Poster: Cytoskeleton structure & dynamics

Abs # 686: Is the pre prophase band site used to position the anaphase spindle?

Presenter:	Cyr, Richard , rjc8@psu.edu
Authors	Fisher, Deborah  (A)   Cyr, Richard  (A)
Affiliations:	(A): Penn State

In the vast majority of plant cells, a transient microtubule array of microtubules appears late in G2 and persists into early prometaphase. This array is notable for its role in positioning the nascent spindle and in serving as a signpost for the future position of the new cell plate. We have produced a stable BY-2 tobacco cell culture that expresses a dsRed microtubule reporter gene (MBD::dsRed) and a chromosome reporter gene (histone::YFP). We have identified optimal microscopic viewing conditions (to visualize both genes, along with DIC) that allow us to study cells progressing through mitosis. In cells that have just completed anaphase, we note a transient association of cytoplasmic strands that emanate from either the spindle midzones, or the two spindle poles, and connect to the cell cortex at the location previously occupied by the pre prophase band. The formation of these strands in many cells is accompanied by a swiveling of the spindle so that the midzone microtubules (and hence the young phragmoplast) become oriented more precisely relative to the pre prophase band site. These observations suggest that the cortical area defined by the pre prophase band of microtubules acts at late anaphase to preposition the future phragmoplast.