External Ca2+ is essential for chloroplast movement induced by mechanical stimulation but not by light stimulation
External Ca2+ is essential for chloroplast movement induced by mechanical stimulation but not by light stimulation
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DOI：
10.1104/pp.010405
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发表时间：
2001-10-01
期刊：
影响因子：
7.4
通讯作者：
Kadota, A
中科院分区：
文献类型：
--
作者：
Sato, Y;Wada, M;Kadota, A
在蕨类植物Adiantum capillus-veneris中，叶绿体运动既受光刺激也受机械刺激。这两种类型的定向运动都依赖于基于动作的运动系统。为了探讨机械信号和光信号在叶绿体运动调控中的生理关系，我们研究了在光定位后运动已经受到限制的叶绿体的机械响应。在所有的光定位条件下，叶绿体的机械回避运动都被诱导，这表明机械刺激产生的机械特异性信号比光信号更重要，并重新激活了叶绿体的运动。当外部Ca2+对机械和光反应的诱导作用进行检查时，发现每个外部Ca2+的需求明显不同。在不含Ca2+的培养基中，机械响应受到抑制，但光响应没有受到影响。100 muM镧（La3+）和10 muM钆（Gd3+）（拉伸激活通道阻滞剂）可抑制叶绿体的机械再定位运动。然而，相同浓度的这些药物根本不影响光定位运动。这些结果表明，外部Ca2+的流入对叶绿体机械迁移的早期信号步骤至关重要，但对光迁移的早期信号步骤并不重要。这是首次报道叶绿体机械定位和光定位信号通路的分离。
In the fern Adiantum capillus-veneris, chloroplast movement is induced by mechanical stimulation as well as by light stimulation. Directional movement of both types depends an an actin-based motile system. To investigate the physiological relationship between mechanical and light signaling in the regulation of chloroplast movement, we examined the mechano-response of chloroplasts whose motility had been already restricted after photo-relocation. Chloroplast mechano-avoidance movement was induced under all of the photo-relocation conditions tested, indicating that mechano-specific signals generated by mechanical stimulation dominate over the light signals and reactivate the motility of chloroplasts. When the effects of external Ca2+ on the induction of mechano- and light responses were examined, strikingly different requirements of external Ca2+ were found for each. In medium without Ca2+, the mechano-response was suppressed but no effects were observed on photo-response. Mechano-relocation movement of chloroplasts was inhibited by 100 muM lanthanum (La3+), a plasma membrane calcium channel blocker, and by 10 muM gadolinium (Gd3+), a stretch-activated channel blocker. However, the same concentrations of these drugs did not affect the photo-relocation movement at all. These results suggest that the influx of external Ca2+ is crucial for the early signaling step of chloroplast mechano-relocation but not for that of photo-relocation. This is the first report showing the separation of signaling pathways in mechano- and photo-relocation of chloroplasts.