A Novel Wheat C-bZIP Gene, TabZIP14-B, Participates in Salt and Freezing Tolerance in Transgenic Plants.

Lina Zhang,Lichao Zhang,Lifeng Gao,Guangyao Zhao,Jizeng Jia,Chenyang Hao,Xiuying Kong,Chuan Xia

doi:10.3389/fpls.2017.00710

Abstract

The group C-bZIP transcription factors (TFs) are involved in diverse biological processes, such as the regulation of seed storage protein (SSP) production and the responses to pathogen challenge and abiotic stress. However, our knowledge of the abiotic functions of group C-bZIP genes in wheat remains limited. Here, we present the function of a novel TabZIP14-B gene in wheat. This gene belongs to the group C-bZIP TFs and contains six exons and five introns; three haplotypes were identified among accessions of tetraploid and hexaploid wheat. A subcellular localization analysis indicated that TabZIP14-B was targeted to the nucleus of tobacco epidermal cells. A transactivation assay demonstrated that TabZIP14-B showed transcriptional activation ability and was capable of binding the abscisic acid (ABA) responsive element (ABRE) in yeast. RT-qPCR revealed that TabZIP14-B was expressed in the roots, stems, leaves, and young spikes and was up-regulated by exogenous ABA, salt, low-temperature, and polyethylene glycol (PEG) stress treatments. Furthermore, Arabidopsis plants overexpressing TabZIP14-B exhibited enhanced tolerance to salt, freezing stresses and ABA sensitivity. Overexpression of TabZIP14-B resulted in increased expression of the AtRD29A, AtCOR47, AtRD20, AtGSTF6, and AtRAB18 genes and changes in several physiological characteristics. These results suggest that TabZIP14-B could function as a positive regulator in mediating the abiotic stress response.

Highlights

Wheat is widely cultivated around the world
The promoter region of TabZIP14-B carried the abiotic stressresponsive elements LTR and MBS, the biotic stress-related elements TCA and ERE, and light-responsive elements. These regulatory elements suggest that TabZIP14-B is involved in plant development and stress tolerance; TabZIP14-B was upregulated when wheat seedlings were stressed by salt, lowtemperature, polyethylene glycol (PEG) and abscisic acid (ABA) treatments, and overexpression of TabZIP14-B could increase plant tolerance to salt and freezing but could not yield drought tolerance
This result is consistent with previous reports on other C-basic leucine zipper (bZIP) transcription factors (TFs), such as GmbZIP62 (Liao et al, 2008), possibly because TabZIP14-B is heterologously expressed in Arabidopsis plants

Summary

Introduction

Wheat is widely cultivated around the world. Unfavorable conditions restrict wheat growth, development, and yields. The improvement of abiotic tolerance is a significant challenge in wheat breeding program, and novel gene discovery and utilization are critical for improving the tolerance of wheat to adverse conditions. Transcription factors (TFs) are vital regulators that mediate abiotic stress signal transduction. The basic leucine zipper (bZIP) TF is a large family characterized by a conserved bZIP domain with a basic region and a leucine zipper. Proteins of the bZIP family can bind to ACGT cis-elements, including abscisic acid (ABA) responsive element (ABRE) and G-box, C-box, and A-box elements (Izawa et al, 1993).

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Conclusion