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The Arabidopsis B‐type response regulator 18 homomerizes and positively regulates cytokinin responses
Author(s) -
Veerabagu Manikandan,
Elgass Kirstin,
Kirchler Tobias,
Huppenberger Peter,
Harter Klaus,
Chaban Christina,
MiraRodado Virtudes
Publication year - 2012
Publication title -
the plant journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 3.058
H-Index - 269
eISSN - 1365-313X
pISSN - 0960-7412
DOI - 10.1111/j.1365-313x.2012.05101.x
Subject(s) - arabidopsis , response regulator , regulator , biology , phosphorylation , microbiology and biotechnology , two component regulatory system , transcriptional regulation , cytokinin , gene , genetics , transcription factor , auxin , mutant
Summary 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.