GLOBAL CHANGES IN PROTEIN-SYNTHESIS DURING ADAPTATION OF THE YEAST SACCHAROMYCES-CEREVISIAE TO 0.7 M NACL

Exponentially growing Saccharomyces cerevisiae was challenged to increased salinity by transfer to 0.7 M NaCl medium, and changes in protein synthesis were examined during the 1st h of adaptation by use of two-dimensional gel electrophoresis coupled to computerized quantification. An impressive number of proteins displayed changes in the relative rate of synthesis, with most differences from nonstressed cells being found at between 20 and 40 min. During this period, 18 proteins exhibited more than eightfold increases in their rates of synthesis and were classified as highly NaCl responsive. Only two proteins were repressed to the same level. Most of these highly NaCl-responsive proteins seemed to constitute gene products not earlier reported to respond to dehydration, Applying a selection criterion to subsequent samples of a twofold change in the relative rate of synthesis, 14 different regulatory patterns were discerned. Most identified glycolytic enzymes exhibited a delayed response, and their rates of synthesis did not change until the middle phase of adaptation, with only a minor decrease in the rate of production. A slight salt-stimulated response was observed for some members of the HSP70 gene family. Overall, the data presented indicate complex intracellular signalling as well as involvement of diverse regulatory mechanisms during the period of adaptation to NaCl.