Plant Cell Monogr (9)
D.P.S. Verma and Z. Hong: Cell Division Control in Plants
DOI 10.1007/7089_2007_128/Published online: 28 July 2007
©Springer-Verlag Berlin Heidelberg 2007
Open Mitosis: Nuclear Envelope Dynamics
Annkatrin Rose
Department of Biology, Appalachian State University, 572 Rivers Street,
Boone, NC 28608, USA
[email protected]
AbstractThe nuclear envelope separating the cell nucleus from the cytoplasm is a com-
mon feature of all eukaryotic cells, but its origin is still an enigma. Its early evolution
appears closely linked with the evolution of the mitotic spindle apparatus. Many regula-
tory proteins are playing critical dual roles in spindle assembly as well as nuclear envelope
and nuclear pore complex formation. During the evolution of higher eukaryotes, open
mitosis evolved independently in the plant and animal lineages, leading to a marked di-
versification of nuclear envelope compositions and roles in mitosis. Unique features of
the plant nuclear envelope include its function as mitotic spindle organizing center and
the lack of nuclear lamins and associated proteins. Nuclear envelope dynamics observed
during mitosis appear to be similar between plants and animals. The nuclear envelope is
absorbed into the endoplasmic reticulum after breakdown and reformed from the endo-
plasmic reticulum membrane pool after mitosis. In addition, nuclear envelope material
contributes to the newly forming cell plate in plant cells. Plant and animal cells might use
the same underlying molecular signals for nuclear envelope reassembly, but modified as
variations of a common theme.
1
Introduction
In all eukaryotic cells, the nucleus containing the genetic material is separated
from the cytoplasm by a double-membrane structure termed the nuclear en-
velope. The outer nuclear membrane is continuous with the endoplasmic
reticulum and presents a surface for the organization of cytoskeletal com-
ponents. The inner nuclear membrane serves similarly as anchoring surface
for chromatin. Both membranes are connected by nuclear pore complexes
forming channels to allow for the exchange of macromolecules between the
nucleoplasm and the cytoplasm.
The compartmentalization of the genetic material within a membrane-
bound nucleus poses a challenge to the cell during mitosis: The cell has to
segregate the nuclear material before cytokinesis to ensure the equal distri-
bution of the genetic material onto the daughter cells. How do eukaryotic cells
solve this problem?
The answer is two-pronged:
- To achieve segregation of the genetic material, the eukaryotic cell utilizes
a dynamic microtubule array, the mitotic spindle, attached to specialized