The regulation of Saccharomyces cerevisiae FLO gene expression and Ca2+-dependent flocculation by Flo8p and Mss11p

The ability of many microorganisms to modify adhesion-related properties of their cell surface is of importance for many processes, including substrate adhesion, cell-cell adhesion, invasive growth, pathogenic behaviour and biofilm formation. In the yeast Saccharomyces cerevisiae, a group of structurally related, cell-wall associated proteins encoded by the FLO gene family are directly responsible for many of the cellular adhesion phenotypes displayed by this organism. Previous research has suggested that the differential transcription of FLO genes determines specific adhesion phenotypes. However, the transcriptional regulation of most FLO genes remains poorly understood. Here we show that the transcriptional activator Mss11p, which has previously been shown to be involved in the regulation of starch degradation, the formation of pseudohyphae and haploid invasive growth, also acts as a strong inducer of flocculation. The data indicate that Mss11p induces flocculation together with Flo8p, and that FLO1 is the dominant target gene of the two factors in this process. The deletion of MSS11 leads to a non-flocculent phenotype, and specific domains of Mss11p that are critical for the induction of flocculation are identified. The data clearly show that several essential transcription factors are shared by at least two flocculation genes that control different adhesion phenotypes.