Analysis on the relocation movement of chloroplasts in fern and moss cells

本文分析了光和机械刺激诱导蕨类植物和藓类植物细胞叶绿体移位运动的机制，通过改变细胞外培养液中Ca^2+浓度和应用Ca^2+转运抑制剂（La^3+，Gd^3+）分析了Ca^2+在这些响应信号转导中的作用。在蕨类植物和藓类植物细胞中，外源Ca^2+的内流在机械力诱导的叶绿体移位中起重要作用，而在光诱导的叶绿体移位中则不起作用，这表明Ca^2+在机械力和光诱导的叶绿体移位的信号转导中起不同的作用。在荧光显微镜下观察到转化体细胞内肌动蛋白丝和微管的结构。在光迁移过程中和光迁移后，微管与叶绿体紧密相连。肌动蛋白丝的重组过程中也观察到photorelocation运动。在叶绿体聚集处周围出现网状肌动蛋白结构。这些结果表明两种细胞骨架在叶绿体移位运动中的重要作用。在蕨类细胞中，这些GFP融合构建体不起作用。然而，通过改变荧光标记，我们成功地在活蕨类植物细胞中的肌动蛋白丝的可视化。

Mechanisms of chloroplast relocation movement induced by light and mechanical stimuli were analyzed in fern and moss cells.Contribution of Ca^<2+> in the signal transduction of these responses was analyzed by changing the Ca^<2+> concentration of external media and by application of Ca^<2+> transport inhibitors (La^<3+>, Gd^<3+>). In both fern and moss cells, influx of Ca^<2+> from the external source was found to be essential in mechano-induced chloroplast relocation but not in the light-induced one, showing the different role of Ca^<2+> in the signal transduction of mechano- and light-induced responses.GFP-tubulin and GFP-talin genes were introduced to moss cells and stable transformants were obtained. In the transformants, intracellular architecture of actin filaments and of microtubules in the live cells was easily observed under fluorescence microscope. During and after photorelocation movement, tight association of microtubules to the chloroplasts was noticed. Reorganization of actin filaments was also observed during photorelocation movement. Reticulate actin structure appeared around the place of chloroplast accumulation. These results indicate the significant roles of both cytoskeletons in the chloroplast relocation movement. In fern cells, these GFP-fusion constructs did not work. However, by changing the fluorescent label, we succeeded in the visualization of actin filaments in live fern cells.