A Novel Sweetpotato WRKY Transcription Factor, IbWRKY2, Positively Regulates Drought and Salt Tolerance in Transgenic Arabidopsis.

Hong Zhu,Yuanyuan Zhou,Qingchang Liu,Ning Zhao,Hong Zhai,Shaozhen He

doi:10.3390/biom10040506

Abstract

WRKYs play important roles in plant growth, defense regulation, and stress response. However, the mechanisms through which WRKYs are involved in drought and salt tolerance have been rarely characterized in sweetpotato [Ipomoea batatas (L.) Lam.]. In this study, we cloned a WRKY gene, IbWRKY2, from sweetpotato and its expression was induced with PEG6000, NaCl, and abscisic acid (ABA). The IbWRKY2 was localized in the nucleus. The full-length protein exhibited transactivation activity, and its active domain was located in the N-terminal region. IbWRKY2-overexpressing Arabidopsis showed enhanced drought and salt tolerance. After drought and salt treatments, the contents of ABA and proline as well as the activity of superoxide dismutase (SOD) were higher in transgenic plants, while the malondialdehyde (MDA) and H2O2 contents were lower. In addition, several genes related to the ABA signaling pathway, proline biosynthesis, and the reactive oxygen species (ROS)-scavenging system, were significantly up-regulated in transgenic lines. These results demonstrate that IbWRKY2 confers drought and salt tolerance in Arabidopsis. Furthermore, IbWRKY2 was able to interact with IbVQ4, and the expression of IbVQ4 was induced by drought and salt treatments. These results provide clues regarding the mechanism by which IbWRKY2 contributes to the regulation of abiotic stress tolerance.

Highlights

Ever-changing environmental stresses, such as drought, high salinity, and extreme temperature, have become increasingly major constraints for crop production [1,2]
The result showed that this protein shared the highest identity with AtWRKY2 and AtWRKY34, and the amino acid sequence of this protein shared 51.98% and 43.00% similarity to AtWRKY2 and AtWRKY34, respectively; for this reason, it was designated as IbWRKY2 (Figure 1a)
Multiple protein sequence alignments among IbWRKY2 and homeotic WRKYs of other plants showed that IbWRKY2 possessed two highly conserved WRKY domains, both composed of 58 aa, belonging to WRKY transcription factors (TFs) family group I (Figure 1b)

Summary

Introduction

Ever-changing environmental stresses, such as drought, high salinity, and extreme temperature, have become increasingly major constraints for crop production [1,2]. To respond and adapt to these environmental stresses, plants activate a series of elaborate and sensitive defense mechanisms to promote their survival [5,6]. A change in the expression of genes, especially transcription factors (TFs), is generally the earliest response to stress conditions, and TFs often act as central regulators and molecular switches in stress signal transduction and adaptation networks [9,10,11]. A large number of TF families, such as NAC, MYB, bHLH, and WRKY, have been demonstrated to participate in the regulation of stress responses and tolerance in plants [12]

Methods

Results

Discussion

Conclusion