Microtubules and the Evolution of Mitosis

Abstract The microtubular cytoskeleton of higher plants diverges considerably from its animal counterpart. This divergence involves a fundamentally different organization with microtubule arrays, which are specific to higher plants, such as cortical microtubules or the phragmoplast. On the other hand, centrioles, which are central organizers of mi-crotubules in cells of animals and lower plants, have been progressively reduced in the course of plant evolution, and are now absent, as in most seed plants. In addition to these structural differences, the molecular composition of associated proteins also devi-ates to a degree that sequence homologues of important animal microtubule associated proteins (MAPs) seem to be absent in higher plants. The transition towards multicel-lular plants was intimately linked to rhythmic changes of division axis, and, thus, to the spatial regulation of mitotic microtubule arrays. To understand the peculiarities of plant microtubules, we have to combine cell biology with a more phylogenetic view-point. Therefore, this chapter is dedicated to the role of microtubules in the evolution of mitosis. It is shown that the microtubule divergence between plants and animals is already laid down in the prokaryotic ancestors, when the walled eubacteria are com