Biology subjects

Mukhi, N.

Publications and source records attributed to Mukhi, N..

3 recordsLinked to original sources

bioRxiv2025

Recognition-dependent activation of the RRS1-R/RPS4 immune receptor complex

The Arabidopsis TIR-NLR immune receptors RPS4 and RRS1 function together to enable recognition of multiple effector proteins including AvrRps4 and PopP2. We show here that both in the presence and absence of effector, RPS4 and RRS1 form an oligomer that does not change in size upon effector provision. Oligomer formation involves interactions between the RPS4 and RRS1 TIR domains and requires nucleotide binding capacity in RPS4. RPS4 mutants that lose TIR domain NADase activity abrogate immune activation but retain oligomerization. A cysteine residue in the RPS4 LRR domain contributes to oligomer stabilization. We propose that upon effector recognition, conformational changes in the complex relieve inhibition of RPS4 TIR domains by RRS1 TIR domains, enabling proximity between RPS4 TIR domains to create NADase activity.

plant biology↗

bioRxiv2021

Perception of structurally distinct effectors by the integrated WRKY domain of a plant immune receptor.

Plants use intracellular immune receptors (NLRs) to detect pathogen-derived effector proteins. The Arabidopsis NLR pair RRS1-R/RPS4 confers disease resistance to different bacterial pathogens by perceiving structurally distinct effectors AvrRps4 from Pseudomonas syringae pv. pisi and PopP2 from Ralstonia solanacearum via an integrated WRKY domain in RRS1-R. How the WRKY domain of RRS1 (RRS1WRKY) perceives distinct classes of effector to initiate an immune response is unknown. We report here the crystal structure of the in planta processed C-terminal domain of AvrRps4 (AvrRps4C) in complex with RRS1WRKY. Perception of AvrRps4C by RRS1WRKY is mediated by the {beta}2-{beta}3 segment of RRS1WRKY that binds an electronegative patch on the surface of AvrRps4C. Structure-based mutations that disrupt AvrRps4C/RRS1WRKY interactions in vitro compromise RRS1/RPS4-dependent immune responses. We also show that AvrRps4C can associate with the WRKY domain of the related but distinct RRS1B/RPS4B NLR pair, and the DNA binding domain of AtWRKY41, with similar binding affinities. This work demonstrates how integrated domains in plant NLRs can directly bind structurally distinct effectors to initiate immunity. SignificanceThis study reveals a mechanism of effector recognition by a plant NLR immune receptor that carries an integrated domain (ID) which mimics an authentic pathogen effector target. An Arabidopsis immune receptor carrying RRS1 and RPS4 NLR proteins detects the Pseudomonas syringae pv. pisi secreted effector AvrRps4 via a WRKY ID in RRS1. We used structural biology to reveal the mechanisms of AvrRps4/WRKY interaction and demonstrated that this binding is essential for effector recognition in planta. Our analysis revealed distinctive features of the WRKY ID that mediate the recognition of structurally distinct effectors from different bacterial pathogens. These insights could enable engineering NLRs with novel recognition specificities, and enhances our understanding of how effectors interact with host proteins.

plant biology↗

bioRxiv2019

BjuWRR1, a CC-NB-LRR gene identified in Brassica juncea, confers resistance to white rust caused by Albugo candida

White rust caused by oomycete pathogen Albugo candida is a significant disease of crucifer crops including Brassica juncea (mustard), a major oilseed crop of the Indian subcontinent. Earlier a resistance-conferring locus named AcB1-A5.1 was mapped in an east European gene pool line of B. juncea - Donskaja-IV. This line was tested along with some other lines of B. juncea (AABB), B. rapa (AA) and B. nigra (BB) for resistance to six isolates of A. candida collected from different mustard growing regions of India. Donskaja-IV was found to be completely resistant to all the tested isolates. Sequencing of a BAC spanning the locus AcB1-A5.1 showed the presence of a single CC-NB-LRR protein encoding R gene. The genomic sequence of the putative R gene with its native promoter and terminator was used for the genetic transformation of a susceptible Indian gene pool line Varuna and was found to confer complete resistance to all the isolates. This is the first white rust resistance-conferring gene described from Brassica species and has been named BjuWRR1. Allelic variants of the gene in B. juncea germplasm and orthologues in the Brassicaceae genomes were studied to understand the evolutionary dynamics of the BjuWRR1 gene.\n\nHighlightBjuWRR1, a CNL type R gene, was identified from an east European gene pool line of Brassica juncea and validated for conferring resistance to white rust by genetic transformation.

plant biology↗