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Research Project: Mining Collections of Wild Germplasm and Novel Defense Regulators for Enhanced Plant Defenses

Location: Plant Gene Expression Center

Title: A natural diversity screen in Arabidopsis thaliana reveals determinants for HopZ1a recognition in the ZAR1-ZED1 immune complex

item BAUDIN, MAEL - University Of California
item MARTIN, ELIZA - Institute Of Biochemistry Of The Romanian Academy
item SASS, CHODON - University Of California
item HASSAN, JANA - University Of California
item Bendix, Claire
item SAUCEDA, ROLIN - University Of California
item DIPLOCK, NATHAN - University Of California
item SPECHT, CHELSEA - Cornell University
item PETRESCU, ANDREI - Institute Of Biochemistry Of The Romanian Academy
item Lewis, Jennifer

Submitted to: Plant Cell and Environment
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/20/2020
Publication Date: 10/26/2020
Citation: Baudin, M., Martin, E., Sass, C., Hassan, J.A., Bendix, C.L., Sauceda, R., Diplock, N., Specht, C.D., Petrescu, A., Lewis, J.D. 2020. A natural diversity screen in Arabidopsis thaliana reveals determinants for HopZ1a recognition in the ZAR1-ZED1 immune complex. Plant Cell and Environment. 44(2):629-644.

Interpretive Summary: Plants have developed a sensitive surveillance system to detect modification of their own proteins by pathogens. This surveillance system must be carefully modulated 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 identified genetic diversity that affects the ability of the immune receptor to recognize a bacterial effector protein. 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: Pathogen pressure on hosts can lead to the evolution of genes regulating the innate immune response. By characterizing naturally occurring polymorphisms in immune receptors, we can better understand the molecular determinants of pathogen recognition. ZAR1 is an ancient Arabidopsis thaliana NLR (Nucleotide-binding [NB] Leucine-rich-repeat [LRR] Receptor) that recognizes multiple secreted effector proteins from the pathogenic bacteria Pseudomonas syringae and Xanthomonas campestris through its interaction with receptor-like cytoplasmic kinases (RLCKs). ZAR1 was first identified for its role in recognizing P. syringae effector HopZ1a, through its interaction with the RLCK ZED1. To identify additional determinants of HopZ1a recognition, we performed a computational screen for ecotypes from the 1001 genomes project that were likely to lack HopZ1a recognition, and tested ~300 ecotypes. We identified ecotypes containing polymorphisms in ZAR1 and ZED1. Using our previously established Nicotiana benthamiana transient assay and Arabidopsis ecotypes, we tested for the effect of naturally occurring polymorphisms on ZAR1 interactions and the immune response. We identified key residues in the NB or LRR domain of ZAR1 that impact the interaction with ZED1. We demonstrate that natural diversity combined with functional assays can help define the molecular determinants and interactions necessary to regulate immune induction in response to pathogens.