Calcium‐dependent flagellar motility activation in Chlamydomonas reinhardtii in response to mechanical agitation

Abstract Flagellar beating in Chlamydomonas was found to be activated by mechanical stimulation. Immediately after a wild‐type cell suspension was vortexed, the average swimming velocity of cells increased from 130 μm/second to 150 μm/second, due to an elevation of flagellar beat frequency from ∼60 Hz to ∼70 Hz without detectable change in the flagellar waveforms. This response required outer arm dynein. Treatment with EGTA, Ca 2+ ‐channel blockers, or mechanosensitive‐channel blockers inhibited it. In demembranated and reactivated cell models, a modest increase in Ca 2+ concentration elevated the axonemal beat frequency. These data indicate that the mechanical agitation increases beat frequency because it causes Ca 2+ influx into flagella, which then activates outer arm dynein. Cell Motil. Cytoskeleton 2009. © 2009 Wiley‐Liss, Inc.