PHASE-SPECIFIC PROTEIN EXPRESSION IN THE DIMORPHIC YEAST SACCHAROMYCES-CEREVISIAE

In oxygen-limited continuous culture, Saccharomyces cerevisiae formed pseudohyphae by unipolar budding. We developed a continuous cultivatio n sequence to discriminate phase-specific from metabolically regulated proteins during dimorphism. Computer-aided substractive analysis of 2 D-PAGE protein patterns allowed the detection of proteins specifically expressed during yeast and pseudohyphal phases. Image analysis resolv ed 3 spots that were specific to the pseudohyphal phase and 2 spots th at were specific to yeast phase. In addition to phase-specific protein s, important regulation of protein expression took place. A group of 9 proteins was highly over-expressed during the yeast phase when anothe r group of 12 was underexpressed. This phenomenon was reversed during the pseudohyphal phase. These experiments showed that dimorphism in S. cerevisiae is associated with the expression of specific proteins and suggest that yeast phase-specific proteins maintain the yeast form or repress pseudohyphae formation. (C) 1997 Academic Press.