Ubiquitin ligase switch in plant photomorphogenesis: A hypothesis.
Ubiquitin ligase switch in plant photomorphogenesis: A hypothesis.
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DOI：
10.1016/j.jtbi.2010.11.021
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发表时间：
2011-02-07
影响因子：
2
通讯作者：
Millar, Andrew J.
中科院分区：
文献类型：
--
作者：
Pokhilko, Alexandra;Ramos, Jason A.;Holtan, Hans;Maszle, Don R.;Khanna, Rajnish;Millar, Andrew J.
E3泛素连接酶COP1 （CONSTITUTIVE PHOTOMORPHOGENIC1）在黑暗条件下抑制植物光形态形成的过程中起关键作用。在有光的情况下，COP1通过一种尚未完全了解的机制失活。这导致COP1的靶转录因子积累，启动光形态发生，导致幼苗生理发生剧烈变化。本文基于在光形态发生中起关键作用的两个COP1靶蛋白HY5和HFR1的数据，利用数学模型探讨COP1调控拟南芥暗/光转换的可能机制。我们模型中的主要反应是COP1被一种光感受器相关抑制剂I失活，以及COP1与CUL4 （CULLIN4）连接酶之间的相互作用。为了建立和验证模型，我们使用了现有的已发表的HY5和HFR1的动力学数据和我们的新数据，以及COP1丰度的数据。HY5的积累速度比HFR1慢。为了描述观察到的“慢”靶标HY5和“快”靶标HFR1在时间过程上的差异，我们假设COP1和CUL4连接酶在暗/光转换时活性之间存在切换，其中COP1主要在黑暗中活跃，而CUL4在光明中活跃。该模型预测了植物暴露于光后COP1活性的双相动力学，在初始下降后恢复，随后COP1总含量缓慢耗尽。预计在有光的情况下CUL4的活性会增加。我们认为泛素连接酶开关在植物发育过程中对多种转录因子的复杂调控起着重要作用。此外，这也提供了一种新的光期感知机制，这对植物发育的季节变化具有重要意义。
The E3 ubiquitin ligase COP1 (CONSTITUTIVE PHOTOMORPHOGENIC1) plays a key role in the repression of the plant photomorphogenic development in darkness. In the presence of light, COP1 is inactivated by a mechanism which is not completely understood. This leads to accumulation of COP1’s target transcription factors, which initiates photomorphogenesis, resulting in dramatic changes of the seedling’s physiology. Here we use a mathematical model to explore the possible mechanism of COP1 modulation upon dark/light transition in Arabidopsis thaliana based upon data for two COP1 target proteins: HY5 and HFR1, which play critical roles in photomorphogenesis. The main reactions in our model are the inactivation of COP1 by a proposed photoreceptor-related inhibitor I and interactions between COP1 and a CUL4 (CULLIN4)-based ligase. For building and verification of the model, we used the available published and our new data on the kinetics of HY5 and HFR1 together with the data on COP1 abundance. HY5 has been shown to accumulate at a slower rate than HFR1. To describe the observed differences in the timecourses of the “slow” target HY5 and the “fast” target HFR1, we hypothesize a switch between the activities of COP1 and CUL4 ligases upon dark/light transition, with COP1 being active mostly in darkness and CUL4 in light. The model predicts a bi-phasic kinetics of COP1 activity upon the exposure of plants to light, with its restoration after the initial decline and the following slow depletion of the total COP1 content. CUL4 activity is predicted to increase in the presence of light. We propose that the ubiquitin ligase switch is important for the complex regulation of multiple transcription factors during plants development. In addition, this provides a new mechanism for sensing the duration of light period, which is important for seasonal changes in plant development.
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