Graduate School of Science and Engineering, Ritsumeikan University, 1-1-1 Nojihigashi, Kusatsu, Shiga, 525-8577, Japan.
Planta. 2012 Dec;236(6):1889-97. doi: 10.1007/s00425-012-1735-6. Epub 2012 Aug 30.
Chloroplasts change their intracellular distribution in response to light intensity. CHUP1 (CHLOROPLAST UNUSUAL POSITIONING1) is indispensable for this response in Arabidopsis thaliana. However, involvement of CHUP1 in light-induced chloroplast movement is unknown in other plants. In this study, CHUP1 orthologues were isolated from a moss, Physcomitrella patens, and a fern, Adiantum capillus-veneris, by cDNA library screening and PCR cloning based on the P. patens genome sequence. Functional motifs found in CHUP1 of A. thaliana were conserved among the CHUP1 orthologues. In addition to the putative functional regions, the C-terminal regions (approximately 250 amino acids), which are unique in CHUP1s, were highly conserved. Green fluorescent protein (GFP) fusions of P. patens CHUP1s (PpCHUP1A, PpCHUP1B and PpCHUP1C) were transiently expressed in protoplast cells. All GFP fusions were localized on the chloroplasts. Light-induced chloroplast avoidance movement of chup1 disruptants of P. patens was examined in the presence of cytoskeletal inhibitors because of the utilization of both microtubules and actin filaments for the movement in P. patens. When actin filaments were disrupted by cytochalasin B, the wild type (WT) and all chup1 disruptants showed chloroplast avoidance movement. However, when microtubules were disrupted by Oryzalin, chloroplasts in ∆chup1A and ∆chup1A/B rarely moved and stayed in the strong light-irradiated area. On the other hand, WT, ∆chup1B and ∆chup1C showed chloroplast avoidance movement. These results suggest that PpCHUP1A predominantly mediates the actin-based light-induced chloroplast avoidance movement. This study reveals that CHUP1 functions on the chloroplasts and is involved in the actin-based light-induced chloroplast avoidance movement in P. patens.
叶绿体根据光强改变其在细胞内的分布。CHUP1（叶绿体异常定位 1）在拟南芥中对此响应是不可或缺的。然而，CHUP1 在其他植物的光诱导叶绿体运动中的参与情况尚不清楚。在这项研究中，通过 cDNA 文库筛选和基于 P. patens 基因组序列的 PCR 克隆，从苔藓 Physcomitrella patens 和蕨类植物 Adiantum capillus-veneris 中分离出 CHUP1 的同源物。在拟南芥 CHUP1 中发现的功能基序在 CHUP1 同源物中是保守的。除了假定的功能区域外，在 CHUP1s 中特有的 C 末端区域（约 250 个氨基酸）高度保守。P. patens CHUP1s（PpCHUP1A、PpCHUP1B 和 PpCHUP1C）的绿色荧光蛋白（GFP）融合体在原生质体细胞中瞬时表达。所有 GFP 融合物都定位于叶绿体上。由于在 P. patens 中运动需要微管和肌动蛋白丝，因此在存在细胞骨架抑制剂的情况下检查了 P. patens chup1 突变体的光诱导叶绿体回避运动。当用细胞松弛素 B 破坏肌动蛋白丝时，野生型（WT）和所有 chup1 突变体都表现出叶绿体回避运动。然而，当用 Orzalin 破坏微管时，Δchup1A 和 Δchup1A/B 中的叶绿体很少移动并停留在强光照射区域。另一方面，WT、Δchup1B 和 Δchup1C 显示出叶绿体回避运动。这些结果表明，PpCHUP1A 主要介导基于肌动蛋白的光诱导叶绿体回避运动。本研究表明，CHUP1 定位于叶绿体上，并参与 P. patens 中基于肌动蛋白的光诱导叶绿体回避运动。
