Physiological and Biochemical Response of Saccharomyces cerevisiae to Desiccation and Rehydration

Abstract

Baker's yeast (Saccharomyces cerevisiae) undergoes major biochemical and structural rearrangements in order to survive cycles of desiccation and rehydration, yet a firm understanding of the response is lacking. The purpose of this study was to examine the response of S. cerevisiae to desiccation and rehydration at both the physiological and molecular levels. Transmission electron microscopy was used to show that loss of vacuolar structure, enlarged nuclear boundaries, as well as cell wall thickening were all associated with the desiccation response. Molecular analysis focused on glyceraldehyde-3-phosphate dehydrogenase (GAPDH, E.C. 1.2.1.13), a multifunctional protein that is involved in several cellular processes other than glycolysis, including nuclear translocation under stress and intracellular sensing of oxidative stress during apoptosis. Here, GAPDH was studied primarily to determine its potential role in mediating the changes in cell wall physiology identified through our structural studies. GAPDH appears to be shuttled between the cell wall and the cytoplasm during the desiccation/rehydration process. Western analyses in combination with the use of inhibitors of translation (cycloheximide) suggest that the shuttling process does not require de novo protein synthesis. Western analyses also identified an immuno-reactive peptide in the cell wall and cytoplasmic fractions of lower molecular mass than native GAPDH (27 KDa vs. 37 KDa). This lower molecular weight peptide exhibited the translocation process similar to that of the full length GAPDH. Studies with GAPDH deletion strains suggested that the 27 kDa fragment is encoded by tdh3. The importance of this lower molecular weight form is yet to be determined.