期刊名称：Proceedings of the National Academy of Sciences
印刷版ISSN：0027-8424
电子版ISSN：1091-6490
出版年度：2021
卷号：118
期号：50
DOI：10.1073/pnas.2113996118
语种：English
出版社：The National Academy of Sciences of the United States of America
摘要：Significance
This study reveals a mechanism for effector perception by a plant NLR immune receptor that contains an integrated domain (ID) that mimics an authentic effector target. The
Arabidopsis immune receptors RRS1 and RPS4 detect the
Pseudomonas syringae pv.
pisi secreted effector AvrRps4 via a WRKY ID in RRS1. We used structural biology to reveal the mechanisms of AvrRps4
C–WRKY interaction and demonstrated that this binding is essential for effector recognition in planta. Our analysis revealed features of the WRKY ID that mediate perception of structurally distinct effectors from different bacterial pathogens. These insights could enable engineering NLRs with novel recognition specificities, and enhance our understanding of how effectors interact with host proteins to promote virulence.
Plants use intracellular nucleotide-binding domain (NBD) and leucine-rich repeat (LRR)–containing 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 the 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 (RRS1
WRKY) perceives distinct classes of effector to initiate an immune response is unknown. Here, we report the crystal structure of the in planta processed C-terminal domain of AvrRps4 (AvrRps4
C) in complex with RRS1
WRKY. Perception of AvrRps4
C by RRS1
WRKY is mediated by the β2-β3 segment of RRS1
WRKY that binds an electronegative patch on the surface of AvrRps4
C. Structure-based mutations that disrupt AvrRps4
C–RRS1
WRKY interactions in vitro compromise RRS1/RPS4-dependent immune responses. We also show that AvrRps4
C 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 and how effector binding interferes with WRKY–W-box DNA interactions. This work demonstrates how integrated domains in plant NLRs can directly bind structurally distinct effectors to initiate immunity.
关键词：disease resistance; effector proteins; virulence; protein structure; plant biology
