Figure 3. A potassium transporter, Trk1p, mediates EF response in shmoos.

(A) Average shmoo orientation after 3 h in the absence or in the presence of an EF for a population of WT and trk1Δ cells treated with α-factor (αF) (n>50 cells). (B) Sixteen-color images of WT and trk1Δ cells stained with the membrane-potential-sensitive dye DiBAC₄(3), which depicts reduced membrane fluorescence upon membrane hyperpolarization. (C) Quantification of DiBAC₄(3) dye membrane staining intensity in WT and trk1Δ cells. (D) Mating efficiency of trk1Δ cells relative to WT. (E) Confocal single focal plane time-lapse images of Trk1-GFP in WT cells grown in the presence of α-factor. White arrowheads indicate shmoo growth sites. Below is the mean fluorescence intensity along the cell contour at times 0 and 80 min after α-factor treatment, averaged on five independent cells. Distances are normalized between 0 and 1 so that the value 0.5 corresponds to the site of shmoo emergence.