Many oomycetes, such as the notorious potato late blight pathogen Phytophthora infestans, have devastating effects on crops. Recent findings have implied that eukaryotic plant pathogens deliver effector proteins inside host cells to facilitate colonization by modulating plant defences. Although the translocation mechanisms remain unknown, in oomycetes this process depends on a short conserved amino acid sequence located near the signal peptide of many secreted proteins. This sequence, termed the RxLR motif, is strikingly similar to the core RxLxE/D/Q host cell targeting-signal that is found in virulence proteins from the malaria parasite Plasmodium falciparum. Common infection strategies have been described for these divergent pathogens, albeit one is a plant pathogen while the other infects human cells. In this thesis, stable transformation of P. infestans, combined with a validated assay based on the intracellular recognition of the RxLR effector, A vr3a, was used to study the specificity of effector translocation in oomycetes and to demonstrate the functional similarity between translocation motifs from Plasmodium and two distantly related oomycetes. While accumulating evidence shows that RxLR effectors are delivered into the host cell, the subcellular targeting of these proteins is still unclear. Throughout this PhD project, the difficulty of visualizing translocated effectors during infection was tackled by seeking alternative approaches allowing the detection of fluorescently- tagged effectors once delivered into the plant cell. A further key research question addressed in this thesis was whether the mechanism of translocation required pathogen-encoded proteins or a pathogen- induced environment. Purified fluorescent protein fusions of A vr3a were used to demonstrate that this plant pathogen effector may hold the intrinsic ability to traverse the plasma membrane of animal cells.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:553798 |
| Date | January 2011 |
| Creators | Grouffaud, Séverine |
| Publisher | University of Aberdeen |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Source | http://digitool.abdn.ac.uk:80/webclient/DeliveryManager?pid=174719 |
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