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DELLA proteins are nuclear repressors of plant gibberellin (GA) responses. Here, we investigate the properties of SLN1, a DELLA protein from barley that is destabilized by GA treatment. Using specific inhibitors of proteasome function, we show that proteasome-mediated protein degradation is necessary for GA-mediated destabilization of SLN1. We also show that GA responses, such as the aleurone alpha-amylase response and seedling leaf extension growth, require proteasome-dependent GA-mediated SLN1 destabilization. In further experiments with protein kinase and protein phosphatase inhibitors, we identify two additional signaling steps that are necessary for GA response and for GA-mediated destabilization of SLN1. Thus, GA signaling involves protein phosphorylation and dephosphorylation steps and promotes the derepression of GA responses via proteasome-dependent destabilization of DELLA repressors.

Type

Journal article

Journal

Plant Cell

Publication Date

12/2002

Volume

14

Pages

3191 - 3200

Keywords

Alleles, Aprotinin, Cysteine Endopeptidases, Enzyme Induction, Enzyme Inhibitors, Gibberellins, Hordeum, Multienzyme Complexes, Mutation, Okadaic Acid, Phenylmethylsulfonyl Fluoride, Plant Leaves, Plant Proteins, Proteasome Endopeptidase Complex, Seeds, Signal Transduction, Sulfones, Vanadates, alpha-Amylases