title: The Clubroot Pathogen (Plasmodiophora brassicae) Influences Auxin Signaling to Regulate Auxin Homeostasis in Arabidopsis.
abstract: The clubroot disease, caused by the obligate biotrophic protist Plasmodiophora brassicae, affects cruciferous crops worldwide. It is characterized by root swellings as symptoms, which are dependent on the alteration of auxin and cytokinin metabolism. Here, we describe that two different classes of auxin receptors, the TIR family and the auxin binding protein 1 (ABP1) in Arabidopsis thaliana are transcriptionally upregulated upon gall formation. Mutations in the TIR family resulted in more susceptible reactions to the root pathogen. As target genes for the different pathways we have investigated the transcriptional regulation of selected transcriptional repressors (Aux/IAA) and transcription factors (ARF). As the TIR pathway controls auxin homeostasis via the upregulation of some auxin conjugate synthetases (GH3), the expression of selected GH3 genes was also investigated, showing in most cases upregulation. A double gh3 mutant showed also slightly higher susceptibility to P. brassicae infection, while all tested single mutants did not show any alteration in the clubroot phenotype. As targets for the ABP1-induced cell elongation the effect of potassium channel blockers on clubroot formation was investigated. Treatment with tetraethylammonium (TEA) resulted in less severe clubroot symptoms. This research provides evidence for the involvement of two auxin signaling pathways in Arabidopsis needed for the establishment of the root galls by P. brassicae.
authors.affiliation: Institut für Botanik, Technische Universität Dresden, 01062 Dresden, Germany. Linda.Jahn@mailbox.tu-dresden.de.
authors.forename: Linda
authors.initials: L
authors.lastname: Jahn
authors.affiliation: Institut für Botanik, Technische Universität Dresden, 01062 Dresden, Germany. Mucha.Stefanie@web.de.
authors.forename: Stefanie
authors.initials: S
authors.lastname: Mucha
authors.affiliation: Institut für Botanik, Technische Universität Dresden, 01062 Dresden, Germany. bine.schu@web.de.
authors.forename: Sabine
authors.initials: S
authors.lastname: Bergmann
authors.affiliation: Institut für Botanik, Technische Universität Dresden, 01062 Dresden, Germany. Cornelia.Horn@mailbox.tu-dresden.de.
authors.forename: Cornelia
authors.initials: C
authors.lastname: Horn
authors.affiliation: Department of Agronomy and Horticulture, University of Nebraska, 379 Keim, Lincoln, NE 68521 USA. pstaswick1@unl.edu.
authors.forename: Paul
authors.initials: P
authors.lastname: Staswick
authors.affiliation: Botanisches Institut, Universität Kiel, Am Botanischen Garten 5, 24118 Kiel, Germany. bsteffens@bot.uni-kiel.de.
authors.forename: Bianka
authors.initials: B
authors.lastname: Steffens
authors.affiliation: Institut für Botanik, Technische Universität Dresden, 01062 Dresden, Germany. Johannes.Siemens@hu-berlin.de.
authors.forename: Johannes
authors.initials: J
authors.lastname: Siemens
authors.affiliation: Institut für Botanik, Technische Universität Dresden, 01062 Dresden, Germany. Ludwig-Mueller@tu-dresden.de.
authors.forename: Jutta
authors.initials: J
authors.lastname: Ludwig-Müller
keywords: ABP1; Arabidopsis thaliana; GH3 proteins; Plasmodiophora brassicae; TIR1; auxin homeostasis; auxin receptors; clubroot disease; potassium channel inhibitors; tetraethylammonium