Reverse motion of organelles with myosin molecules along bundles of the actin filaments in a Characean internodal cell.

We have visualized bundles of the actin filaments of a Characean internodal cell and investigated the sliding motion of organelles with myosin on the bundles. The investigation revealed that a power spectrum of the sliding velocity time series of the organelle has two remarkable peaks near 4 and 7.5 Hz. This suggests that myosin molecules attached to the organelle not independently but cooperatively produce the sliding force. Moreover, we have found that some organelles move in the opposite direction of their sliding motion for several hundred milliseconds along the bundles. The fluctuation analysis of that motion showed that a power spectrum profile of the reverse velocity time series almost agreed with that of the sliding velocity time series. This result suggests that the dynamics of the reverse motion is the same as that of the sliding motion.