Figure 2

Fig. 2. Fluorescence imaging of MTs in living cytoplasts. In centrosome-containing cytoplasts (upper row), microtubules showed dynamic instability at their plus ends while free microtubules rapidly shortened from their minus ends. In centrosome-free cytoplasts (middle row), MTs persistently grew at one end and shortened at the other end. Injection of tubulin at low concentration resulted in nonuniform incorporation of subunits along MTs and produced "speckles" along their length. "Speckles" remained stationary indicating that the mechanism of translocation was treadmilling (bottom row). Black arrowheads point to shortening and white arrowheads to growing ends. White arrows point to"speckles". Numbers indicate time in s. Bars, 1 µm. Video sequences of MT dynamics in cytoplasts can be seen and downloaded here.