ALLOSTERIC ACTIVATION OF A PLANT IMMUNE RECEPTOR KINASE COMPLEX

ABSTRACT: 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 proposed to activate the receptor complex. Originally conceived 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. The EFR cytoplasmic domain is an active protein kinase in vitro and is phosphorylated in a ligand-dependent manner in vivo. Nevertheless, 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-type 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-type protein kinase may be activated by an allosteric mechanism triggered by activation segment phosphorylation and possibly involving conformational changes of the protein kinase domain of the ligand-binding receptor.

INSTRUMENT(S):

ORGANISM(S): Arabidopsis Thaliana (mouse-ear Cress)

TISSUE(S): Plant Cell, Leaf

SUBMITTER: FRank Menke  

LAB HEAD: Frank L.H. Menke

PROVIDER: PXD025597 | Pride | 2021-10-27

REPOSITORIES: Pride