Fig. 5. Localization of Sho1 to sites of polarized growth. Localization of the Sho1 protein was determined using a Sho1–GPF fusion construct (pSHO1–GFP). Expression of the Sho1–GFP fusion protein is maintained at physiological levels by using a low copy-number vector (pRS416) and the promoter of the SHO1 gene itself. (A) The majority of the Sho1–GFP protein is localized to the incipient bud (top panel), and to the plasma membrane of the growing bud (lower panels), during vegetative growth. pSHO1–GFP is expressed in the yeast strain FP66 (sho1Δ), and exponentially growing cells in YPD medium were examined by fluorescence microscopy. (B) Sho1–GFP is localized at the shmoo tip during the mating response. pSHO1–GFP is expressed in the wild-type strain TM141 in the presence of 3 µM α mating factor.