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Mar Biotechnol (2014) 16:657673 DOI 10.1007/s10126-014-9582-z
ORIGINAL ARTICLE
A Dehydration-Responsive Element Binding (DREB) Transcription Factor from the Succulent Halophyte Salicornia brachiata Enhances Abiotic Stress Tolerancein Transgenic Tobacco
Kapil Gupta & Bhavanath Jha & Pradeep K. Agarwal
Received: 23 November 2013 /Accepted: 3 June 2014 /Published online: 15 July 2014 # Springer Science+Business Media New York 2014
Abstract Dehydration-responsive element binding (DREB) transcription factor (TF) plays a key role for abiotic stress tolerance in plants. Earlier, we have published the isolation and characterisation of an A-2-type SbDREB2A TF from an extreme halophyte Salicornia brachiata. The SbDREB2A protein lacks potential proline (P), glutamic acid (E), serine(S) and threonine (T) (PEST) sequence which is known to act as signal peptide for protein degradation. In this study, SbDREB2A TF was over-expressed in tobacco plants without any modification in polypeptide sequence. Transgenic plants showed better seed germination and growth characteristics in both hyperionic and hyperosmotic stresses. Transgenic plants exhibited higher water content, membrane stability and less electrolyte leakage in stress conditions. The transgenic plants accumulated less Na+ and higher K+ than wildtype (WT) plants. The transgenic plants revealed higher chlorophyll content, water use efficiency (WUE) and net photosynthesis rate. Transgenics exhibited higher level of proline and low amount of MDA and H2O2 under stress conditions. The real-time PCR of transgenics showed higher expression of downstream heat shock genes (Hsp18, Hsp26 and Hsp70), TFs (AP2 domain containing TF, HSF2 and ZFP), signalling components (PLC3 and Ca2+/calmodulin) and dehydrins (ERD10B, ERD10D and LEA5) under different abiotic stress treatments.
Keywords Abiotic stress tolerance . Salicornia brachiata . SbDREB2A . Transgenics
Introduction
The abiotic stresses like salinity, drought and high temperature negatively affect plant growth and productivity. Plants follow different adaptation strategies at physiological, biochemical and molecular level to resist these challenges. Numerous abiotic stress-related genes and transcription factors (TFs) have been isolated from different plant species and over-expressed in homologous and heterologous systems to engineer stress tolerance (Agarwal et al. 2012). TFs up-regulate specific set of stress-responsive genes by interacting with cis-elements in the promoter region of the target genes, as well as other regulatory proteins to provide stress tolerance (Chen and Zhu 2004; Yamaguchi-Shinozaki and Shinozaki 2006; Agarwal et al. 2006). AP2/EREBP is an important TF family and plays a crucial role...