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Front Plant Sci. 2014 Nov 25;5:606. doi: 10.3389/fpls.2014.00606. eCollection 2014.

A novel conserved mechanism for plant NLR protein pairs: the "integrated decoy" hypothesis.

Author information

1
Institut National de la Recherche Agronomique, Unité Mixtes de Recherche Biology and Genetics of Plant-Pathogen Interactions Montpellier, France ; Centre de Coopération Internationale en Recherche Agronomique pour le Développement, Unité Mixtes de Recherche Biology and Genetics of Plant-Pathogen Interactions Montpellier, France ; Agriculture Flagship, Commonwealth Scientific and Industrial Research Organisation Canberra, ACT, Australia.
2
Agriculture Flagship, Commonwealth Scientific and Industrial Research Organisation Canberra, ACT, Australia.
3
Commonwealth Scientific and Industrial Research Organisation, Digital Productivity and Service Canberra, ACT, Australia.
4
Institut National de la Recherche Agronomique, Unité Mixtes de Recherche Biology and Genetics of Plant-Pathogen Interactions Montpellier, France ; Centre de Coopération Internationale en Recherche Agronomique pour le Développement, Unité Mixtes de Recherche Biology and Genetics of Plant-Pathogen Interactions Montpellier, France.

Abstract

Plant immunity is often triggered by the specific recognition of pathogen effectors by intracellular nucleotide-binding, leucine-rich repeat receptors (NLR). Plant NLRs contain an N-terminal signaling domain that is mostly represented by either a Toll-interleukin1 receptor (TIR) domain or a coiled coil (CC) domain. In many cases, single NLR proteins are sufficient for both effector recognition and signaling activation. However, many paired NLRs have now been identified where both proteins are required to confer resistance to pathogens. Recent detailed studies on the Arabidopsis thaliana TIR-NLR pair RRS1 and RPS4 and on the rice CC-NLR pair RGA4 and RGA5 have revealed for the first time how such protein pairs function together. In both cases, the paired partners interact physically to form a hetero-complex receptor in which each partner plays distinct roles in effector recognition or signaling activation, highlighting a conserved mode of action of NLR pairs across both monocotyledonous and dicotyledonous plants. We also describe an "integrated decoy" model for the function of these receptor complexes. In this model, a plant protein targeted by an effector has been duplicated and fused to one member of the NLR pair, where it acts as a bait to trigger defense signaling by the second NLR upon effector binding. This mechanism may be common to many other plant NLR pairs.

KEYWORDS:

Arabidopsis thaliana; NLR protein pairs; integrated decoy; pathogen recognition; plant immunity; rice

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