Molecular basis of plant cell death suppression by the phytophthora infestans effector AVR3a

Chaparro Garcia, Angela (2012) Molecular basis of plant cell death suppression by the phytophthora infestans effector AVR3a. Doctoral thesis, University of East Anglia .

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Abstract

Plants actively perceive pathogens and activate their immune system upon pathogen
recognition. The first encounter with the pathogen relies on the recognition of highly
conserved microbial molecules known as pathogen-associated molecular patterns
(PAMPs) by cell surface receptors called pattern-recognition receptors (PPRs).
Successful pathogens have evolved effectors to overcome plant defense and to
colonize their host. INF1 is a P. infestans elicitin with features of PAMPs that requires
the co-regulator receptor-like kinase SERK3/BAK1 to trigger cell death. AVR3a is an
effector translocated by P. infestans that suppresses INF1-triggered cell death (ICD).
However, the potato protein R3a can recognize AVR3a. The avirulence and
suppression activities of this effector are conditioned by distinct amino acids but the
precise series of events leading to ICD suppression by AVR3a, the nature of the INF1
receptor, and the composition of the receptor complex remain unknown.
This study investigates mechanisms underlying AVR3a interference with basal
immunity and its importance for P. infestans pathogenicity. Homologs of SERK3/BAK1
in N. benthamiana were shown to be required for resistance against P. infestans. To
further our understanding of the molecular events after INF1 elicitation, a receptor-like
protein (RLP) implicated in ICD was characterized. Using a combination of
fluorescence microscopy and biochemistry, I showed that this RLP localizes to the
endoplasmic reticulum and plasma membrane and forms a complex with SERK3/BAK1.
I assessed the extent to which AVR3a interferes with SERK3/BAK1-dependent
signaling pathways and found that variants of AVR3a suppress defense responses
elicited by diverse PAMPs to different degrees. Additional plant proteins interacting
with AVR3a were searched using in planta complex purification and mass spectrometry
analysis. A host GTPase (dynamin) protein involved in endocytosis was found.
Dynamin was shown to be required for ICD suppression activity by AVR3a. Notably,
dynamin accumulates around P. infestans (Pi) haustoria possibly pointing to its role in
the plant-Pi interaction.

Item Type:	Thesis (Doctoral)
Faculty \ School:	Faculty of Science > School of Biological Sciences
Depositing User:	Zoe White
Date Deposited:	20 Nov 2013 15:32
Last Modified:	20 Nov 2013 15:32
URI:	https://ueaeprints.uea.ac.uk/id/eprint/41941
DOI:

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