INVOLVEMENT OF CIF1 (GGS1 TPS1) IN OSMOTIC-STRESS RESPONSE IN SACCHAROMYCES-CEREVISIAE/

The transcriptional responses of the osmotically induced genes ALD2, C TT1, ENA1, GPD1, HSP12 and HSP104, were studied in Saccharomyces cerev isiae strains differing in CIF1 gene function following application of osmotic stress. The CIF1 gene (allelic to GGS1 and TPS1) encodes a su bunit of the trehalose synthase complex that affects trehalose synthes is, Recent work has implicated this gene in various signalling events in the cell, including transcriptional response to heat-shock treatmen t. Because many genetic factors can influence S. cerevisiae osmorespon se, we have compared the expression of osmotically induced genes and g lycerol production in isogenic strains differing only in functionality of CIF1, growing logarithmically on galactose medium. When cultures w ere exposed to 0.8 M NaCl or 1.5 M sorbitol the cif1 strain showed gre atly reduced transcription of osmotically induced genes compared to th e wild type, These treatments did not affect viability of the yeast st rains, Treatment with 0.3 M NaCl produced no significant differences i n transcription of these genes in CIF1 or cif1 strains, Treatment with 0.6 M sorbitol induced small but reproducible differences,,vith gene expression higher in the CIF1 strain compared to the cif1 mutant. When cultures were treated with 0.3 M NaCl or 0.6 M sorbitol for 1 h, glyc erol production was similar for both strains, but after 3 h of the sam e treatment, total glycerol production was higher in the CIF1 strain, When cultures were treated with 0.8 M NaCl for 3 h, the wild type stra in produced more glycerol than the mutant strain, Both strains produce d similar amounts of glycerol following exposure to 1.5 M sorbitol for 3 h, although the wild type strain showed enhanced ability to retain glycerol inside the cell, The results are discussed in the context of the possible role that the CIF1 gene product has in response to osmoti c stress. (C) 1997 Federation of European Biochemical Societies.