Department of Biological Sciences, Oakland University, Rochester, Michigan, USA.
Cytoskeleton (Hoboken). 2021 Feb;78(2):36-51. doi: 10.1002/cm.21656. Epub 2021 Mar 15.
The mechanism that allows the axoneme of eukaryotic cilia and flagella to produce both helical and planar beating is an enduring puzzle. The nine outer doublets of eukaryotic cilia and flagella are arranged in a circle. Therefore, each doublet pair with its associated dynein motors, should produce torque to bend the flagellum in a different direction. Sequential activation of each doublet pair should, therefore result in a helical bending wave. In reality, most cilia and flagella have a well-defined bending plane and many exhibit an almost perfectly flat (planar) beating pattern. In this analysis we examine the physics that governs flagellar bending, and arrive at two distinct possibilities that could explain the mechanism of planar beating. Of these, the mechanism with the best observational support is that the flagellum behaves as two ribbons of doublets interacting with a central partition. We also examine the physics of torsion in flagella and conclude that torsion could play a role in transitioning from a planar to a helical beating modality in long flagella. Lastly, we suggest some tests that would provide theoretical and/or experimental evaluation of our proposals.
让真核纤毛和鞭毛的轴丝产生螺旋和平面运动的机制一直是个谜。真核纤毛和鞭毛的九个外部二联体按圆形排列。因此，每一对二联体及其相关的动力蛋白都应该产生扭矩，使鞭毛向不同的方向弯曲。因此，每个二联体对的顺序激活应该导致螺旋弯曲波。实际上，大多数纤毛和鞭毛都有一个明确的弯曲平面，许多表现出几乎完全平坦（平面）的拍打模式。在这项分析中，我们研究了控制鞭毛弯曲的物理学，并得出了两种可能的解释平面运动机制的独特可能性。在这些可能性中，最有观察支持的机制是鞭毛表现为两个与中央隔板相互作用的二联体带。我们还研究了鞭毛的扭转物理学，并得出结论，扭转可能在长鞭毛中从平面到螺旋拍打模式的转变中发挥作用。最后，我们提出了一些测试，这些测试将对我们的建议进行理论和/或实验评估。
