ORIGINAL ARTICLE VuDREB2A, a novel DREB2-type transcription factor in the drought-tolerant legume cowpea, mediates DRE-dependent expression of stress-responsive genes and confers enhanced drought resistance in transgenic Arabidopsis Ayan Sadhukhan • Yasufumi Kobayashi • Yuriko Kobayashi • Mutsutomo Tokizawa • Yoshiharu Y. Yamamoto • Satoshi Iuchi • Hiroyuki Koyama • Sanjib Kumar Panda • Lingaraj Sahoo Received: 16 April 2014 / Accepted: 17 June 2014 / Published online: 17 July 2014 Ó Springer-Verlag Berlin Heidelberg 2014 Abstract Main conclusion VuDREB2A exists in cowpea as a canonical DREB2-type transcription factor, having the ability to bind dehydration-responsive elements in vitro and confer enhanced drought resistance in transgenic Arabidopsis. Cowpea (Vigna unguiculata L. Walp) is an important cultivated legume that can survive better in arid conditions than other crops. But the molecular mechanisms involved in the drought tolerance of this species remain elusive with very few reported candidate genes. The Dehydration- Responsive Element-Binding Protein2 (DREB2) group of transcription factors plays key roles in plant responses to drought. However, no DREB2 ortholog has been reported from cowpea so far. In this study, we isolated and characterized a gene from cowpea, namely VuDREB2A, encoding a protein of 377 amino acids exhibiting features of reported DREB2-type proteins. In cowpea, VuDREB2A transcript accumulation was highly induced by desiccation, heat and salt, but slightly by exogenous abscisic acid (ABA) treatment. We also isolated the VuDREB2A pro- moter and predicted stress-responsive cis-elements in it using Arabidopsis microarray data. The E. coli-expressed VuDREB2A protein showed binding to synthetic oligo- nucleotides with Dehydration-Responsive Elements (DREs) from Arabidopsis, in electrophoretic mobility shift assays. Heterologous expression of VuDREB2A in Arabidopsis significantly improved plant survival under drought. In addition, overexpression of a truncated ver- sion of VuDREB2A, after removal of a putative negative regulatory domain (between amino acids 132–182) led to a dwarf phenotype in the transgenic plants. Microarray and quantitative PCR analyses of VuDREB2A over- expressing Arabidopsis revealed up-regulation of stress- responsive genes having DRE overrepresented in their promoters. In summary, our results indicate that Vu- DREB2A conserves the basic functionality and mode of regulation of DREB2A in Arabidopsis and could be a potent candidate gene for the genetic improvement of drought resistance in cowpea. Keywords Arabidopsis Á Cis-elements Á Cowpea Á DREB2A Á Drought Abbreviations ABA Abscisic acid ABRE ABA-responsive element DRE Dehydration-responsive element DREB DRE-binding protein EMSA Electrophoretic mobility shift assay Electronic supplementary material The online version of this article (doi:10.1007/s00425-014-2111-5) contains supplementary material, which is available to authorized users. A. Sadhukhan Á L. Sahoo (&) Department of Biotechnology, Indian Institute of Technology Guwahati, Guwahati 781039, Assam, India e-mail: ls@iitg.ernet.in Y. Kobayashi Á Y. Kobayashi Á M. Tokizawa Á Y. Y. Yamamoto Á H. Koyama Laboratory of Plant Cell Technology, Faculty of Applied Biological Sciences, Gifu University, Gifu 501-1193, Japan S. Iuchi RIKEN BioResource Center Tsukuba, Tsukuba, Ibaraki 305-0074, Japan S. K. Panda Department of Life Science and Bioinformatics, Assam University, Silchar 788011, India 123 Planta (2014) 240:645–664 DOI 10.1007/s00425-014-2111-5