Figure 2.

Fluorescence imaging of MTs in living cytoplasts. In centrosome containing cytoplasts (Top), MTs showed dynamic instability at their plus ends whereas free MTs rapidly shortened from their minus ends. In centrosome-free cytoplasts (Middle), 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). Black arrowheads point to shortening and white arrowheads to growing ends. White arrows point to speckles. Numbers indicate time in seconds. (Bars = 1 μm.) Video sequences of MT dynamics in cytoplasts can be seen and downloaded from our web site (http://borisy.bocklabs.wisc.edu).