Wilson Kate S, Gonzalez Olivia, Dutcher Susan K, Bayly Philip V
Department of Mechanical Engineering and Materials Science, Washington University, St. Louis, Missouri.
Department of Genetics, Washington University, St. Louis, Missouri.
Cytoskeleton (Hoboken). 2015 Sep;72(9):477-90. doi: 10.1002/cm.21252. Epub 2015 Sep 16.
Changes in the flagellar waveform in response to increased viscosity were investigated in uniflagellate mutants of Chlamydomonas reinhardtii. We hypothesized that the waveforms of mutants lacking different dynein arms would change in different ways as viscosity was increased, and that these variations would illuminate the feedback pathways from force to dynein activity. Previous studies have investigated the effects of viscosity on cell body motion, propulsive force, and power in different mutants, but the effect on waveform has not yet been fully characterized. Beat frequency decreases with viscosity in wild-type uniflagellate (uni1) cells, and outer dynein arm deficient (oda2) mutants. In contrast, the inner dynein arm mutant ida1 (lacking I1/f) maintains beat frequency at high viscosity but alters its flagellar waveform more than either wild-type or oda2. The ida1 waveform is narrower than wild-type, primarily due to an abbreviated recovery stroke; this difference is amplified at high viscosity. The oda2 mutant in contrast, maintains a consistent waveform at high and low viscosity with a slightly longer power stroke than wild-type. Analysis of the delays and shear displacements between bends suggest that direct force feedback in the outer dynein arm system may initiate switching of dynein activity. In contrast, I1/f dynein appears to delay switching, most markedly at the initiation of the power stroke, possibly by controlling inter-doublet separation.
在莱茵衣藻的单鞭毛突变体中，研究了鞭毛波形对粘度增加的响应。我们假设，随着粘度增加，缺乏不同动力蛋白臂的突变体的波形会以不同方式变化，并且这些变化将阐明从力到动力蛋白活性的反馈途径。以前的研究调查了粘度对不同突变体细胞体运动、推进力和功率的影响，但对波形的影响尚未完全明确。在野生型单鞭毛（uni1）细胞和外动力蛋白臂缺陷（oda2）突变体中，搏动频率随粘度降低。相比之下，内动力蛋白臂突变体ida1（缺乏I1/f）在高粘度下保持搏动频率，但比野生型或oda2更改变其鞭毛波形。ida1波形比野生型窄，主要是由于恢复冲程缩短；这种差异在高粘度下会放大。相比之下，oda2突变体在高粘度和低粘度下保持一致的波形，动力冲程比野生型略长。对弯曲之间的延迟和剪切位移的分析表明，外动力蛋白臂系统中的直接力反馈可能启动动力蛋白活性的切换。相比之下，I1/f动力蛋白似乎会延迟切换，在动力冲程开始时最为明显，可能是通过控制双联体间的间距。
