DeBlasio Stacy L, Luesse Darron L, Hangarter Roger P
Department of Biology, Indiana University, Bloomington, 47405, USA.
Plant Physiol. 2005 Sep;139(1):101-14. doi: 10.1104/pp.105.061887. Epub 2005 Aug 19.
In Arabidopsis (Arabidopsis thaliana), light-dependent chloroplast movements are induced by blue light. When exposed to low fluence rates of light, chloroplasts accumulate in periclinal layers perpendicular to the direction of light, presumably to optimize light absorption by exposing more chloroplast area to the light. Under high light conditions, chloroplasts become positioned parallel to the incoming light in a response that can reduce exposure to light intensities that may damage the photosynthetic machinery. To identify components of the pathway downstream of the photoreceptors that mediate chloroplast movements (i.e. phototropins), we conducted a mutant screen that has led to the isolation of several Arabidopsis mutants displaying altered chloroplast movements. The plastid movement impaired1 (pmi1) mutant exhibits severely attenuated chloroplast movements under all tested fluence rates of light, suggesting that it is a necessary component for both the low- and high-light-dependant chloroplast movement responses. Analysis of pmi1 leaf cross sections revealed that regardless of the light condition, chloroplasts are more evenly distributed in leaf mesophyll cells than in the wild type. The pmi1-1 mutant was found to contain a single nonsense mutation within the open reading frame of At1g42550. This gene encodes a plant-specific protein of unknown function that appears to be conserved among angiosperms. Sequence analysis of the protein suggests that it may be involved in calcium-mediated signal transduction, possibly through protein-protein interactions.
在拟南芥（Arabidopsis thaliana）中，蓝光可诱导依赖光的叶绿体运动。当暴露于低光通量率下时，叶绿体聚集在垂直于光方向的平周层中，推测这是为了通过使更多的叶绿体面积暴露于光下来优化光吸收。在高光条件下，叶绿体以一种能减少对可能损害光合机制的光强度暴露的反应，变得与入射光平行排列。为了鉴定介导叶绿体运动的光感受器（即向光素）下游途径的成分，我们进行了一次突变体筛选，该筛选已导致分离出几个显示叶绿体运动改变的拟南芥突变体。质体运动受损1（pmi1）突变体在所有测试的光通量率下都表现出严重减弱的叶绿体运动，这表明它是低光和高光依赖的叶绿体运动反应的必要成分。对pmi1叶片横切面的分析表明，无论光照条件如何，叶绿体在叶肉细胞中的分布都比野生型更均匀。发现pmi1-1突变体在At1g42550的开放阅读框内含有一个单一的无义突变。该基因编码一种功能未知的植物特异性蛋白，这种蛋白似乎在被子植物中保守。对该蛋白的序列分析表明，它可能参与钙介导的信号转导，可能是通过蛋白质-蛋白质相互作用。
