Molecular basis of the functional specificities of phototropin 1 and 2
Molecular basis of the functional specificities of phototropin 1 and 2
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DOI：
10.1111/j.1365-313x.2008.03605.x
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发表时间：
2008-11-01
期刊：
影响因子：
7.2
通讯作者：
Nagatani, Akira
中科院分区：
文献类型：
--
作者：
Aihara, Yusuke;Tabata, Ryohei;Nagatani, Akira
向光素是植物中的一种蓝光感受器，它介导向光性、叶绿体迁移、气孔开放和叶片扁平化反应。趋光素分为两个功能部分，N-末端光敏部分和C-末端信号传导部分。Phototropin通过N端的光、氧或电压（LOV）结构域感知光刺激;然后将信号分子内转导至C端激酶结构域。拟南芥中存在两种功能不同但相互重叠的趋光蛋白phot 1和phot 2。Phot 1介导的反应灵敏度高于phot 2。Phot 2介导的特异性反应，如叶绿体回避反应和叶绿体暗定位。为了阐明phot 1和phot 2功能特异性的分子基础，我们交换了phot 1和phot 2的N末端和C末端部分，将它们与GFP融合，并在phot 1 phot 2突变背景中在PHOT 2启动子下表达它们。对于向光性和其他反应，嵌合phototropin组成的phot 1 N-末端和phot 2C-末端部分（P1 n/2cG）是几乎一样敏感的phot 1，而反向组合（P2 n/1cG）的功能与较低的敏感性。因此，N-末端部分主要决定了向光蛋白的敏感性。出乎意料的是，P1 n/2cG和P2 n/1cG介导的叶绿体回避反应，这是特定的光2。因此，叶绿体回避活动似乎被抑制的N-和C-末端部分的phot 1的组合。与叶绿体回避反应，叶绿体暗定位观察到P2 G和P2 n/1cG，但不是P1 G或P1 n/2cG，这表明，一个特定的结构中的N-末端部分的phot 2是需要这种活性。
A blue-light photoreceptor in plants, phototropin, mediates phototropism, chloroplast relocation, stomatal opening, and leaf-flattening responses. Phototropin is divided into two functional moieties, the N-terminal photosensory and the C-terminal signaling moieties. Phototropin perceives light stimuli by the light, oxygen or voltage (LOV) domain in the N-terminus; the signal is then transduced intramolecularly to the C-terminal kinase domain. Two phototropins, phot1 and phot2, which have overlapping and distinct functions, exist in Arabidopsis thaliana. Phot1 mediates responses with higher sensitivity than phot2. Phot2 mediates specific responses, such as the chloroplast avoidance response and chloroplast dark positioning. To elucidate the molecular basis for the functional specificities of phot1 and phot2, we exchanged the N- and C-terminal moieties of phot1 and phot2, fused them to GFP and expressed them under the PHOT2 promoter in the phot1 phot2 mutant background. With respect to phototropism and other responses, the chimeric phototropin consisting of phot1 N-terminal and phot2 C-terminal moieties (P1n/2cG) was almost as sensitive as phot1; whereas the reverse combination (P2n/1cG) functioned with lower sensitivity. Hence, the N-terminal moiety mainly determined the sensitivity of the phototropins. Unexpectedly, both P1n/2cG and P2n/1cG mediated the chloroplast avoidance response, which is specific to phot2. Hence, chloroplast avoidance activity appeared to be suppressed specifically in the combination of N- and C-terminal moieties of phot1. Unlike the chloroplast avoidance response, chloroplast dark positioning was observed for P2G and P2n/1cG but not for P1G or P1n/2cG, suggesting that a specific structure in the N-terminal moiety of phot2 is required for this activity.