Biology subjects

zipfel, c.

Publications and source records attributed to zipfel, c..

6 recordsLinked to original sources

bioRxiv2025

β-sheet stabilization of the island domain underlies ligand-induced LRR-RP activation of plant immune signaling

Leucine-rich repeat (LRR) receptor kinases (RKs) and receptor proteins (RPs) are important classes of plant pattern recognition receptors (PRRs) activating pattern-triggered immunity. While both classical and AI-based structural approaches have recently provided crucial insights into ligand-LRR-RK binding mechanisms, our understanding of ligand perception by LRR-RPs remains limited. In contrast to LRR-RKs, many LRR-RPs typically embed one or more loopout regions in their extracellular domains that are crucial for functionality. Here, we employed an AI-based approach to reveal a novel ligand-binding mechanism shared by the Arabidopsis LRR-RPs RLP23 and RLP42 - the PRRs for the short peptide ligands nlp20 and pg13, derived from NECROSIS- AND ETHYLENE-INDUCING PEPTIDE 1-like proteins (NLPs) and fungal endopolygalacturonases (PGs), respectively. This mechanism relies on a {beta}-strand interaction with the N-terminal part of the island domain (ID) loopout, which adopts an antiparallel {beta}-sheet conformation. Additionally, we investigated the larger and more complex binding interface of RLP32 - the PRR for proteobacterial TRANSLATION INITIATION FACTOR 1 (IF1), a folded protein ligand that requires its tertiary structure for recognition. Finally, we describe a mechanistic role of the ID for co-receptor recruitment conserved across LRR-RPs. Together, our results shed light on the ligand-binding mechanisms and receptor complex formation of this important class of PRRs. This opens avenues for a molecular understanding of the plant-pathogen co-evolution, as well as the engineering of plant immune receptors for crop disease resistance.

plant biology↗

bioRxiv2025

New alleles of Arabidopsis BIK1 reinforce its predominant role in pattern-triggered immunity and caution interpretations of other reported functions

The receptor-like cytoplasmic kinase BIK1 and its close homolog PBL1 have been widely recognized as central components of plant immunity. However, most genetic studies of BIK1 and PBL1 functions were carried out with single T-DNA insertional mutant alleles. Some phenotypes observed in these mutants, e.g. autoimmunity, have been difficult to reconcile with the proposed role of BIK1 and PBL1 in pattern-triggered immunity. In this study, we generated multiple new alleles of bik1 and pbl1 by CRISPR-Cas9-based gene editing and systematically analyzed these mutants alongside existing T-DNA insertional lines. These analyses reinforced the central role of BIK1 and PBL1 in pattern-triggered immunity mediated by both receptor kinases and receptor-like proteins. At the same time, however, we revealed several pleiotropic phenotypes associated with T-DNA insertions that are not necessarily linked to loss of BIK1 or PBL1 function. Further analyses of newly generated bik1 pbl1 double mutants uncovered an even greater contribution of these kinases to immune signaling and disease resistance than previously appreciated. These findings clarify longstanding ambiguities surrounding BIK1 and PBL1 functions.

plant biology↗

bioRxiv2024

Chitin soil amendment triggers systemic plant disease resistance through enhanced pattern-triggered immunity

Chitin triggers localised and systemic plant immune responses, making it a promising treatment for sustainable disease resistance. However, the precise molecular mechanisms underlying chitin-induced systemic effects in plants remain unknown. In this study, we investigated the effects of soil amendment with crab chitin flakes (hereafter chitin) on pattern-triggered immunity (PTI) and systemic disease resistance in various plant species. We found that soil amendment with chitin potentiates PTI and disease resistance against the bacterial pathogen Pseudomonas syringae pv. tomato DC3000 in lettuce, tomato, and Arabidopsis as well as against the fungal pathogen Blumeria graminis causing powdery mildew in wheat. Using micrografting in Arabidopsis, we demonstrated that this systemic effect is dependent on active chitin perception in the roots. We also showed that induced systemic resistance (ISR) and pattern-recognition receptors (PRRs)/co-receptors, but not systemic acquired resistance (SAR), are involved in the systemic effects triggered by chitin soil amendment. This systemic effect correlated with the transcriptional up-regulation of key PTI components in distal leaves upon chitin soil amendment. Notably, chitin-triggered systemic immunity was independent of microbes present in soil or chitin flakes. Together, these findings contribute to a better understanding of chitin-triggered systemic immunity, from active chitin perception in roots to the potentiation of PTI in the leaves, ultimately priming plants to mount enhanced defense responses against pathogen attacks. Our study provides valuable insights into the molecular mechanisms of chitin soil amendment and resulting induced immunity, and highlights its potential use for sustainable crop protection strategies.

