Circadian rhythms of behavior have been well characterized in organisms including
mammals, plants, insects, fungi, and photosynthetic bacteria. Cyanobacteria, such as the
unicellular Synechococcus elongatus PCC 7942, display near 24-h circadian rhythms of
gene expression. These rhythms persist in the absence of external cues, can be reset by
the same stimuli to which they entrain, and are relatively insensitive to changes in
ambient temperature within their physiological range. Key components have been
identified as belonging to the central oscillator that comprises the timekeeping units,
output pathways that relay temporal information to clock-controlled processes, and input
pathways that synchronize the oscillator with local time. The emerging model of the
cyanobacterial clock depicts the internal timekeeping elements KaiA, KaiB, and KaiC
interacting with one another to form a large, multimeric complex that assembles and
disassembles over the course of a day. Information is sent into and out of the oscillator
via signal transduction pathways that include proteins involved in bacterial twocomponent
systems. The research presented in this dissertation explores the regulatory
mechanisms that exist at each level of the clock system. New components were identified that interact with an important protein in the input pathway; these new players
are involved in clock-associated phenomena, such as resetting the internal oscillation to
external stimuli and maintaining proper circadian periodicity, as well as the process of
cell division. The model formerly associated with the temporal, transcriptional
regulation of the kai genes was redefined to reflect the unique properties of the
prokaryotic oscillator. The differential output of the clock was examined by studying the
circadian regulation of the psbA gene family. Overall, these data provide insight into the
complex molecular events that occur to create a circadian timing circuit in S. elongatus.
| Identifer | oai:union.ndltd.org:tamu.edu/oai:repository.tamu.edu:1969.1/ETD-TAMU-1812 |
| Date | 02 June 2009 |
| Creators | Mackey, Shannon Rose |
| Contributors | Golden, Susan S. |
| Source Sets | Texas A and M University |
| Language | en_US |
| Detected Language | English |
| Type | Book, Thesis, Electronic Dissertation, text |
| Format | electronic, application/pdf, born digital |
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