Figure 5.

Synthetic lethality between spa2Δ and myo1Δ. (A) Wild-type (YEF473A), myo1Δ(YEF1813), spa2Δ(JSY120), and spa2Δ myo1Δ(JSY235) strains were grown on YEPD plates at 25, 30, or 37°C. Plates were photographed after 3–4 d. At 30°C, only the spa2Δ myo1Δ strain exhibited slow growth compared with wild type. At 37°C, the myo1Δ strain exhibited a slow-growth phenotype compared with wild type, and the spa2Δ myo1Δ strain was not viable. (B) spa2Δ exacerbates the cell separation defect of myo1Δ. Log-phase (a) wild-type, (b) spa2Δ, (c) myo1Δ, and (d) spa2Δ myo1Δ cells grown in YEPD culture at 25°C were shifted to 30°C for 3.5 h and then examined under DIC microscopy. (C) The percentage of cells displaying three or more cells connected together was determined for each strain at 25°C, after shift to 30°C for 3.5 h, and after shift to 37°C for 3.5 h (after mild sonication). The assay was done three times and at least 200 cells were scored for each strain. Less than 1% of wild-type and spa2Δ cells exhibited a cell-separation defect after 3.5 h at 30°C compared with 19% of myo1Δ cells and 78% of spa2Δ myo1Δ cells. This defect was enhanced in both myo1Δ and spa2Δ myo1Δ strains after a shift to 37°C for 3.5 h.