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Media type:
E-Article
Title:
Fluidization of Membrane Lipids Enhances the Tolerance of Saccharomyces cerevisiae to Freezing and Salt Stress
Contributor:
Rodríguez-Vargas, Sonia;
Sánchez-García, Alicia;
Martínez-Rivas, Jose Manuel;
Prieto, Jose Antonio;
Randez-Gil, Francisca
imprint:
American Society for Microbiology, 2007
Published in:Applied and Environmental Microbiology
Language:
English
DOI:
10.1128/aem.01360-06
ISSN:
0099-2240;
1098-5336
Origination:
Footnote:
Description:
<jats:title>ABSTRACT</jats:title>
<jats:p>
Unsaturated fatty acids play an essential role in the biophysical characteristics of cell membranes and determine the proper function of membrane-attached proteins. Thus, the ability of cells to alter the degree of unsaturation in their membranes is an important factor in cellular acclimatization to environmental conditions. Many eukaryotic organisms can synthesize dienoic fatty acids, but
<jats:italic>Saccharomyces cerevisiae</jats:italic>
can introduce only a single double bond at the Δ
<jats:sup>9</jats:sup>
position. We expressed two sunflower (
<jats:italic>Helianthus annuus</jats:italic>
) oleate Δ
<jats:sup>12</jats:sup>
desaturases encoded by
<jats:italic>FAD2-1</jats:italic>
and
<jats:italic>FAD2-3</jats:italic>
in yeast cells of the wild-type W303-1A strain (
<jats:italic>trp1</jats:italic>
) and analyzed their effects on growth and stress tolerance. Production of the heterologous desaturases increased the content of dienoic fatty acids, especially 18:2Δ
<jats:sup>9,12</jats:sup>
, the unsaturation index, and the fluidity of the yeast membrane. The total fatty acid content remained constant, and the level of monounsaturated fatty acids decreased. Growth at 15°C was reduced in the
<jats:italic>FAD2</jats:italic>
strains, probably due to tryptophan auxotrophy, since the
<jats:italic>trp1</jats:italic>
(
<jats:italic>TRP1</jats:italic>
) transformants that produced the sunflower desaturases grew as well as the control strain did. Our results suggest that changes in the fluidity of the lipid bilayer affect tryptophan uptake and/or the correct targeting of tryptophan transporters. The expression of the sunflower desaturases, in either Trp
<jats:sup>+</jats:sup>
or Trp
<jats:sup>−</jats:sup>
strains, increased NaCl tolerance. Production of dienoic fatty acids increased the tolerance to freezing of wild-type cells preincubated at 30°C or 15°C. Thus, membrane fluidity is an essential determinant of stress resistance in
<jats:italic>S. cerevisiae</jats:italic>
, and engineering of membrane lipids has the potential to be a useful tool of increasing the tolerance to freezing in industrial strains.
</jats:p>