An auxilin-like J-domain protein, JAC1, regulates phototropin-mediated chloroplast movement in Arabidopsis
An auxilin-like J-domain protein, JAC1, regulates phototropin-mediated chloroplast movement in Arabidopsis
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DOI：
10.1104/pp.105.067371
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发表时间：
2005-09-01
期刊：
影响因子：
7.4
通讯作者：
Wada, M
中科院分区：
文献类型：
--
作者：
Suetsugu, N;Kagawa, T;Wada, M
环境光条件调节植物细胞中叶绿体的重新定位。在弱光条件下，叶绿体在光中积累(积累反应)，而在强光条件下，它们避开光(回避反应)。在拟南芥中，积累反应是由两个蓝光受体介导的，这两个蓝光受体称为趋光素(PHIt1和PHY2)，它们相互冗余地作用，而回避反应仅由PHY2介导。突变体是叶绿体积累反应所需的J结构域蛋白，在弱蓝光下缺乏积累反应，但在强蓝光下表现出正常的回避反应。在黑暗适应的野生型细胞中，叶绿体积累在细胞底部。在黑暗中，Jac1和Pho2突变体在这种叶绿体运动中都是有缺陷的。JAC1基因的定位克隆表明，该基因编码一个J-结构域的蛋白，类似于C末端的网状蛋白脱壳因子Axin。JAC1转录本和JAC1蛋白的数量不受光和促光激素的调节。在拟南芥叶肉细胞和洋葱(Allium Cepa)表皮细胞的瞬时表达实验中，绿色荧光蛋白-JAC1融合蛋白显示出与单独绿色荧光蛋白相似的定位模式，表明JAC1蛋白可能是一种可溶性胞质蛋白。综上所述，这些结果表明JAC1是光敏素介导的叶绿体运动的重要组成部分。
The ambient-light conditions mediate chloroplast relocation in plant cells. Under the low-light conditions, chloroplasts accumulate in the light (accumulation response), while under the high-light conditions, they avoid the light (avoidance response). In Arabidopsis (Arabidopsis thaliana), the accumulation response is mediated by two blue-light receptors, termed phototropins (phot1 and phot2) that act redundantly, and the avoidance response is mediated by phot2 alone. A mutant, J-domain protein required for chloroplast accumulation response 1 (jac1), lacks the accumulation response under weak blue light but shows a normal avoidance response under strong blue light. In dark-adapted wild-type cells, chloroplasts accumulate on the bottom of cells. Both the jac1 and phot2 mutants are defective in this chloroplast movement in darkness. Positional cloning of JAC1 reveals that this gene encodes a J-domain protein, resembling clathrin-uncoating factor auxilin at its C terminus. The amounts of JAC1 transcripts and JAC1 proteins are not regulated by light and by phototropins. A green fluorescent protein-JAC1 fusion protein showed a similar localization pattern to green fluorescent protein alone in a transient expression assay using Arabidopsis mesophyll cells and onion (Allium cepa) epidermal cells, suggesting that the JAC1 protein may be a soluble cytosolic protein. Together, these results suggest that JAC1 is an essential component of phototropin-mediated chloroplast movement.