Figure 5.
As the central apparatus rotates clockwise, the C1 microtubule contacts specific radial spokes, which in turn relay a regulatory signal to the dynein arms on specific subsets of doublet microtubules. The doublets and associated dynein arms actively engaged in microtubule sliding are indicated by light shading. In each subsequent transverse section (left to right), microtubule sliding is visualized as progressive loss of doublet microtubules from the axoneme.