Physiological and genetic characterisation of osmosensitive mutants of Saccharomyes cerevisiae |
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Authors: | Adrian R N E Brüning Jürgen Bauer Bernhard Krems Karl-Dieter Entian B A Prior |
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Institution: | Department of Microbiology and Biochemistry, University of the Orange Free State, P.O. Box 339, Bloemfontein, South Africa 9300, ZA Institut für Mikrobiologie, Biozentrum der Johan Wolfgang Goethe-Universit?t, D-60439 Niederursel, Germany, DE
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Abstract: | The screening of 20,000 Saccharomyces cerevisiae random mutants to identify genes involved in the osmotic stress response yielded 14 mutants whose growth was poor in the
presence of elevated concentrations of NaCl and glucose. Most of the mutant strains were more sensitive to NaCl than to glucose
at the equivalent water activity (aw) and were classified as salt-sensitive rather than osmosensitive. These mutants fell into 11 genetic complementation groups
and were designated osr1–osr11 (osmotic stress response). All mutations were recessive and showed a clear 2+ : 2– segregation of the salt-stress phenotype upon tetrad analysis when crossed to a wild-type strain. The complementation groups
osr1, osr5 and osr11 were allelic to the genes PBS2, GPD1 and KAR3, respectively. Whereas intracellular and extracellular levels of glycerol increased in the wild-type strains when exposed
to NaCl, all mutants demonstrated some increase in extracellular glycerol production upon salt stress, but a number of the
mutants showed little or no increase in intracellular glycerol concentrations. The mutants had levels of glycerol-3-phosphate
dehydrogenase, an enzyme induced by osmotic stress, either lower than or similar to those of the parent wild-type strain in
the absence of osmotic stress. In the presence of NaCl, the increase in glycerol-3-phosphate dehydrogenase activity in the
mutants did not match that of the parent wild-type strain. None of the mutants had defective ATPases or were sensitive to
heat stress. It is evident from this study and from others that a wide spectrum of genes is involved in the osmotic stress
response in S. cerevisiae.
Received: 5 January 1998 / Accepted: 24 March 1998 |
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Keywords: | Osmosis Yeast Mutant Glycerol Solute Complementation group |
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