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ARS Home » Pacific West Area » Albany, California » Plant Gene Expression Center » Research » Publications at this Location » Publication #358473
Research Project: Mining Collections of Wild Germplasm and Novel Defense Regulators for Enhanced Plant Defenses

Location: Plant Gene Expression Center

Title: Structure-function analysis of the immune receptor ZAR1 reveals key molecular interactions for activity

Author
item BAUDIN, M - University Of California
item MARTIN, ELIZA - University Of Romania
item PETRESCU, ANDREI - University Of Romania
item Lewis, Jennifer

Submitted to: The Plant Cell
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/16/2019
Publication Date: 9/26/2019
Citation: Baudin, M., Martin, E.C., Petrescu, A.J., Lewis, J.D. 2019. Structure-function analysis of the immune receptor ZAR1 reveals key molecular interactions for activity. The Plant Cell. 101(2):352-370. https://doi.org/10.1111/tpj.14547.
DOI: https://doi.org/10.1111/tpj.14547

Interpretive Summary: Plants have developed a sensitive surveillance system to detect modification of their own proteins by pathogens. This surveillance system must be exquisitely fine-tuned to prevent activity in the absence of a pathogen, and to activate extremely rapidly once the pathogen is detected. We previously identified a plant pseudokinase that works with a resistance protein to act as a “mousetrap” for recognition of a bacterial effector protein. We developed a transient expression system in Nicotiana benthamiana that demonstrated the resistance protein was active in diverse plant families. This system allowed us to identify key requirements for immune receptor function and activation. By identifying the molecular requirements for effector recognition, this work will aid in informing the rational design of a decoy protein for recognition of other pathogens or effector proteins.

Technical Abstract: NLR (Nucleotide-binding [NB] Leucine-rich repeat [LRR] Receptor) proteins are critical for inducing immune responses in response to pathogen proteins, and must be tightly regulated to prevent spurious activation in the absence of a pathogen. The ZAR1 NLR recognizes diverse effector proteins from Pseudomonas syringae, including HopZ1a, and Xanthomonas species. Receptor-like cytoplasmic kinases (RLCKs) such as ZED1, interact with ZAR1 and provide specificity for different effector proteins, such as HopZ1a. We previously developed a transient expression system in Nicotiana benthamiana, that allowed us to demonstrate ZAR1 function is conserved from the Brassicaceae to the Solanaceae. Here, we combined structural modeling of ZAR1, with molecular and functional assays in our transient system, to show that multiple intramolecular and intermolecular interactions regulate ZAR1 activity. We found that the coiled-coil (CC) domain dimerized in a MLA10-like fashion, and induced immunity. The CC and NB domains interact, and CC autoactivity is suppressed by the NB domain. Interactions between the NB and LRR domains were impaired by specific mutations in either domain. The CC and LRR domains competed for interactions with the NB domain. Lastly, ZED1 stabilized the interaction between the LRR and NB domains. This work identifies molecular constraints on immune receptor function and activation.