title: Loss of Arabidopsis thaliana Dynamin-Related Protein 2B reveals separation of innate immune signaling pathways.
abstract: Vesicular trafficking has emerged as an important means by which eukaryotes modulate responses to microbial pathogens, likely by contributing to the correct localization and levels of host components necessary for effective immunity. However, considering the complexity of membrane trafficking in plants, relatively few vesicular trafficking components with functions in plant immunity are known. Here we demonstrate that Arabidopsis thaliana Dynamin-Related Protein 2B (DRP2B), which has been previously implicated in constitutive clathrin-mediated endocytosis (CME), functions in responses to flg22 (the active peptide derivative of bacterial flagellin) and immunity against flagellated bacteria Pseudomonas syringae pv. tomato (Pto) DC3000. Consistent with a role of DRP2B in Pattern-Triggered Immunity (PTI), drp2b null mutant plants also showed increased susceptibility to Pto DC3000 hrcC-, which lacks a functional Type 3 Secretion System, thus is unable to deliver effectors into host cells to suppress PTI. Importantly, analysis of drp2b mutant plants revealed three distinct branches of the flg22-signaling network that differed in their requirement for RESPIRATORY BURST OXIDASE HOMOLOGUE D (RBOHD), the NADPH oxidase responsible for flg22-induced apoplastic reactive oxygen species production. Furthermore, in drp2b, normal MAPK signaling and increased immune responses via the RbohD/Ca2+-branch were not sufficient for promoting robust PR1 mRNA expression nor immunity against Pto DC3000 and Pto DC3000 hrcC-. Based on live-cell imaging studies, flg22-elicited internalization of the plant flagellin-receptor, FLAGELLIN SENSING 2 (FLS2), was found to be partially dependent on DRP2B, but not the closely related protein DRP2A, thus providing genetic evidence for a component, implicated in CME, in ligand-induced endocytosis of FLS2. Reduced trafficking of FLS2 in response to flg22 may contribute in part to the non-canonical combination of immune signaling defects observed in drp2b. In conclusion, this study adds DRP2B to the relatively short list of known vesicular trafficking proteins with roles in flg22-signaling and PTI in plants.
authors.affiliation: Division of Biochemistry, University of Missouri-Columbia, Columbia, Missouri, United States of America; Interdisciplinary Plant Group (IPG), University of Missouri-Columbia, Columbia, Missouri, United States of America; Division of Plant Sciences, University of Missouri-Columbia, Columbia, Missouri, United States of America.
authors.forename: John M
authors.initials: JM
authors.lastname: Smith
authors.affiliation: Division of Biochemistry, University of Missouri-Columbia, Columbia, Missouri, United States of America; Interdisciplinary Plant Group (IPG), University of Missouri-Columbia, Columbia, Missouri, United States of America.
authors.forename: Michelle E
authors.initials: ME
authors.lastname: Leslie
authors.affiliation: Division of Biochemistry, University of Missouri-Columbia, Columbia, Missouri, United States of America; Interdisciplinary Plant Group (IPG), University of Missouri-Columbia, Columbia, Missouri, United States of America.
authors.forename: Samuel J
authors.initials: SJ
authors.lastname: Robinson
authors.affiliation: Division of Biochemistry, University of Missouri-Columbia, Columbia, Missouri, United States of America; Interdisciplinary Plant Group (IPG), University of Missouri-Columbia, Columbia, Missouri, United States of America.
authors.forename: David A
authors.initials: DA
authors.lastname: Korasick
authors.affiliation: Division of Biochemistry, University of Missouri-Columbia, Columbia, Missouri, United States of America; Interdisciplinary Plant Group (IPG), University of Missouri-Columbia, Columbia, Missouri, United States of America.
authors.forename: Tong
authors.initials: T
authors.lastname: Zhang
authors.affiliation: Department of Biochemistry, University of Wisconsin-Madison, Madison, Wisconsin, United States of America.
authors.forename: Steven K
authors.initials: SK
authors.lastname: Backues
authors.affiliation: Division of Biochemistry, University of Missouri-Columbia, Columbia, Missouri, United States of America.
authors.forename: Peter V
authors.initials: PV
authors.lastname: Cornish
authors.affiliation: Division of Biochemistry, University of Missouri-Columbia, Columbia, Missouri, United States of America; Interdisciplinary Plant Group (IPG), University of Missouri-Columbia, Columbia, Missouri, United States of America.
authors.forename: Abraham J
authors.initials: AJ
authors.lastname: Koo
authors.affiliation: Department of Biochemistry, University of Wisconsin-Madison, Madison, Wisconsin, United States of America.
authors.forename: Sebastian Y
authors.initials: SY
authors.lastname: Bednarek
authors.affiliation: Division of Biochemistry, University of Missouri-Columbia, Columbia, Missouri, United States of America; Interdisciplinary Plant Group (IPG), University of Missouri-Columbia, Columbia, Missouri, United States of America.
authors.forename: Antje
authors.initials: A
authors.lastname: Heese
mesh_terms: D017360:Arabidopsis / Q000235:genetics / Q000502:physiology*; D029681:Arabidopsis Proteins / Q000235:genetics / Q000276:immunology / Q000502:physiology; D005408:Flagellin / Q000276:immunology; D019204:GTP-Binding Proteins / Q000172:deficiency* / Q000235:genetics / Q000502:physiology; D007113:Immunity, Innate / Q000502:physiology*; D009154:Mutation / Q000235:genetics; D019255:NADPH Oxidases / Q000502:physiology; D057865:Plant Immunity / Q000502:physiology*; D011494:Protein Kinases / Q000276:immunology; D015398:Signal Transduction
chemical_list: D029681:Arabidopsis Proteins; D005408:Flagellin; C568857:AT5G47910 protein, Arabidopsis; D019255:NADPH Oxidases; D011494:Protein Kinases; C411853:FLS2 protein, Arabidopsis; C539085:DRP2B protein, Arabidopsis; D019204:GTP-Binding Proteins