Arabidopsis CONSERVED BINDING OF EIF4E1 negatively regulates the NADPH oxidase RESPIRATORY BURST OXIDASE HOMOLOG D

Abstract

Cell-surface pattern recognition receptors sense invading pathogens by binding microbial or endogenous elicitors to activate plant immunity. These responses are under tight control to avoid excessive or untimely activation of cellular responses, which may otherwise be detrimental to host cells. How this fine-tuning is accomplished is an area of active study. We previously described a suppressor screen that identified Arabidopsis thaliana mutants with regained immune signaling in the immunodeficient genetic background bak1-5, which we named modifier of bak1-5 (mob) mutants. Here, we report that bak1-5 mob7 restores elicitor-induced signaling. Using a combination of map-based cloning and whole-genome resequencing, we identified MOB7 as CONSERVED BINDING OF EIF4E1 (CBE1), a plant-specific protein that interacts with highly-conserved eukaryotic translation initiation factor eIF4E1. Our data demonstrate that CBE1 regulate the accumulation of RESPIRATORY BURST OXIDASE HOMOLOG D (RBOHD), the NADPH oxidase responsible for elicitor-induced apoplast reactive oxygen species (ROS) production. Furthermore, several mRNA decapping and translation initiation factors co-localize with CBE1 and similarly regulate immune signaling. This study thus identifies a novel regulator of immune signaling and provides new insights into ROS regulation, and more generally translational control during plant stress responses.