RATNAKUMAR, S*; TUNNACLIFFE, A; Univ. of Cambridge, UK; Univ. of Cambridge, UK: Desiccation tolerance of Saccharomyces cerevisiae does not correlate with its intracellular trehalose accumulation

The literature shows that, in Saccharomyces cerevisiae, an increase in desiccation tolerance during heat shock and stationary phase correlates with a corresponding rise in intracellular trehalose accumulation. While our experiments with wild-type yeast confirm these earlier findings, mutant strains and stress experiments prove this correlation to be weak and inconsistent. A trehalose phosphate synthase (tps1) mutant, although unable to produce trehalose, showed increasing desiccation tolerance on progression into post-diauxic phase. Also, while its desiccation tolerance increased following heat shock, there was no corresponding rise in trehalose levels. A trehalose-6-phosphate phosphatase (tps2) mutant demonstrated low survival rates as well as trehalose levels regardless of stage of culture or heat stress. Subjecting wild-type cells to osmotic stress considerably elevated intracellular trehalose concentration, but without any concomitant improvement in desiccation tolerance. Since we observed desiccation tolerance as well as trehalose levels of wild-type cells rise in the post-diauxic phase, we investigated if the switch in the type of metabolism from fermentation to respiration played any role. On growing the wild-type strains in mineral media with glycerol as the carbon source, we noted high desiccation tolerance even during exponential phase of growth; these cells produced much lower levels of trehalose than those cultured in rich media. Therefore, while trehalose could play a minor role in desiccation tolerance of yeast, it might be less significant than other adaptations associated with growth in non-fermentative carbon sources and thermal stress.