Analysis of the ability of high temperature growth, one of the major virulence traits, in clinical isolate of Saccharomyces cerevisiae in Taiwan
Date Issued
2008
Date
2008
Author(s)
Lee, Cheng-Kuang
Abstract
Saccharomyces. cerevisiae has recognized as “generally regarded as safe” organism, but recent evidence indicated that the clinical isolates were virulent and had been implicated in the induction of a disease. The pathogenic isolates exhibit the ability to grow at 42°C and are capable of pseudohyphal growth. Our lab got three clinical isolates(YYC1、YYC2、YYC3) from NTUH . We found there were two of them having the ability of growth at 42°C and pseudohyphal formation. My target is studying the ability of growth at 42°C. The previous report mapped a S. cerevisiae high temperature growth QTL and identified MKT1, END3, and RHO2 as QTGs. There were some important SNPs (ex.MKT1 A1358G、END3 C733T )contributing to HTG phenotype. In our case, we found that the SNPs in YYC1, MKT1 (A1057G) and RHO2 (T271G), are nonsynonymous changes and heterozygous in these two gene locus. Next, we use tetrad dissection, making the homozygous segregants, try to observe the contribution of these SNPs to HTG. After tetrad dissection analysis, we found that there were few segregants(4/60) having the HTG phenotype. Then, we cloned the MKT1, from one of the segregants which had thermo-tolerance, into a mkt1 deletion strain. However, the clone did not change its phenotype. This indicated that the single genotype alternation did not affect the HTG phenotype. When the yeast cells encounter heat stress, the cellular ROS (reactive oxygen species) will be induced. Excess ROS causes damages by attacking DNA and proteins. Our hypothesis was that the thermo-tolerant strains might have more strong ability to clear up cellular ROS. But the experiment result indicated that the thermo-tolerant strains did not have lower ROS level than thermo-sensitive strains. We still do not find the key factor contribution to the ability of HTG.. It needs advanced researches to figure out the mechanism of high temperature growth.
Subjects
Saccharomyces cerevisiae
high temperature growth
ROS
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