An ABRE Promoter Sequence is Involved in Osmotic Stress-Responsive Expression of the DREB2A Gene, Which Encodes a Transcription Factor Regulating Drought-Inducible Genes in Arabidopsis

Abstract

In plants, osmotic stress-responsive transcriptional regulation depends mainly on two major classes of cis-acting elements found in the promoter regions of stress-inducible genes: ABA-responsive elements (ABREs) and dehydration-responsive elements (DREs). ABRE has been shown to perceive ABA-mediated osmotic stress signals, whereas DRE is known to be involved in an ABA-independent pathway. Previously, we reported that the transcription factor DRE-BINDING PROTEIN 2A (DREB2A) regulates DRE-mediated transcription of target genes under osmotic stress conditions in Arabidopsis (Arabidopsis thaliana). However, the transcriptional regulation of DREB2A itself remains largely uncharacterized. To elucidate the transcriptional mechanism associated with the DREB2A gene under osmotic stress conditions, we generated a series of truncated and base-substituted variants of the DREB2A promoter and evaluated their transcriptional activities individually. We found that both ABRE and coupling element 3 (CE3)-like sequences located approximately -100 bp from the transcriptional initiation site are necessary for the dehydration-responsive expression of DREB2A. Coupling our transient expression analyses with yeast one-hybrid and chromatin immunoprecipitation (ChIP) assays indicated that the ABRE-BINDING PROTEIN 1 (AREB1), AREB2 and ABRE-BINDING FACTOR 3 (ABF3) bZIP transcription factors can bind to and activate the DREB2A promoter in an ABRE-dependent manner. Exogenous ABA application induced only a modest accumulation of the DREB2A transcript when compared with the osmotic stress treatment. However, the osmotic stress-induced DREB2A expression was found to be markedly impaired in several ABA-deficient and ABA-insensitive mutants. These results suggest that in addition to an ABA-independent pathway, the ABA-dependent pathway plays a positive role in the osmotic stress-responsive expression of DREB2A.

Arabidopsis GROWTH-REGULATING FACTOR7 Functions as a Transcriptional Repressor of Abscisic Acid– and Osmotic Stress–Responsive Genes, Including DREB2A

“…In a previous report, we performed a truncation analysis of the DREB2A promoter under dehydration stress conditions (Kim et al, 2011). Arabidopsis plants containing various promoter-GUS (for b-glucuronidase) constructs were exposed to controlled dehydration conditions, and the transcript levels of endogenous DREB2A and GUS were measured by quantitative RT-PCR (qRT-PCR).…”

“…Recently, three heat shock transcription factors, HsfA1a, HsafA1b, and HsfA1d, were demonstrated to play critical roles in the heat stress-induced expression of DREB2A via a heat shock element in the promoter region (Liu et al, 2011;Yoshida et al, 2011). In the osmotic stress response, an abscisic acid-responsive element (ABRE) and a coupling element 3-like sequence in the promoter region were identified as essential cis-elements (Kim et al, 2011). The ABRE binding proteins/factors (AREBs/ABFs) were found to be major transcription factors that activate the transcription of DREB2A via the ABRE sequence in response to osmotic stress; however, the transcription factors that recognize the coupling element 3-like sequence have not been identified (Kim et al, 2011).…”

“…In the osmotic stress response, an abscisic acid-responsive element (ABRE) and a coupling element 3-like sequence in the promoter region were identified as essential cis-elements (Kim et al, 2011). The ABRE binding proteins/factors (AREBs/ABFs) were found to be major transcription factors that activate the transcription of DREB2A via the ABRE sequence in response to osmotic stress; however, the transcription factors that recognize the coupling element 3-like sequence have not been identified (Kim et al, 2011).…”

GmDREB2A;2, a Canonical DEHYDRATION-RESPONSIVE ELEMENT-BINDING PROTEIN2-Type Transcription Factor in Soybean, Is Posttranslationally Regulated and Mediates Dehydration-Responsive Element-Dependent Gene Expression

“…1, A and B;Kim et al, 2011). GmDREB2A;2 was targeted to the nucleus and exhibited significant transactivation activity toward the DRE-containing reporter in Arabidopsis and soybean protoplasts (Fig.…”

“…The transcription of DREB2A in response to dehydration and heat shock is independently regulated by different regions in the DREB2A promoter Yoshida et al, 2011). The region that is responsible for dehydration inducibility contains two essential elements, a coupling element3-like sequence and an ABA-responsive element (ABRE; Kim et al, 2011), while a heat shock element in another region is necessary for the inducibility of DREB2A in response to heat shock . The inducibility in response to stress conditions is a common feature among DREB2-type transcription factors of various plants, and the promoter structure including these cis-elements is conserved among many eudicot species Mizoi et al, 2012).…”