Received June 30, 2005
Returned for revision August 25, 2005
Accepted October 7, 2005
AREB1 Is a Transcription Activator of Novel ABRE-Dependent ABA Signaling That Enhances Drought Stress Tolerance in Arabidopsis
Yasunari Fujita 1, Miki Fujita 2, Rie Satoh 3, Kyonoshin Maruyama 1, Mohammad M. Parvez 1, Motoaki Seki 4, Keiichiro Hiratsu 5, Masaru Ohme-Takagi 5, Kazuo Shinozaki 6, and Kazuko Yamaguchi-Shinozaki 7*
1 Biological Resources Division, Japan International Research Center for Agricultural Sciences, Tsukuba, Ibaraki 305-8686, Japan
2 Laboratory of Plant Molecular Biology, RIKEN Tsukuba Institute, Tsukuba, Ibaraki 305-0074, Japan; Core Research for Evolutional Science and Technology, Japan Science and Technology Agency Corporation, Kawaguchi, Saitama 332-0012, Japan
3 Biological Resources Division, Japan International Research Center for Agricultural Sciences, Tsukuba, Ibaraki 305-8686, Japan; Core Research for Evolutional Science and Technology, Japan Science and Technology Agency Corporation, Kawaguchi, Saitama 332-0012, Japan
4 Laboratory of Plant Molecular Biology, RIKEN Tsukuba Institute, Tsukuba, Ibaraki 305-0074, Japan; Plant Functional Genomics Group, RIKEN Genomic Sciences Center, Yokohama, Kanagawa 230-0045, Japan
5 Core Research for Evolutional Science and Technology, Japan Science and Technology Agency Corporation, Kawaguchi, Saitama 332-0012, Japan; Gene Function Research Center, National Institute of Advanced Industrial Science and Technology, Central 4, Tsukuba, Ibaraki 305-8562, Japan
6 Laboratory of Plant Molecular Biology, RIKEN Tsukuba Institute, Tsukuba, Ibaraki 305-0074, Japan; Core Research for Evolutional Science and Technology, Japan Science and Technology Agency Corporation, Kawaguchi, Saitama 332-0012, Japan; Plant Functional Genomics Group, RIKEN Genomic Sciences Center, Yokohama, Kanagawa 230-0045, Japan
7 Biological Resources Division, Japan International Research Center for Agricultural Sciences, Tsukuba, Ibaraki 305-8686, Japan; Core Research for Evolutional Science and Technology, Japan Science and Technology Agency Corporation, Kawaguchi, Saitama 332-0012, Japan; Laboratory of Plant Molecular Physiology, Graduate School of Agricultural and Life Sciences, University of Tokyo, Tokyo 113-8657, Japan
* To whom correspondence should be addressed. E-mail: kazukoys{at}jircas.affrc.go.jp.
ABSCISIC ACID-RESPONSIVE ELEMENT BINDING PROTEIN1 (AREB1) (i.e., ABF2) is a basic domain/leucine zipper transcription factor that binds to the abscisic acid (ABA)-responsive element (ABRE) motif in the promoter region of ABA-inducible genes. Here, we show that expression of the intact AREB1 gene on its own is insufficient to lead to expression of downstream genes under normal growth conditions. To overcome the masked transactivation activity of AREB1, we created an activated form of AREB1 (AREB1
QT). AREB1QT-overexpressing plants showed ABA hypersensitivity and enhanced drought tolerance, and eight genes with two or more ABRE motifs in the promoter regions in two groups were greatly upregulated: late embryogenesis abundant class genes and ABA- and drought stress-inducible regulatory genes. By contrast, an areb1 null mutant and a dominant loss-of-function mutant of AREB1 (AREB1:RD) with a repression domain exhibited ABA insensitivity. Furthermore, AREB1:RD plants displayed reduced survival under dehydration, and three of the eight greatly upregulated genes were downregulated, including genes for linker histone H1 and AAA ATPase, which govern gene expression and multiple cellular activities through protein folding, respectively. Thus, these data suggest that AREB1 regulates novel ABRE-dependent ABA signaling that enhances drought tolerance in vegetative tissues.
