Cyanobacteria are the simplest organisms known in which to explore the mechanisms of circadian biological clocks. We have identified a gene, cikA, which is integral to relaying environmental information to reset the phase of the circadian clock in Synechococcus sp. strain PCC 7942, the model system for prokaryotic circadian rhythm studies. With the goal of elucidating the molecular basis of the clock and its entrainment to the photic environment, we will exploit this discovery by determining whether CikA acts directly as a photoreceptor and by identifying its signaling partners and their biochemical activities. CikA is a member of the phytochrome family of proteins, but lacks the expected cysteine residue that provides a ligand for bilin chromophore attachment in phytochromes and some other phytochrome-like proteins. The C-terminal domain has a well-conserved histidine protein kinase motif, and a segment of similarity with the receiver domains of response regulator proteins of bacteria. We will purify CikA directly from the cyanobacterium to determine whether a chromophore is attached, and if so, its chemical identity and influence on CikA function. This will be facilitated by modifying the cikA gene to add an affinity tag to the protein, and confirming that the modified gene is functional through complementation of a cikA null mutant. The role of autophosphorylation of the histidine protein kinase domain in resetting will be assessed. Genetic screens, both by a yeast two-hybrid assay and transposon mutagenesis in the cyanobacterium, will be used to identify proteins with which CikA interacts. The roles of these CikA partners in the phase resetting input pathway will be determined as well. In addition to providing fundamental insights into this most basic of biological processes, the project is also likely to uncover functional properties of currently cryptic phytochrome homologs that are present in the genomes of diverse prokaryotes.

Agency
National Institute of Health (NIH)
Institute
National Institute of General Medical Sciences (NIGMS)
Type
Research Project (R01)
Project #
5R01GM062419-02
Application #
6520388
Study Section
Microbial Physiology and Genetics Subcommittee 2 (MBC)
Program Officer
Tompkins, Laurie
Project Start
2001-03-01
Project End
2005-02-28
Budget Start
2002-03-01
Budget End
2003-02-28
Support Year
2
Fiscal Year
2002
Total Cost
$181,875
Indirect Cost
Name
Texas A&M University
Department
Biology
Type
Schools of Arts and Sciences
DUNS #
047006379
City
College Station
State
TX
Country
United States
Zip Code
77845
Boyd, Joseph S; Cheng, Ryan R; Paddock, Mark L et al. (2016) A Combined Computational and Genetic Approach Uncovers Network Interactions of the Cyanobacterial Circadian Clock. J Bacteriol 198:2439-47
Cohen, Susan E; Golden, Susan S (2015) Circadian Rhythms in Cyanobacteria. Microbiol Mol Biol Rev 79:373-85
Shultzaberger, Ryan K; Boyd, Joseph S; Diamond, Spencer et al. (2015) Giving Time Purpose: The Synechococcus elongatus Clock in a Broader Network Context. Annu Rev Genet 49:485-505
Chang, Yong-Gang; Cohen, Susan E; Phong, Connie et al. (2015) Circadian rhythms. A protein fold switch joins the circadian oscillator to clock output in cyanobacteria. Science 349:324-8
Kim, Yong-Ick; Boyd, Joseph S; Espinosa, Javier et al. (2015) Detecting KaiC phosphorylation rhythms of the cyanobacterial circadian oscillator in vitro and in vivo. Methods Enzymol 551:153-73
Espinosa, Javier; Boyd, Joseph S; Cantos, Raquel et al. (2015) Cross-talk and regulatory interactions between the essential response regulator RpaB and cyanobacterial circadian clock output. Proc Natl Acad Sci U S A 112:2198-203
Shultzaberger, Ryan K; Paddock, Mark L; Katsuki, Takeo et al. (2015) High-throughput and quantitative approaches for measuring circadian rhythms in cyanobacteria using bioluminescence. Methods Enzymol 551:53-72
Taton, Arnaud; Unglaub, Federico; Wright, Nicole E et al. (2014) Broad-host-range vector system for synthetic biology and biotechnology in cyanobacteria. Nucleic Acids Res 42:e136
Shultzaberger, Ryan K; Boyd, Joseph S; Katsuki, Takeo et al. (2014) Single mutations in sasA enable a simpler ?cikA gene network architecture with equivalent circadian properties. Proc Natl Acad Sci U S A 111:E5069-75
Paddock, Mark L; Boyd, Joseph S; Adin, Dawn M et al. (2013) Active output state of the Synechococcus Kai circadian oscillator. Proc Natl Acad Sci U S A 110:E3849-57

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