The Role of Microtubule Movement in Bidirectional Organelle Transport

We study the role of microtubule movement in bidirectional organelle transport in Drosophila S2 cells and show thatEGFP-tagged peroxisomes in cells serve as sensitive probes of motor induced, noisy cytoskeletal motions. Multipleperoxisomes move in unison over large time-windows and show correlations with microtubule tip positions,indicating rapid microtubule fluctuations in the longitudinal direction. We report the first high resolutionmeasurement of longitudinal microtubule fluctuations performed by tracing such pairs of co-moving peroxisomes.The resulting picture shows that motor-dependent longitudinal microtubule oscillations contribute significantly tocargo movement along microtubules. Thus, contrary to the conventional view, organelle transport cannot bedescribed solely in terms of cargo movement along stationary microtubule tracks, but instead includes a strongcontribution from the movement of the tracks.