In higher plants, DREB1/CBF-type transcription factors play an important role in tolerance to low temperatures, drought, and high-salt stress. These transcription factors bind to CRT/DRE elements in promoter regions of target genes, regulating their expression. In this study, we cloned and characterized a novel gene encoding a DREB1 transcription factor from dwarf apple, Malus baccata (GenBank accession number: EF582842). Expression of MbDREB1 was induced by cold, drought, and salt stress, and also in response to exogenous ABA. Subcellular localization analyses revealed that MbDREB1 localizes in the nucleus. A yeast activity assay demonstrated that the MbDREB1 gene encodes a transcription activator, which specifically binds to DRE/CRT elements. Compared with wild-type plants, transgenic Arabidopsis overexpressing MbDREB1 showed increased tolerance to low temperature, drought, and salt stresses. Analysis of the MbDREB1 promoter revealed an ABA-responsive element (ABRE), an inducer of CBF expression 1 (ICE1)-like binding site, two MYB recognition sites, and three stress-inducible GT-1 boxes. GUS activities driven by the MbDREB1 promoter in transgenic Arabidopsis increased in response to ABA, cold temperature, drought, and salt treatments. Interestingly, the expression of both ABA-independent and ABA-dependent stress-induced genes (COR15a and rd29B, respectively) was activated under normal growth conditions in Arabidopsis overexpressing MbDREB1. These results suggest that MbDREB1 functions as a transcription factor and increases plant tolerance to low temperature, drought, and salt stress via both ABA-dependent and ABA-independent pathways.
BackgroundPlants involved in highly complex and well-coordinated systems have evolved a considerable degree of developmental plasticity, thus minimizing the damage caused by stress. MicroRNAs (miRNAs) have recently emerged as key regulators in gene regulation, developmental processes and stress tolerance in plants.ResultsIn this study, soybean miRNAs associated with stress responses (drought, salinity, and alkalinity) have been identified and analyzed in combination with deep sequencing technology and in-depth bioinformatics analysis. One hundred and thirty three conserved miRNAs representing 95 miRNA families were expressed in soybeans under three treatments. In addition, 71, 50, and 45 miRNAs are either uniquely or differently expressed under drought, salinity, and alkalinity, respectively, suggesting that many miRNAs are inducible and are differentially expressed in response to certain stress.ConclusionOur study has important implications for further identification of gene regulation under abiotic stresses and significantly contributes a complete profile of miRNAs in Glycine max.
The topmost 16 metres of the loess section at Xifeng (central Chinese loess plateau), which cover the last 128000 years, consist of two palaeosol beds interlayered by a loess horizon. Hysteresis parameters, frequency-dependent, field-and temperaturedependent susceptibility show very similar and stable magnetic mineral constituents in both loess and palaeosol samples. The concentration and grain size of magnetite, maghaemite and haematite control the magnetic properties of Chinese loess. Susceptibility and loess thickness are closely related to geographic position and (present) climate across the loess plateau. The loess and palaeosol magnetic properties are largely controlled by the fine-grained magnetite formed in various quantities and grain sizes under the influence of pedogenesis during variable palaeoclimatic conditions. Therefore regional and global palaeoclimatic development during the last 2.5 Myr can be reconstructed from susceptibility records in the loess plateau.
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