A Cryophyte Transcription Factor, CbABF1, Confers Freezing, and Drought Tolerance in Tobacco.

Xiule Yue,Zhixing Zhao,Lizhe An,Mengjun Sui,Zhenyu Wang,Yulan Shi,Guanghua Meng,Xiaohong Pu,Zhen Zhao,Guoyan Zhang,Jinli Yue,Yi Zhan

doi:10.3389/fpls.2019.00699

Abstract

Abscisic acid responsive element binding factors (ABFs) play crucial roles in plant responses to abiotic stress. However, little is known about the roles of ABFs in alpine subnival plants, which can survive under extreme environmental conditions. Here, we cloned and characterized an ABF1 homolog, CbABF1, from the alpine subnival plant Chorispora bungeana. Expression of CbABF1 was induced by cold, drought, and abscisic acid. Subcellular localization analysis revealed that CbABF1 was located in the nucleus. Further, CbABF1 had transactivation activity, which was dependent on the N-terminal region containing 89 residues. A Snf1-related protein kinase, CbSnRK2.6, interacted with CbABF1 in yeast two-hybrid analysis and bimolecular fluorescence complementation assays. Transient expression assay revealed that CbSnRK2.6 enhanced the transactivation of CbABF1 on ABRE cis-element. We further found that heterologous expression of CbABF1 in tobacco improved plant tolerance to freezing and drought stress, in which the survival rates of the transgenic plants increased around 40 and 60%, respectively, compared with wild-type plants. Moreover, the transgenic plants accumulated less reactive oxygen species, accompanied by high activities of antioxidant enzymes and elevated expression of stress-responsive genes. Our results thus suggest that CbABF1 is a transcription factor that plays an important role in cold and drought tolerance and is a candidate gene in molecular breeding of stress-tolerant crops.

Highlights

Plant growth, development, and productivity can be adversely affected by environmental stresses including cold, drought and high salinity
The deduced protein has a basic leucine zipper (bZIP) domain of 54 amino acids composed of a leucine zipper and a basic region, four conserved phosphorylation sites (C1–C4), and a putative nuclear localization signal (NLS) (Uno et al, 2000), but lacked a glutamine-rich domain and a casein kinase II phosphorylation site compare with ABF1 in Arabidopsis (Figure 2A)
Based on the analysis of conserved domains and phylogenetic comparisons with other acid responsive element binding factors (ABFs)/ABRE-binding proteins (AREBs) proteins, we concluded that CbABF1 belonged to the subfamily of AREB in the bZIP family (Jakoby et al, 2002), and designated it C. bungeana ABF1 (CbABF1)

Summary

Introduction

Development, and productivity can be adversely affected by environmental stresses including cold, drought and high salinity. CbABF1 a Cryophyte Transcription Factor elements in the promoters of stress-responsive genes, enabling the plant to withstand adverse environmental conditions (Cutler et al, 2010; Song et al, 2016). Among these transcription factors, basic leucine zipper (bZIP) is a large family that harbors a bZIP domain containing a basic region and a leucine zipper (Jakoby et al, 2002); many of these factors have important functions in plant stress-response and hormone signal transduction (Kim, 2005). Several ABF/AREB transcription factors have been characterized in Arabidopsis thaliana (Yoshida et al, 2015; Wang et al, 2018), rice (Oryza sativa) (Xiang et al, 2008; Amir Hossain et al, 2010), wheat (Triticum aestivum) (Johnson et al, 2008), soybean (Glycine max) (Gao et al, 2011), and tomato (Solanum lycopersicum) (Orellana et al, 2010)

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Conclusion