, Volume 251, Issue 6, pp 707-715

Molecular cloning and analysis of the dominant flocculation geneFLO8 fromSaccharomyces cerevisiae

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Abstract

A flocculation gene was cloned from aSaccharomyces cerevisiae ATCC60715 genomic library, known to contain theFLO8 gene, on the basis of its ability to confer a flocculation phenotype on a non-flocculent strain. From a total of 11 130 clones, four clones sharing the several restriction fragments were isolated, suggesting that these were derived from the same locus. The results of integration mapping and disruption of the cloned gene indicated that this gene was theFLO8 gene. After disruption of theFLO8 gene, the strain lost its ability to flocculate. The DNA sequence of theFLO8 gene was determined. This gene includes a 2187-bp open reading frame that encodes a 729-amino acid protein. Computer analysis indicated that theFLO8 gene has a significant degree of homology with aS. cerevisiae chromosome V DNA sequence, but no homology with theFLO1 gene. The hydrophobicity profile of the putativeFLO8 gene product did not indicate the presence of any significantly hydrophobic regions. Southern analysis of theFLO8 gene present in various yeast strains indicated that theFLO8 gene is highly conserved in yeast strains having a variety of flocculation phenotypes and genotypes. Northern analysis revealed that the level ofFLO1 gene transcription is dependent on the rate of transcription of theFLO8 gene. These results suggest that theFLO8 gene mediates flocculation via transcriptional activation of theFLO1 gene.

Communicated by C. P. Hollenberg