title: The ubiquitin ligase PUB22 targets a subunit of the exocyst complex required for PAMP-triggered responses in Arabidopsis.
abstract: Plant pathogens are perceived by pattern recognition receptors, which are activated upon binding to pathogen-associated molecular patterns (PAMPs). Ubiquitination and vesicle trafficking have been linked to the regulation of immune signaling. However, little information exists about components of vesicle trafficking involved in immune signaling and the mechanisms that regulate them. In this study, we identified Arabidopsis thaliana Exo70B2, a subunit of the exocyst complex that mediates vesicle tethering during exocytosis, as a target of the plant U-box-type ubiquitin ligase 22 (PUB22), which acts in concert with PUB23 and PUB24 as a negative regulator of PAMP-triggered responses. We show that Exo70B2 is required for both immediate and later responses triggered by all tested PAMPs, suggestive of a role in signaling. Exo70B2 is also necessary for the immune response against different pathogens. Our data demonstrate that PUB22 mediates the ubiquitination and degradation of Exo70B2 via the 26S Proteasome. Furthermore, degradation is regulated by the autocatalytic turnover of PUB22, which is stabilized upon PAMP perception. We therefore propose a mechanism by which PUB22-mediated degradation of Exo70B2 contributes to the attenuation of PAMP-induced signaling.
authors.affiliation: Leibniz Institute of Plant Biochemistry, D-06120 Halle (Saale), Germany.
authors.forename: Martin
authors.initials: M
authors.lastname: Stegmann
authors.forename: Ryan G
authors.initials: RG
authors.lastname: Anderson
authors.forename: Kazuya
authors.initials: K
authors.lastname: Ichimura
authors.forename: Tamara
authors.initials: T
authors.lastname: Pecenkova
authors.forename: Patrick
authors.initials: P
authors.lastname: Reuter
authors.forename: Viktor
authors.initials: V
authors.lastname: Žársky
authors.forename: John M
authors.initials: JM
authors.lastname: McDowell
authors.forename: Ken
authors.initials: K
authors.lastname: Shirasu
authors.forename: Marco
authors.initials: M
authors.lastname: Trujillo
mesh_terms: D017360:Arabidopsis / Q000235:genetics / Q000276:immunology* / Q000382:microbiology / Q000469:parasitology / Q000502:physiology; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism*; D016923:Cell Death; D018506:Gene Expression Regulation, Plant / Q000276:immunology*; D054884:Host-Pathogen Interactions; D009154:Mutation; D009868:Oomycetes / Q000502:physiology; D010802:Phylogeny; D010935:Plant Diseases / Q000276:immunology* / Q000382:microbiology / Q000469:parasitology; D018515:Plant Leaves / Q000235:genetics / Q000276:immunology / Q000382:microbiology / Q000469:parasitology / Q000502:physiology; D018517:Plant Roots / Q000235:genetics / Q000276:immunology / Q000382:microbiology / Q000469:parasitology / Q000502:physiology; D046988:Proteasome Endopeptidase Complex; D059748:Proteolysis; D044224:Pseudomonas syringae / Q000502:physiology; D051192:Receptors, Pattern Recognition / Q000235:genetics / Q000378:metabolism; D011993:Recombinant Fusion Proteins; D036226:Seedlings / Q000235:genetics / Q000276:immunology / Q000382:microbiology / Q000469:parasitology / Q000502:physiology; D015398:Signal Transduction / Q000276:immunology*; D020798:Two-Hybrid System Techniques; D025801:Ubiquitin / Q000378:metabolism; D044767:Ubiquitin-Protein Ligases / Q000235:genetics / Q000378:metabolism; D054875:Ubiquitination; D033921:Vesicular Transport Proteins / Q000235:genetics / Q000378:metabolism
chemical_list: D029681:Arabidopsis Proteins; C582895:Exo70B2 protein, Arabidopsis; D051192:Receptors, Pattern Recognition; D011993:Recombinant Fusion Proteins; D025801:Ubiquitin; D033921:Vesicular Transport Proteins; C582896:PUB22 protein, Arabidopsis; D044767:Ubiquitin-Protein Ligases; D046988:Proteasome Endopeptidase Complex; C061553:ATP dependent 26S protease