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Title: A cross-species microarray and systems approach to investigate aroma and stress response with tea and Arabidopsis
Author: Marshall, Alexandra Ahrens
Awarding Body: University of Nottingham
Current Institution: University of Nottingham
Date of Award: 2011
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Tea (Ozmellia sinensis) aroma is tmderpinned by two stresses, withering and wounding, which are part of the tea manufacturing process. A cross-species approach has been employed, where the tea DNA was hybridised to the Affymetrix ATHI chip, which extended coverage beyond Unilever's 3()(X) tea-gene rnicroarray to a potentia118,509 probes. This filter was then used for subsequent microarray analyses of both a factory trial. and a more robust laboratory trial. The observed changes in gene expression were consistent with the stress responses, adding confidence to the cross-species approach. The same RNA samples were used on the Unilever Agilent microarray as a comparison, and found that both platforms followed a similar trend, though there were too many ambiguities to draw firm conclusions. Arabidopsis drought and wounding microarray datasets were analysed and compared with the tea data, revealing a set of 90 core genes both conserved between species and common to the two stresses. The mapping of the microarray data onto KEGG pathways was informative in terms of aroma metabolism, however this was limited. This prompted the merging of Arabidopsis protein interaction, gene regulatory, coexpression and metabolic networks as a way to increase our understanding of the interactions taking place in Arabidopsis and tea. Firstly, a network was filtered based on the sets of core genes. This revealed that in Arabidopsis the lipoxygenase path• way (to hexenol and jasmonate) and 4-cownerate ligase (of phenylpropanoid pathway) appear to be regulated by the same mechanism, as they have well correlated coexpression across NASCArrays. Their high-level expression in tea suggests they may be coregulated in this plant as well. Other aspects of stress mediated gene regulation and cell Signalling were also uncovered. The merged network was also filtered for genes with GO-terms for "response to stress" and "aroma metabolism", and revealed further connections between parts of the processes linking stress with aroma metabolism. nus PhD has used transcriptomics linked with network biology as a way for us to understand tea withering and wounding, and generated a resource for further investigation of the links between stress and tea metabolism. This could be applied to flavour, colour and the stimulatory effects of tea.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available