phase contrast microscopy revealed that PA-expressing yeast exhibit significantly more cells having a granulated cytoplasm compared to control strain (P = 0.007). Cytoplasmic granulation is a key feature of heterokaryon incompatibility in filamentous fungi. B) Significantly more PA-expressing yeast cells exhibit cytoplasmic acidification in comparison to control strain (P = 0.015) based on neutral red staining. The frequency of PA-expressing cells that exhibited an acidified cytoplasm did not differ from that of the vATPase-defective strain, YPL234C. For both A and B, error bars represent standard deviation based on 5 biological replicates where a minimum of 100 cells were counted. C) PA-expressing yeast had a slower growth rate in YPD compared to the control strain (P < 0.001). Growth was monitored by using a microplate reader and CFU was calculated from a standard curve of CFU versus OD₆₀₀ (not shown). Error bars represent standard deviation based on three biological replicates.