Understanding the role of Rab GTPases in plant immunity

Postma, Jelle (2018) Understanding the role of Rab GTPases in plant immunity. Doctoral thesis, University of East Anglia.

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Abstract

Plants employ cell-surface localized receptor-like kinase (RLK) and receptor-like protein (RLP)-type pattern recognition receptors to monitor their surroundings for the presence of infectious pathogens. RLPs interact with the SUPPRESSOR OF BIR1-1 (SOBIR1) RLK for stability and signaling, but it is unclear how signaling is activated. Here, I reveal that the SERK3 RLK is recruited to the tomato Cf-4 RLP upon activation by the Cladosporium fulvum effector Avr4, followed by Cf-4-SOBIR1 co-internalization into late endosomes/multivesicular bodies (LE/MVBs). This extends known RLK-type early activation mechanisms and subcellular localization changes to RLP-SOBIR1-based detection systems, pointing at a widely generalisable mechanism for receptor turnover. Secretory and endocytic membrane trafficking pathways underlie the potentiation and execution of defence. Membrane-associated Rab GTPases are critical regulators of specific pathways, and accumulate at pathogen infection sites, yet their roles in immunity are poorly understood. Here, proteomic analysis of the secretory ARA5/RABD2a complex upon elicitation with bacterial flagellin revealed increased secretion of several uncharacterized RLKs and modules of cell-surface based chemical defences. Comparison between proteomic changes on ARA5/RABD2a and the endocytic ARA7/RABF2b points at flagellin-induced turnover of cell-surface proteins that monitor cell wall integrity and function in processes involving reactive oxygen species. ARA7/RABF2b concentrated under bacterial infection sites, and upon flagellin elicitation recruited the atypical resistance proteins TIR-NBS3 (TN3) and HOMOLOG OF RPW8 4 (HR4). TN3 and HR4 were required for immunity against non-adapted powdery mildew and could be monitoring Rab GTPase-mediated endosomal activity in plant defence.

Item Type: Thesis (Doctoral)
Faculty \ School: Faculty of Science > School of Biological Sciences
Depositing User: Gillian Aldus
Date Deposited: 21 May 2019 08:55
Last Modified: 21 May 2019 08:55
URI: https://ueaeprints.uea.ac.uk/id/eprint/71079
DOI:

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