Study Of Acetic Acid And Lactic Acid Effected Yeast Apoptosis And The Expression Of Apoptosis-related Gene

Yeast is widespread existence microorganism in human life and industrial production, because its own characteristic and advantages make it not only usesd for wine-making, but also used for the production of glycerol, edible yeast, organic acids, enzyme preparation and so on in the modern industry. Many factors can lead to yeast apoptosis in industrial production and experimental studies, since apoptosis was found in yeast that has been a hot issue academic. With a detailed study, the people had determined that the genes presence in yeast apoptosis process had a similar features on fuction regulating with each kind of function gene in the multicellular organisms apoptosis. Yeast as a simple biological model system, may help to clarify the regulation mechanism of apoptosis. Therefore, the research of yeast apoptosis not only help to instruct theoretical guidance for the production of practice, but also for clarifing the regulatory mechanism of apoptosis in mammalian.The acetic acid is the normal finally product of yeast executing alcohol fermentation, acetic acid can cause yeast cells death in the form of apoptosis when it achieves the certain density. The lactic acid is also the normal finally product of some special yeast fermentation, in brewing beer, it can regulat the pH value to promote saccharification, adjustment beer flavor, improve the beer quality, but whether the lactic acid can lead to yeast apoptosis has not been reported. Therefore, the study of acetic acid and lactic acid induced yeast apoptosis and changes in the expression of certain genes is good for practice production and pave the way for in-depth study on pathway of apoptosis.In this study, the growth of yeast cells to the index to the early (OD600=0.6-0.9) in YPD culture medium supplemented with different final concentrations (40mM, 80mM, 120mM) of acetic acid and different final concertrations (200mM, 250mM,300mM) of lactic acid treatment 200min, among the middle of the final concentration of acetic acid (80mM) and lactic acid (250mM) treatment yeast cells at different time (120min, 200min, 260min), the rate of mortality and apoptosis can be obtained by methylene blue, TUNEL and DAPI staining separately. The study of expression changes of some apoptosis-related genes by RT-PCR can pave the way for yeast apoptosis pathway.The results:1. The methylene blue staining showed that the yeast cells increasing the mortality rate, as increasing the acetic acid concentration and treatment time , However, about lactic acid, only increasing the concentration can raise the mortality rate, but not extending time. 2. The TUNEL staining showed that the acetic acid caused the yeast cell death by the form of apoptosis, 40mM final concentration of acetic acid caused about 25% of apopotosis in 200min,when the final concentration of acetic acid increased to 120mM, the rate of apoptosis achieved the maximum level over 80%. The final concertration of 80mM acetic acid caused about 20% of apoptosis in 120min, when the time was extended to 260min, achieved the maximum level of apoptosis about 80%. Therefore, acetic acid caused yeast cell apoptosis in a concentration and time dependent.3. The TUNEL staining showed that the lactic acid caused the yeast cell death by the form of apoptosis, 200mM final concentration of lactic acid caused about 25% of apopotosis in 200min, when the final concentration of lactic acid increased to 300mM, the rate of apoptosis achieved the maximum level over 80%. 250mM final concentration of lactic acid treated yeast 120min, 200min, 260min separately, the apoptosis rate is around 60%, no significant change. Therefore, lactic acid caused yeast cell apoptosis in a concentration-dependent,but not time-dependent.4. Expression changes of some apoptosis-related gene detected by RT-PCR showed that as the acetic acid and lactic acid increased the yeast apoptosis, Fis1, Bir1, SOD1, SOD2 gene expression decreased, while Yca1, Nma111, Nuc1, Aif1, Ndi1 gene expression did not change significantly,essentially unchanged.The above result indicated: acetic acid and lactic acid can lead to yeast apoptosis, acetic acid caused yeast apoptosis in a dose and time dependent, while lactic acid caused yeast apoptosis only in a dose-dependent. The RT-PCR detected some apoptosis-related genes, with the yeast apoptosis increased by the two acid caused, the expression of Fis1, Bir1, SOD1, SOD2 gene decreased, so they have common points about the two acid caused apoptosis. But how they to work in apoptosis need a deep research.