Diploid strains of baker's yeast Saccharomyces cermisiae can grow in a cellular yeast form or in filaments called pseudohyphae. This dimorphic transition from yeast to pseudohyphae is induced by starvation for nitrogen. Not all laboratory strains are capable of this dimorphic switch; many grow only in the yeast form and fail to form pseudohyphae when starved for nitrogen. Analysis of the standard laboratory strain S288C shows that this defect in dimorphism results from a nonsense mutation in the FL08 gene. This defect in FL08 blocks pseudohyphal growth in diploids, haploid invasive growth, and flocculation. Since feral strains of S. cerevisiae are dimorphic and have a functional FL08 gene, we suggest that the fl08 mutation was selected during laboratory cultivation.
- Received May 15, 1996.
- Accepted August 8, 1996.
- Copyright © 1996 by the Genetics Society of America