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Reconstitution of a Minimal Signaling-Active Plant Receptor Kinase Complex - Towards the Structural Determination of Ligand-Induced Activation Mechanisms

Project description

Structure and function of the minimal receptor kinase signalling complex in plants

Plasma membrane-localised receptor kinases (RKs) function in plant signalling pathways during development, reproduction, and response to environmental stresses. They have different biochemical functions, and in addition to ligand-binding, some RKs play a regulatory role within RK complexes. The proposed EU-funded MINIREX project aims to discover the minimal components linking ligand binding to receptor activation and to the initiation of cellular processes, as well as the structural mechanisms of receptor complex activation. The objective is to analyse ligand-induced structural changes by cryo-electron microscopy of membrane-embedded RK complexes, using the plant immune receptor FLS2 (which perceives bacterial flagellin) as a model system.

Objective

Plasma membrane-localized receptor kinases (RKs) perceive diverse extracellular ligands, allowing plants to react to various stimuli. They function in signaling processes during all aspects of plants’ life, including development, biotic and abiotic stress responses as well as reproduction. In the last decade, a major paradigm has emerged that individual RKs have different biochemical functions. There are e.g. ligand-binding RKs, which require the formation of stable complexes with RK co-receptors in order to initiate signaling. In addition to this common mode of activation, it has been revealed that additional RKs can have regulatory functions within RK complexes, and that in planta several other proteins are part of these complexes to regulate – either positively or negatively – complex formation and initiation of downstream signaling.
The proposed project aims to understand what the minimal components linking ligand binding to receptor activation and to the initiation of cellular outputs are. Furthermore, it has the goal to elucidate the structural mechanisms of receptor complex activation. To achieve this, two interconnected approaches will be pursued. The first will utilize protein expression in cell-culture to reconstitute the signaling pathway from ligand perception to activation of downstream targets. The second approach will use a cell-free in vitro expression system to reconstitute the complete RK complex in synthetic, membrane-mimicking nanodiscs. This will ultimately allow the analysis of ligand induced structural changes by cryo-electron microscopy within full length, membrane embedded RK complexes.
The well-characterized RK FLAGELLIN SENSING 2 (FLS2) and its co-receptor RK BRI1-ASSOCIATED KINASE 1 (BAK1), which are core elements of the receptor complex mediating the perception of bacterial Flagellin and function in the induction of antibacterial immune responses, will be to this end employed as a model for the proposed project.

Coordinator

UNIVERSITAT ZURICH
Net EU contribution
€ 203 149,44
Address
RAMISTRASSE 71
8006 Zurich
Switzerland

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Region
Schweiz/Suisse/Svizzera Zürich Zürich
Activity type
Higher or Secondary Education Establishments
Links
Total cost
€ 203 149,44