WRKY group IId transcription factors interact with calmodulin

Abstract
Calmodulin (CaM) is a ubiquitous Ca2+‐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 Ca2+‐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 Ca2+/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.