Subprojects D05: Molecular specificity of signal input and signal output in plant receptor kinases
Principal investigator:
Prof. Dr. Georg Felix
Universität Tübingen
ZMBP, Pflanzenbiochemie
Auf der Morgenstelle 5,72076 Tübingen
Tel 07071 - 29 726672
georg.felix@zmbp.uni-tuebingen.de
Summary:
Surface exposed receptor kinases regulate intracellular processes according to the presence of extracellular signal molecules. Higher plants have >600 'receptor like kinases' (RLKs), most of them still orphan with respect to their ligands and physiological functions. In the running period of the CRC we augmented the number of known ligand/receptor pairs by the RLKs CORE and SR470 that detect the so far orphan ligands csp22, a peptide representing bacterial cold shock protein, and the wound hormone systemin, respectively. CORE and SR470 have ligand-binding domains composed of leucine-rich repeats (LRRs). They extend our toolbox of LRR-RLKs, including RLKs like FLS2, EFR, Eli (EFR-like), HSL2, BRI1, BAK1 and BIRs, that we want to use to identify molecular determinants that define ligand recognition and specificity of signalling output.
First, using the LRR domain of the well-characterized receptor EFR as a model scaffold, we will produce site-directed modifications of surface sites, introduced by mutagenesis or by exchanging individual LRRs with synthetic LRRs or LRRs of related RLKs (Eli and CORE). This aims to identify amino acid positions that determine affinity for a particular ligand, and those that have general functions for receptor activation. Second, we will study the molecular determinants that specify distinct cytoplasmic outputs. So far, we could show that reciprocal exchanges of the cytoplasmic domains between the EFR and BRI1 result in receptors that trigger growth in response to elf18 and defense responses to brassinolide, respectively. Further studies proposed here will use this modular architecture of RLKs to identify the molecular cues and downstream targets that determine the output programs.