The Arabidopsis GAI gene defines a signaling pathway that negatively regulates gibberellin responses.
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.
Peng
J
J
Department of Molecular Genetics, John Innes Centre, Norwich Research Park, Norwich NR4 7UJ, UK.
Carol
P
P
Richards
D E
DE
King
K E
KE
Cowling
R J
RJ
Murphy
G P
GP
Harberd
N P
NP
D000483:Alleles; D000595:Amino Acid Sequence; D017360:Arabidopsis / Q000187:drug effects / Q000235:genetics* / Q000254:growth & development; D029681:Arabidopsis Proteins; D001483:Base Sequence; D003001:Cloning, Molecular; D016384:Consensus Sequence; D018744:DNA, Plant; D017343:Genes, Plant; D005875:Gibberellins / Q000037:antagonists & inhibitors* / Q000494:pharmacology; D006899:Mixed Function Oxygenases / Q000235:genetics; D008969:Molecular Sequence Data; D016254:Mutagenesis, Insertional; D019913:Nuclear Localization Signals / Q000235:genetics; D016366:Open Reading Frames; D010937:Plant Growth Regulators / Q000494:pharmacology; D010940:Plant Proteins / Q000235:genetics* / Q000378:metabolism; D018749:RNA, Plant / Q000378:metabolism; D017386:Sequence Homology, Amino Acid; D015398:Signal Transduction; D013489:Suppression, Genetic; D014230:Triazoles / Q000494:pharmacology
D029681:Arabidopsis Proteins; D018744:DNA, Plant; C109555:GAI protein, Arabidopsis; C109556:GRS protein, Arabidopsis; D005875:Gibberellins; D019913:Nuclear Localization Signals; D010937:Plant Growth Regulators; D010940:Plant Proteins; D018749:RNA, Plant; D014230:Triazoles; C053370:paclobutrazol; D006899:Mixed Function Oxygenases; C089210:gibberellin, 2-oxoglutarate-oxygen oxidoreductase (20-hydroxylating, oxidizing)