The GSK3-like Kinase BIN2 Phosphorylates and Destabilizes BZR1, A Positive Regulator of the Brassinosteroid Signaling Pathway in Arabidopsis

Brassinosteroids (BRs) are a class of steroid hormones essential for normal growth and development in plants. BR signaling involves the cell-surface receptor BRI1, the glycogen synthase kinase-3-like kinase BIN2 as a negative regulator, and nuclear proteins BZR1 and BZR2/BES1 as positive regulators....

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Published in:Proceedings of the National Academy of Sciences - PNAS 2002-07, Vol.99 (15), p.10185-10190
Main Authors: He, Jun-Xian, Gendron, Joshua M., Yang, Yanli, Li, Jianming, Wang, Zhi-Yong
Format: Article
Language:English
Subjects:
Arabidopsis - genetics
Arabidopsis - physiology
Arabidopsis Proteins - metabolism
Biological Sciences
Biosynthesis
Calcium-Calmodulin-Dependent Protein Kinases - metabolism
DNA-Binding Proteins
Flowers & plants
Gene expression regulation
Gene Expression Regulation, Plant
Genetic mutation
Glycogen Synthase Kinase 3
Glycogen Synthase Kinases
Green Fluorescent Proteins
Hormones
Luminescent Proteins - genetics
Nuclear Proteins - metabolism
Phosphatases
Phosphorylation
Phytosterols - metabolism
Plant growth
Plant growth regulators
Plants
Plants, Genetically Modified
Protein Kinases - metabolism
Proteins
Regulator genes
Signal Transduction - genetics
Yeasts
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Summary:Brassinosteroids (BRs) are a class of steroid hormones essential for normal growth and development in plants. BR signaling involves the cell-surface receptor BRI1, the glycogen synthase kinase-3-like kinase BIN2 as a negative regulator, and nuclear proteins BZR1 and BZR2/BES1 as positive regulators. The interactions among these components remain unclear. Here we report that BRs induce dephosphorylation and accumulation of BZR1 protein. Experiments using a proteasome inhibitor, MG132, suggest that phosphorylation of BZR1 increases its degradation by the proteasome machinery. BIN2 directly interacts with BZR1 in yeast two-hybrid assays, phosphorylates BZR1 in vitro, and negatively regulates BZR1 protein accumulation in vivo. These results strongly suggest that BIN2 phosphorylates BZR1 and targets it for degradation and that BR signaling causes BZR1 dephosphorylation and accumulation by inhibiting BIN2 activity.
ISSN:0027-8424
1091-6490
DOI:10.1073/pnas.152342599