Department of Biological Sciences, Graduate School of Science and Engineering, Tokyo Metropolitan University, Tokyo 192-0397, Japan.
Plant Physiol. 2011 Mar;155(3):1205-13. doi: 10.1104/pp.110.171553. Epub 2011 Jan 19.
Chloroplasts change their positions in the cell depending on the light conditions. In the dark, chloroplasts in fern prothallia locate along the anticlinal wall (dark position). However, chloroplasts become relocated to the periclinal wall (light position) when the light shines perpendicularly to the prothallia. Red light is effective in inducing this relocation in Adiantum capillus-veneris, and neochrome1 (neo1) has been identified as the red light receptor regulating this movement. Nevertheless, we found here that chloroplasts in neo1 mutants still become relocated from the dark position to the light position under red light. We tested four neo1 mutant alleles (neo1-1, neo1-2, neo1-3, and neo1-4), and all of them showed the red-light-induced chloroplast relocation. Furthermore, chloroplast light positioning under red light occurred also in Pteris vittata, another fern species naturally lacking the neo1-dependent phenomenon. The light positioning of chloroplasts occurred independently of the direction of red light, a response different to that of the neo1-dependent movement. Photosynthesis inhibitors 3-(3,4 dichlorophenyl)-1,1-dimethylurea or 2,5-dibromo-3-isopropyl-6-methyl-p-benzoquinone blocked this movement. Addition of sucrose (Suc) or glucose to the culture medium induced migration of the chloroplasts to the periclinal wall in darkness. Furthermore, Suc could override the effects of 3-(3,4 dichlorophenyl)-1,1-dimethylurea. Interestingly, the same light positioning was evident for nuclei under red light in the neo1 mutant. The nuclear light positioning was also induced in darkness with the addition of Suc or glucose. These results indicate that photosynthesis-dependent nondirectional movement contributes to the light positioning of these organelles in addition to the neo1-dependent directional movement toward light.
叶绿体根据光照条件改变在细胞中的位置。在黑暗中，蕨类原叶体中的叶绿体位于垂周壁上（黑暗位置）。然而，当光线垂直照射到原叶体时，叶绿体被重新定位到平周壁（光照位置）。红光有效地诱导维纳斯发蕨中的这种重定位，并且已经鉴定出作为调节该运动的红光受体的新色素 1（neo1）。然而，我们在这里发现，在 neo1 突变体中，叶绿体仍然在红光下从黑暗位置重新定位到光照位置。我们测试了四个 neo1 突变等位基因（neo1-1、neo1-2、neo1-3 和 neo1-4），它们都表现出红光诱导的叶绿体重定位。此外，在另一种自然缺乏 neo1 依赖性现象的蕨类植物蜈蚣草中，叶绿体在红光下的光定位也发生了。叶绿体在红光下的光定位独立于红光的方向，与 neo1 依赖性运动的反应不同。光合作用抑制剂 3-(3,4-二氯苯基）-1,1-二甲基脲或 2,5-二溴-3-异丙基-6-甲基-p-苯醌阻断了这种运动。在培养基中添加蔗糖（Suc）或葡萄糖会诱导叶绿体在黑暗中向平周壁迁移。此外，Suc 可以覆盖 3-(3,4-二氯苯基）-1,1-二甲基脲的作用。有趣的是，在 neo1 突变体中，细胞核在红光下也表现出相同的光定位。在黑暗中添加 Suc 或葡萄糖也会诱导细胞核的光定位。这些结果表明，除了 neo1 依赖性的朝向光的定向运动之外，光合作用依赖性的无方向运动有助于这些细胞器的光定位。
