| Project/Area Number |
08833008
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| Research Category |
Grant-in-Aid for Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
海洋生物学
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| Research Institution | Tokyo University of Agriculture and Technology |
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Principal Investigator |
TAKEYAMA Haruo Tokyo University of Agriculture and Technology, Faculty of Technology, Assistant Professor, 工学部, 助手 (60262234)
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| Project Period (FY) |
1996 – 1997
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| Project Status |
Completed (Fiscal Year 1997)
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| Budget Amount *help |
¥2,100,000 (Direct Cost: ¥2,100,000)
Fiscal Year 1997: ¥1,100,000 (Direct Cost: ¥1,100,000)
Fiscal Year 1996: ¥1,000,000 (Direct Cost: ¥1,000,000)
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| Keywords | Marine cyanobacteria / Plasmid / Salinity / Copy number / repA gene / Replication / 複製 |
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| Research Abstract |
The marine cyanobacterium Synechococcus sp. NKBG042902 grows well in the presence of 0-5% NaCl. The copy number of the marine plasmid pSY10 (2561bp) from this strain was found to be controlled by changing the NaCl concentration of the culture medium. The pSY10 was maintained at a high copy number under seawater conditions, and at a low copy number under fresh water conditions. The RepA protein sequence was found on pSY10 and RepA protein revealed to participate in pSY10 replication. The mechanism of pSY10 replication involving the RepA protein and regulation of repA gene expression have been elucidated under different salinities. The region for stabilizing replication of plasmid was found at downstream of the repA gene. This region was consisted of two parts depressing (m region) or enhancing (p region) replication of plasmid. Band-shift assay indicated that RepA protein in the extract from cells grown under seawater conditions bound to the m region, resulting in a high copy number. On the other hand, no binding was observed in the extract from cells grown under fresh water conditions. Transcription of the repA gene was speculated to be depressed under fresh water conditions and small amount of RepA protein was available to bind to the m region. The extract from the cells grown under fresh water conditions not showed the existence of a certain protein bound to the promoter of the repA gene. This phenomenon was observed in Synechococcus sp. NKBG042902 not in another cyanobacterial host transformed by pSY10-hybrid plasmid. This suggests that the protein regulating transcription of the repA gene is expressed from the host chromosome under fresh water conditions. A stress-responsive protein is expressed from chromosome of NKBG042902 under fresh water conditions and depress the expression of RepA protein, resulting in a low copy number of pSY10. This is a novel plasmid replication mechanism involving chromosomal control.
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