The Arabidopsis GAI gene defines a signaling pathway that negatively regulates gibberellin responses
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 thegai 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.
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Footnotes
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↵1 These authors contributed equally to this work.
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Present addresses: 2Laboratoire de Génétique Moléculaire Végétale, Université Joseph Fourier, 38041 Grenoble CEDEX, France; 3Laboratoire de Biologie Cellulaire, Institut National de la Recherche Agronomique, Route de Saint Cyr, 78026 Versailles CEDEX, France.
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↵4 Corresponding author.
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E-MAIL harberd{at}bbsrc.ac.uk; FAX +44 1603 505725.
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- Received August 6, 1997.
- Accepted September 17, 1997.
- Cold Spring Harbor Laboratory Press
