Abstract
Cold stress is a major environmental factor that impairs plant growth and development, geographic distribution, and crop productivity. The C-repeat binding factor (CBF) regulatory pathway has an essential role in response to cold stress. Here, we characterized a bHLH transcription factor from Nicotiana tabacum, NtbHLH123, in response to cold stress (4°C). Overexpression of NtbHLH123 enhanced cold tolerance in transgenic tobacco plants. Based on yeast one-hybrid, chromatin immunoprecipitation PCR, and transient expression analysis assays, NtbHLH123 binds directly to the G-box/E-box motifs in the promoter of the NtCBF genes and positively regulates their expression. Furthermore, NtbHLH123-overexpressing plants showed lower electrolyte leakage, reduced malondialdehyde contents, H2O2 and reactive oxygen species (ROS) accumulation under cold stress, which contributed to alleviating oxidative damage to the cell membrane after cold stress treatment. And NtbHLH123 increased stress tolerance by improving the expression of a number of abiotic stress-responsive genes to mediate the ROS scavenging ability and other stress tolerance pathways. Taken together, we present a model suggesting that NtbHLH123 is a transcriptional activator that functions as a positive regulator of cold tolerance by activating NtCBF, ROS scavenging-related, and stress-responsive genes.
Highlights
Many environmental factors limit the growth and development, geographic distribution, yield, and quality of crop plants (Xiong et al, 2002)
Cold stress can rapidly induce the expression of many transcription factors (TFs), such as C-repeat-binding factor/dehydration-responsive binding protein (CBF/DREB), ABA-responsive element-binding protein/ABAbinding factor, APETALA2 (AP2)/ethylene responsive factor, basic region/leucine zipper motif, MYB, basic helix-loophelix, and NAM, ATAF1, 2, and CUC2 (NAC) families, which in turn bind the promoter of numerous stress-responsive genes and regulate their expression (Chinnusamy et al, 2003; Vogel et al, 2005; Agarwal et al, 2006; Yamaguchi-Shinozaki and Shinozaki, 2006; Puranik et al, 2012; Shi et al, 2012)
Transcriptome analysis, which was conducted using cDNA samples extracted from tobacco seedlings treated with or without cold stress, showed that NtbHLH123 was upregulated by cold treatment (Jin et al, 2017), suggesting that NtbHLH123 might be a cold-responsive basic helix-loophelix (bHLH) TF gene
Summary
Many environmental factors (e.g., high or low temperature, salt and drought) limit the growth and development, geographic distribution, yield, and quality of crop plants (Xiong et al, 2002). NtbHLH123 Regulates the Cold Tolerance of plants, including phosphatases, protein kinases, transcription factors (TFs), and so on (Pearce, 1999; Shinozaki and Yamaguchi-Shinozaki, 2000). Cold stress can rapidly induce the expression of many TFs, such as C-repeat-binding factor/dehydration-responsive binding protein (CBF/DREB), ABA-responsive element-binding protein/ABAbinding factor, APETALA2 (AP2)/ethylene responsive factor, basic region/leucine zipper motif (bZIP), MYB, basic helix-loophelix (bHLH), and NAM, ATAF1, 2, and CUC2 (NAC) families, which in turn bind the promoter of numerous stress-responsive genes and regulate their expression (Chinnusamy et al, 2003; Vogel et al, 2005; Agarwal et al, 2006; Yamaguchi-Shinozaki and Shinozaki, 2006; Puranik et al, 2012; Shi et al, 2012)
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