To characterise the circadian transcriptome, the expression profiles of transcripts in whole leaves of mature, soil grown <i>A. thaliana </i>plants were analysed. Circadian-regulated transcripts constituted approximately 9.5% of the transcripts detected, and were found to encode proteins involved both a well-described circadian processes and in pathways that have not been previously identified as having circadian regulation. Transcripts encoding proteins involved in core metabolic processes and stress response pathways were particularly highly representative in the dataset, which suggested a potential basis for the fitness benefits associated with the possession of a functional biological clock. To determine the correlation between rhythms in transcript abundance in whole leaves and in a single cell type, the stomatal guard cell was selected as a model system. However, assessment of two published methods of guard cell isolation, epidermal fragmentation and guard cell protoplasting, revealed that neither method was suitable for analysis of circadian rhythms in transcript abundance. Consequently, single cell analysis was not pursued. Nevertheless, bio-informatic analysis of the whole leaf circadian transcriptome and published microarray data was employed in order to characterise components of the intra-cellular circadian signalling pathway. This analysis revealed a relationship between the circadian oscillator and the regulator of [Ca<sup>2+</sup>]<sub>cyt</sub> release, cyclic adenosine disphosphate ribose (cADPR). Evidence is presented suggesting that circadian [Ca<sup>2+</sup>]<sub>cyt</sub> oscillations form a component of the oscillator that maintains the periodicity of circadian rhythms in transcript abundance. Collectively the data presented provide an overview of the biological clock in <i>A. thaliana</i>, and form a resource for further analysis of the structure of the clock and its role in integrating diverse cellular and physiological processes into a coherent biological programme.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:599310 |
| Date | January 2006 |
| Creators | Gardner, M. J. |
| Publisher | University of Cambridge |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
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