Department of Molecular Biophysics and Biochemistry, Yale University, New Haven, CT 06511, USA.
Max Planck Institute for the Physics of Complex Systems, Dresden 01187, Germany.
Curr Biol. 2016 Apr 25;26(8):1098-103. doi: 10.1016/j.cub.2016.02.053. Epub 2016 Mar 31.
When the green alga Chlamydomonas reinhardtii swims, it uses the breaststroke beat of its two flagella to pull itself forward [1]. The flagellar waveform can be decomposed into a static component, corresponding to an asymmetric time-averaged shape, and a dynamic component, corresponding to the time-varying wave [2]. Extreme lightening conditions photoshock the cell, converting the breaststroke beat into a symmetric sperm-like beat, which causes a reversal of the direction of swimming [3]. Waveform conversion is achieved by a reduction in magnitude of the static component, whereas the dynamic component remains unchanged [2]. The coupling between static and dynamic components, however, is poorly understood, and it is not known whether the static component requires the dynamic component or whether it can exist independently. We used isolated and reactivated axonemes [4] to investigate the relation between the two beat components. We discovered that, when reactivated in the presence of low ATP concentrations, axonemes displayed the static beat component in absence of the dynamic component. Furthermore, we found that the amplitudes of the two components depend on ATP in qualitatively different ways. These results show that the decomposition into static and dynamic components is not just a mathematical concept but that the two components can independently control different aspects of cell motility: the static component controls swimming direction, whereas the dynamic component provides propulsion.
当绿藻衣藻游动时，它使用两条鞭毛的蛙泳动作将自己向前拉[1]。鞭毛的波形可以分解为静态分量，对应于不对称的时间平均形状，和动态分量，对应于时变波[2]。极端的光照条件会使细胞休克，将蛙泳动作转换为对称的精子状动作，从而导致游动方向反转[3]。波形转换是通过静态分量的幅度减小来实现的，而动态分量保持不变[2]。然而，静态和动态分量之间的耦合理解得很差，并且不知道静态分量是否需要动态分量，或者它是否可以独立存在。我们使用分离和重新激活的轴丝[4]来研究这两个拍打成分之间的关系。我们发现，当在低 ATP 浓度下重新激活时，轴丝在没有动态分量的情况下显示出静态拍打成分。此外，我们还发现两个分量的幅度取决于 ATP 的方式在定性上是不同的。这些结果表明，分解为静态和动态分量不仅仅是一个数学概念，而是这两个分量可以独立控制细胞运动的不同方面：静态分量控制游动方向，而动态分量提供推进力。
