Figure 4.

Basal body number and maturation in green algae. (A) The mammalian centrosome consists of one mother centriole (1), which might bear a primary cilium, and a daughter basal body (2); a new generation of basal bodies (3) is formed in S phase. Saccharomyces cerevisiae possess a single spindle pole body (SPB) corresponding to one generation of a centrosomal organizer. By comparison green algal centrosomes are more variable with respect to the number of basal bodies, flagella development. (B) TEM images of basal bodies of the green alga S. similis. In mature basal bodies (a), the cartwheel typically consists of three tiers embedded into the axonemal cylinder (green arrowhead). In premitotic cells, the No. 2 basal bodies (b,c) dock to the plasma membrane and develop a protruding cartwheel of ~8 tiers that touches the nuclear envelope (N). Microtubules radiate from the protruding cartwheel suggesting a microtubule organizing center (MTOC) activity. Note the developing TZ. Reprinted with permission from Lechtreck and Grunow (1999) [83].