Abstract
The Arabidopsis gai mutant allele confers a reduction in gibberellin (GA) responsiveness. Here we report the molecular cloning of GAI and a closely related gene GRS. The predicted GAI (wild-type) and gai (mutant) proteins differ only by the deletion of a 17-amino-acid segment from within the amino-terminal region. GAI and GRS contain nuclear localization signals, a region of homology to a putative transcription factor, and motifs characteristic of transcriptional coactivators. Genetic analysis indicates that GAI is a repressor of GA responses, that GA can release this repression, and that gai is a mutant repressor that is relatively resistant to the effects of GA. Mutations at SPY and GAR2 suppress the gai phenotype, indicating the involvement of GAI, SPY, and GAR2 in a signaling pathway that regulates GA responses negatively. The existence of this pathway suggests that GA modulates plant growth through derepression rather than through simple stimulation.
Publication types
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Research Support, Non-U.S. Gov't
MeSH terms
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Alleles
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Amino Acid Sequence
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Arabidopsis / drug effects
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Arabidopsis / genetics*
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Arabidopsis / growth & development
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Arabidopsis Proteins*
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Base Sequence
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Cloning, Molecular
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Consensus Sequence
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DNA, Plant
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Genes, Plant*
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Gibberellins / antagonists & inhibitors*
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Gibberellins / pharmacology
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Mixed Function Oxygenases / genetics
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Molecular Sequence Data
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Mutagenesis, Insertional
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Nuclear Localization Signals / genetics
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Open Reading Frames
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Plant Growth Regulators / pharmacology
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Plant Proteins / genetics*
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Plant Proteins / metabolism
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RNA, Plant / metabolism
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Sequence Homology, Amino Acid
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Signal Transduction*
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Suppression, Genetic
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Triazoles / pharmacology
Substances
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Arabidopsis Proteins
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DNA, Plant
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GAI protein, Arabidopsis
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GRS protein, Arabidopsis
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Gibberellins
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Nuclear Localization Signals
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Plant Growth Regulators
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Plant Proteins
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RNA, Plant
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Triazoles
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paclobutrazol
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Mixed Function Oxygenases
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gibberellin, 2-oxoglutarate-oxygen oxidoreductase (20-hydroxylating, oxidizing)
Associated data
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GENBANK/Y15193
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GENBANK/Y15194