Journal Article

The APRR3 Component of the Clock-Associated APRR1/TOC1 Quintet is Phosphorylated by a Novel Protein Kinase Belonging to the WNK Family, the Gene for which is also Transcribed Rhythmically in <i>Arabidopsis thaliana</i>

Masaya Murakami-Kojima, Norihito Nakamichi, Takafumi Yamashino and Takeshi Mizuno

in Plant and Cell Physiology

Published on behalf of Japanese Society of Plant Physiologists

Volume 43, issue 6, pages 675-683
Published in print June 2002 | ISSN: 0032-0781
Published online June 2002 | e-ISSN: 1471-9053 | DOI: http://dx.doi.org/10.1093/pcp/pcf084
The APRR3 Component of the Clock-Associated APRR1/TOC1 Quintet is Phosphorylated by a Novel Protein Kinase Belonging to the WNK Family, the Gene for which is also Transcribed Rhythmically in Arabidopsis thaliana

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In higher plants, clock-controlled circadian rhythms are a longstanding issue in physiology, and a newly emerging paradigm of molecular biology. In the model higher plant Arabidopsis thaliana, several genes have been proposed to encode potential clock-associated components, including a member (APRR1/TOC1) of the pseudo-response regulator family. We previously showed that transcripts of the APRR1/TOC1 family start accumulating after dawn rhythmically and sequentially at approximately 2 h intervals in the order of APRR9→APRR7→APRR5→APRR3→APRR1/ TOC1. This and other results led us to propose that this APRR1/TOC1 quintet might play coordinate roles in the mechanism underlying circadian rhythms in higher plants. To gain further insight as to such an idea, we here attempt to identify proteins that interact with one of the quintet members, APRR3. The identified component is a novel protein kinase, named WNK1, which is considerably similar to, but clearly distinct from, mitogen-activated protein kinases (MAPKs). It was found that APRR3 is a substrate of this novel protein kinase, the gene for which also shows a rhythmic transcription profile that is well coincident with the APRR3 rhythm. These findings give new insight into the mechanisms underlying the circadian rhythm in A. thaliana, providing a molecular link between the putative clock component, APRR3, and WNK1, a novel protein kinase that might be implicated as a signal transducer.

Keywords: Keywords: Arabidopsis — Circadian rhythm — Clock component — Protein kinase.

Journal Article.  5555 words.  Illustrated.

Subjects: Biochemistry ; Molecular and Cell Biology ; Plant Sciences and Forestry

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