Transcriptional Activation of OsDERF1 in OsERF3 and OsAP2-39 Negatively Modulates Ethylene Synthesis and Drought Tolerance in Rice

Liyun Wan,Zhijin Zhang,Jianfei Zhang,Rongfeng Huang,Haiwen Zhang,Shirong Zhou,Ruidang Quan,Edward Newbigin

doi:10.1371/journal.pone.0025216

Abstract

The phytohormone ethylene is a key signaling molecule that regulates a variety of developmental processes and stress responses in plants. Transcriptional modulation is a pivotal process controlling ethylene synthesis, which further triggers the expression of stress-related genes and plant adaptation to stresses; however, it is unclear how this process is transcriptionally modulated in rice. In the present research, we report the transcriptional regulation of a novel rice ethylene response factor (ERF) in ethylene synthesis and drought tolerance. Through analysis of transcriptional data, one of the drought-responsive ERF genes, OsDERF1, was identified for its activation in response to drought, ethylene and abscisic acid. Transgenic plants overexpressing OsDERF1 (OE) led to reduced tolerance to drought stress in rice at seedling stage, while knockdown of OsDERF1 (RI) expression conferred enhanced tolerance at seedling and tillering stages. This regulation was supported by negative modulation in osmotic adjustment response. To elucidate the molecular basis of drought tolerance, we identified the target genes of OsDERF1 using the Affymetrix GeneChip, including the activation of cluster stress-related negative regulators such as ERF repressors. Biochemical and molecular approaches showed that OsDERF1 at least directly interacted with the GCC box in the promoters of ERF repressors OsERF3 and OsAP2-39. Further investigations showed that OE seedlings had reduced expression (while RI lines showed enhanced expression) of ethylene synthesis genes, thereby resulting in changes in ethylene production. Moreover, overexpression of OsERF3/OsAP2-39 suppressed ethylene synthesis. In addition, application of ACC recovered the drought-sensitive phenotype in the lines overexpressing OsERF3, showing that ethylene production contributed to drought response in rice. Thus our data reveal that a novel ERF transcriptional cascade modulates drought response through controlling the ethylene synthesis, deepening our understanding of the regulation of ERF proteins in ethylene related drought response.

Highlights

Abiotic stresses, such as drought are primary factors that limit crop cultivation and yield worldwide
We reported that a novel ethylene response factor (ERF) transcriptional activator at least modulated the expression of ERF repressors OsERF3 and OsAP2-39 in rice, evidencing a novel transcriptional cascade that involves the activation of multiple transcription factors that play antagonistic roles in gene regulation
The application of ACC recovered the drought-sensitive phenotype in transgenic lines overexpressing OsERF3, demonstrating that the reduced ethylene production caused by the OsDERF1–ERF complex might contribute to the drought response in rice

Summary

Introduction

Abiotic stresses, such as drought are primary factors that limit crop cultivation and yield worldwide. For the characteristics that trigger global changes in drought-related genes, the application of transcription factor genes is becoming a powerful approach in the engineering of crop plants with enhanced tolerance to drought stress [1,2]. Sub1A is an ERF-like protein that confers tolerance to submergence and drought in rice through affecting ethylene synthesis [4,7]. Tomato JERF1 modulates the expression of an abscisic acid (ABA) biosynthesis-related gene that enhances tolerance to drought, salinity and cold in tobacco [17]. The potato homolog of the tomato ERF transcriptional activator Pti, which interacts with the repressor SEBF, represses the expression of potato PR-10a gene [19]

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Conclusion