OSMOREGULATION AND PROTEIN EXPRESSION IN A PBS2-DELTA MUTANT OF SACCHAROMYCES-CEREVISIAE DURING ADAPTATION TO HYPERSALINE STRESS

We deleted the PBS2 gene encoding the MAP kinase activator of the osmo signaling HOG pathway in Saccharomyces cerevisiae and examined the eff ects on the kinetics of the osmoregulatory glycerol response and prote in induction during adaptation to 0.7 M NaCl. Changes in protein expre ssion as analyzed by two-dimensional polyacrylamide gel electrophoresi s (2D PAGE) demonstrated that for the 29 proteins showing a 6-fold ind uction in wild-type cells during adaptation to NaCl stress, all displa yed a decreased and delayed response in pbs2 Delta cells. Of the seven proteins that were identified, two were previously not known to be un der HOG pathway control: Ald6p, an isoform of aldehyde dehydrogenase a nd Dak1p, a putative dihydroxyacetone kinase. The presence of a remain ing significant induction in pbs2 Delta cells for about half of the ex amined proteins indicates existence of alternative osmosignaling pathw ay(s). Northern analysis of the salt induced transcription of GPD1 and GPP2, encoding the cytosolic glycerol-3-phosphate dehydrogenase and g lycerol-3-phosphatase involved in the osmostress induced glycerol prod uction, demonstrated an about 20-fold PBS2-dependent transient activat ion, in agreement with the previously reported transient nature of the signal transduced by the HOG pathway. (C) 1997 Federation of European Biochemical Societies.