CLONING OF A NEW FLO GENE FROM THE FLOCCULATING SACCHAROMYCES-CEREVISIAE IM1-8B STRAIN

A flocculation conferring gene was cloned from a genomic library of th e flocculating strain Saccharomyces cerevisiae IM1-8b as a 5 kb DNA fr agment. The shortest DNA fragment (XbaI-XbaI) able to confer the flocc ulating phenotype was 3.1 kb. Southern analysis revealed that this gen e was not homologous to the already reported FLO1 gene since strong hy bridization signals were obtained when chromosomes IV and XII were pro bed with a digoxygenin-labelled fragment and no signal at all was dete cted for chromosome I. Partial sequencing data unequivocally ascribed the cloned fragment to chromosome XII. The gene was detected in a vari ety of S. cerevisiae strains regardless of their being phenotypically flocculating. This gene which, we propose as FLO2, is able to compleme nt the flo1 mutation and is suppressed by suppressors (fsu3) that do n ot affect other FLO genes.