Distinct Responses of Chloroplasts to Blue and Green Laser Microbeam Irradiations in the Centric Diatom Pleurosira laevis
Distinct Responses of Chloroplasts to Blue and Green Laser Microbeam Irradiations in the Centric Diatom Pleurosira laevis
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中心硅藻侧膜藻叶绿体对蓝色和绿色激光微束照射的独特反应
DOI：
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发表时间：
2007
影响因子：
3.3
通讯作者：
Masakatsu Watanabe
中科院分区：
文献类型：
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作者：
I. Shihira;Takanori Nakamura;S. Higashi;Masakatsu Watanabe
中心型光滑侧链藻是一种大型单细胞藻，其中约200个叶绿体响应于蓝光照射通过跨液泡细胞质链向核细胞质迁移，相反，响应于绿色光照射向皮层细胞质迁移。我们使用共聚焦显微镜提供的扫描激光微束进行细胞内照射，分析了这些光诱导的叶绿体迁移。点照射的蓝色激光微束诱导的快速组装成核细胞质的叶绿体无论斑点的位置和斑点的数量。另一方面，一个或两个点的绿色激光微束诱导叶绿体积累的点，虽然增加点数抑制叶绿体积累在每个点。在我们的实验条件下，约1分钟的蓝光照射足以刺激运动，而绿色光照射需要不间断和更长的照射时间（约15分钟）。 蓝光诱导的叶绿体组装需要胞外Ca 2+，且可被Ca 2+通道拮抗剂抑制。此外，当单个光斑破碎并分散在更大面积的质膜上时，叶绿体的迁移效率更高。这些观察结果表明，蓝光诱导质膜的反应，随后激活Ca2+渗透通道。这一系列的生理事件与以前观察到的机械刺激引起的叶绿体运动是相同的。此外，用细胞骨架破坏剂秋水仙碱和细胞松弛素D进行的实验表明，蓝光诱导的叶绿体运动需要微管，而绿色光诱导的对光束点的反应需要肌动蛋白丝。
The centric diatomPleurosira laevis is a large unicellular alga, in which ca 200 chloroplasts migrate toward the nuclear cytoplasm through the transvacuolar cytoplasmic strands in response to blue‐light irradiation and, on the contrary, toward the cortical cytoplasm in response to green‐light irradiation. We analyzed these light‐induced chloroplast migrations using a scanning laser microbeam provided by a confocal microscope for intracellular irradiation. Spot irradiation of a blue laser microbeam induced rapid assemblage of chroloplasts into the nuclear cytoplasm regardless of the spot position and spot number. On the other hand, one or two spots of green laser microbeam induced chloroplast accumulation at the spots, although increasing spot numbers suppressed chloroplast accumulation at each spot. In our experimental condition, ca 1 min of blue‐light irradiation was sufficient to stimulate movement, whereas green‐light irradiation required uninterrupted and longer irradiation time (ca 15 min). Chloroplast assemblage induced by blue‐light required extracellular Ca2+, and was inhibited by Ca2+channel antagonists. Furthermore, higher efficiencies of chloroplast migration were obtained when a single beam spot was fragmented and scattered over wider area of plasma membrane. These observations suggested that blue‐light induced a response at the plasma membrane, which subsequently activated Ca2+permeable channels. This sequence of physiological events is identical to what was previously observed with chloroplast movement in response to mechanical stimulation. Furthermore, experiments with the cytoskeleton‐disrupting agents, colchicine and cytochalasin D, indicated that blue‐light‐induced chloroplast movement required microtubules whereas the green‐light‐induced response to beam spot required actin filaments.