Role of Osmotic and Salt Stress in the Expression of Erythrose Reductase in Candida magnoliae
2011
Park, E.H., Kangwon National University, Chuncheon, Republic of Korea | Lee, H.Y., Kangwon National University, Chuncheon, Republic of Korea | Ryu, Y.W., Ajou University, Suwon, Republic of Korea | Seo, J.H., Seoul National University, Seoul, Republic of Korea | Kim, M.D., Kangwon National University, Chuncheon, Republic of Korea
The osmotolerant yeast, Candida magnoliae, which was isolated from honeycomb, produces erythritol from sugars such as fructose, glucose, and sucrose. Erythrose reductase in C. magnoliae (CmER) reduces erythrose to erythritol with concomitant oxidation of NAD(P)H. Sequence analysis of the 5'-flanking region of the CmER gene indicated that one putative stress response element (STRE, 5'-AGGGG-3'), found in Saccharomyces cerevisiae, exists 72 nucleotides upstream of the translation initiation codon. An enzyme activity assay and semiquantitative reverse transcription polymerase chain reaction revealed that the expression of CmER is upregulated under osmotic and salt stress conditions caused by a high concentration of sugar, KCl, and NaCl. However, CmER was not affected by osmotic and oxidative stress induced by sorbitol and H₂O₂, respectively. The basal transcript level of CmER in the presence of sucrose was higher than that in cells treated with fructose and glucose, indicating that the response of CmER to sugar stress is different from that of GRE3 in S. cerevisiae, which expresses aldose reductase in a sugar-independent manner. It was concluded that regulation of CmER differs from that of other aldose reductases in S. cerevisiae.
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