The molecular mechanism of wheat stripe rust resistance in barley conferred by a leucine-rich repeat receptor kinase (PUR1) and a novel EXO70 (EXO70FX12)

Bergum, Molly Mae (2024) The molecular mechanism of wheat stripe rust resistance in barley conferred by a leucine-rich repeat receptor kinase (PUR1) and a novel EXO70 (EXO70FX12). Doctoral thesis, University of East Anglia.

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Abstract

In barley (Hordeum vulgare), Rps8-mediated resistance to the non-adapted fungal pathogen wheat stripe rust requires two genes: HvExo70FX12 and HvPur1. HvEXO70FX12 belongs to a family of EXO70s that canonically mediate vesicle trafficking as subunits of the exocyst complex, and HvPUR1 is a subfamily XII leucine-rich repeat (LRR)-receptor kinase (RK). We discovered that Rps8 confers isolate-specific resistance; however, overexpression of HvPur1 and HvExo70FX12 overcomes an Rps8-virulent isolate. While the fungal ligand is unknown, we predict HvPUR1 recognises wheat stripe rust, eliciting pattern-triggered immunity (PTI) in a similar mechanism to related RKs: OsXA21, AtFLS2, and AtEFR. Supporting the role of HvPUR1 as a pattern recognition receptor (PRR), I demonstrate that the HvPUR1 kinase domain is interchangeable with the kinase domain of AtEFR and induces a ROS burst upon activation.

I initially hypothesised that the role of HvEXO70FX12 in immunity was either through exocyst-mediated vesicle trafficking or through a novel mechanism. Using structural predictions and protein-protein interaction assays, I demonstrate that HvEXO70FX12 has lost the ability to serve as a subunit within the exocyst complex and predict that the EXO70FX clade has experienced neofunctionalization. While the mechanistic connection between HvEXO70FX12 and HvPUR1 is currently unclear, I predict based on candidate associated proteins that HvEXO70FX12 is involved in remorin-mediated PTI nanodomain organisation or that HvEXO70FX12 is activated downstream of HvPUR1 to elicit immune responses. Alternatively, we cannot exclude the possibilities that HvEXO70FX12 may be involved in HvPUR1 ligand modification or receptor complex activation. Determining the role of HvEXO70FX12 within the HvPUR1-mediated defence pathway and the greater role EXO70FX members play in immunity will shed light on the evolution of a lineage-specific feature of plant immunity.

Item Type:	Thesis (Doctoral)
Faculty \ School:	Faculty of Science > The Sainsbury Laboratory
Depositing User:	James Tweddle
Date Deposited:	18 Feb 2025 11:34
Last Modified:	18 Feb 2025 11:34
URI:	https://ueaeprints.uea.ac.uk/id/eprint/98532
DOI:

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