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Published August 20, 1996 | Published
Journal Article Open

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

Abstract

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.

Additional Information

© 1996 National Academy of Sciences. Communicated by Bernard O. Phinney, University of California, Los Angeles, CA, May 16, 1996 (received for review February 3, 1996). We thank K. Feldmann and the Arabidopsis Biological Resource Center for providing the Agrobacterium seed transformant lines; Monjula Gopalraj, Scott Sattler, and Daryl Laflur for technical assistance; Leonard Medrano and Elliot Meyerowitz for RFLP mapping; members of the Meyerowitz lab for reviewing the manuscript; and Elliot Meyerowitz for allowing S.E.J. to complete this work in his laboratory. We also thank Jason Reed for communicating unpublished data. This work was supported by the National Institutes of Health (Grant GM40553 to N.E.O.) and the National Science Foundation (Grant IBN-9317524 to N.E.O.), and by predoctoral and postdoctoral fellowships to S.E.J. from the National Institutes of Health (Grants GM07323 and GM15964, respectively). The publication costs of this article were defrayed in part by page charge payment. This article must therefore be hereby marked "advertisement" in accordance with 18 U.S.C. §1734 solely to indicate this fact.

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