Journal Article

Reconstitution and structure of a plant NLR resistosome conferring immunity

Qi, Yijun, Wang, Guoxun, Wang, Jizong, Zhou, Jian-Min, Hu, Meijuan, Qi, Jinfeng, Han, Zhifu, Wang, Jia, Wang, Hong-Wei, Chai, Jijie

2019

Overview

Nucleotide-binding, leucine-rich repeat receptors (NLRs) initiate immune responses when they sense a pathogen-associated effector. In animals, oligomerization of NLRs upon binding their effectors is key to downstream activity, but plant systems differ in many ways and their activation mechanisms have been less clear. In two papers, Wang et al. studied the composition and structure of an NLR called ZAR1 in the small mustard plant Arabidopsis (see the Perspective by Dangl and Jones). They determined cryo–electron microscopy structures that illustrate differences between inactive and intermediate states. The active, intermediate state of ZAR1 forms a wheel-like pentamer, called the resistosome. In this activated complex, a set of helices come together to form a funnel-shaped structure required for immune responsiveness and association with the plasma membrane. Science , this issue p. eaav5868 , p. eaav5870 ; see also p. 31 Structural, biochemical, and functional studies show how a plant immune resistosome complex mediates cell death and disease resistance. Nucleotide-binding, leucine-rich repeat receptors (NLRs) perceive pathogen effectors to trigger plant immunity. Biochemical mechanisms underlying plant NLR activation have until now remained poorly understood. We reconstituted an active complex containing the Arabidopsis coiled-coil NLR ZAR1, the pseudokinase RKS1, uridylated protein kinase PBL2, and 2′-deoxyadenosine 5′-triphosphate (dATP), demonstrating the oligomerization of the complex during immune activation. The cryo–electron microscopy structure reveals a wheel-like pentameric ZAR1 resistosome. Besides the nucleotide-binding domain, the coiled-coil domain of ZAR1 also contributes to resistosome pentamerization by forming an α-helical barrel that interacts with the leucine-rich repeat and winged-helix domains. Structural remodeling and fold switching during activation release the very N-terminal amphipathic α helix of ZAR1 to form a funnel-shaped structure that is required for the plasma membrane association, cell death triggering, and disease resistance, offering clues to the biochemical function of a plant resistosome.

• Publisher: American Association for the Advancement of Science,The American Association for the Advancement of Science
• Subject: Activation / Adenosine Diphosphate - chemistry / Adenosine triphosphate / Apoptosis / Arabidopsis - enzymology / Arabidopsis - immunology / Arabidopsis - microbiology / Arabidopsis Proteins - chemistry / Arabidopsis Proteins - metabolism / Arabidopsis thaliana / ATP / Bacterial Proteins - metabolism / Biochemistry / Carrier Proteins - chemistry / Cell death / Cell proliferation / Coils / Cryoelectron Microscopy / Death / Defensive behavior / Deoxyadenosine / Disease Resistance / Domains / Effectors / Electron microscopy / Filtration / Gel filtration / Helices / Host-Pathogen Interactions - immunology / Hypersensitive response / Immune response / Immunity / Inflammasomes / Intracellular Signaling Peptides and Proteins - chemistry / Kinases / Leucine / Ligands / Membrane Proteins / Microorganisms / Microscopy / Mortality / Mustard / Mutagenesis / Mutation / Nlr protein / NLR Proteins - chemistry / Nucleoside-Phosphate Kinase - metabolism / Oligomerization / Pathogens / Phosphoproteins - chemistry / Plant cells / Plant immunity / Protein Domains / Protein kinase / Protein Structure, Secondary / Protein-Serine-Threonine Kinases - chemistry / Protein-Serine-Threonine Kinases - metabolism / Proteins / Receptors / RESEARCH ARTICLE SUMMARY / Switching / Transmission electron microscopy / Xanthomonas campestris / Xanthomonas campestris - enzymology