Figure 3.

Extracellular Ca²⁺ suppresses cell lysis in prm1Δ × prm1Δ mating reactions. (A) Fusion of prm1Δ × prm1Δ mating pairs is highly sensitive to EGTA. Mating mixtures were incubated on YPD plates with (Ca²⁺, −) or without (Ca²⁺, +) 20 mM EGTA. (B) Sensitivity of prm1Δ × prm1Δ mating pairs to EGTA is due to a lack of Ca²⁺. Liquid media cell fusion assays were performed in synthetic media treated with resin-bound BAPTA and supplemented either with water (−) or divalent cation salts at concentrations found in synthetic complete media: 900 μM calcium chloride, 1 μM zinc sulfate, 10 μM manganese sulfate, 1 mM magnesium sulfate, and 1 μM copper sulfate. (C) Extracellular calcium suppresses the prm1Δ × prm1Δ mating defect. Liquid media cell fusion assays were performed as in B by using media supplemented with calcium chloride as indicated. Error bars indicate SEs for at least three independent experiments with 300 mating pairs scored per experiment.