Both Phototropin 1 and 2 Localize on the Chloroplast Outer Membrane with Distinct Localization Activity
Both Phototropin 1 and 2 Localize on the Chloroplast Outer Membrane with Distinct Localization Activity
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DOI：
10.1093/pcp/pcs151
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发表时间：
2013-01-01
影响因子：
4.9
通讯作者：
Wada, Masamitsu
中科院分区：
文献类型：
--
作者：
Kong, Sam-Geun;Suetsugu, Noriyuki;Wada, Masamitsu
叶绿体改变它们的位置以适应细胞活动以适应波动的环境光条件。向光蛋白（Phototropins，拟南芥中的phot 1和phot 2）是植物特有的蓝光光感受器，能感知光强度和方向的变化，并介导基于肌动蛋白的叶绿体光迁移运动。phot 1和phot 2都调节叶绿体积累反应，而phot 2主要负责调节回避反应。虽然它已被广泛接受，不同的细胞内定位的phototropins是牵连的特异性，phot 2特异性回避反应的机制仍然难以捉摸。在这项研究中，我们研究的phot 2定位模式的叶绿体光迁移运动的关系。首先，核定位信号与phot 2的融合，有效地减少了细胞质中phot 2的量，保留了积累和回避反应的活性，表明膜定位的phot 2而不是细胞质phot 2是功能性介导的反应。重要的是，phot 2和phot 1在较小程度上的一些分数，定位于叶绿体外膜上。此外，phot 2，这是以前被证明是有缺陷的蓝光诱导的高尔基体定位和回避反应的C-末端区域的删除，影响叶绿体外膜上的定位模式。两者合计，这些结果表明，动态phot 2运输从质膜到高尔基体和叶绿体外膜可能参与回避反应。
Chloroplasts change their position to adapt cellular activities to fluctuating environmental light conditions. Phototropins (phot1 and phot2 in Arabidopsis) are plant-specific blue light photoreceptors that perceive changes in light intensity and direction, and mediate actin-based chloroplast photorelocation movements. Both phot1 and phot2 regulate the chloroplast accumulation response, while phot2 is mostly responsible for the regulation of the avoidance response. Although it has been widely accepted that distinct intracellular localizations of phototropins are implicated in the specificity, the mechanism underlying the phot2-specific avoidance response has remained elusive. In this study, we examined the relationship of the phot2 localization pattern to the chloroplast photorelocation movement. First, the fusion of a nuclear localization signal with phot2, which effectively reduced the amount of phot2 in the cytoplasm, retained the activity for both the accumulation and avoidance responses, indicating that membrane-localized phot2 but not cytoplasmic phot2 is functional to mediate the responses. Importantly, some fractions of phot2, and of phot1 to a lesser extent, were localized on the chloroplast outer membrane. Moreover, the deletion of the C-terminal region of phot2, which was previously shown to be defective in blue light-induced Golgi localization and avoidance response, affected the localization pattern on the chloroplast outer membrane. Taken together, these results suggest that dynamic phot2 trafficking from the plasma membrane to the Golgi apparatus and the chloroplast outer membrane might be involved in the avoidance response.