plant biology↗

bioRxiv2021

ACTIVATION LOOP PHOSPHORYLATION OF A NON-RD RECEPTOR KINASE INITIATES PLANT INNATE IMMUNE SIGNALING

Receptor kinases (RKs) play fundamental roles in extracellular sensing to regulate development and stress responses across kingdoms. In plants, leucine-rich repeat receptor kinases (LRR-RKs) function primarily as peptide receptors that regulate myriad aspects of plant development and response to external stimuli. Extensive phosphorylation of LRR-RK cytoplasmic domains is among the earliest detectable responses following ligand perception, and reciprocal transphosphorylation between a receptor and its co-receptor is thought to activate the receptor complex. Originally proposed based on characterization of the brassinosteroid receptor, the prevalence of complex activation via reciprocal transphosphorylation across the plant RK family has not been tested. Using the LRR-RK ELONGATION FACTOR TU RECEPTOR (EFR) as a model RK, we set out to understand the steps critical for activating RK complexes. While the EFR cytoplasmic domain is an active protein kinase in vitro and is phosphorylated in a ligand-dependent manner in vivo, catalytically deficient EFR variants are functional in anti-bacterial immunity. These results reveal a non-catalytic role for the EFR cytoplasmic domain in triggering immune signaling and indicate that reciprocal transphoshorylation is not a ubiquitous requirement for LRR-RK complex activation. Rather, our analysis of EFR along with a detailed survey of the literature suggests a distinction between LRR-RK complexes with RD- versus non-RD protein kinase domains. Based on newly identified phosphorylation sites that regulate the activation state of the EFR complex in vivo, we propose that LRR-RK complexes containing a non-RD protein kinase may be regulated by phosphorylation-dependent conformational changes of the ligand-binding receptor which could initiate signaling in a feed-forward fashion either allosterically or through driving the dissociation of negative regulators of the complex.

biochemistry↗

bioRxiv2021

A conserved regulatory module regulates receptor kinase signaling in immunity and development

Ligand recognition by cell-surface receptors underlies development and immunity in both animals and plants. Modulating receptor signaling is critical for appropriate cellular responses but the mechanisms ensuring this are poorly understood. Here, we show that signaling by plant receptors for pathogen-associated molecular patterns (PAMPs) in immunity and CLAVATA3/EMBRYO SURROUNDING REGION-RELATED peptides (CLEp) in development employ a similar regulatory module. In the absence of ligand, signaling is dampened through association with specific type-2C protein phosphatases (PP2Cs). Upon activation, PAMP and CLEp receptors phosphorylate divergent cytosolic kinases, which, in turn, phosphorylate the phosphatases, thereby promoting their release from the receptor complexes. Our work reveals a regulatory circuit shared between immune and developmental receptor signaling, which may have broader important implications for plant receptor kinase-mediated signaling in general.

plant biology↗

bioRxiv2020

FERONIA regulates FLS2 plasma membrane nanoscale dynamics to modulate plant immune signaling

Spatial partitioning is a propensity of biological systems orchestrating cell activities in space and time. The dynamic regulation of plasma membrane nano-environments has recently emerged as a key fundamental aspect of plant signaling, but the molecular components governing it are still mostly unclear. The receptor kinase FERONIA (FER) controls complex formation of the immune receptor kinase FLAGELLIN SENSING 2 (FLS2) with its co-receptor BRASSINOSTEROID INSENSITIVE 1-ASSOCIATED KINASE 1 (BAK1), and this function is inhibited by the FER ligand RAPID ALKALANIZATION FACTOR 23 (RALF23). Here, we show that FER regulates the plasma membrane nanoscale organization of FLS2 and BAK1. Our study demonstrates that akin to FER, leucine-rich repeat (LRR) extensin (LRXs) proteins contribute to RALF23 responsiveness, regulate BAK1 nanoscale organization and immune signaling. Furthermore, RALF23 perception leads to rapid modulation of FLS2 and BAK1 nanoscale organization and its inhibitory activity on immune signaling relies on FER kinase activity. Our results suggest that perception of RALF peptides by FER and LRXs actively modulates the plasma membrane nanoscale landscape to regulate cell surface signaling by other receptor kinases.

plant biology↗