Rieu Jean-Paul, Delanoë-Ayari Hélène, Takagi Seiji, Tanaka Yoshimi, Nakagaki Toshiyuki
Institut Lumière Matière, UMR5306 Université Lyon 1-CNRS, Université de Lyon, 69622 Villeurbanne cedex, France
Institut Lumière Matière, UMR5306 Université Lyon 1-CNRS, Université de Lyon, 69622 Villeurbanne cedex, France.
J R Soc Interface. 2015 May 6;12(106). doi: 10.1098/rsif.2015.0099.
The slime mould Physarum polycephalum is a giant multinucleated cell exhibiting well-known Ca(2+)-dependent actomyosin contractions of its vein network driving the so-called cytoplasmic shuttle streaming. Its actomyosin network forms both a filamentous cortical layer and large fibrils. In order to understand the role of each structure in the locomotory activity, we performed birefringence observations and traction force microscopy on excised fragments of Physarum. After several hours, these microplasmodia adopt three main morphologies: flat motile amoeba, chain types with round contractile heads connected by tubes and motile hybrid types. Each type exhibits oscillations with a period of about 1.5 min of cell area, traction forces and fibril activity (retardance) when fibrils are present. The amoeboid types show only peripheral forces while the chain types present a never-reported force pattern with contractile rings far from the cell boundary under the spherical heads. Forces are mostly transmitted where the actomyosin cortical layer anchors to the substratum, but fibrils maintain highly invaginated structures and contribute to forces by increasing the length of the anchorage line. Microplasmodia are motile only when there is an asymmetry in the shape and/or the force distribution.
多头绒泡菌是一种巨大的多核细胞，其静脉网络表现出众所周知的依赖于Ca(2+)的肌动球蛋白收缩，驱动所谓的细胞质穿梭流动。其肌动球蛋白网络形成丝状皮层和大纤维。为了了解每个结构在运动活动中的作用，我们对多头绒泡菌的切除片段进行了双折射观察和牵引力显微镜观察。几小时后，这些微原质团呈现出三种主要形态：扁平能动变形虫、由管子连接圆形收缩头部的链状类型和能动混合类型。当存在纤维时，每种类型都表现出细胞面积、牵引力和纤维活性（延迟）约1.5分钟周期的振荡。变形虫类型仅显示外周力，而链状类型呈现一种从未报道过的力模式，在球形头部下方远离细胞边界处有收缩环。力大多在肌动球蛋白皮层锚定到基质的地方传递，但纤维维持高度内陷的结构，并通过增加锚定线的长度对力有贡献。微原质团只有在形状和/或力分布不对称时才会运动。
