The C-terminal kinase fragment of Arabidopsis phototropin 2 triggers constitutive phototropin responses
The C-terminal kinase fragment of Arabidopsis phototropin 2 triggers constitutive phototropin responses
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DOI：
10.1111/j.1365-313x.2007.03187.x
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发表时间：
2007-09-01
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：
Kong, Sam-Geun;Kinoshita, Toshinori;Nagatani, Akira
向光蛋白介导植物的向光性、叶绿体移位、气孔开放和叶片扁平等蓝光反应。趋光蛋白是主要结合在质膜上的亲水性色素蛋白。光2是拟南芥中两种向光蛋白之一，它以光依赖的方式与高尔基体结合。在这项研究中，我们分析了光2的N-末端光敏和C-末端激酶结构域的生物活性。为了这个目的，这些结构域融合到绿色荧光蛋白（GFP）和异位表达的野生型和拟南芥的phot 1 phot 2双突变体。激酶域融合到绿色荧光蛋白（P2CG）定位于质膜和高尔基体，而光敏域融合到绿色荧光蛋白（P2 NG）均匀定位在胞质溶胶中。因此，激酶结构域而不是感光结构域负责膜缔合。有趣的是，即使在黑暗条件下，P2 CG植物也表现出组成性蓝光反应，即气孔开放，叶绿体处于回避位置。相比之下，具有消除激酶活性的突变（P2C[D 720/N]G）的P2CG未能表现出这些反应。因此，建议phot 2激酶正确定位于细胞中的功能位点，并通过其激酶活性触发光信号转导。与P2CG相比，P2 NG除了部分抑制内源性向光蛋白引起的向光反应外，不影响光2反应。
Phototropins mediate various blue-light responses such as phototropism, chloroplast relocation, stomatal opening and leaf flattening in plants. Phototropins are hydrophilic chromoproteins that are mainly bound to the plasma membrane. One of two phototropins in Arabidopsis thaliana, phot2, associates with the Golgi apparatus in a light-dependent manner. In this study, we analyzed the biological activities of the N-terminal photosensory and C-terminal kinase domains of phot2. For this purpose, these domains were fused to green fluorescent protein (GFP) and ectopically expressed in the wild-type and a phot1 phot2 double mutant of Arabidopsis. The kinase domain fused to GFP (P2CG) was localized to the plasma membrane and the Golgi apparatus, whereas the photosensory domain fused to GFP (P2NG) was uniformly localized in the cytosol. Hence, the kinase domain rather than the photosensory domain is responsible for the membrane association. Interestingly, the P2CG plants exhibited constitutive blue-light responses even in dark conditions, i.e. stomata were open and chloroplasts were in the avoidance position. By contrast, P2CG with a mutation that abolishes the kinase activity (P2C[D720/N]G) failed to exhibit these responses. phot2 kinase is therefore suggested to be correctly localized to functional sites in the cell and to trigger light signal transduction through its kinase activity. In contrast to P2CG, P2NG did not affect the phot2 responses, except for partial inhibition of the phototropic response caused by the endogenous phototropins.