WRKY group IId transcription factors interact with calmodulin

Abstract

Calmodulin (CaM) is a ubiquitous Ca 2+ -binding protein known to regulate diverse cellular functions by modulating the activity of various target proteins. We isolated a cDNA encoding AtWRKY7, a novel CaM-binding transcription factor, from an Arabidopsis expression library with horseradish peroxidase-conjugated CaM. CaM binds specifically to the Ca 2+ -dependent CaM-binding domain (CaMBD) of AtWRKY7, as shown by site-directed mutagenesis, a gel mobility shift assay, a split-ubiquitin assay, and a competition assay using a Ca 2+ / CaM-dependent enzyme. Furthermore, we show that the CaMBD of AtWRKY7 is a conserved structural motif (C-motif) found in group IId of the WRKY protein family.

Functional Characterization of Arabidopsis thaliana WRKY39 in Heat Stress

“…An earlier study has shown that WRKY39 is a calmodulin-binding protein ( Fig. 1A; Park et al, 2005).…”

“…The role of WRKY39 as a positive regulator in thermotolerance is also consistent with possible regulation of WRKY39 by calcium, a second messenger in A. thaliana. Calmodulin (CaM) interacts with the WRKY39 protein (Park et al, 2005) and calcium is involved in HS in plants through CaM (Liu et al, 2008;Zhang et al, 2009). Calcium does not appear to be involved in the classic HS signaling pathways, i.e.…”

“…After 1 h heat stress at 42°C, the transcript levels of WRKY39 increased by an average of 5.3-fold over non-treatment controls, and WRKY25 was up-regulated 4.9-fold (data not shown). Earlier findings that showed WRKY39 is a calmodulin (CaM)-binding transcript factor with a protein structure close to WRKY7 (Park et al, 2005) allowed us to explore its thermotolerance function in A. thaliana. In the present study, we characterized the positive role of the A. thaliana WRKY39 transcription factor in plant responses to high temperature, by analyzing its potential upstream and downstream targets, and its loss-offunction and over-expression phenotypes.…”

A systems biology perspective on the role of WRKY transcription factors in drought responses in plants

“…It has also been shown that wRKY TFs interact with calmodulin, which binds to the C-motif (DxxvxKFKxvISLLxxxR) that is present in some group IId wRKY proteins (Park et al 2005). This implicates group IId wRKY TFs in transducing Ca 2+ signals.…”

The rice transcription factor OsWRKY47 is a positive regulator of the response to water deficit stress

“…CaM can bind to a highly conserved Ca 2+ -dependent CaMbinding domain (CaMBD) in the WRKY TFs belonging to the Group IId (Park et al 2005). Although OsWRKY47 does not contain typical CaM binding domains, its interaction with a CaMBP would suggest a possible role in the propagation of signals triggered by changes in cellular Ca 2+ homeostasis.…”