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Title: Identification of novel regulators and mechanisms of auxin signalling
Author: Neve , Joshua Thomas
Awarding Body: University of Leeds
Current Institution: University of Leeds
Date of Award: 2011
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The plant hormone auxin is essential for plant development and controls growth and patterning of cells and tissues by strict regulation of gene expression. Past studies have elucidated a succinct auxin signal transduction pathway but some functions of the core components have only been partially explored. Several published studies have provided evidence for the existence of different mechanisms for the repressive functions of Auxin/Indole Acetic Acid (Aux/IAA) repressors and part of this study has sought to quantify the extent to which TOPLESS (TPL) and TOPLESS-RELATED proteins contribute to their [unction in plants. Yeast Two Hybrid (Y2H) suggests that differential interactions occur between Aux/IAAs and TPL/TPRs but genetic analyses carried out with Arabidopsis thaliana mutants did not substantiate findings in yeast. Published studies show that Auxin Response Factors (ARPs) interact with proteins other than Aux/IAAs in planta to carry out wild type function. Current understanding supports a formal possibility that novel' regulators of auxin signalling have yet to be discovered, and so two distinct screening procedures have been carried out to find novel components. 7000 Full-length Arabidopsis cDNA Over-eXpression (FOX) lines, each over-expressing on average 1.2 Arabidopsis cDNAs have been systematically screened for resistance to exogenous auxin and have revealed a novel allele of A UX I but no novel regulators of auxin signalling. Alternatively the transcriptional activator, ARF7, and repressor, ARFI, have each been used in Y2H screens resulting in the identification of novel interacting protein partners that have been corroborated by biochemical analysis. Results suggest possible links between auxin and jasmonic acid signalling, and suggest a physical interaction between both AR FL and ARF7 and several members of the Type-One Protein Phosphatase (TOPP) family of Protein Phosphatase I (PP I) catalytic subunits. Up-regulation of TOPP1 expression confers changes in more than one auxin-regulated developmental process and therefore suggests a novel role of phosphorylation in auxin-regulated development.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available