Jing Y, Yi K, Ren H
Institute of Cell Biology, Beijing Normal University, People's Republic of China.
Protoplasma. 2003;222(3-4):183-91. doi: 10.1007/s00709-003-0007-5. Epub 2003 Dec 19.
Pollen and skeletal muscle actins were purified and labeled with fluorescent dyes that have different emission wavelengths. Observation by electron microscopy shows that the fluorescent actins are capable to polymerize into filamentous actin in vitro, bind to myosin S-1 fragments, and have a critical concentration similar to unlabeled actin, indicating that they are functionally active. The globular actins from two sources were mixed and polymerized by the addition of ATP and salts. The copolymerization experiment shows that when excited by light of the appropriate wavelength, both red actin filaments (pollen actin) and green actin filaments (muscle actin) can be visualized under the microscope, but no filaments exhibiting both green and red colors are detected. Furthermore, coprecipitations of labeled pollen actin with unlabeled pollen and skeletal muscle actin were performed. Measurements of fluorescent intensity show that the amount of labeled pollen actin precipitating with pollen actin was much higher than that with skeletal muscle actin, indicating that pollen and muscle actin tend not to form heteropolymers. Injection of labeled pollen actin into living stamen hair cells results in the formation of normal actin filaments in transvacuolar strands and the cortical cytoplasm. In contrast, labeled skeletal muscle actin has detrimental effects on the cellular architecture. The results from coinjection of the actin-disrupting reagent cytochalasin D with pollen actin show that overexpression of pollen actin prolongs the displacement of the nucleus and facilitates the recovery of the nuclear position, actin filament architecture, and transvacuolar strands. However, muscle actin perturbs actin filaments when injected into stamen hair cells. Moreover, nuclear displacement occurs more rapidly when cytochalasin D and muscle actin are coinjected into the cell. It is concluded that actins from plant and animal sources behave differently in vitro and in vivo and that they are functionally not interchangeable.
花粉肌动蛋白和骨骼肌肌动蛋白被纯化并用具有不同发射波长的荧光染料标记。电子显微镜观察表明，荧光肌动蛋白能够在体外聚合成丝状肌动蛋白，与肌球蛋白S-1片段结合，并且具有与未标记肌动蛋白相似的临界浓度，表明它们具有功能活性。将来自两种来源的球状肌动蛋白混合，并通过添加ATP和盐使其聚合。共聚合实验表明，当用适当波长的光激发时，红色肌动蛋白丝（花粉肌动蛋白）和绿色肌动蛋白丝（肌肉肌动蛋白）在显微镜下均可被观察到，但未检测到同时呈现绿色和红色的丝。此外，还进行了标记的花粉肌动蛋白与未标记的花粉和骨骼肌肌动蛋白的共沉淀实验。荧光强度测量表明，与花粉肌动蛋白共沉淀的标记花粉肌动蛋白的量远高于与骨骼肌肌动蛋白共沉淀的量，表明花粉肌动蛋白和肌肉肌动蛋白倾向于不形成异源聚合物。将标记的花粉肌动蛋白注射到活的雄蕊毛细胞中会导致在液泡间链和皮层细胞质中形成正常的肌动蛋白丝。相比之下，标记的骨骼肌肌动蛋白对细胞结构有有害影响。将肌动蛋白破坏试剂细胞松弛素D与花粉肌动蛋白共同注射的结果表明，花粉肌动蛋白的过表达延长了细胞核的位移，并促进了核位置、肌动蛋白丝结构和液泡间链的恢复。然而，肌肉肌动蛋白注射到雄蕊毛细胞中时会扰乱肌动蛋白丝。此外，当细胞松弛素D和肌肉肌动蛋白共同注射到细胞中时，核位移发生得更快。得出的结论是，来自植物和动物来源的肌动蛋白在体外和体内表现不同，并且它们在功能上不可互换。
