Ace2p, a regulator of CTS1 (chitinase) expression, affects pseudohyphal production in Saccharomyces cerevisiae

Some diploid strains of Saccharomyces cerevisiae can grow both as a spherical yeast form and as a filamentous pseudohyphal form. Most yeasts capable of forming pseudohyphae possess a functional FLO8 gene. We show that disrupting the ACE2 transcription factor results in the production of pseudohyphae in a flo8-1 background. Disrupting the CTS1 (chitinase) gene also produces pseudohyphal growth in this background, but at a reduced level. Invasion of solid media by haploid and diploid cells is increased in ACE2 disruptions, but the diploids adhere poorly to the agar. Sigma1278b-derived strains, which generally produce pseudohyphae, have about 30-fold lower chitinase activity than other strains.