Abstract
The rice basic domain/Leu zipper factor TRAB1 binds to abscisic acid (ABA) response elements and mediates ABA signals to activate transcription. We show that TRAB1 is phosphorylated rapidly in an in vivo labeling experiment and by phosphatase-sensitive mobility shifts on SDS-polyacrylamide gels. We had shown previously that a chimeric promoter containing GAL4 binding sites became ABA inducible when a GAL4 binding domain-TRAB1 fusion protein was present. This expression system allowed us to assay the ABA response function of TRAB1. Using this system, we show that Ser-102 of TRAB1 is critical for this function. Because no ABA-induced mobility shift was observed when Ser-102 was replaced by Ala, we suggest that this Ser residue is phosphorylated in response to ABA. Cell fractionation experiments, as well as fluorescence microscopy observations of transiently expressed green fluorescent protein-TRAB1 fusion protein, indicated that TRAB1 was localized in the nucleus independently of ABA. Our results suggest that the terminal or nearly terminal event of the primary ABA signal transduction pathway is the phosphorylation in the nucleus of preexisting TRAB1.
Publication types
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Research Support, Non-U.S. Gov't
MeSH terms
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Abscisic Acid / pharmacology*
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Amino Acid Sequence
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Basic-Leucine Zipper Transcription Factors
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Conserved Sequence / genetics
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Conserved Sequence / physiology
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Gene Expression Regulation, Plant / drug effects
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Green Fluorescent Proteins
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Leucine Zippers / drug effects
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Leucine Zippers / genetics
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Leucine Zippers / physiology
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Luminescent Proteins / genetics
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Luminescent Proteins / metabolism
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Molecular Sequence Data
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Nuclear Proteins / genetics
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Nuclear Proteins / metabolism
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Oryza / genetics
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Oryza / metabolism*
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Phosphorylation / drug effects
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Plant Proteins / genetics
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Plant Proteins / metabolism
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Plants, Genetically Modified
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Recombinant Fusion Proteins / genetics
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Recombinant Fusion Proteins / metabolism
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Sequence Homology, Amino Acid
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Serine / genetics
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Serine / metabolism
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Signal Transduction / drug effects
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Transcription Factors / drug effects
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Transcription Factors / genetics
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Transcription Factors / metabolism*
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Transcription, Genetic / drug effects
Substances
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Basic-Leucine Zipper Transcription Factors
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Luminescent Proteins
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Nuclear Proteins
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Plant Proteins
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Recombinant Fusion Proteins
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TRAB1 protein, plant
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Transcription Factors
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Green Fluorescent Proteins
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Serine
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Abscisic Acid