Involvement of CIF1 (GGS1/TPS1) in osmotic stress response in Saccharomyces cerevisiae

The transcriptional responses of the osmotically induced genes ALD2, CTT1, ENA1, GPD1, HSP12 and HSP104, were studied in Saccharomyces cerevisiae strains differing in CLF1 gene function following application of osmotic stress. The CIF1 gene (allelic to GGS1 and TPS1) encodes a subunit of the trehalose synthase complex that affects trehalose synthesis. Recent work has implicated this gene in various signalling events in the cell, including transcriptional response to heat-shock treatment. Because many genetic factors can influence S. cerevisiae osmoresponse, we have compared the expression of osmotically induced genes and glycerol production in isogenic strains differing only in functionality of CIF1, growing logarithmically on galactose medium. When cultures were exposed to 0.8 M NaCl or 1.5 M sorbitol the cif1 strain showed greatly reduced transcription of osmotically induced genes compared to the wild type. These treatments did not affect viability of the yeast strains. Treatment with 0.3 M NaCl produced no significant differences in transcription of these genes in CIF1 or cif1 strains. Treatment with 0.6 M sorbitol induced small but reproducible differences, with gene expression higher in the CIF1 strain compared to the cif1 mutant. When cultures mere treated with 0.3 M NaCl or 0.6 hi sorbitol for 1 h, glycerol production was similar for both strains, but after 3 h of the same 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 strain produced more glycerol than the mutant strain. Both strains produced similar amounts of glycerol following exposure to 1.5 hi 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 osmotic stress.