Cytoplasmic calcium increases in response to changes in the gravity vector in hypocotyls and petioles of Arabidopsis seedlings
Cytoplasmic calcium increases in response to changes in the gravity vector in hypocotyls and petioles of Arabidopsis seedlings
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DOI：
10.1104/pp.107.106450
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发表时间：
2008-02-01
期刊：
影响因子：
7.4
通讯作者：
Sokabe, Masahiro
中科院分区：
文献类型：
--
作者：
Toyota, Masatsugu;Furuichi, Takuya;Sokabe, Masahiro
植物对各种各样的环境信号做出反应，包括重力矢量的变化（重力刺激）。在拟南芥（Arabidopsis thaliana）幼苗中，已知重力刺激增加细胞质游离钙浓度（[Ca 2 +]（c））。然而，负责[Ca 2 +]（c）增加的器官和潜在的细胞/分子机制仍有待解决。在这项研究中，使用拟南芥幼苗表达脱辅基水母发光蛋白，与超灵敏的光子计数相机相结合，我们澄清了器官的[Ca 2 +]（c）增加响应重力刺激和特征的[Ca 2 +]（c）增加的生理和药理学特性。当幼苗通过转动180度进行重力刺激时，它们的下胚轴和叶柄中的[Ca 2 +]（c）表现出短暂的双相增加。[Ca ~（2+）]（c）增加的第二个峰依赖于旋转角度而不是旋转速度，而初始峰则表现出完全相反的特征。这表明，第二个[Ca 2 +]（c）的增加是特定的重力矢量的变化。潜在的机械敏感性Ca 2+渗透通道（MSCC）抑制剂Gd 3+和La 3+，Ca 2+螯合剂1，2-双（2-氨基苯氧基）乙烷-N，N，N '，N'-四乙酸（BAPTA）和内膜Ca ~（2+）渗透通道抑制剂钌红抑制第二次[Ca ~（2+）]（c）增加，这表明它是由Ca 2+通过质膜中推定的MSCC流入和Ca 2+从细胞内Ca 2+库释放引起的。此外，第二个[Ca 2 +]（c）的增加被肌动蛋白破坏药物细胞松弛素B和latrunculin B衰减，但不是由微管破坏药物安磺灵和诺考达唑，这意味着肌动蛋白丝部分参与了假设的Ca 2+渗透通道的激活。这些结果表明，第二个[Ca 2 +]（c）增加通过MSCCs的拟南芥幼苗下胚轴和叶柄是重力反应。
Plants respond to a large variety of environmental signals, including changes in the gravity vector (gravistimulation). In Arabidopsis (Arabidopsis thaliana) seedlings, gravistimulation is known to increase the cytoplasmic free calcium concentration ([Ca2+](c)). However, organs responsible for the [Ca2+](c) increase and the underlying cellular/molecular mechanisms remain to be solved. In this study, using Arabidopsis seedlings expressing apoaequorin, a Ca2+-sensitive luminescent protein in combination with an ultrasensitive photon counting camera, we clarified the organs where [Ca2+](c) increases in response to gravistimulation and characterized the physiological and pharmacological properties of the [Ca2+](c) increase. When the seedlings were gravistimulated by turning 180 degrees, they showed a transient biphasic [Ca2+](c) increase in their hypocotyls and petioles. The second peak of the [Ca2+](c) increase depended on the angle but not the speed of rotation, whereas the initial peak showed diametrically opposite characters. This suggests that the second [Ca2+](c) increase is specific for changes in the gravity vector. The potential mechanosensitive Ca2+-permeable channel (MSCC) inhibitors Gd3+ and La3+, the Ca2+ chelator 1,2-bis(2-aminophenoxy) ethaneN, N,N',N'-tetraacetic acid (BAPTA), and the endomembrane Ca2+-permeable channel inhibitor ruthenium red suppressed the second [Ca2+](c) increase, suggesting that it arises from Ca2+ influx via putative MSCCs in the plasma membrane and Ca2+ release from intracellular Ca2+ stores. Moreover, the second [Ca2+](c) increase was attenuated by actin-disrupting drugs cytochalasin B and latrunculin B but not by microtubule-disrupting drugs oryzalin and nocodazole, implying that actin filaments are partially involved in the hypothetical activation of Ca2+-permeable channels. These results suggest that the second [Ca2+](c) increase via MSCCs is a gravity response in the hypocotyl and petiole of Arabidopsis seedlings.