|BAUDIN, MAEL - University Of California|
|HASSAN, JANA - University Of California|
|SCHREIBER, KARL - University Of California|
Submitted to: Plant Physiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/22/2017
Publication Date: 6/30/2017
Citation: Baudin, M., Hassan, J.A., Schreiber, K.J., Lewis, J.D. 2017. Analysis of the ZAR1 immune complex reveals determinants for immunity and molecular interactions. Plant Physiology. doi:10.1104/pp.17.00441.
Interpretive Summary: We identified a plant pseudokinase that functions with a plant resistance protein as a trap for bacterial effector recognition. We developed a transient assay system in Nicotiana benthamiana to dissect the molecular interactions among a bacterial effector protein and the two plant proteins that are required for its recognition. 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: Plants depend on innate immunity to prevent disease. Plant pathogenic bacteria, like Pseudomonas syringae and Xanthomonas campestris, use the type III secretion system as a molecular syringe to inject type III secreted effector (T3SE) proteins in plants. The primary function of most T3SEs is to suppress immunity, however the plant can evolve NBD-LRR domain-containing (NLR) proteins to recognize specific T3SEs. The AtZAR1 NLR induces strong defense responses against P. syringae and X. campestris. The P. syringae T3SE HopZ1a is an acetyltransferase that acetylates the pseudokinase AtZED1, and triggers recognition by AtZAR1. However, little is known about the molecular mechanisms that lead to AtZAR1-induced immunity in response to HopZ1a. We established a transient expression system in Nicotiana benthamiana to study detailed interactions among HopZ1a, AtZED1 and AtZAR1. We show that the AtZAR1 immune pathway is conserved in N. benthamiana, and identify residues in AtZAR1 and AtZED1, and AtZAR1 domains, that are important for immunity and protein-protein interactions in planta and in yeast. We show that the coiled-coil domain of AtZAR1 oligomerizes, and this domain acts as a signal to induce immunity. This detailed analysis of the AtZAR1-AtZED1 protein complex provides a better understanding of the immune signaling hub controlled by AtZAR1.