Abstract
C-repeat (CRT)/dehydration responsive element (DRE)-binding factor CBFs, a small family of genes encoding transcriptional activators, play important roles in plant cold tolerance. In this study, a comprehensive genome-wide analysis was carried out to identify and characterize the functional dynamics of CsCBFs in tea plant (Camellia sinensis). A total of 6 CBF genes were obtained from the tea plant genome and named CBF1-6. All of the CsCBFs had an AP2/ERF DNA-binding domain and nuclear localization signal (NLS) sequence. CsCBF-eGFP fusion and DAPI staining analysis confirmed the nuclear localization of the CsCBFs. Transactivation assays showed that the CsCBFs, except CsCBF1, had transcriptional activity. CsCBF expression was differentially induced by cold, heat, PEG, salinity, ABA, GA, MeJA, and SA stresses. In particular, the CsCBF genes were significantly induced by cold treatments. To further characterize the functions of CsCBF genes, we overexpressed the CsCBF3 gene in Arabidopsis thaliana plants. The resulting transgenic plants showed increased cold tolerance compared with the wild-type Arabidopsis plant. The enhanced cold tolerance of the transgenic plants was potentially achieved through an ABA-independent pathway. This study will help to increase our understanding of CsCBF genes and their contributions to stress tolerance in tea plants.
Highlights
Abiotic stresses in the natural environment, including low temperature, drought, and high salinity, seriously affect the growth, development, distribution, and productivity of plants (Kulik et al, 2011)
Alignment of the sequences obtained from cDNA and genomic DNA indicated that the CsCBF genes were intronless
The results indicated that CsCBF2, CsCBF3, CsCBF4, CsCBF5, and CsCBF6 have transcriptional activity, while CsCBF1 has no transcriptional activity (Figure 5)
Summary
Abiotic stresses in the natural environment, including low temperature, drought, and high salinity, seriously affect the growth, development, distribution, and productivity of plants (Kulik et al, 2011). Previous studies have identified a number of CBF/DREB1 genes and verified their functions in Arabidopsis thaliana (Novillo et al, 2007) and other plant species, such as cotton (Gossypium hirsutum) (Shan et al, 2007), wheat (Triticum aestivum) (Shen et al, 2003), rice (Oryza sativa) (Wang et al, 2008), maize (Zea mays) (Qin et al, 2004), soybean (Glycine max) (Kidokoro et al, 2015), and tomato (Lycopersicon esculentum) (Zhang et al, 2004) These findings suggested the conserved roles of CBF/DREB1 genes in the regulation of freezing tolerance across diverse plant species. In addition to the cold response, CBFs could respond to other abiotic stresses and hormones, such as heat, drought, salt, and abscisic acid (ABA) (Dubouzet et al, 2003; Xiao et al, 2006; Nada and Abogadallah, 2015)
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