title: Mechanistic insight into a peptide hormone signaling complex mediating floral organ abscission.
abstract: Plants constantly renew during their life cycle and thus require to shed senescent and damaged organs. Floral abscission is controlled by the leucine-rich repeat receptor kinase (LRR-RK) HAESA and the peptide hormone IDA. It is unknown how expression of IDA in the abscission zone leads to HAESA activation. Here we show that IDA is sensed directly by the HAESA ectodomain. Crystal structures of HAESA in complex with IDA reveal a hormone binding pocket that accommodates an active dodecamer peptide. A central hydroxyproline residue anchors IDA to the receptor. The HAESA co-receptor SERK1, a positive regulator of the floral abscission pathway, allows for high-affinity sensing of the peptide hormone by binding to an Arg-His-Asn motif in IDA. This sequence pattern is conserved among diverse plant peptides, suggesting that plant peptide hormone receptors may share a common ligand binding mode and activation mechanism.
authors.affiliation: Structural Plant Biology Laboratory, Department of Botany and Plant Biology, University of Geneva, Geneva, Switzerland.
authors.forename: Julia
authors.initials: J
authors.lastname: Santiago
authors.affiliation: Structural Plant Biology Laboratory, Department of Botany and Plant Biology, University of Geneva, Geneva, Switzerland.
authors.forename: Benjamin
authors.initials: B
authors.lastname: Brandt
authors.affiliation: Department of Biosciences, Section for Genetic and Evolutionary Biology, University of Oslo, Oslo, Norway.
authors.forename: Mari
authors.initials: M
authors.lastname: Wildhagen
authors.affiliation: Structural Plant Biology Laboratory, Department of Botany and Plant Biology, University of Geneva, Geneva, Switzerland.
authors.forename: Ulrich
authors.initials: U
authors.lastname: Hohmann
authors.affiliation: Institute of Biostatistics, Leibniz University, Hannover, Germany.
authors.forename: Ludwig A
authors.initials: LA
authors.lastname: Hothorn
authors.affiliation: Department of Biosciences, Section for Genetic and Evolutionary Biology, University of Oslo, Oslo, Norway.
authors.forename: Melinka A
authors.initials: MA
authors.lastname: Butenko
authors.affiliation: Structural Plant Biology Laboratory, Department of Botany and Plant Biology, University of Geneva, Geneva, Switzerland.
authors.forename: Michael
authors.identifier: 0000-0002-3597-5698
authors.initials: M
authors.lastname: Hothorn
mesh_terms: D017360:Arabidopsis / Q000502:physiology*; D029681:Arabidopsis Proteins / Q000096:biosynthesis* / Q000737:chemistry / Q000378:metabolism*; D001665:Binding Sites; D018360:Crystallography, X-Ray; D035264:Flowers / Q000502:physiology*; D018506:Gene Expression Regulation, Plant; D011485:Protein Binding; D011487:Protein Conformation; D011494:Protein Kinases / Q000378:metabolism*; D017346:Protein Serine-Threonine Kinases / Q000096:biosynthesis* / Q000737:chemistry; D015398:Signal Transduction
chemical_list: D029681:Arabidopsis Proteins; C512213:IDA protein, Arabidopsis; D011494:Protein Kinases; C089427:RLK5 protein, Arabidopsis; C440035:SERK1 protein, Arabidopsis; D017346:Protein Serine-Threonine Kinases
keywords: <i>a. thaliana</i>; biophysics; floral abscission; membrane signaling; peptide hormone; plant biology; plant development; protein complexes; receptor kinase; structural biology