title: Arabidopsis response regulator 22 inhibits cytokinin-regulated gene transcription in vivo.
abstract: Cytokinin signaling in Arabidopsis is carried out by a two-component system (TCS) multi-step phosphorelay mechanism that involves three different protein families: histidine kinases (AHKs), phosphotransfer proteins (AHPs), and response regulators (ARRs) that are in turn, subdivided into A-, B- and C-type ARRs depending on their function and structure. Upon cytokinin perception, AHK proteins autophosphorylate; this phosphate is then transferred from the AHKs to the AHPs to finally reach the ARRs. When B-type ARRs are activated by phosphorylation, they function as transcription factors that regulate the expression of cytokinin-dependent genes such as the A-type ARRs, among many others. In cytokinin signaling, while A- and B-type ARR function is well understood, it is still unclear if C-type ARRs (ARR22 and ARR24) play a role in this mechanism. Here, we describe a novel method suitable to study TCS activity natively as an in vivo system. We also show that ARR22 inhibits gene transcription of an A-type ARR upon cytokinin treatment in vivo. Consequently, we propose that ARR22, by acting as a phosphatase on specific AHPs, disrupts the TCS phosphorelay and prevents B-type ARR phosphorylation, and thus their activation as transcription factors, explaining the observed deactivation of cytokinin-responsive genes.
authors.affiliation: Center for Plant Molecular Biology (ZMBP), Department of Plant Physiology, University of Tübingen, Auf der Morgenstelle 32, D-72076, Tübingen, Germany.
authors.forename: Niklas
authors.initials: N
authors.lastname: Wallmeroth
authors.affiliation: Center for Plant Molecular Biology (ZMBP), Department of Plant Physiology, University of Tübingen, Auf der Morgenstelle 32, D-72076, Tübingen, Germany.
authors.forename: Anna Katharina
authors.initials: AK
authors.lastname: Anastasia
authors.affiliation: Center for Plant Molecular Biology (ZMBP), Department of Plant Physiology, University of Tübingen, Auf der Morgenstelle 32, D-72076, Tübingen, Germany.
authors.forename: Klaus
authors.initials: K
authors.lastname: Harter
authors.affiliation: Center for Plant Molecular Biology (ZMBP), Central Facilities, University of Tübingen, Auf der Morgenstelle 32, D-72076, Tübingen, Germany. kenneth.berendzen@zmbp.uni-tuebingen.de.
authors.forename: Kenneth Wayne
authors.initials: KW
authors.lastname: Berendzen
authors.affiliation: Center for Plant Molecular Biology (ZMBP), Department of Plant Physiology, University of Tübingen, Auf der Morgenstelle 32, D-72076, Tübingen, Germany. virtudes.mira-rodado@zmbp.uni-tuebingen.de.
authors.forename: Virtudes
authors.identifier: http://orcid.org/0000-0003-0492-7885
authors.initials: V
authors.lastname: Mira-Rodado
mesh_terms: D017360:Arabidopsis / Q000187:drug effects / Q000235:genetics*; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism*; D003583:Cytokinins / Q000494:pharmacology*; D018506:Gene Expression Regulation, Plant / Q000187:drug effects*; D017343:Genes, Plant; D015398:Signal Transduction / Q000187:drug effects / Q000235:genetics; D014158:Transcription, Genetic / Q000187:drug effects*
chemical_list: C493632:ARR22 protein, Arabidopsis; D029681:Arabidopsis Proteins; D003583:Cytokinins
keywords: ARR22; ARR5; Cytokinin; Phosphatase; TCS