Possible association of actin filaments with chloroplasts of spinach mesophyll cells in vivo and in vitro
Possible association of actin filaments with chloroplasts of spinach mesophyll cells in vivo and in vitro
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DOI：
10.1007/s00709-006-0189-8
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发表时间：
2006-11-01
期刊：
影响因子：
2.9
通讯作者：
Takagi, S.
中科院分区：
文献类型：
--
作者：
Kumatani, T.;Sakurai-Ozato, N.;Takagi, S.
菠菜（Spinacia oleracea L.）在低强度白色光下，叶绿体明显不动，似乎被肌动蛋白细丝的细束包围。高强度的蓝光诱导肌动蛋白依赖的叶绿体运动伴随着一对夫妇的外观，在每个细胞中的肌动蛋白丝直束，而高强度的红光基本上是无效的，在诱导这些反应。在低强度白色光下观察到的肌动蛋白组织被假定通过与叶绿体的直接相互作用在适当的细胞内位置锚定叶绿体中起作用。完整的叶绿体，保留其外包膜，叶片匀浆和Percoll离心后分离。在低强度白色光或黑暗下保存的叶片中，通过免疫印迹法在最后的完整叶绿体部分中没有检测到内源性肌动蛋白。然而，在与外源性添加骨骼肌丝状肌动蛋白的共沉淀试验中，在低速离心后沉淀的完整叶绿体部分中检测到肌动蛋白。肌动蛋白与叶绿体的结合明显依赖于孵育时间和叶绿体密度。用胰蛋白酶处理分离的叶绿体的外被膜，部分破坏后，肌动蛋白不再共沉淀。结果表明，菠菜叶片中的叶绿体可以直接与肌动蛋白相互作用，这种相互作用可能参与叶绿体的细胞内定位的调节。
In palisade mesophyll cells of spinach (Spinacia oleracea L.) kept under low-intensity white light, chloroplasts were apparently immobile and seemed to be surrounded by fine bundles of actin filaments. High-intensity blue light induced actin-dependent chloroplast movement concomitant with the appearance of a couple of long, straight bundles of actin filaments in each cell, whereas high-intensity red light was essentially ineffective in inducing these responses. The actin organization observed under low-intensity white light has been postulated to function in anchoring chloroplasts at proper intracellular positions through direct interaction with the chloroplasts. Intact chloroplasts, which retained their outer envelopes, were isolated after homogenization of leaves and Percoll centrifugation. No endogenous actin was detected by immunoblotting in the final intact-chloroplast fraction prepared from the leaves kept under low-intensity white light or in darkness. In cosedimentation assays with exogenously added skeletal muscle filamentous actin, however, actin was detected in the intact-chloroplast fraction precipitated after low-speed centrifugation. The association of actin with chloroplasts was apparently dependent on incubation time and chloroplast density. After partial disruption of the outer envelope of isolated chloroplasts by treatment with trypsin, actin was no longer coprecipitated. The results suggest that chloroplasts in spinach leaves can directly interact with actin, and that this interaction may be involved in the regulation of intracellular positioning of chloroplasts.