Stress tolerance in a yeast lipid mutant: membrane lipids influence tolerance to heat and ethanol independently of heat shock proteins and trehalose

Abstract

The response of a yeast unsaturated fatty acid auxotroph, defective in delta 9-desaturase activity, to heat and ethanol stresses was examined. The most heat- and ethanol-tolerant cells had membranes enriched with oleic acid (C18:1), followed in order by cells enriched with linoleic (C18:2) and linolenic (C18:3) acids. Cells subjected to a heat shock (25-37 degrees C for 30 min) accumulated trehalose and synthesized typical heat shock proteins. Although there were no obvious differences in protein profiles attributable to lipid supplementation of the mutant, relative protein synthesis as determined by densitometric analysis of autoradiograms suggested that hsp expression was different. However, there was no consistent relationship between the synthesis of heat shock proteins and the acquisition of thermotolerance in the lipid supplemented auxotroph or related wild type. Furthermore, trehalose accumulation was also not closely related to stress tolerance. On the other hand, the data presented indicated a more consistent role for membrane lipid composition in stress tolerance than trehalose, heat shock proteins, or ergosterol. We suggest that the sensitivity of C18:3-enriched cells to heat and ethanol may be attributable to membrane damage associated with increases in membrane fluidity and oxygen-derived free radical attack of membrane lipids.

A multi-level study of recombinant Pichia pastoris in different oxygen conditions

“…Sterols for example, long time relegated as passive metabolites modulating the membrane structure, play an important role as primary sensors of environmental stresses by adjusting the fluidity of the plasma membrane to such perturbations [46,47]. The cellular lipid metabolism is highly susceptible to hypoxia since the biosynthesis routes for the most essential lipids - ergosterol and fatty acids - require molecular oxygen.…”

Mutants and isolates of Metarhizium anisopliae are diverse in their relationships between conidial pigmentation and stress tolerance

“…Mutation in other fungi has been correlated with altered cell wall assembly (Claverie-Martin et al, 1988;Ram et al, 2004); as well as changes in wall thickness (Claverie-Martin et al, 1988;Osherov and May, 2001), conidial surface features (Jahn et al, 1997), and composition of fatty acids (e.g. increased fatty acid unsaturation in plasma membrane as stress tolerance decreases) (Swan and Watson, 1999;Chatterjee et al, 2000). The mutants DWR 031 and 033, on the other hand, had high tolerance for both irradiations types, indicating that cell wall and membranes are more important to heat protection (improving thermotolerance) than UV-B radiation.…”

Ethanol-induced changes in expression profiles of cell growth, fatty acid and desaturase genes of Mucor rouxii

“…In the presence of ethanol S. cerevisiae, which contains only mono-unsaturated fatty acids, showed an increase in palmitoleic acid (C16:1D9), whereas a decrease in fatty acid desaturation was found in K. lactis, which contains monoenoic, dienoic and trienoic fatty acids. It has also been reported that S. cerevisiae enriched with C18:3 by fatty acid supplementation showed sensitivity to ethanol, which may be attributable to membrane damage associated with increases in membrane fluidity (Swan and Watson, 1999).…”