Biology subjects

Ahn, Y. J.

Publications and source records attributed to Ahn, Y. J..

4 recordsLinked to original sources

bioRxiv2026

Decoy diversification underpins the regulation of an NLR-mediated autoimmunity

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.

plant biology↗

bioRxiv2025

The recognition of YopJ family effectors depends on ZAR1/JIM2 immune complex in Nicotiana benthamiana.

Pathogens deploy effector proteins to manipulate host physiology and promote infection. YopJ family effectors are highly conserved across bacterial genera that cause crop diseases. Nucleotide-binding leucine-rich repeat receptors (NLRs) play a central role in direct or indirect recognition of effectors and trigger immune responses, including hypersensitive cell death (HR). Two NLRs, Nicotiana benthamiana homologs of Pseudomonas tomato race 1 (NbPtr1) and HOPZ-ACTIVATED RESISTANCE 1 (NbZAR1) were recently identified as independently recognizing two YopJ family effectors, HopZ5 and AvrBsT/XopJ2. NbZAR1 also detects XopJ4 via the receptor-like cytoplasmic kinase XOPJ4 IMMUNITY 2 (JIM2). Here, we conducted Agrobacterium-mediated transient expression assays with 20 YopJ family effectors from five phytopathogenic bacterial genera and identified 12 YopJ family effectors that are recognized either by NbZAR1 or independently by NbZAR1 and NbPtr1. Furthermore, we show that YopJ family effector-induced HR was differentially suppressed by the deacetylase SUPPRESSOR OF AVRBST-ELICITED RESISTANCE 1, suggesting more than one mechanism for YopJ family effector recognition. This work provides the genetic basis of the recognition of YopJ family effectors in N. benthamiana and lays a foundation for the mechanistic study of NbZAR1/JIM2 and NbPtr1 mode of activation.

plant biology↗

bioRxiv2023

The Ralstonia pseudosolanacearum effector RipE1 is recognized at the plasma membrane by NbPtr1, Nicotiana benthamiana homolog of Pseudomonas tomato race 1.

The bacterial wilt disease caused by soil-borne bacteria of the Ralstonia solanacearum species complex (RSSC) threatens important crops worldwide. Only a few immune receptors conferring resistance to this devastating disease are known so far. Individual RSSC strains deliver around 70 different type III secretion system effectors into host cells to manipulate the plant physiology and dampen immune responses. RipE1 is an effector conserved across RSSC isolated from diverse plant species and triggers immune responses in the model Solanaceae Nicotiana benthamiana. Here, we used multiplexed virus-induced gene silencing of the nucleotide-binding and leucine-rich repeat receptor family to identify the genetic basis of RipE1 recognition in N. benthamiana. Specific silencing of the N. benthamiana homolog of Solanum lycopersicoides Pseudomonas tomato race 1 gene (NbPtr1) completely abolished RipE1-induced hypersensitive response and immunity to Ralstonia pseudosolanacearum. In Nb-ptr1 knock-out plants, expression of the native NbPtr1 coding sequence was sufficient to restore RipE1 recognition. In addition to the putative catalytic triad Cys-His-Asp, RipE1 association with the host cell plasma membrane was found necessary for NbPtr1-dependent recognition. Furthermore, we found that NbPtr1-dependent recognition of RipE1 natural variants is polymorphic suggesting the coevolutionary nature of this interaction. This work hence provides an additional evidence for the indirect mode of activation of NbPtr1 and supports NbPtr1 relevance for resistance to bacterial wilt disease in Solanaceae.

plant biology↗

bioRxiv2022

Ptr1 and ZAR1 immune receptors confer overlapping and distinct bacterial pathogen effector specificities

Nucleotide-binding and leucine-rich repeat receptors (NLRs) detect pathogen effectors inside the plant cell. To identify Nicotiana benthamiana NLRs (NbNLRs) with novel effector recognition specificity, we designed an NbNLR VIGS library and conducted a rapid reverse genetic screen. During the NbNLR VIGS library screening, we identified that N. benthamiana homolog of Ptr1 (PSEUDOMONAS SYRINGAE PV. TOMATO RACE 1 RESISTANCE) recognizes the Pseudomonas effectors AvrRpt2, AvrRpm1, and AvrB. We demonstrated that recognition of the Xanthomonas effector AvrBsT and the Pseudomonas effector HopZ5 in N. benthamiana is conferred independently by N. benthamiana homolog of Ptr1 and ZAR1 (HOPZ-ACTIVATED RESISTANCE 1). In addition, we showed that the RLCK XII family protein JIM2 (XOPJ4 IMMUNITY 2) physically interacts with AvrBsT and HopZ5 and is required for the NbZAR1-dependent recognition of AvrBsT and HopZ5. The recognition of multiple bacterial effectors by Ptr1 and ZAR1 in N. benthamiana demonstrates a convergent evolution of effector recognition across plant species. Identification of key components involved in Ptr1 and ZAR1 mediated immunity would reveal unique mechanisms of expanded effector recognition and be useful for engineering resistance in solanaceous crops.

plant biology↗