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This study investigates how the plant immune receptor NbPtr1, an NLR protein found in Solanaceae, recognizes six different bacterial effector proteins from Pseudomonas syringae, Xanthomonas perforans, and Ralstonia pseudosolanacearum. The researchers identified a group of NOI-domain containing proteins that interact with NbPtr1 to suppress its activity, and demonstrated that removal of these proteins causes stunted plant growth dependent on NbPtr1. A conserved threonine residue in the NOI proteins is required for this suppressive interaction and serves as a modification target for recognized effector proteins, providing a mechanistic explanation for how a single NLR can detect multiple pathogen effectors.
Why it matters
Understanding how plant immune receptors are regulated and how they detect diverse pathogen effectors could inform the development of disease-resistant crops, which has direct implications for agricultural productivity and food security in the face of evolving bacterial pathogens.
⚠️ Preprint – Noch nicht peer-reviewed
Dieser Artikel wurde noch nicht von unabhängigen Experten begutachtet. Die Ergebnisse sind vorläufig und sollten mit Vorsicht interpretiert werden.
Appropriate activation of innate immune receptors is vital for the plant immune system. Immune activation must be strong and robust upon invasion by rapidly evolving pathogen species, while staying inactive in the absence of a pathogen to avoid constitutive defense responses that inhibit plant growth. Nucleotide-binding leucine-rich repeat receptors (NLRs) are intracellular proteins that surveil for pathogen invasion, often by direct or indirect perception of pathogen effector proteins. Indirect recognition of pathogen effector proteins, through monitoring the integrity of guardee or decoy proteins, can allow for a single NLR to detect a wide range of pathogen effectors. In this work, we investigated how the Solanaceae NLR NbPtr1 can recognize six different effector proteins from the bacterial pathogens Pseudomonas syringae, Xanthomonas perforans, and Ralstonia pseudosolanacearum. We identified several NOI-domain containing proteins that are guarded by NbPtr1. These NOI proteins share homology with, but are distinct from, RPM1 INTERACTING PROTEIN 4 (RIN4), a well-known guardee in Arabidopsis. Virus-induced gene silencing and CRISPR/Cas9-assisted deletion of NbNOI genes resulted in stunted growth dependent on NbPtr1 activity. Negative regulation of NbPtr1 requires the interaction between NbPtr1 and the suppressor NbNOIs. A conserved threonine residue of the NOI proteins is required for this interaction and fits into a putative binding pocket of NbPtr1 based on protein modeling. This threonine residue is modified by some of the recognized effector proteins. Our study uncovers the regulatory mechanism of an autoactive NLR and highlights the importance of decoy diversification in establishing compatibility with NLRs.
Source: Decoy diversification underpins the regulation of an NLR-mediated autoimmunity