BSKs Mediate Signal Transduction from the Receptor Kinase BRI1 in Arabidopsis

• DOI: 10.1126/science.1156973
• Publication Date: 2008-07-24T21:24:54Z
• Authors: Wenqiang Tang; Tae-Wuk Kim; Juan A. Oses-Prieto; Yu Sun; Zhiping Deng; Shengwei Zhu; Ruiju Wang; Alma L. Burlingame; Zhi-Yong Wang
• Keywords: Proteomics; 0301 basic medicine; Arabidopsis Proteins; Recombinant Fusion Proteins; Cell Membrane; Molecular Sequence Data; Arabidopsis; Protein Serine-Threonine Kinases; Plants, Genetically Modified; Protein Structure, Tertiary; Mutagenesis, Insertional; 03 medical and health sciences; Steroids, Heterocyclic; Brassinosteroids; Amino Acid Sequence; Phosphorylation; Protein Kinases; Cholestanols; Signal Transduction

Brassinosteroids (BRs) bind to the extracellular domain of the receptor kinase BRI1 to activate a signal transduction cascade that regulates nuclear gene expression and plant development. Many components of the BR signaling pathway have been identified and studied in detail. However, the substrate of BRI1 kinase that transduces the signal to downstream components remains unknown. Proteomic studies of plasma membrane proteins lead to the identification of three homologous BR-signaling kinases (BSK1, BSK2, and BSK3). The BSKs are phosphorylated by BRI1 in vitro and interact with BRI1 in vivo. Genetic and transgenic studies demonstrate that the BSKs represent a small family of kinases that activate BR signaling downstream of BRI1. These results demonstrate that BSKs are the substrates of BRI1 kinase that activate downstream BR signal transduction.