Molecular specificity of signal input and signal output in plant receptor kinases2017-08-14
Time: 9:30 am
Day/Date: September 7th, 2017 (Thursday)
Host PI: Prof. Alberto Macho
Venue: PSC Auditorium
Plant genomes encode multi-membered families of structurally related LRR-receptor kinases (LRR-RKs) that regulate developmental processes in response to endogenous ligands or act as immunoreceptors detecting a variety of microbe- or pathogen associated molecular patterns (M-/PAMPs). For studying receptors with respect to their specificity of input we try to match old ligands with novel receptors and we use well characterized receptors such as FLS2 and EFR to determine how specificity for ligands is encoded on their LRR-domains. FLS2 and functional perception of the flg22 epitope of flagellin is found in many plant species but plant pathogens like Agrobacterium tumefacienshave modified flg22-epitopes that cannot be detected by FLS2. We screened for plants that, in turn, have evolved a detection system for flg22Atum and we found that some Vitis species have evolved a FLS2XL(extended ligand recognition) that detects flg22Atum as efficiently as flg22.
In contrast to FLS2, occurrence of functional EFR is restricted species of the Brassicaceae. However, structurally closely related receptor kinases are present many angiosperms. These receptors include XA21 from rice and CORE from tomato which also act as pattern recognition receptors (PRRs) but have specificities for structurally unrelated bacterial MAMPs. Replacements of specific LRRs in EFR with the corresponding LRRs from other members of this receptor family show that most of the 23 LRRs are relevant for elf18 specificity. This indicates that many positions on the surface of LRR-domain are required to determine ligand specificity.
Using chimeric approaches we currently also address questions aiming at the identification of molecular determinants that distinguish LRR-RKs involved in defense from those involved in developmental programs.