Cross talk between gibberellin and cytokinin: The Arabidopsis GA response inhibitor SPINDLY plays a positive role in cytokinin signaling

Yaarit Greenboim-Wainberg, Inbar Maymon, Roy Borochov, John Alvarez, Neil Olszewski, Naomi Ori, Yuval Eshed, David Weiss

Research output: Contribution to journalArticlepeer-review

206 Scopus citations

Abstract

SPINDLY (SPY) is a negative regulator of gibberellin (GA) responses; however, spy mutants exhibit various phenotypic alterations not found in GA-treated plants. Assaying for additional roles for SPY revealed that spy mutants are resistant to exogenously applied cytokinin. GA also repressed the effects of cytokinin, suggesting that there is cross talk between the two hormone-response pathways, which may involve SPY function. Two spy alleles showing severe (spy-4) and mild (spy-3) GA-associated phenotypes exhibited similar resistance to cytokinin, suggesting that SPY enhances cytokinin responses and inhibits GA signaling through distinct mechanisms. GA and spy repressed numerous cytokinin responses, from seedling development to senescence, indicating that cross talk occurs early in the cytokinin-signaling pathway. Because GA3 and spy-4 inhibited induction of the cytokinin primary-response gene, type-A Arabidopsis response regulator 5, SPY may interact with and modify elements from the phosphorelay cascade of the cytokinin signal transduction pathway. Cytokinin, on the other hand, had no effect on GA biosynthesis or responses. Our results demonstrate that SPY acts as both a repressor of GA responses and a positive regulator of cytokinin signaling. Hence, SPY may play a central role in the regulation of GA/cytokinin cross talk during plant development.

Original languageEnglish (US)
Pages (from-to)92-102
Number of pages11
JournalPlant Cell
Volume17
Issue number1
DOIs
StatePublished - 2005

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