IGEM:Harvard/2006/Brainstorming Papers - Zhipeng

Cyanobacteria

1. Kondo T and Ishiura M. The circadian clock of cyanobacteria. Bioessays. 2000 Jan;22(1):10-5. DOI:10.1002/(SICI)1521-1878(200001)22:1<10::AID-BIES4>3.0.CO;2-A |
2. Kucho K, Okamoto K, Tsuchiya Y, Nomura S, Nango M, Kanehisa M, and Ishiura M. Global analysis of circadian expression in the cyanobacterium Synechocystis sp. strain PCC 6803. J Bacteriol. 2005 Mar;187(6):2190-9. DOI:10.1128/JB.187.6.2190-2199.2005 |
3. Takigawa-Imamura H and Mochizuki A. Transcriptional autoregulation by phosphorylated and non-phosphorylated KaiC in cyanobacterial circadian rhythms. J Theor Biol. 2006 Jul 21;241(2):178-92. DOI:10.1016/j.jtbi.2005.11.013 |
4. Kutsuna S, Nakahira Y, Katayama M, Ishiura M, and Kondo T. Transcriptional regulation of the circadian clock operon kaiBC by upstream regions in cyanobacteria. Mol Microbiol. 2005 Sep;57(5):1474-84. DOI:10.1111/j.1365-2958.2005.04781.x |

Kondo et al.

Circadian organization (Kondo et al 2004).

• gene cluster KaiABC involved
• no homology to eukarayotic circadian systems
• Central oscillator controls output patterns; phase of oscillator controlled by input
• Photosynthesis by day, nitrogen fixation by night (2 incompatible in unicellular)
• Used luciferase DNA expressed downstream as a reporter
• Genome 2.7kb in size (e. coli 6.1kb)
• Put luxAB on a psbA plasmid, luxAB luciferase related protein  volatile
  • See diagram in paper for circuitry
• KaiABC system
  • Overexpression of KaiC represses KaiA and KaiB
  • Overexpression of KaiA activates KaiBC
  • KaiC center of oscillation
• Question TBA: why 24h period?
  • Single point mutations in KaiC can change period from 14h to 60h
• Drosophila and Neurospora also have clock models
• Cyanobacteria has no nuclear envelope, can divide 6h/time
• KaiABC analogues only found on archaeobacteria

Kucho et al.

• Purpose of regulation to prepare cell for night in cyanobacteria
• Tested Synechocystis, which is a different strain of cyanobacteria
• 77% in Synechocystis rhymic clones; 100% in Synechococcus
• In cyanobacteria
  • KaiC regulated by negative feedback autoreg. loop
  • KaiA activates kaiBC
• Used DNA microarray to determine mRNA cyclic nature
• cycling genes detected; peak expression from day to night
  • Genes mostly:
    • unassigned
    • carbohydrate metabolism
    • energy metabolism purposes
    • transcription!
    • translation!
• 2 Sigma factors have circadian rhythm: sll1689, sll0687 on RNAPol

Other

• (Wikipedia)Cyanobacteria are the only group of organisms that are able to reduce nitrogen and carbon in aerobic conditions