SPINDLY, a tetratricopeptide repeat protein involved in gibberellin signal transduction in Arabidopsis

Steven E. Jacobsen, Kalli A. Binkowski, Neil E. Olszewski

Research output: Contribution to journalArticlepeer-review

287 Scopus citations


Gibberellins (GAs) are a major class of plant hormones that control many developmental processes, including seed development and germination, flower and fruit development, and flowering time. Genetic studies with Arabidopsis thaliana have identified two genes involved in GA perception or signal transduction. A semidominant mutation at the GIBBERELLIN INSENSITIVE (GAI) locus results in plants resembling GA-deficient mutants but exhibiting reduced sensitivity to GA. Recessive mutations at the SPINDLY (SPY) locus cause a phenotype that is consistent with constitutive activation of GA signal transduction. Here we show that a strong allele of spy is completely epistatic to gai, indicating that SPY acts downstream of GAI. We have cloned the SPY gene and shown that it encodes a new type of signal transduction protein, which contains a tetratricopeptide repeat region, likely serving as a protein interaction domain, and a novel C-terminal region. Mutations in both domains increase GA signal transduction. The presence of a similar gene in Caenorhabditis elegans suggests that SPY represents a class of signal transduction proteins that is present throughout the eukaryotes.

Original languageEnglish (US)
Pages (from-to)9292-9296
Number of pages5
JournalProceedings of the National Academy of Sciences of the United States of America
Issue number17
StatePublished - Aug 20 1996


  • gibberellin response mutants
  • plant hormones


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