title: The Arabidopsis B-type response regulator 18 homomerizes and positively regulates cytokinin responses.
abstract: In higher plants, the two-component system (TCS) is a signaling mechanism based on a His-to-Asp phosphorelay. The Arabidopsis TCS involves three different types of proteins, namely the histidine kinases (AHKs), the histidine phosphotransfer proteins (AHPs) and the response regulators (ARRs). The ARRs comprise three different families, namely A, B and C types, according to their protein structure. While some members of the B-type family of ARRs have been studied extensively and reported to act as DNA-binding transcriptional regulators, very limited information is available for other B-type ARRs such as ARR18. In this study, we characterize in detail the molecular and functional properties of ARR18. ARR18 acts as a transcriptional regulator in plant cells and forms homodimers in planta as shown by FRET-FLIM studies. As demonstrated by mutational analysis, the aspartate at position 70 (D70) in the receiver domain of ARR18 acts as crucial phosphorylation site. The modification of D70 affects the response regulator's ability to homodimerize and to activate its target genes. Furthermore, physiological investigations of Arabidopsis lines ectopically expressing ARR18 introduce ARR18 as a new member within the cytokinin-regulated response pathway regulating root elongation.
authors: Center for Plant Molecular Biology-ZMBP, Department of Plant Physiology, University of Tübingen, Auf der Morgenstelle 1, 72076 Tübingen, Germany.
authors: Manikandan
authors: M
authors: Veerabagu
authors: Kirstin
authors: K
authors: Elgass
authors: Tobias
authors: T
authors: Kirchler
authors: Peter
authors: P
authors: Huppenberger
authors: Klaus
authors: K
authors: Harter
authors: Christina
authors: C
authors: Chaban
authors: Virtudes
authors: V
authors: Mira-Rodado
mesh_terms: D017360:Arabidopsis / Q000235:genetics / Q000378:metabolism*; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism*; D001224:Aspartic Acid / Q000235:genetics; D003583:Cytokinins / Q000378:metabolism*; D018506:Gene Expression Regulation, Plant; D010766:Phosphorylation; D018517:Plant Roots / Q000254:growth & development / Q000378:metabolism; D030821:Plants, Genetically Modified; D055503:Protein Multimerization; D017434:Protein Structure, Tertiary; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism*
chemical_list: C576644:ARR18 protein, Arabidopsis; D029681:Arabidopsis Proteins; D003583:Cytokinins; D014157:Transcription Factors; D001224:Aspartic Acid