Mol Genet Genomics (2011) 286:321–332 DOI 10.1007/s00438-011-0647-7 123 ORIGINAL PAPER Arabidopsis HsfA1 transcription factors function as the main positive regulators in heat shock-responsive gene expression Takumi Yoshida · Naohiko Ohama · Jun Nakajima · Satoshi Kidokoro · Junya Mizoi · Kazuo Nakashima · Kyonoshin Maruyama · Jong-Myong Kim · Motoaki Seki · Daisuke Todaka · Yuriko Osakabe · Yoh Sakuma · Friedrich SchöZ · Kazuo Shinozaki · Kazuko Yamaguchi-Shinozaki Received: 28 April 2011 / Accepted: 29 August 2011 / Published online: 20 September 2011  Springer-Verlag 2011 Abstract Arabidopsis DREB2A is a key transcription factor of heat- and drought-responsive gene expression, and DREB2A expression is induced by these stresses. We ana- lyzed the DREB2A promoter and found a heat shock ele- ment that functions as a cis-acting element in the heat shock (HS)-responsive expression of DREB2A. Among the 21 Arabidopsis heat shock factors, we chose 4 HsfA1-type proteins as candidate transcriptional activators (HsfA1a, HsfA1b, HsfA1d, and HsfA1e) based on transactivation activity and expression patterns. We generated multiple mutants and found that the HS-responsive expression of DREB2A disappeared in hsfa1a/b/d triple and hsfa1a/b/d/e quadruple mutants. Moreover, HS-responsive gene expres- sion, including that of molecular chaperones and transcrip- tion factors, was globally and drastically impaired in the hsfa1a/b/d triple mutant, which exhibited greatly reduced tolerance to HS stress. HsfA1 protein accumulation in the nucleus was negatively regulated by their interactions with HSP90, and other factors potentially strongly activate the HsfA1 proteins under HS stress. The hsfa1a/b/d/e quadru- ple mutant showed severe growth retardation, and many genes were downregulated in this mutant even under non- stress conditions. Our study indicates that HsfA1a, HsfA1b, and HsfA1d function as main positive regulators in HS- responsive gene expression and four HsfA1-type proteins are important in gene expression for normal plant growth. Keywords Heat shock transcription factors · DREB2A · Heat stress tolerance · HSP90 · Plant growth Abbreviations BiFC Bimolecular Xuorescence complementation CFP Cyan Xuorescent protein ChIP Chromatin immunoprecipitation DRE Dehydration-responsive element DREB2A Dehydration-responsive element binding protein 2A GDA Geldanamycin GFP Green Xuorescent protein GM Germination medium GUS -Glucuronidase HS Heat shock HSE Heat shock element HSF Heat shock factor HSP Heat shock protein LUC Luciferase Communicated by A. Schnittger. Electronic supplementary material The online version of this article (doi:10.1007/s00438-011-0647-7) contains supplementary material, which is available to authorized users. T. Yoshida · N. Ohama · J. Nakajima · S. Kidokoro · J. Mizoi · D. Todaka · Y. Osakabe · Y. Sakuma · K. Yamaguchi-Shinozaki (&) Laboratory of Plant Molecular Physiology, Graduate School of Agricultural and Life Sciences, The University of Tokyo, Tokyo 113-8657, Japan e-mail: akys@mail.ecc.u-tokyo.ac.jp S. Kidokoro · J. Mizoi · K. Nakashima · K. Maruyama · D. Todaka · Y. Sakuma · K. Yamaguchi-Shinozaki Biological Resources and Post-harvest Division, Japan International Research Center for Agricultural Sciences, Tsukuba, Ibaraki 305-8686, Japan J.-M. Kim · M. Seki · K. Shinozaki RIKEN Plant Science Center, Yokohama, Kanagawa 230-0045, Japan F. SchöZ ZMBP-Allgemeine Genetik, Universitaet Tübingen, 72075 Tübingen, Germany