Caveats of Using Bacterial Type Three Secretion Assays for Validating Fungal Avirulence Effectors in Wheat

Functional characterization of effector proteins of fungal obligate biotrophic pathogens, especially confirmation of avirulence (Avr) properties, has been notoriously difficult, due to the experimental intractability of many of these organisms. Previous studies in wheat have shown promising data sug...

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Bibliographic Details
Published in:Molecular plant-microbe interactions 2022-12, Vol.35 (12), p.1061-1066
Main Authors: Jensen, Cassandra, Korolev, Andrey, Corredor-Moreno, Pilar, Minter, Francesca, Dodds, Peter N, Saunders, Diane G O
Format: Article
Language:English
Subjects:
avirulence cereal pathogens
Bacteria
Cell death
effector delivery
Effectors
EtHAn
fungal effectors of wheat pathogens
Fungi
Hypersensitive response
Pathogens
pEDV
Phenotypes
Plant Diseases - microbiology
Pseudomonas fluorescens
Screening
Secretion
Seedlings
Triticum - microbiology
type III secretion system
Wheat
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Summary:Functional characterization of effector proteins of fungal obligate biotrophic pathogens, especially confirmation of avirulence (Avr) properties, has been notoriously difficult, due to the experimental intractability of many of these organisms. Previous studies in wheat have shown promising data suggesting the type III secretion system (T3SS) of bacteria may be a suitable surrogate for delivery and detection of Avr properties of fungal effectors. However, these delivery systems were tested in the absence of confirmed Avr effectors. Here, we tested two previously described T3SS-mediated delivery systems for their suitability when delivering two confirmed Avr effectors from two fungal pathogens of wheat, f. sp. and pathotype . We showed that both effectors (AvrSr50 and AvrRmg8) were unable to elicit a hypersensitive response on wheat seedlings with the corresponding resistance gene when expressed by the "Effector to Host Analyser" (EtHAn) system. Furthermore, we found the utility of for screening Avr phenotypes is severely limited, as the wild-type strain elicits nonhost cell death in multiple wheat accessions. These results provide valuable insight into the suitability of these systems for screening fungal effectors for Avr properties that may help guide further development of surrogate bacterial delivery systems in wheat. [Formula: see text] Copyright © 2022 The Author(s). This is an open access article distributed under the CC BY-NC-ND 4.0 International license.
ISSN:0894-0282
1943-7706
DOI:10.1094/MPMI-08-22-0167-SC