Poster
Sera Choi
Postdoctoral researcher
Institute of Plant and Microbial Biology, University of Zurich
Zurich, Zurich, Switzerland
Marie Le Naour--Vernet, PhD (she/her/hers)
Postdoctoral researcher
Institute of Plant and Microbial Biology, University of Zurich
Zurich, Zurich, Switzerland
Ryan Toth
PhD student
Institute of Plant and Microbial Biology, University of Zurich
Zurich, Zurich, Switzerland
Yoonyoung Lee
PhD student
Institute of Plant and Microbial Biology, University of Zurich
Zurich, Zurich, Switzerland
Álvaro D. Fernández-Fernández
Institute of Plant and Microbial Biology, University of Zurich
Zurich, Zurich, Switzerland
Hee-Kyung Ahn
Royal Society University Research Fellow
University of Edinburgh
EDINBURGH, Scotland, United Kingdom
Jonathan D. G. Jones
Prof. Group leader
The Sainsbury Laboratory
Norwich, England, United Kingdom
Thomas A. DeFalco
Assistant professor
Department of Biology, Western University
London, Ontario, Canada
Cyril Zipfel
Institute of Plant and Microbial Biology, University of Zurich / The Sainsbury Laboratory
Zurich, Zurich, Switzerland
Plants rely on two types of immune receptors to defend against pathogens. At the cell surface, pattern recognition receptors (PRRs) detect microbial signatures activating pattern-triggered immunity (PTI), while intracellularly, nucleotide-binding leucine-rich repeat proteins (NLRs) perceive pathogen effectors initiating effector-triggered immunity (ETI). Traditionally viewed as independent pathways, emerging evidence indicates that PTI and ETI are interconnected, but the underlying molecular mechanisms are largely unknown. The receptor-like cytoplasmic kinase BIK1 functions downstream of multiple PRRs and serves as a key regulator of PTI. Here, we show that BIK1 directly phosphorylates several NLRs and regulates their activation in Arabidopsis. Phosphomimetic mutants at BIK1 phosphorylation sites showed impaired effector-induced cell death and bacterial growth restriction, whereas phosphoablative mutants retained wild-type immune responses. Furthermore, phosphomimetic mutants displayed compromised effector-induced or pre-infection oligomerization. These findings suggest that BIK1 phosphorylation constrains NLR activation by compromising oligomerization, thereby acting as a negative regulator of ETI. We also show that upon PTI activation, BIK1 dissociates from NLRs, leading to their derepression and full activation of ETI. Our findings reveal the dynamic regulation of NLRs by BIK1, a key PTI kinase, positioning it as a central regulator of both plant immune perception layers.