Probing the role of mechanical properties of axonemes in flagellar motion in Chlamydomonas reinhardtii

Brian Lewis1, Susan K. Dutcher2, Ruth Okamoto3, Ellyn Ranz3, Junyi Ying3, Jin-Yu Shao3, and Philip V. Bayly3

1) Department of Pediatrics, Washington University Medical School, St. Louis, MO 63110 2) Department of Genetics, Washington University Medical School, St. Louis, MO 63110 3) School of Engineering, Washington University, St. Louis, MO 63105

Flagellar motion in Chlamydomonas reinhardtii arises from the coordinated propagation of bends along the flagella. This propagation is caused by the dynein driven sliding of the microtubules relative to one another. Dyneins are protein motors that promote sliding via ATP hydrolysis. They work in a coordinated fashion with other elements of the 9+2 axoneme that include the nexin links, radial spokes and central pair to generate flagellar motion. The mechanics that are responsible for dynein activity are not very well understood. We want to gain insight on the role of flagellar stiffness on dynein coordination and the generation of waveforms. TaxolŽ (paclitaxel) is reported to alter the stiffness of microtubules. Flagella are treated with 18µM Taxol, which a concentration that arrests cells in mitosis. The flagellar waveforms of these cells were quantitatively analyzed by a new method with good spatial and temporal resolution using high-speed video microscopy as described previously (Bayly et al., 2010). This technique provides the shape, shear angle, curvature, and bend propagation speeds along the length of the flagellum. The waveforms of the Taxol treated cells have a lower beat frequency than control cells. Also, bends initiated less reliably and propagated at a slower rate along the flagellum in cells treated with Taxol. To measure the effects of Taxol on microtubule stiffness, we are developing methods for capturing cells in an optical trap system.

e-mail address of presenting author: dutcher@genetics.wustl.edu