Cell plate formation in Chara zeylanica was compared with recent model
s of cytokinesis in higher plants in order to gain insight into the ev
olutionary origin of plant cytokinetic processes. Transmission electro
n microscopy (TEM) reveals that while cytokinesis in C. zeylanica bear
s many features in common with that in higher plants, there are signif
icant differences. Unlike that in higher plants, cytokinesis in C. zey
lanica begins with a congregation of smooth membrane tubules that are
closely associated with endoplasmic reticulum (ER) and Golgi membranes
. Mitochondria and other organelles excluded by the phragmoplast in hi
gher plants are present as well. Unlike in higher plants, phragmoplast
microtubules persist throughout cytokinesis in C, zeylanica, and the
cell plate generally forms across the whole cell at once, though devel
opment is patchy, due to small regions developing at different rates;
the ends of the plate form last. By identifying aspects of cytokinesis
that are different in C. zeylanica and plants, our study indicates wh
ich cytokinetic features are more likely to be derived, and which are
more likely to be ancestral. In addition, we demonstrated that all nod
al cells of C. zeylanica are interconnected via plasmodesmata, lending
support to the idea that, while Chara spp. are generally considered t
o be filamentous organisms, nodal regions may be thought of as meriste
m-like tissues.