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Updated: Jan 6, 2026
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Applying an Inducible Expression System to Study Interference of Bacterial Virulence Factors with Intracellular Signaling
Published on: June 25, 2015
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Individually redundant effectors are collectively required for bacterial pathogen virulence
Lauren M Hemara1,2, Mark T Andersen2, Haileigh R Patterson1,2
1School of Biological Sciences, The University of Auckland, Auckland 1010, New Zealand.
The ISME Journal
|November 26, 2025
Summary
Pseudomonas syringae pv. actinidiae (Psa) maintains over 30 effectors, but all are collectively required for virulence. Host-specific effector needs explain this large repertoire and pathogen evolution.
Area of Science:
- Plant pathology
- Microbial genetics
- Evolutionary biology
Background:
- Host specificity in plant pathogens is determined by effector proteins.
- The necessity of the entire effector repertoire for pathogenicity is not fully understood.
- Pseudomonas syringae pv. actinidiae (Psa) in kiwifruit has a large effector set, making it a model for studying effector evolution.
Purpose of the Study:
- To investigate effector requirements, redundancies, and repertoire refinement in Psa across different host genotypes.
- To understand how host-mediated selection shapes pathogen evolution and effector maintenance.
- To determine if the complete effector complement is essential for Psa pathogenicity.
Main Methods:
- Utilized a mutated effector-leveraging evolution experiment (MELEE).
- Serially passaged competitive populations of Psa effector knockout strains.
- Assessed pathogen virulence through competition assays against wild-type Psa.
Main Results:
- Wild-type Psa dominated competition experiments, indicating all effectors are collectively required for virulence.
- Identified host-specific effector requirements, suggesting differential selection pressures.
- Demonstrated that individual effectors, previously thought nonessential, contribute collectively to Psa pathogenicity.
Conclusions:
- The full complement of Psa effectors is collectively essential for successful virulence.
- Host-specific effector requirements contribute to the maintenance of large effector repertoires in plant pathogens.
- This study provides insights into effector redundancy and pathogen evolution dynamics following host incursions.
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