title: Probing the Arabidopsis flagellin receptor: FLS2-FLS2 association and the contributions of specific domains to signaling function.
abstract: Flagellin sensing2 (FLS2) is a transmembrane receptor kinase that activates antimicrobial defense responses upon binding of bacterial flagellin or the flagellin-derived peptide flg22. We find that some Arabidopsis thaliana FLS2 is present in FLS2-FLS2 complexes before and after plant exposure to flg22. flg22 binding capability is not required for FLS2-FLS2 association. Cys pairs flank the extracellular leucine rich repeat (LRR) domain in FLS2 and many other LRR receptors, and we find that the Cys pair N-terminal to the FLS2 LRR is required for normal processing, stability, and function, possibly due to undescribed endoplasmic reticulum quality control mechanisms. By contrast, disruption of the membrane-proximal Cys pair does not block FLS2 function, instead increasing responsiveness to flg22, as indicated by a stronger oxidative burst. There was no evidence for intermolecular FLS2-FLS2 disulfide bridges. Truncated FLS2 containing only the intracellular domain associates with full-length FLS2 and exerts a dominant-negative effect on wild-type FLS2 function that is dependent on expression level but independent of the protein kinase capacity of the truncated protein. FLS2 is insensitive to disruption of multiple N-glycosylation sites, in contrast with the related receptor EF-Tu receptor that can be rendered nonfunctional by disruption of single glycosylation sites. These and additional findings more precisely define the molecular mechanisms of FLS2 receptor function.
authors.affiliation: Department of Plant Pathology, University of Wisconsin, Madison, Wisconsin 53706, USA.
authors.forename: Wenxian
authors.initials: W
authors.lastname: Sun
authors.forename: Yangrong
authors.initials: Y
authors.lastname: Cao
authors.forename: Kristin
authors.initials: K
authors.lastname: Jansen Labby
authors.forename: Pascal
authors.initials: P
authors.lastname: Bittel
authors.forename: Thomas
authors.initials: T
authors.lastname: Boller
authors.forename: Andrew F
authors.initials: AF
authors.lastname: Bent
mesh_terms: D017360:Arabidopsis / Q000235:genetics / Q000378:metabolism*; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism*; D003001:Cloning, Molecular; D018506:Gene Expression Regulation, Plant; D006031:Glycosylation; D008024:Ligands; D016297:Mutagenesis, Site-Directed; D054730:Protein Interaction Domains and Motifs; D011494:Protein Kinases / Q000235:genetics / Q000378:metabolism*; D015398:Signal Transduction
chemical_list: D029681:Arabidopsis Proteins; D008024:Ligands; D011494:Protein Kinases; C411853:FLS2 protein, Arabidopsis