Abstract
ABSTRACT The first division of Pelvetia zygotes is an unequal division which produces two cells with distinct developmental fates. The smaller rhizoid cell gives rise to the holdfast of the mature plant, and the larger thallus cell is the progenitor of the stipe and fronds. We have investigated the role of the cytoskeleton in determining the orientation of this invariant division. Prior to mitosis, microtubuleorganizing centers (MtOCs) associated with the nuclear envelope undergo a precise realignment from transverse to axial with respect to the rhizoid/thallus axis. This is accomplished by a 90° rotation of the entire nuclear/MtOC complex. After rotation, each MtOC serves as a spindle pole during mitosis, and subsequently cytokinesis bisects the spindle. Both nocodazole and cytochalasin D cause incorrect alignment of MtOCs, indicating that both microtubules and microfilaments are required for nuclear/MtOC rotation. These inhibitors also result in aberrant orientation of the first division plane. Microtubules visualized by confocal microscopy connect the rotating nucleus to the apical cortex and may provide the force for rotation.
Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
