LOCALIZATION OF THE DOMINANT FLOCCULATION GENES FLO5 AND FLO8 OF SACCHAROMYCES-CEREVISIAE

In the yeast Saccharomyces cerevisiae three dominant flocculation gene s, FLO1, FLO5 and FLO8 have been described. Until now only the FLO1 ge ne, which is located at chromosome I, has been cloned and sequenced. F LO5 and FLO8 were previously localized at chromosomes I and VIII respe ctively (Vezinhet, F., Blondin, B. and Barre, P. (1991). Mapping of th e FLO5 gene of Saccharomyces cerevisiae by transfer of a chromosome du ring cytoduction. Biotechnol. Lett. 13, 47-52; Yamashita, I. and Fukui , S. (1983). Mating signals control expression of both starch fermenta tion genes and a novel flocculation gene FLO8 in the yeast Saccharomyc es. Agric. Biol. Chem. 47, 2889-2896). This was not in agreement with our results. Here, we report the location of FLO5 and FLO8 on chromoso mes VIII and I respectively. By induced chromosome loss and genetic ma pping, the FLO5 gene was localized at the right end of chromosome VIII approximately 34 cM centromere distal of PET3. This is part of the re gion that is present both at chromosome I and chromosome VIII. The loc ation of FLO5 in this area of chromosome VIII made it necessary to re- evaluate the localization of FLO8, which was previously thought to occ ur in this region. Both genetic and physical mapping showed that FLO8 is allelic to FLO1. Hence, there are only two known dominant flocculat ion genes, FLO1 and FLO5. Analysis of the nucleotide sequence of chrom osome VIII of a non-flocculent strain revealed an open reading frame e ncoding a putative protein that is approximately 96% identical to the Flo1 protein. This suggests that both dominant flocculation genes enco de similar, cell wall-associated, proteins with the same function in t he flocculation mechanism.