212 A. Rose
omastigont duplication, for example in the model organismChlamydomonas
(Brugerolle and Mignot 2003; Coss 1974), and a large variety of diverse mech-
anisms (summarized in Fig. 2). In addition to the occurrence of open and
closed mitosis as well as cytokinesis via cleavage furrow or cell plate, two fun-
damentally different modes of microtubule organization can be observed at
the end of mitosis. Members of theChlorophyceaeand somePrasinophyceae
Fig. 3 Schematic representation of mitotic stages during the development of open mito-
sis in the plant lineage.A Chlamydomonas-type mitosis:Chlamydomonasloses its flagella
before undergoing karyomastigont-type karyokinesis followed by cytokinesis via cleav-
age furrow.B Pyramimonas (Prasinophyceae)-type mitosis:Pyramimonascontains four
basal bodies with flagella, but only two are shown for simplification. Mitosis is open
and followed by cytokinesis via cleavage furrow.CColeochaete-type mitosis: Mitosis is
open and utilizes cytoplasmic centrioles as microtubule organizing centers. Cytokine-
sis is achieved by a phragmoplast and centrifugal cell plate formation.DHigher plant
mitosis: Microtubules form a preprophase band at the cell periphery and are organized
around the nuclear envelope before it breaks down. Cytokinesis is achieved by a phrag-
moplast and centrifugal cell plate formation.IPreprophase,IIprophase,IIImetaphase,
IVtelophase,Vinterphase. Nuclei are shown inlight blueand nuclear envelope disas-
sembly and reassembly is represented bybroken lines. Microtubules are represented by
red lines.BBmembrane-bound basal bodies,CCcondensed chromosomes,CENcytoplas-
mic centrioles,PPphragmoplast with new forming cell plate,PPBpreprophase band of
microtubules