title: Analysis of Phosphorylation of the Receptor-Like Protein Kinase HAESA during Arabidopsis Floral Abscission.
abstract: Receptor-like protein kinases (RLKs) are the largest family of plant transmembrane signaling proteins. Here we present functional analysis of HAESA, an RLK that regulates floral organ abscission in Arabidopsis. Through in vitro and in vivo analysis of HAE phosphorylation, we provide evidence that a conserved phosphorylation site on a region of the HAE protein kinase domain known as the activation segment positively regulates HAE activity. Additional analysis has identified another putative activation segment phosphorylation site common to multiple RLKs that potentially modulates HAE activity. Comparative analysis suggests that phosphorylation of this second activation segment residue is an RLK specific adaptation that may regulate protein kinase activity and substrate specificity. A growing number of RLKs have been shown to exhibit biologically relevant dual specificity toward serine/threonine and tyrosine residues, but the mechanisms underlying dual specificity of RLKs are not well understood. We show that a phospho-mimetic mutant of both HAE activation segment residues exhibits enhanced tyrosine auto-phosphorylation in vitro, indicating phosphorylation of this residue may contribute to dual specificity of HAE. These results add to an emerging framework for understanding the mechanisms and evolution of regulation of RLK activity and substrate specificity.
authors.affiliation: Division of Biological Science, University of Missouri, Columbia, Missouri, United States of America.|Interdisciplinary Plant Group, University of Missouri, Columbia, Missouri, United States of America.
authors.forename: Isaiah
authors.initials: I
authors.lastname: Taylor
authors.affiliation: Division of Biological Science, University of Missouri, Columbia, Missouri, United States of America.|Interdisciplinary Plant Group, University of Missouri, Columbia, Missouri, United States of America.
authors.forename: Ying
authors.initials: Y
authors.lastname: Wang
authors.affiliation: Division of Biological Science, University of Missouri, Columbia, Missouri, United States of America.|Interdisciplinary Plant Group, University of Missouri, Columbia, Missouri, United States of America.
authors.forename: Kati
authors.initials: K
authors.lastname: Seitz
authors.affiliation: Division of Biological Science, University of Missouri, Columbia, Missouri, United States of America.|Interdisciplinary Plant Group, University of Missouri, Columbia, Missouri, United States of America.
authors.forename: John
authors.initials: J
authors.lastname: Baer
authors.affiliation: Division of Biological Science, University of Missouri, Columbia, Missouri, United States of America.|Interdisciplinary Plant Group, University of Missouri, Columbia, Missouri, United States of America.
authors.forename: Stefan
authors.initials: S
authors.lastname: Bennewitz
authors.affiliation: Interdisciplinary Plant Group, University of Missouri, Columbia, Missouri, United States of America.|Charles W. Gehrke Proteomics Center and Division of Biochemistry, Bond Life Sciences Center, University of Missouri, Columbia, Missouri, United States of America.
authors.forename: Brian P
authors.initials: BP
authors.lastname: Mooney
authors.affiliation: Division of Biological Science, University of Missouri, Columbia, Missouri, United States of America.|Interdisciplinary Plant Group, University of Missouri, Columbia, Missouri, United States of America.
authors.forename: John C
authors.initials: JC
authors.lastname: Walker
mesh_terms: D017360:Arabidopsis / Q000201:enzymology* / Q000502:physiology*; D029681:Arabidopsis Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D020134:Catalytic Domain; D035264:Flowers / Q000201:enzymology / Q000502:physiology; D018506:Gene Expression Regulation, Plant; D008958:Models, Molecular; D009154:Mutation; D010766:Phosphorylation; D017346:Protein Serine-Threonine Kinases / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D013379:Substrate Specificity; D014443:Tyrosine / Q000378:metabolism*
chemical_list: D029681:Arabidopsis Proteins; D014443:Tyrosine; C089427:RLK5 protein, Arabidopsis; D017346:Protein Serine-Threonine Kinases