The role of effectors in nonhost resistance to filamentous plant pathogens.

Remco Stam,Hazel Mclellan,Gaã«Tan Thilliez,Sophie Mantelin

doi:10.3389/fpls.2014.00582

Remco Stam, Hazel Mclellan + Show 2 more

Open Access

https://doi.org/10.3389/fpls.2014.00582

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Abstract

In nature, most plants are resistant to a wide range of phytopathogens. However, mechanisms contributing to this so-called nonhost resistance (NHR) are poorly understood. Besides constitutive defenses, plants have developed two layers of inducible defense systems. Plant innate immunity relies on recognition of conserved pathogen-associated molecular patterns (PAMPs). In compatible interactions, pathogenicity effector molecules secreted by the invader can suppress host defense responses and facilitate the infection process. Additionally, plants have evolved pathogen-specific resistance mechanisms based on recognition of these effectors, which causes secondary defense responses. The current effector-driven hypothesis is that NHR in plants that are distantly related to the host plant is triggered by PAMP recognition that cannot be efficiently suppressed by the pathogen, whereas in more closely related species, nonhost recognition of effectors would play a crucial role. In this review we give an overview of current knowledge of the role of effector molecules in host and NHR and place these findings in the context of the model. We focus on examples from filamentous pathogens (fungi and oomycetes), discuss their implications for the field of plant-pathogen interactions and relevance in plant breeding strategies for development of durable resistance in crops.

Highlights

In nature, successful pathogens are the exception, as the majority of plants are resistant to most pests and pathogen species
This form of disease resistance is known as nonhost resistance (NHR) and can be defined as resistance exhibited by an entire plant species to all genetic variants of a non-adapted pathogen species or forma specialis (f. sp.)
Given that P. infestans has a predicted RXLR effector complement of >500 sequences and that 65% of the effectors tested in this study are detected and trigger a hypersensitive reaction (HR), this strongly suggests that NHR to P. infestans may be determined by recognition of multiple effector proteins

Summary

The role of effectors in nonhost resistance to filamentous plant pathogens

Mechanisms contributing to this so-called nonhost resistance (NHR) are poorly understood. Plant innate immunity relies on recognition of conserved pathogen-associated molecular patterns (PAMPs). Pathogenicity effector molecules secreted by the invader can suppress host defense responses and facilitate the infection process. Plants have evolved pathogen-specific resistance mechanisms based on recognition of these effectors, which causes secondary defense responses.The current effector-driven hypothesis is that NHR in plants that are distantly related to the host plant is triggered by PAMP recognition that cannot be efficiently suppressed by the pathogen, whereas in more closely related species, nonhost recognition of effectors would play a crucial role. In this review we give an overview of current knowledge of the role of effector molecules in host and NHR and place these findings in the context of the model.

INTRODUCTION

Findings

CONCLUSION