title: Complementary function of two transketolase isoforms from Moniliella megachiliensis in relation to stress response.
abstract: Two transketolase isogenes, MmTKL1 and MmTKL2, isolated from Moniliella megachiliensis were investigated for their roles in stress response and erythritol biosynthesis. The encoded proteins were highly homologous in amino acid sequence and domain structure. Two stress response elements (STREs) were found upstream of MmTKL1, while no STRE was found upstream of MmTKL2. In contrast, two Ap-1 elements were present upstream of MmTKL2, but none were detected upstream of MmTKL1. MmTKL2 partially complemented the aromatic amino acid auxotrophy of a Saccharomyces cerevisiae tkl1 deletion mutant, suggesting that at least one of the MmTKLs functioned as a transketolase in vivo. In response to short-term osmotic stress (20% glucose or 1.2 M NaCl) in Moniliella cells, MmTKL1 expression increased rapidly through the first 40 min before subsequently decreasing gradually, while MmTKL2 expression showed no significant change. In contrast, short-term oxidative stress (0.15 mM menadione) induced considerable increases in MmTKL2, while MmTKL1 expression remained low under the same conditions. Long-term osmotic stress (20% glucose) yielded increased expression of both genes starting at 12 h and continuing through 72 h. During either osmotic or oxidative stress, intracellular erythritol accumulation could clearly be correlated with the pattern of expression of either MmTKL1 or MmTKL2. These results strongly suggested that MmTKL1 is responsible primarily for the response to osmotic stress, while MmTKL2 is responsible primarily for the response to oxidative stress. Thus, we postulate that the two transketolase isoforms of M. megachiliensis play distinct and complementary roles in coordinating erythritol production in response to distinct environmental stresses.
authors.affiliation: Applied Microbiology and Biotechnology Laboratory, Department of Chemistry and Lifescience, Nihon University, 1866 Kameino, Fujisawa, Kanagawa, 252-0880, Japan.
authors.forename: Hisashi
authors.initials: H
authors.lastname: Iwata
authors.affiliation: Applied Microbiology and Biotechnology Laboratory, Department of Chemistry and Lifescience, Nihon University, 1866 Kameino, Fujisawa, Kanagawa, 252-0880, Japan.|Bioproduction Research Institute, National Institute of Advanced Industrial Science and Technology, 1-1-1 Higashi, Tsukuba, Ibaraki, 305-8566, Japan.
authors.forename: Yosuke
authors.initials: Y
authors.lastname: Kobayashi
authors.affiliation: Applied Microbiology and Biotechnology Laboratory, Department of Chemistry and Lifescience, Nihon University, 1866 Kameino, Fujisawa, Kanagawa, 252-0880, Japan.|Biomolecular Engineering Laboratory, National Food Research Institute, National Agriculture and Food Research Organization, 2-1-12, Kannondai, Tsukuba, Ibaraki, 305-8542, Japan.
authors.forename: Daiki
authors.initials: D
authors.lastname: Mizushima
authors.affiliation: Applied Microbiology and Biotechnology Laboratory, Department of Chemistry and Lifescience, Nihon University, 1866 Kameino, Fujisawa, Kanagawa, 252-0880, Japan.
authors.forename: Taisuke
authors.initials: T
authors.lastname: Watanabe
authors.affiliation: Applied Microbiology and Biotechnology Laboratory, Department of Chemistry and Lifescience, Nihon University, 1866 Kameino, Fujisawa, Kanagawa, 252-0880, Japan.
authors.forename: Jun
authors.initials: J
authors.lastname: Ogihara
authors.affiliation: Applied Microbiology and Biotechnology Laboratory, Department of Chemistry and Lifescience, Nihon University, 1866 Kameino, Fujisawa, Kanagawa, 252-0880, Japan. kasumi@brs.nihon-u.ac.jp.
authors.forename: Takafumi
authors.initials: T
authors.lastname: Kasumi
keywords: Erythritol; Moniliella megachiliensis; Stress response; Transketolase isogenes