Downstream nuclear events in brassinosteroid signalling

• Published in: Nature Vol. 441; no. 7089; pp. 96 - 100
• Main Authors: Vert, G, Chory, J
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group UK 04.05.2006; Nature Publishing; Nature Publishing Group
• Subjects: Arabidopsis - cytology; Arabidopsis - drug effects; Arabidopsis - metabolism; Arabidopsis Proteins - metabolism; binding capacity; Biological and medical sciences; Botany; brassinosteroids; Cell biochemistry; cell nucleolus; Cell Nucleus - drug effects; Cell Nucleus - metabolism; Cell physiology; Deoxyribonucleic acid; DNA; DNA - metabolism; DNA-Binding Proteins; Fundamental and applied biological sciences. Psychology; Glycogen Synthase Kinase 3 - metabolism; Hormones; Humanities and Social Sciences; letter; Molecular and cellular biology; multidisciplinary; Nuclear Proteins - metabolism; Phosphorylation; Plant growth; Plant physiology and development; plants; promoter regions; Protein Kinases - metabolism; protein phosphorylation; Science; Science (multidisciplinary); Signal transduction; Signal Transduction - drug effects; Steroid hormones; Steroids; Steroids - pharmacology; transcription (genetics); transcription factors; Transcriptional Activation; Signal transduction; Brassinosteroid; Membrane receptor; Regulation(control); Enzyme; Kinase; Transferases; Plant growth substance; Models; Gene expression; Transcription factor; Mechanism of action; beta-catenin; transcription factor; kinase; receptor; transduction; bzr1; pathway; growth; gene-expression; arabidopsis
• ISSN: 0028-0836; 1476-4687; 1476-4687; 1476-4679
• DOI: 10.1038/nature04681

Brassinosteroids (BRs) are steroid hormones that control many aspects of plant growth and development. BRs bind to the plasma membrane receptor kinase BRI1, and act through a signalling pathway that involves a glycogen synthase kinase-3-like kinase (BIN2) and a serine/threonine phosphatase (BSU1). Previous models proposed that BIN2 negatively regulates BR signalling by controlling the stability and subcellular localization of the related transcription factors BES1 and BZR1 by phosphorylation, in a manner reminiscent of the canonical Wnt signalling pathway of metazoans. Here we present strong evidence for a different mode of regulation of BR signalling. We show that BES1 is localized constitutively to the nucleus, where its activity is modulated by nuclear-localized BIN2 kinase. BIN2-mediated phosphorylation of BES1 inhibits its DNA-binding activity on BR-responsive target promoters and its transcriptional activity through impaired multimerization. Our observations demonstrate that phosphorylation-dependent inhibition of DNA binding and trans-activation is the key primary mechanism of BES1 regulation.