title: The Pseudomonas type III effector HopQ1 activates cytokinin signaling and interferes with plant innate immunity.
abstract: We characterized the molecular function of the Pseudomonas syringae pv. tomato DC3000 (Pto) effector HopQ1. In silico studies suggest that HopQ1 might possess nucleoside hydrolase activity based on the presence of a characteristic aspartate motif. Transgenic Arabidopsis lines expressing HopQ1 or HopQ1 aspartate mutant variants were characterized with respect to flagellin triggered immunity, phenotype and changes in phytohormone content by high-performance liquid chromatography-MS (HPLC-MS). We found that HopQ1, but not its aspartate mutants, suppressed all tested immunity marker assays. Suppression of immunity was the result of a lack of the flagellin receptor FLS2, whose gene expression was abolished by HopQ1 in a promoter-dependent manner. Furthermore, HopQ1 induced cytokinin signaling in Arabidopsis and the elevation in cytokinin signaling appears to be responsible for the attenuation of FLS2 expression. We conclude that HopQ1 can activate cytokinin signaling and that moderate activation of cytokinin signaling leads to suppression of FLS2 accumulation and thus defense signaling.
authors.affiliation: Section of Plant Physiology, Botanical Institute, Hebelstrasse 1, CH-4056, Basel, Switzerland.
authors.forename: Dagmar R
authors.initials: DR
authors.lastname: Hann
authors.affiliation: Section of Plant Physiology, Botanical Institute, Hebelstrasse 1, CH-4056, Basel, Switzerland.
authors.forename: Ana
authors.initials: A
authors.lastname: Domínguez-Ferreras
authors.affiliation: Institute of Experimental Botany AS CR, Rozvojová 263, 165 02, Praha 6 - Lysolaje, Czech Republic.
authors.forename: Vaclav
authors.initials: V
authors.lastname: Motyka
authors.affiliation: Institute of Experimental Botany AS CR, Rozvojová 263, 165 02, Praha 6 - Lysolaje, Czech Republic.
authors.forename: Petre I
authors.initials: PI
authors.lastname: Dobrev
authors.affiliation: The Sainsbury Laboratory, Cambridge University, Cambridge, CB2 1LR, UK.
authors.forename: Sebastian
authors.initials: S
authors.lastname: Schornack
authors.affiliation: Forschungsgruppe Pflanzenbiochemie, ZMBP - Zentrum für Molekularbiologie der Pflanzen, Eberhard-Karls-Universität Tübingen, Auf der Morgenstelle 5, 72076, Tübingen, Germany.
authors.forename: Anna
authors.initials: A
authors.lastname: Jehle
authors.affiliation: Forschungsgruppe Pflanzenbiochemie, ZMBP - Zentrum für Molekularbiologie der Pflanzen, Eberhard-Karls-Universität Tübingen, Auf der Morgenstelle 5, 72076, Tübingen, Germany.
authors.forename: Georg
authors.initials: G
authors.lastname: Felix
authors.affiliation: Section of Plant Physiology, Botanical Institute, Hebelstrasse 1, CH-4056, Basel, Switzerland.
authors.forename: Delphine
authors.initials: D
authors.lastname: Chinchilla
authors.affiliation: The Australian National University, The Linnaeus Building, Building 134, Linnaeus Way, Canberra, ACT, 0200, Australia.
authors.forename: John P
authors.initials: JP
authors.lastname: Rathjen
authors.affiliation: Section of Plant Physiology, Botanical Institute, Hebelstrasse 1, CH-4056, Basel, Switzerland.
authors.forename: Thomas
authors.initials: T
authors.lastname: Boller
mesh_terms: D017360:Arabidopsis / Q000187:drug effects / Q000276:immunology* / Q000502:physiology; D029681:Arabidopsis Proteins / Q000378:metabolism; D001426:Bacterial Proteins / Q000235:genetics / Q000502:physiology*; D002851:Chromatography, High Pressure Liquid; D003583:Cytokinins / Q000378:metabolism* / Q000494:pharmacology; D060467:Disease Resistance; D010937:Plant Growth Regulators / Q000378:metabolism; D030821:Plants, Genetically Modified / Q000378:metabolism; D011494:Protein Kinases / Q000378:metabolism; D044224:Pseudomonas syringae / Q000235:genetics / Q000502:physiology*; D015398:Signal Transduction
chemical_list: D029681:Arabidopsis Proteins; D001426:Bacterial Proteins; D003583:Cytokinins; D010937:Plant Growth Regulators; D011494:Protein Kinases; C411853:FLS2 protein, Arabidopsis
keywords: FLS2; HopQ1; cytokinin; flagellin; innate immunity; type III effector