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Title: Integration of multiple environmental stresses for compound gene regulation in Arabidopsis thaliana
Author: Lee, Sang Yun
ISNI:       0000 0004 7427 6691
Awarding Body: Imperial College London
Current Institution: Imperial College London
Date of Award: 2016
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Plants are known to respond to various types of environmental stresses arising from physicochemical changes and other organisms. As plants often simultaneously experience multiple stress factors due to their immobility, capacity to appropriately regulate gene expression by integrating multiple stress signals is crucial for successful adaptation to hostile environments. Although significant progress has been made in elucidating the molecular mechanisms for regulation of stress response genes under single stress, little is known about the effects of combined stress signals on gene regulation and their associated mechanisms. This thesis aimed to contribute to the understanding of plant stress response by studying the signal integration mechanisms under various perspectives: first, the thesis explored how multiple stress signals affect the choices over discretised regulatory outcomes, such as up-regulation or down-regulation. We propose that processing of multiple signals can be described as logical operations, and subsequently investigate the mechanisms for each signal integration outcome by constructing logical model of intracellular signalling network. The resulting insight was applied to analyse a transcriptomic dataset from the model plant Arabidopsis thaliana, leading to novel hypotheses about potential crosstalk interactions that are missing between multiple stress signalling pathways. In parallel, the thesis also explored the cases where integration of multiple stress signals modulates dynamics of gene expression. An experimental study of the expression profile of Response-to-Dehydration 29A (RD29A), a model stress response gene, was conducted to show that combination of multiple stress inputs introduces a unique qualitative effect on dynamics of gene expression. The origin of this behaviour was investigated via a dynamical model of the RD29A regulatory network, which subsequently revealed potential interactions in the regulatory network that are currently unknown. Taken together, this thesis argues that systematic comparison between gene regulatory outcomes under single and combined stress inputs provides a crucial source of information for discovering functionally significant regulatory interactions in the stress signalling network.
Supervisor: Tanaka, Reiko ; Tweedy, Jennifer Sponsor: Imperial College London
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral