Abstract
Soybean (Glycine max) is an important crop around the world. Abiotic stress conditions, such as drought and heat, adversely affect its survival, growth, and production. The DEHYDRATION-RESPONSIVE ELEMENT-BINDING PROTEIN2 (DREB2) group includes transcription factors that contribute to drought and heat stress tolerance by activating transcription through the cis-element dehydration-responsive element (DRE) in response to these stress stimuli. Two modes of regulation, transcriptional and posttranslational, are important for the activation of gene expression by DREB2A in Arabidopsis (Arabidopsis thaliana). However, the regulatory system of DREB2 in soybean is not clear. We identified a new soybean DREB2 gene, GmDREB2A;2, that was highly induced not only by dehydration and heat but also by low temperature. GmDREB2A;2 exhibited a high transactivation activity via DRE and has a serine/threonine-rich region, which corresponds to a negative regulatory domain of DREB2A that is involved in its posttranslational regulation, including destabilization. Despite the partial similarity between these sequences, the activity and stability of the GmDREB2A;2 protein were enhanced by removal of the serine/threonine-rich region in both Arabidopsis and soybean protoplasts, suggestive of a conserved regulatory mechanism that involves the recognition of serine/threonine-rich sequences with a specific pattern. The heterologous expression of GmDREB2A;2 in Arabidopsis induced DRE-regulated stress-inducible genes and improved stress tolerance. However, there were variations in the growth phenotypes of the transgenic Arabidopsis, the induced genes, and their induction ratios between GmDREB2A;2 and DREB2A. Therefore, the basic function and regulatory machinery of DREB2 have been maintained between Arabidopsis and soybean, although differentiation has also occurred.
Highlights
Soybean (Glycine max) is an important crop around the world
The regulatory mechanism of stability by negative regulatory domain (NRD) is not clear. Whether this posttranslational regulation is common among other plant species is unclear, the removal of a region that corresponds to the DEHYDRATION-RESPONSIVE ELEMENT-BINDING PROTEIN2A (DREB2A) NRD from MtDREB2A of Medicago truncatula enhanced activity in yeast (Saccharomyces cerevisiae; Chen et al, 2009a)
We reported that the DEHYDRATION-RESPONSIVE ELEMENT-BINDING PROTEIN2 (DREB2)-type transcription factors in Arabidopsis and rice are classified into four subtypes (Matsukura et al, 2010)
Summary
Soybean (Glycine max) is an important crop around the world. Abiotic stress conditions, such as drought and heat, adversely affect its survival, growth, and production. 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 (Kim et al, 2011; Mizoi et al, 2012). The overexpression of DREB2A CA in transgenic Arabidopsis resulted in the induction of dehydrationor heat shock-inducible genes and enhanced tolerance to both drought and heat shock, indicating the substantial importance of posttranslational regulation (Sakuma et al, 2006a, 2006b). The regulatory mechanism of stability by NRD is not clear Whether this posttranslational regulation is common among other plant species is unclear, the removal of a region that corresponds to the DREB2A NRD from MtDREB2A of Medicago truncatula enhanced activity in yeast (Saccharomyces cerevisiae; Chen et al, 2009a)
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