Abstract
BackgroundPlant WRKY DNA-binding transcription factors are key regulators in certain developmental programs. A number of studies have suggested that WRKY genes may mediate seed germination and postgermination growth. However, it is unclear whether WRKY genes mediate ABA-dependent seed germination and postgermination growth arrest.ResultsTo determine directly the role of Arabidopsis WRKY2 transcription factor during ABA-dependent seed germination and postgermination growth arrest, we isolated T-DNA insertion mutants. Two independent T-DNA insertion mutants for WRKY2 were hypersensitive to ABA responses only during seed germination and postgermination early growth. wrky2 mutants displayed delayed or decreased expression of ABI5 and ABI3, but increased or prolonged expression of Em1 and Em6. wrky2 mutants and wild type showed similar levels of expression for miR159 and its target genes MYB33 and MYB101. Analysis of WRKY2 expression level in ABA-insensitive and ABA-deficient mutants abi5-1, abi3-1, aba2-3 and aba3-1 further indicated that ABA-induced WRKY2 accumulation during germination and postgermination early growth requires ABI5, ABI3, ABA2 and ABA3.ConclusionABA hypersensitivity of the wrky2 mutants during seed germination and postgermination early seedling establishment is attributable to elevated mRNA levels of ABI5, ABI3 and ABI5-induced Em1 and Em6 in the mutants. WRKY2-mediated ABA responses are independent of miR159 and its target genes MYB33 and MYB101. ABI5, ABI3, ABA2 and ABA3 are important regulators of the transcripts of WRKY2 by ABA treatment. Our results suggest that WRKY2 transcription factor mediates seed germination and postgermination developmental arrest by ABA.
Highlights
Plant WRKY DNA-binding transcription factors are key regulators in certain developmental programs
WRKY2 T-DNA insertion mutants are hypersensitive to Abscisic acid (ABA) during seed germination and postgermination early growth To analyze the molecular events in ABA-regulated germination and seedling growth, we sought to identify WRKY transcription factors associated with these growth and developmental stages
Transcription factors ABI5 is an important regulator of postgermination developmental arrest mediated by ABA
Summary
Plant WRKY DNA-binding transcription factors are key regulators in certain developmental programs. Abscisic acid (ABA) is a phytohormone regulating plant responses to a variety of environmental stress, water deprivation, notably by regulating stomatal aperture [1,2,3,4]. It plays an essential role in mediating the initiation and maintenance of seed dormancy [5]. The embryo develops and enters a dormant state that is triggered by an increase in the ABA concentration This leads to the cessation of cell division and activation of genes encoding seed storage proteins and proteins required to establish desiccation tolerance [6]. ABA-mediated postgermination arrest allows germinating seedlings to (page number not for citation purposes)
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