To obtain information on cell wall synthesis and its relationship to morphology, we examined the induction of cell extensions of yeast upon the addition of isoamyl alcohol in osmotically fragile mutants that had mutations in genes related to the cell integrity pathway through activation of the mitogen-activated protein kinase cascade. We found that isoamyl alcohol induces cell extensions inpkc1deletion mutants but not in mutants with mutations in genes positioned downstream or upstream of thePKC1gene. These results suggest that Pkc1p functions not only in the integrity pathway but also in the induction. We characterized the elongated cells; many had two or more nuclei. We found no difference in cell surface structure between round and elongated cells from the results of chitin staining and cell wall extraction. Actin cytoskeleton was organized in elongated cells, as well as round cells. Cytochalasin D (0.08 mg/mL) inhibited the formation of actin cable but did not affect the induction of cell extensions.Key words:Saccharomyces cerevisiae,pkc1, isoamyl alcohol, cell extension.