Edinburgh, Scotland, United Kingdom - TAIR
Edinburgh, Scotland, United Kingdom - TAIR
Edinburgh, Scotland, United Kingdom - TAIR
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The brassinosteroid signal transduction<br />
pathway<br />
Molecular genetic studies in Arabidopsis have identified several brassinosteroid<br />
(BR) signaling components and provided an outline of the BR signal transduction<br />
pathway from the cell surface receptor to nuclear gene expression. When BR<br />
levels are low, the BIN2 kinase phosphorylates the BZR1 and BZR2 (also named<br />
BES1) transcription factors to inhibit their DNA binding and reduce their nuclear<br />
localization through the phosphopeptide-binding 14-3-3 proteins. BRs bind to<br />
the BRI1 receptor kinase at the cell surface and activate a signalling cascade<br />
that leads to dephosphorylation and activation of the BZR1 and BZR2<br />
transcription factors, presumably by inhibiting the BIN2 kinase or activating the<br />
BSU1 phosphatase. How activation of BRI1 leads to inhibition of BIN2 or<br />
activation of BSU1 has remained a major gap in our understanding of the BR<br />
signalling pathway. This gap is now filled by proteomic and biochemical studies.<br />
Using quantitative proteomic studies we identified a class of BR signalling<br />
kinases (BSKs) as BRI1’s substrates. Biochemical studies demonstrated that<br />
BRI1 phosphorylation of BSKs promotes BSKs’ interaction with a downstream<br />
component that inactivates BIN2 by dephosphorylation. Our study has thus<br />
closed the last gaps in the BR signalling cascade from receptor kinases to<br />
transcription factors. Furthermore, we have performed chromatin immunoprecipitation-microarray<br />
(ChIP-chip) and identified about a thousand BZR1-target<br />
genes that are regulated by BR. These primary targets of BR signalling include<br />
key components of other signalling and developmental pathways as well as<br />
specific cellular structure and functions, providing a global map of steroid actions<br />
in Arabidopsis. As such, a complete BR signalling pathway from signal<br />
perception at cell surface to gene expression and cellular and developmental<br />
responses is emerging.<br />
82<br />
C31<br />
Thursday 14:30 - 15:00<br />
Plant Growth Regulators<br />
Tae-Wuk Kim1<br />
Yu Sun1<br />
Wenqiang Tang1<br />
Zhiping Deng1<br />
Shenheng Guan2<br />
Juan A Oses-Prieto2<br />
Jian-Xiu Shang3<br />
Yihong Yang3<br />
Ying Sun3<br />
Alma L Burlingame2<br />
Zhi-Yong Wang1<br />
1Department of Plant<br />
Biology<br />
Carnegie Institution for<br />
Science<br />
Stanford<br />
CA 94305<br />
2Department of<br />
Pharmaceutical Chemistry<br />
University of California<br />
San Francisco<br />
CA 94143<br />
3Institute of Molecular Cell<br />
Biology<br />
Hebei Normal University<br />
Shijiazhuang<br />
Hebei<br />
050016<br />
China
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