2007 Fiscal Year Final Research Report Summary
Evaluation for genetic robustness in the machinery of period determination of the cyanobacterial circadian clock
| Project/Area Number |
17370088
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| Research Category |
Grant-in-Aid for Scientific Research (B)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
Evolutionary biology
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| Research Institution | Nagoya University |
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Principal Investigator |
OYAMA Tokitaka Nagoya University, Graduate Schcol of Science, Associate Professor (30324396)
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| Co-Investigator(Kenkyū-buntansha) |
KONDO Takao Nagoya University, Graduals School of Science, Professor (10124223)
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| Project Period (FY) |
2005 – 2007
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| Keywords | circadian clock / cyanobacteria / genetic robustness / evolution / mutation / suppressor |
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| Research Abstract |
Synechococcus elongatus PCC 7942 is a model cyanobacterium for analysis of circadian clock. A bioluminescent reporter system can be used for effective monitoring of circadian rhythms of cyanobacterial colonies of this strain. Through a genetic analysis, it was found that the circadian clock of cyanobacteria basically comprises only three clock genes : kaiA, kaiB, and kaiC. In these loci, especially in kaiC, various mutations that altered period lengths ranging from 16 to over 60 hours were identified. Recently, it was found that mixing purified proteins of them and ATP in a test tube brought about a robust cyclic phosphorylation/dephosphorylation of KaiC with a circadian period. Namely, the circadian clock of cyanobacteria is a chemical oscillator that does not require biological processes/networks such as transcription/translation. We have tried to experimentally evaluate the genetic robustness of this simple system against mutations in the three kai loci in the laboratory. Using a set of〜300 single mutations with randomly introduced amino acid substitutions in these loci, we began trying evaluation of effects of those mutations in wildtype background on the phenotype of period lengths. We found that mutations in kaiA had much smaller effects on the circadian rhythm than those in kaiB and kaiC. This suggested that the genetic robustness among the three clock genes is diverged. Further, it was found more than 90% of mutations in kaiB and kaiC showed phenotypes in the rhythm. Thus, it was shown that the genetic robustness of these loci are remarkably low compared to other genetic loci. The molecular basis for the robustness was also analyzed using the in vitro oscillation system. It was shown that the robust periodicity can be attained by the three clock components and this conclusion is consistent with the fact that mutations only in these loci show phenotypes on it.
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[Journal Article] Autonomous synchronization of the circadian KaiC phosphorylation rhythm2007
Author(s)
Ito, H, Kageyama, H, Mutsuda, M, Nakajima, M, *Oyama, T, *Kondo, T(* co-corresponding authors)
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Journal Title
Nat Struct Mol Biol 14
Pages: 1084-1088
Description
「研究成果報告書概要(欧文)」より
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[Journal Article] ATPase activity of KaiC determines the basic timing for circadian clock of cyanobacteria2007
Author(s)
Terauchi, K, Kitayama, K, Nishiwaki, T, Miwa, K, Murayama, Y, Kondo, T
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Journal Title
Proc Nati Aced Sci USA 104
Pages: 16377-16381
Description
「研究成果報告書概要(欧文)」より
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[Journal Article] labA : a novel gene required for negative feedback regulation of the cyanobacterial circadian clock protein KaiC2007
Author(s)
Taniguchi, Y, Katayama, K, Ito, R, Takai, N, *Kondo, T, *Dyarno, T, (* co-corresponding authors)
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Journal Title
Genes & Development 21
Pages: 60-70
Description
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[Journal Article] A KaiC-associating SasA-RpaA two-component regulatory system as a major circadian timing mediator in cyanobacteria2006
Author(s)
Takai, N, Nakajima, M, Kito, R, Sugita, C, Sugita, M, Kondo, T, Iwasaki, H
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Journal Title
Proc Natl Aced Sci USA 103
Pages: 12109-12114
Description
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[Journal Article] Reconstitution of circadian oscillation of cyanobacterial Kale phosphorylation in vitro2005
Author(s)
Nakajima, M, Imai, K, Ito, H, Nishiwaki, T, Murayama, Y, Iwasaki, H, Ovamn, T, Kondo, T
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Journal Title
Science 308
Pages: 414-415
Description
「研究成果報告書概要(欧文)」より
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[Journal Article] Luciferases2005
Author(s)
Oyama, T, Kondo, T
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Journal Title
Shokubutsu-Saibo-Kogaku 21 "Protocols for model plants" Shujun-sha
Pages: 172-175
Description
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