Abstract
The C-repeat (CRT)/dehydration-responsive element (DRE) binding factor (CBF/DREB1) transcription factors play a key role in cold response. However, the detailed roles of many plant CBFs are far from fully understood. A CBF gene (SsCBF1) was isolated from the cold-hardy plant Solanum lycopersicoides. A subcellular localization study using GFP fusion protein indicated that SsCBF1 is localized in the nucleus. We delimited the SsCBF1 transcriptional activation domain to the C-terminal segment comprising amino acid residues 193–228 (SsCBF1193–228). The expression of SsCBF1 could be dramatically induced by cold, drought and high salinity. Transactivation assays in tobacco leaves revealed that SsCBF1 could specifically bind to the CRT cis-elements in vivo to activate the expression of downstream reporter genes. The ectopic overexpression of SsCBF1 conferred increased freezing and high-salinity tolerance and late flowering phenotype to transgenic Arabidopsis. RNA-sequencing data exhibited that a set of cold and salt stress responsive genes were up-regulated in transgenic Arabidopsis. Our results suggest that SsCBF1 behaves as a typical CBF to contribute to plant freezing tolerance. Increased resistance to high-salinity and late flowering phenotype derived from SsCBF1 OE lines lend more credence to the hypothesis that plant CBFs participate in diverse physiological and biochemical processes related to adverse conditions.
Highlights
During the long evolutionary history, plants have developed various strategies to cope with environmental stresses such as drought, high salinity and low temperature
The CBF transcription factors are the key components mediating the activation of many cold-responsive genes [1,3]
A new cold-regulated transcription factor gene was successfully isolated from S. lycopersicoides using rapid amplification of cDNA ends (RACE) method and designated as SsCBF1
Summary
During the long evolutionary history, plants have developed various strategies to cope with environmental stresses such as drought, high salinity and low temperature. An essential cis-acting element, C-repeat (CRT) or dehydrationresponsive element (DRE), was commonly found in the promoter regions of many low-temperature and drought-responsive genes [4,5,6,7]. Two types of AP2 domain-containing transcription factors which bind to the CRT/DRE element and activate the expression of downstream genes were isolated using yeast onehybrid screening [5,8]. The first type, called C-repeat Binding Factor/DRE Binding protein 1 (CBF/DREB1), could recognize the regulatory CRT/DRE element present in the promoters of many cold-inducible genes. The second type of transcription factors, called DRE binding protein 2 (DREB2), are encoded by the genes that are induced by dehydration and salt stresses but not by low temperature stress [8,10]
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