Monogalactosyldiacylglycerol (MGDG) synthase catalyses formation of MGDG, a major structural lipid of chloroplasts. We have already cloned a cDNA for the synthase from a cucumber cDNA library and shown that expression of this gene is regulated by light and a phytohormone, cytokinin. In the present study, we report the molecular basis for transcriptional regulation by light and cytokinin in detail. First, in terms of the enzyme activity, gradual increases in activity mediated by light and cytokinin treatments were observed. At the same time, however, the changes in the mRNA level showed different profiles, with a transient peak during the early stages of light and cytokinin treatment. The interval between the peak level of mRNA and enzyme activation implies the existence of a post-transcriptional regulatory system. In addition, a genomic clone of MGDG synthase isolated from a cucumber genome library was used for a motif search in databases, and this revealed that putative cis-acting elements for light and phytohormones exist in the 5Î-upstream region of the MGD cucumber gene. Detailed analysis of this region for light- and cytokinin-responsive activity was performed using a – 90 truncated 35 S minimal promoter/luciferase (LUC) reporter gene. It resulted in high levels of LUC expression in etiolated cucumber cotyledons in response to illumination and cytokinin treatment. These results indicate that this 5Î-upstream region is involved in light- and cytokinin-enhanced MGD gene expression, and that light- and cytokinin-responsive enhancements of the MGDG synthase activity are regulated, at least in part, at the level of transcription.
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Conference Article|
December 01 2000
Transcriptional regulation by light and phytohormones of the MGD gene in cucumber
Y. Yamaryo;
Y. Yamaryo
1Graduate School of Bioscience and Biotechnology, Tokyo Institute of Technology, Nagatsuta, Yokohama, 226-8501, Japan
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D. Kanai;
D. Kanai
1Graduate School of Bioscience and Biotechnology, Tokyo Institute of Technology, Nagatsuta, Yokohama, 226-8501, Japan
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K. Awai;
K. Awai
1Graduate School of Bioscience and Biotechnology, Tokyo Institute of Technology, Nagatsuta, Yokohama, 226-8501, Japan
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T. Masuda;
T. Masuda
1Graduate School of Bioscience and Biotechnology, Tokyo Institute of Technology, Nagatsuta, Yokohama, 226-8501, Japan
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H. Shimada;
H. Shimada
1Graduate School of Bioscience and Biotechnology, Tokyo Institute of Technology, Nagatsuta, Yokohama, 226-8501, Japan
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K.-i. Takamiya;
K.-i. Takamiya
1Graduate School of Bioscience and Biotechnology, Tokyo Institute of Technology, Nagatsuta, Yokohama, 226-8501, Japan
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H. Ohta
H. Ohta
1
1Graduate School of Bioscience and Biotechnology, Tokyo Institute of Technology, Nagatsuta, Yokohama, 226-8501, Japan
1To whom correspondence should be addressed (e-mail hohta@bio.titech.ac.uk)
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Publisher: Portland Press Ltd
Received:
June 23 2000
Online ISSN: 1470-8752
Print ISSN: 0300-5127
© 2000 Biochemical Society
2000
Biochem Soc Trans (2000) 28 (6): 738–740.
Article history
Received:
June 23 2000
Citation
Y. Yamaryo, D. Kanai, K. Awai, T. Masuda, H. Shimada, K.-i. Takamiya, H. Ohta; Transcriptional regulation by light and phytohormones of the MGD gene in cucumber. Biochem Soc Trans 1 December 2000; 28 (6): 738–740. doi: https://doi.org/10.1042/bst0280738
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