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Correction published on 1 September 2016, see Plants 2016, 5(3), 35.

Open AccessArticle
Plants 2015, 4(3), 691-709; doi:10.3390/plants4030691

Phosphorylation Affects DNA-Binding of the Senescence-Regulating bZIP Transcription Factor GBF1

ZMBP, General Genetics, University of Tuebingen, Auf der Morgenstelle 32, Tuebingen 72076, Germany
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Author to whom correspondence should be addressed.
Academic Editor: Salma Balazadeh
Received: 8 July 2015 / Revised: 12 August 2015 / Accepted: 8 September 2015 / Published: 16 September 2015
(This article belongs to the Special Issue Plant Senescence)
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Abstract

Massive changes in the transcriptome of Arabidopsis thaliana during onset and progression of leaf senescence imply a central role for transcription factors. While many transcription factors are themselves up- or down-regulated during senescence, the bZIP transcription factor G-box-binding factor 1 (GBF1/bZIP41) is constitutively expressed in Arabidopsis leaf tissue but at the same time triggers the onset of leaf senescence, suggesting posttranscriptional mechanisms for senescence-specific GBF1 activation. Here we show that GBF1 is phosphorylated by the threonine/serine CASEIN KINASE II (CKII) in vitro and that CKII phosphorylation had a negative effect on GBF1 DNA-binding to G-boxes of two direct target genes, CATALASE2 and RBSCS1a. Phosphorylation mimicry at three serine positions in the basic region of GBF1 also had a negative effect on DNA-binding. Kinase assays revealed that CKII phosphorylates at least one serine in the basic domain but has additional phosphorylation sites outside this domain. Two different ckII α subunit1 and one α subunit2 T-DNA insertion lines showed no visible senescence phenotype, but in all lines the expression of the senescence marker gene SAG12 was remarkably diminished. A model is presented suggesting that senescence-specific GBF1 activation might be achieved by lowering the phosphorylation of GBF1 by CKII. View Full-Text
Keywords: senescence regulation; GBF1; CASEIN KINASE II; phosphorylation; phosphorylation mimicry senescence regulation; GBF1; CASEIN KINASE II; phosphorylation; phosphorylation mimicry
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This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. (CC BY 4.0).

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MDPI and ACS Style

Smykowski, A.; Fischer, S.M.; Zentgraf, U. Phosphorylation Affects DNA-Binding of the Senescence-Regulating bZIP Transcription Factor GBF1. Plants 2015, 4, 691-709.

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