Dynein‐deficient flagella respond to increased viscosity with contrasting changes in power and recovery strokes

Abstract

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.

Finite element models of flagella with sliding radial spokes and interdoublet links exhibit propagating waves under steady dynein loading

“… The hypothesized flutter instability with steady, suprathreshold axial dynein force is consistent with the abrupt onset of oscillations observed in reactivated axonemes as ATP concentration is increased. Geyer, Sartori, Friedrich, Julicher, and Howard () found that flagella exposed to increasing ATP concentration first display static bending, consistent with steady asymmetric dynein activity, then oscillatory flagellar beating at higher ATP concentrations, also consistent with increased, steady activity. The decrease in frequency with force density (Figure a and b) is consistent with the observed decrease in beat frequency in mutants lacking outer dynein arms (Brokaw & Kamiya, ). The decrease in oscillation frequency with increasing damping coefficient, that is, as the surrounding fluid becomes more viscous (Figure ), agrees with experimental observations of the effect of fluid viscosity on beat frequency (Wilson et al, ). …”

“…Viscosity characterizes the resistance of fluid to shear deformation. It has been observed in experiments that beat frequency decreases with increasing viscosity in uniflagellate mutants of Chlamydomonas reinhardtii while the waveforms of the oscillatory motion are conserved (Brokaw, ; Wilson, Gonzalez, Dutcher, & Bayly, ; Yagi et al, ). The effects of increasing viscosity were investigated in the current FE models by varying the coefficient of mass–proportional damping (distributed forces that oppose motion; Appendix B).…”

Microtubule glycylation promotes attachment of basal bodies to the cell cortex

“…Elevated viscosity has been reported to both alter ciliary and flagellar waveforms and to decrease ciliary beat frequency (Sleigh, 1966;Rikmenspoel, 1971;Minoura and Kamiya, 1995;Machemer, 1972). Ciliary dynein arm mutations alter the ciliary beat pattern and frequency when exposed to higher viscosity media, underscoring the importance of ciliary structure for cellular response to high viscosity conditions (Wilson et al, 2015). Because ttll3Δ mutants harbor shorter cilia, we suspect that ciliary beat patterns of these mutants are affected in ttll3Δ mutant cells at high viscosity to somehow reduce the forces transduced to BBs.…”

Mutations in PIH1D3 Cause X-Linked Primary Ciliary Dyskinesia with Outer and Inner Dynein Arm Defects

“…The CP, N-DRC, and inner dynein arms (IDAs) are responsible for modulation and regulation of the ciliary movement while the outer dynein arms (ODAs) are responsible for beat generation. 2 , 3 , 4 , 5 ODAs and IDAs are large multimeric protein complexes that are pre-assembled in the cytoplasm before being transported to the axonemes. 6 , 7 The identification of proteins responsible for correct assembly, DNAAFs, and the composition of these protein complexes are critical to understand the patho-mechanisms of motile cilia-related diseases such as primary ciliary dyskinesia (PCD).…”