Role of heat shock proteins and plasma membrane on thermotolerance in Saccharomyces cerevisiae-VS3 strain

Aim: Study of HSPs synthesis after heat and cold shock and explanation of thermotolerance by the transport of HSPs to the plasma membrane. Methods and Results: Physical (cold and heat shock) and chemical (lignocaine) damage to plasma membrane was achieved in thermotolerant and mesophilic strains of Saccharomyces cerevisiae . In shocked yeasts K+ ion efflux, leakage of UV280 absorbing material, HSP expression profile and viability at 25 and 45°C were studied. Physical/chemical shock was given for 30 minutes and subsequently yeasts were incubated at 25°C to avoid further membrane damage by stress. In thermotolerant strain, membrane damage increased up to 70 minutes (30 min of shock and 40 min at 25°C) and reduced thereafter. De-novo HSPs in membrane were noted at 60 minutes and reached maximum at 80 minutes in thermotolerant strain. In mesophilic yeast, de-novo HSPs were not synthesized and leakage was continuous up to the studied period (100 minutes). Conclusion: These de-novo HSPs are transported to the membrane for restoring the membrane integrity and to prevent the leakage. The thermotolerant strain can grow at higher temperatures compared to mesophilic strain due to more production of HSPs and HSP associated membrane damage reversal. Significance and Impact of the Study: Several reports established the role of HSPs in thermotolerance but their mode of action is not well characterized. The current method explains the mechanism for acquiring thermotolerance in yeast.