Fig. 2.

Continuous synthesis is required for maintenance of PtdIns(4,5)P₂ anisotropy in the plasma membrane during pheromone response. (A–E) Expression of the GST-GFP-PH^PLCδ1 probe was induced and shut off, as described in Fig. 1A, in either wild-type cells (A) or otherwise isogenic mss4^ts (B), stt4^ts (C), pik1^ts (D), or stt4^ts pik1^ts (E) mutants. After 15 min, each culture was treated with 5 μM α-factor for 30 min, at which point half of each culture was left at the permissive temperature (26 °C) and half was shifted to the restrictive temperature (37 °C). After 1 h, cells in each culture were examined by standard epifluorescence microscopy. Each panel depicts a collage of representative cells at each time point: arrowheads, mating projections with a marked asymmetric distribution of the PtdIns(4,5)P₂ probe; arrows, mating projections lacking a marked asymmetric distribution of the probe.