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Title: The downy mildew effector HaRxL21 suppresses immune responses of Arabidopsis thaliana
Author: Harvey, Sarah
Awarding Body: University of Warwick
Current Institution: University of Warwick
Date of Award: 2013
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The oomycete Hyaloperonospora arabidopsidis (Hpa) is the causal agent of downy mildew of Arabidopsis thaliana; a system that can be used as a model for the study of plant-pathogen interactions. In order for successful colonisation, biotrophic pathogens such as Hpa suppress or evade plant defences through secretion of effector proteins into the plant to manipulate and disrupt the host immune system. Alignment of oomycete effector proteins has revealed a conserved amino acid sequence at the N-terminus with the consensus sequence RxLR (arginine, any, leucine, arginine), thus allowing the use of Bioinformatic approaches to identify putative effector proteins in the Hpa genome. Studying effector action and their targets in the host may help elucidate important components of the plant defence response, eventually leading to more durable crops. Expression of the Hpa effector HaRxL21 in planta has been shown to alter host susceptibility to Hpa, Botrytis cinerea and Pseudomonas syringae. Here the interaction targets of HaRxL21 are presented and interaction with the transcriptional co-repressor TOPLESS (TPL) has been validated in planta using BIFC and Co-IP. Using deletion and mutation analysis, the specificity of the interacting protein domains has been identified as between the CTLH domain of TPL and Leucine residues within the EAR motif of HaRxL21. Microarrays have revealed effects of HaRxL21 on host transcription, particularly up regulation of genes involved in ABA signalling and a decreased induction of SA responsive genes upon SA induction. Finally, work has been carried out to determine the biochemical function of HaRxL21, showing an increased stability of TPL in the presence of this effector.
Supervisor: Not available Sponsor: Biotechnology and Biological Sciences Research Council
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available
Keywords: QK Botany ; SB Plant culture