P-063 - Phosphorylation of ADR1-L2 fine-tunes helper NLR activity

Monday, July 14, 2025

13:30 - 15:15

Location: Confex Hall 3

Extracellular & Intracellular non-self recognition & signaling

Author(s)

FV

Frank Vogt

PhD candidate
ZMBP - University of Tuebingen
Tuebingen, Baden-Wurttemberg, Germany
XZ

Xander C. L Zuijdgeest (he/him/his)

University of Tuebingen
Tubingen, Baden-Wurttemberg, Germany
ML

Marie Le Naour--Vernet, PhD (she/her/hers)

Postdoctoral researcher
Institute of Plant and Microbial Biology, University of Zurich
Zurich, Zurich, Switzerland
SC

Sera Choi

Postdoctoral researcher
Institute of Plant and Microbial Biology, University of Zurich
Zurich, Zurich, Switzerland
PM

Peer Muche

BSc student
ZMBP - University of Tuebingen
Tuebingen, Baden-Wurttemberg, Germany
SS

Svenja C. Saile

Plant Health Institute of Montpellier
Montpellier, Languedoc-Roussillon, France
CZ

Cyril Zipfel

Institute of Plant and Microbial Biology, University of Zurich / The Sainsbury Laboratory
Zurich, Zurich, Switzerland

Presenting Author(s)

FE

Farid El Kasmi

Group Leader
University of Tuebingen
Tuebingen, Baden-Wurttemberg, Germany

Helper NLRs (hNLRs) in Arabidopsis form central signaling hubs involved in both pattern- and effector-triggered immunity. Thus, they convey non-self-recognition by receptor-like kinases/proteins (RLKs/RLPs) and sensor NLRs (mainly TIR domain-containing NLRs – TNLs) into a full immune response. hNLRs are activated by small-molecule induced interaction with EDS1-PAD4/SAG101 heterodimers. However, we know little about how hNLR activity is regulated and whether kinases essential for pattern-triggered immunity are involved in hNLR regulation. We investigated phosphorylation as a potential regulatory mechanism of the hNLR protein ADR1-L2. Through motif predictions and in-vitro kinase assays, we identified several phosphorylation sites in ADR1-L2, including putative BAK1/BKK1- and BIK1-mediated sites. Through phospho-ablative substitutions, we identified combinations of phosphorylation sites that led to enhanced cell death activity of the autoactive mutant ADR1-L2 D484V. Further, ADR1-L2 D484V autoimmunity in Arabidopsis was not altered in bak1, bkk1 or bik1 mutants. This indicated that phosphorylation of these residues negatively affects ADR1-L2 activity. Interestingly, the knockout of several receptor-like cytoplasmic kinases (RLCKs) suppressed ADR1-L2 D484V autoimmunity, suggesting a complex regulation of hNLR-mediated immunity by phosphorylation. We now continue to mechanistically investigate how phosphorylation of hNLRs shapes the plant response to invading pathogens.