Functional Analysis of the Pepper Ethylene-Responsive Transcription Factor, CaAIEF1, in Enhanced ABA Sensitivity and Drought Tolerance.

Eunji Hong,Sung Chul Lee,Chae Woo Lim,Sang-Wook Han

doi:10.3389/fpls.2017.01407

Abstract

Abscisic acid (ABA) is a plant hormone that plays a critical role in the response to environmental stress conditions, especially regulation of the stomatal aperture under water-deficit conditions. The signal transduction occurring during the stress response is initiated by transcription of defense-related genes. Here, we isolated the pepper ethylene-responsive transcription factor CaAIEF1 (Capsicum annuum ABA Induced ERF 1). The CaAIEF1 gene was significantly induced after exposure to ABA, drought, and high salinity. Fusion of the acidic domain in the C-terminal region of CaAIEF1 to the GAL4 DNA-binding domain had a transactivation effect on the reporter gene in yeast. Further, the CaAIEF1-GFP fusion constructs localized in the nucleus. We used CaAIEF1-silenced plants and CaAIEF1-overexpressing (OX) plants to elucidate the biological function of CaAIEF1 in response to ABA and drought stress. CaAIEF1-silenced pepper plants and CaAIEF1-OX Arabidopsis plants displayed drought-sensitive and -tolerant phenotypes, respectively, which were characterized by regulation of transpirational water loss and stomatal aperture. In drought stress condition, quantitative RT-PCR analyses revealed that the expression levels of pepper stress-related genes were higher in CaAIEF1-silenced pepper plants than control plants. Moreover, expression levels of Arabidopsis stress-related genes were significantly reduced in CaAIEF1-OX plants compared with control plants in drought stress condition. Our findings suggest that CaAIEF1 positively regulates the drought stress response and the ABA signaling.

Highlights

Plants are sessile organisms, and their growth and development is affected by abiotic stresses, including drought, high salinity, and extreme temperatures
The predicted protein consisted of an APETALA2/Ethylene-Responsive Factor (AP2/ERF) domain with 65 amino acids (59–123) in the central region and an acidic domain (AD) consisting of 21 amino acids (160–180); these domains bind to promoter regions and activate target genes (Figure 1A) (Licausi et al, 2013)
The expression level of CaAIEF1 was induced by abscisic acid (ABA) and abiotic stresses; we investigated the in vivo function of CaAIEF1 using virus-induced gene silencing (VIGS) in pepper plants and Arabidopsis transgenic plants

Summary

Introduction

Their growth and development is affected by abiotic stresses, including drought, high salinity, and extreme temperatures. Role of CaAIEF1 in Enhanced Drought Tolerance been intensively examined; the plant defense response is a complex phenomenon, and the precise adaptive mechanisms induced by drought stress remain elusive (Lee and Luan, 2012; Murata et al, 2015). ABA is biosynthesized in various tissues and accumulated in the leaf tissue, and this leads to induction of stressadaptive mechanisms—including induction of defense-related genes, promotion of stomatal closure, and accumulation of various protective metabolites (Tan et al, 2003; Lee and Luan, 2012). A number of studies have indicated that the plant defense response to drought stress involves various mechanisms—from transcription to post-translational modification—and these mechanisms are influenced by the ABA signal transduction pathway (Lee and Luan, 2012)

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Conclusion