Arabidopsis WRKY6 Transcription Factor Acts as a Positive Regulator of Abscisic Acid Signaling during Seed Germination and Early Seedling Development.

Yun Huang,Yi-Fang Chen,Cui-Zhu Feng,Wei-Hua Wu,Qing Ye,Xuemei Chen

doi:10.1371/journal.pgen.1005833

Yun Huang, Yi-Fang Chen + Show 4 more

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https://doi.org/10.1371/journal.pgen.1005833

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Abstract

The phytohormone abscisic acid (ABA) plays important roles during seed germination and early seedling development. Here, we characterized the function of the Arabidopsis WRKY6 transcription factor in ABA signaling. The transcript of WRKY6 was repressed during seed germination and early seedling development, and induced by exogenous ABA. The wrky6-1 and wrky6-2 mutants were ABA insensitive, whereas WRKY6-overexpressing lines showed ABA-hypersensitive phenotypes during seed germination and early seedling development. The expression of RAV1 was suppressed in the WRKY6-overexpressing lines and elevated in the wrky6 mutants, and the expression of ABI3, ABI4, and ABI5, which was directly down-regulated by RAV1, was enhanced in the WRKY6-overexpressing lines and repressed in the wrky6 mutants. Electrophoretic mobility shift and chromatin immunoprecipitation assays showed that WRKY6 could bind to the RAV1 promoter in vitro and in vivo. Overexpression of RAV1 in WRKY6-overexpressing lines abolished their ABA-hypersensitive phenotypes, and the rav1 wrky6-2 double mutant showed an ABA-hypersensitive phenotype, similar to rav1 mutant. Together, the results demonstrated that the Arabidopsis WRKY6 transcription factor played important roles in ABA signaling by directly down-regulating RAV1 expression.

Highlights

Abscisic acid (ABA) is a key phytohormone that plays important roles in plant responses to stresses and plant development [1,2]
This study demonstrated that the expression of WRKY6 was obviously repressed during seed germination and significantly induced by exogenous ABA
In the presence of exogenous ABA, the two wrky6 mutants showed ABA-insensitive phenotypes, whereas the WRKY6-overexpressing lines were hypersensitive to ABA

Summary

Introduction

Abscisic acid (ABA) is a key phytohormone that plays important roles in plant responses to stresses and plant development [1,2]. Molecular genetics studies in Arabidopsis identify a number of genes involved in ABA signaling. The abi, abi, and abi mutants show ABA-insensitive phenotypes during seed germination and early seedling development [10,11,12], and the ABI3, ABI4, and ABI5 genes encode B3-type, APETALA2 domain and basic Leucine zipper (bZIP)-type transcription factors, respectively [10,11,12,13]. None of the areb, areb and abf mutants show ABA-sensitive phenotypes compared with wild-type plants, and during the vegetative growth stage, AREB1/ABF2, AREB2/ABF4, and ABF3 are key regulators of ABA signaling in response to osmotic stress [14,15,16]

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