Studies On Stress Response Of Yeast Cell And Derivative Produced Under High Temperature And Oxidative Condition

This study was based on stress response of yeast cell under high temperature and oxidative condition. Live Yeast Cell Derivative (LYCD) was produced by yeast cell, which was pretreated by low dose temperature and oxidative condition. The experiment setup the new method producing LYCD by selecting thermotolerant mutant.With comparative the stress response of yeast and respiratory-deficient strains, the effect of mitochondria under oxidative stress and heat stress were analyzed. Our results indicated that mitochondria! function was required for resistance to oxidative stress in yeast, since respiratory-deficient strains had the less survival than the yeast. But respiratory-deficient strains had the more ability for resistance to high temperature, indicating that it was inhibited by mitochondrial function to resist heat stress. Through pretreating by low dose, yeast and respiratory-deficient strains were able to mount an adaptive response to high temperature and H2O2.It showed that mitochondrial was unrequired in adaptive response of yeast.The following conclusions were drawn by testing the change of antioxidants and MDA in yeast cell: pretreating of low dose could increase the content of GSH and the activities of SOD and CAT, could reduce the accumulation of MDA. And these induced the resistance to lethal concentration of 50 and H2O2. Furthermore study showed that heat and oxidative stress may have a common mechanism of damage.. LYCD1 and LYCD2 were produced by breaking up the yeast cell pretreated with H2O2 and 37 C. The results showed that LYCD1 and LYCD2 could protect cell to resist oxidative condition. The optimum conditions of producing LYCD1 and LYCD2 were as follow: the concentration of H2O2 is 0.4 mmol/L, and the treating time is 60min;the temperature is 37 C,and the treating time is 30min.After UV treating, the thermotolerant mutant was selected. And it had the more ability for resistance to high temperature and oxidative condition. The extract of mutant had biological activities, the content of GSH and the activities of SOD and CAT in mutant were higher than the initial strain.Through two-dimensional gel electrophoresis experiment, the proteins were analysed. Some changes were induced by H2O2 and 37 C,which were not made in untreated cells. Other changes were induced by H2O2 or 37 C. hi addition, the proteins of mutant were analysed. The result indicated that lots of new proteins were synthesized, some were heat-shock proteins and others were relative to anti-oxidative.