Kohno T, Shimmen T
Department of Botany, Faculty of Science, University of Tokyo, Japan.
J Cell Biol. 1988 May;106(5):1539-43. doi: 10.1083/jcb.106.5.1539.
Pollen tubes show active cytoplasmic streaming. We isolated organelles from pollen tubes and tested their ability to slide along actin bundles in characean cell models. Here, we show that sliding of organelles was ATP-dependent and that motility was lost after N-ethylmaleimide or heat treatment of organelles. On the other hand, cytoplasmic streaming in pollen tube was inhibited by either N-ethylmaleimide or heat treatment. These results strongly indicate that cytoplasmic streaming in pollen tubes is supported by the "actomyosin"-ATP system. The velocity of organelle movement along characean actin bundles was much higher than that of the native streaming in pollen tubes. We suggested that pollen tube "myosin" has a capacity to move at a velocity of the same order of magnitude as that of characean myosin. Moreover, the motility was high at Ca2+ concentrations lower than 0.18 microM (pCa 6.8) but was inhibited at concentration higher than 4.5 microM (pCa 5.4). In conclusion, cytoplasmic streaming in pollen tubes is suggested to be regulated by Ca2+ through "myosin" inactivation.
花粉管表现出活跃的细胞质环流。我们从花粉管中分离出细胞器，并在轮藻细胞模型中测试它们沿肌动蛋白束滑动的能力。在此，我们表明细胞器的滑动依赖于ATP，并且在对细胞器进行N - 乙基马来酰亚胺处理或热处理后运动性丧失。另一方面，花粉管中的细胞质环流被N - 乙基马来酰亚胺或热处理所抑制。这些结果有力地表明，花粉管中的细胞质环流由“肌动球蛋白” - ATP系统支持。细胞器沿轮藻肌动蛋白束移动的速度远高于花粉管中天然环流的速度。我们认为花粉管“肌球蛋白”具有以与轮藻肌球蛋白相同数量级的速度移动的能力。此外，在Ca2 +浓度低于0.18微摩尔（pCa 6.8）时运动性较高，但在浓度高于4.5微摩尔（pCa 5.4）时受到抑制。总之，花粉管中的细胞质环流被认为是通过“肌球蛋白”失活由Ca2 +调节的。
