Investigating the role of downy mildew effectors in host resistance and susceptibility
type: CreativeWork
description: Through specialised structures called haustoria, filamentous eukaryotic plant pathogens such as rusts and mildews can deliver “effector” proteins directly into plant cells in order to manipulate specific defence responses and processes. Hyaloperonospora arabidopsidis (Hpa) is a haustorium-producing biotrophic oomycete pathogen that causes downy mildew on Arabidopsis. Over 100 candidate effectors (called “HaRxLs”), carrying a characteristic RxLR protein motif, have been predicted from the Hpa genome sequence. This PhD work focused on the characterisation of some of these effectors and their interaction with plant defences. First, the Pseudomonas syringae pv. tomato (Pst) strain DC3000 type III secretion system was used to examine the effect of single oomycete effectors in planta. One of these, ATR13 from Hpa isolate Emco5 (ATR13Emco5) has been shown to be recognised in some Arabidopsis accessions by the RPP13 protein, preventing Hpa Emco5 from completing its life cycle on such resistant plants. Hpa Emco5 can however complete its life cycle on Ws-0 but paradoxically, ATR13Emco5 is also recognised in this accession. Here, I show that ATR13Emco5 is weakly recognised in Ws-0 by a single RPP13-independent, EDS1-independent dominant gene called RHA13, shown by rough mapping to position on Arabidopsis chromosome 4. Second, I contributed to two independent functional screens performed in our laboratory to experimentally characterise the Hpa effectorome. The first screen focused on HaRxLs effects on bacteria virulence using the EDV system. The second screen was based on HaRxLs subcellular localisation using Agrobacterium-mediated transient expression. As presented in this work, I showed that both screens identified putative interesting effectors which increased plant susceptibility to Pst and Hpa and localised to various plant subcellular compartments. One particular effector candidate, HaRxL79, localised to microtubules in planta and interacted with two microtubule-associate…
abstract: Through specialised structures called haustoria, filamentous eukaryotic plant pathogens such as rusts and mildews can deliver “effector” proteins directly into plant cells in order to manipulate specific defence responses and processes. Hyaloperonospora arabidopsidis (Hpa) is a haustorium-producing biotrophic oomycete pathogen that causes downy mildew on Arabidopsis. Over 100 candidate effectors (called “HaRxLs”), carrying a characteristic RxLR protein motif, have been predicted from the Hpa genome sequence. This PhD work focused on the characterisation of some of these effectors and their interaction with plant defences. First, the Pseudomonas syringae pv. tomato (Pst) strain DC3000 type III secretion system was used to examine the effect of single oomycete effectors in planta. One of these, ATR13 from Hpa isolate Emco5 (ATR13Emco5) has been shown to be recognised in some Arabidopsis accessions by the RPP13 protein, preventing Hpa Emco5 from completing its life cycle on such resistant plants. Hpa Emco5 can however complete its life cycle on Ws-0 but paradoxically, ATR13Emco5 is also recognised in this accession. Here, I show that ATR13Emco5 is weakly recognised in Ws-0 by a single RPP13-independent, EDS1-independent dominant gene called RHA13, shown by rough mapping to position on Arabidopsis chromosome 4. Second, I contributed to two independent functional screens performed in our laboratory to experimentally characterise the Hpa effectorome. The first screen focused on HaRxLs effects on bacteria virulence using the EDV system. The second screen was based on HaRxLs subcellular localisation using Agrobacterium-mediated transient expression. As presented in this work, I showed that both screens identified putative interesting effectors which increased plant susceptibility to Pst and Hpa and localised to various plant subcellular compartments. One particular effector candidate, HaRxL79, localised to microtubules in planta and interacted with two microtubule-associate…
author: Piquerez, Sophie
language: en
date published: 2011-12
date modified: 2026-07-24T02:11:51Z
provider: University of East Anglia
publisher: Networked Digital Library of Theses and Dissertations
type: WebPage
source organization: University of East Anglia