Visualization of BRI1 and BAK1(SERK3) Membrane Receptor Heterooligomers during Brassinosteroid Signaling
Visualization of BRI1 and BAK1(SERK3) Membrane Receptor Heterooligomers during Brassinosteroid Signaling
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DOI：
10.1104/pp.113.220152
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发表时间：
2013-08-01
期刊：
影响因子：
7.4
通讯作者：
de Vries, Sacco C.
中科院分区：
文献类型：
--
作者：
Bucherl, Christoph A.;van Esse, G. Wilma;de Vries, Sacco C.
富含亮氨酸的重复序列受体样激酶油菜素类固醇-不敏感1（BRI 1）是拟南芥（Arabidopsis thaliana）中油菜素类固醇（BR）的主要配体感知受体。BR与位于BRI 1受体的质膜（PM）胞外域的结合启动细胞内信号传导级联反应，影响植物生长和发育的各个方面。尽管BR信号传导的主要成分已经被揭示，并且PM被确定为BRI 1信号传导活性的主要位点，但信号传导的最初步骤仍然是难以捉摸的。最近，研究表明BR信号转导的启动需要BRI 1与其体细胞胚胎发生受体样激酶（SERK）共受体的相互作用。此外，BRI 1胞外域的解析结构表明BRI 1相关激酶1 [BAK 1]（SERK 3）可能构成配体感知受体复合物的组分。因此，我们研究了BRI 1和BAK 1（SERK 3）在自然栖息地的亮氨酸丰富的重复序列受体样激酶，使用比较共定位分析和荧光寿命成像显微镜的空间相关性。我们表明，激活BR信号通过外源配体的应用导致在升高的共定位BRI 1和BAK 1（SERK 3）和一个约50%的增加受体异源寡聚体在活拟南芥根表皮细胞的PM。然而，大量的BRI 1和BAK 1（SERK 3）独立于BR共定位。此外，我们可以看到，在活的根细胞中，大约7%的BRI 1 PM库与BAK 1（SERK 3）组成型异源寡聚。我们提出，只有少数位于PM的BRI 1和BAK 1（SERK 3）受体参与主动BR信号传导，下游信号转导的启动涉及预组装的BRI 1-BAK 1（SERK 3）异源寡聚体。
The leucine-rich repeat receptor-like kinase BRASSINOSTEROID-INSENSITIVE1 (BRI1) is the main ligand-perceiving receptor for brassinosteroids (BRs) in Arabidopsis (Arabidopsis thaliana). Binding of BRs to the ectodomain of plasma membrane (PM)located BRI1 receptors initiates an intracellular signal transduction cascade that influences various aspects of plant growth and development. Even though the major components of BR signaling have been revealed and the PM was identified as the main site of BRI1 signaling activity, the very first steps of signal transmission are still elusive. Recently, it was shown that the initiation of BR signal transduction requires the interaction of BRI1 with its SOMATIC EMBRYOGENESIS RECEPTOR-LIKE KINASE (SERK) coreceptors. In addition, the resolved structure of the BRI1 ectodomain suggested that BRI1-ASSOCIATED KINASE1 [BAK1](SERK3) may constitute a component of the ligand-perceiving receptor complex. Therefore, we investigated the spatial correlation between BRI1 and BAK1(SERK3) in the natural habitat of both leucine-rich repeat receptor-like kinases using comparative colocalization analysis and fluorescence lifetime imaging microscopy. We show that activation of BR signaling by exogenous ligand application resulted in both elevated colocalization between BRI1 and BAK1(SERK3) and an about 50% increase of receptor heterooligomerization in the PM of live Arabidopsis root epidermal cells. However, large populations of BRI1 and BAK1(SERK3) colocalized independently of BRs. Moreover, we could visualize that approximately 7% of the BRI1 PM pool constitutively heterooligomerizes with BAK1(SERK3) in live root cells. We propose that only small populations of PM-located BRI1 and BAK1(SERK3) receptors participate in active BR signaling and that the initiation of downstream signal transduction involves preassembled BRI1-BAK1(SERK3) heterooligomers.