Suetsugu Noriyuki, Higa Takeshi, Kong Sam-Geun, Wada Masamitsu
Department of Biology, Faculty of Sciences, Kyushu University, Fukuoka 812-8581, Japan.
Department of Biology, Faculty of Sciences, Kyushu University, Fukuoka 812-8581, Japan
Plant Physiol. 2015 Oct;169(2):1155-67. doi: 10.1104/pp.15.00214. Epub 2015 Aug 31.
Organelle movement and positioning play important roles in fundamental cellular activities and adaptive responses to environmental stress in plants. To optimize photosynthetic light utilization, chloroplasts move toward weak blue light (the accumulation response) and escape from strong blue light (the avoidance response). Nuclei also move in response to strong blue light by utilizing the light-induced movement of attached plastids in leaf cells. Blue light receptor phototropins and several factors for chloroplast photorelocation movement have been identified through molecular genetic analysis of Arabidopsis (Arabidopsis thaliana). PLASTID MOVEMENT IMPAIRED1 (PMI1) is a plant-specific C2-domain protein that is required for efficient chloroplast photorelocation movement. There are two PLASTID MOVEMENT IMPAIRED1-RELATED (PMIR) genes, PMIR1 and PMIR2, in the Arabidopsis genome. However, the mechanism in which PMI1 regulates chloroplast and nuclear photorelocation movements and the involvement of PMIR1 and PMIR2 in these organelle movements remained unknown. Here, we analyzed chloroplast and nuclear photorelocation movements in mutant lines of PMI1, PMIR1, and PMIR2. In mesophyll cells, the pmi1 single mutant showed severe defects in both chloroplast and nuclear photorelocation movements resulting from the impaired regulation of chloroplast-actin filaments. In pavement cells, pmi1 mutant plants were partially defective in both plastid and nuclear photorelocation movements, but pmi1pmir1 and pmi1pmir1pmir2 mutant lines lacked the blue light-induced movement responses of plastids and nuclei completely. These results indicated that PMI1 is essential for chloroplast and nuclear photorelocation movements in mesophyll cells and that both PMI1 and PMIR1 are indispensable for photorelocation movements of plastids and thus, nuclei in pavement cells.
细胞器的运动和定位在植物基本细胞活动以及对环境胁迫的适应性反应中发挥着重要作用。为了优化光合光利用，叶绿体朝着弱蓝光移动（积累反应）并逃离强蓝光（回避反应）。细胞核也会通过利用叶细胞中附着质体的光诱导运动来响应强蓝光。通过对拟南芥（Arabidopsis thaliana）的分子遗传分析，已鉴定出蓝光受体向光素以及叶绿体光重新定位运动的几个相关因子。质体运动受损1（PMI1）是一种植物特有的C2结构域蛋白，是叶绿体高效光重新定位运动所必需的。拟南芥基因组中有两个与质体运动受损1相关（PMIR）的基因，即PMIR1和PMIR2。然而，PMI1调节叶绿体和细胞核光重新定位运动的机制以及PMIR1和PMIR2在这些细胞器运动中的作用仍不清楚。在这里，我们分析了PMI1、PMIR1和PMIR2突变体品系中的叶绿体和细胞核光重新定位运动。在叶肉细胞中，pmi1单突变体在叶绿体和细胞核光重新定位运动中均表现出严重缺陷，这是由于叶绿体 - 肌动蛋白丝的调节受损所致。在铺板细胞中，pmi1突变体植株在质体和细胞核光重新定位运动中均部分存在缺陷，但pmi1pmir1和pmi1pmir1pmir2突变体品系完全缺乏质体和细胞核的蓝光诱导运动反应。这些结果表明PMI1对于叶肉细胞中的叶绿体和细胞核光重新定位运动至关重要，并且PMI1和PMIR1对于铺板细胞中质体以及细胞核的光重新定位运动都是不可或缺的。
