Cell division in moss and animals more similar than previously thought


Date:
May 5, 2022
Source:
University of Freiburg
Summary:
For a new plant to grow from a seed, cells need to divide numerous
times.

Daughter cells can each take on different tasks and sometimes vary
in size. How plants determine the plane of cell division in this
process, known as mitosis, is currently being researched. Working
with Physcomitrella -- a moss plant, they have now identified
how the mitotic apparatus is localized in the plant cell: "Using
moss cells we were able to observe an unexpected process that is
important for the position of the cell division site in plants.



FULL STORY ==========================================================================
For a new plant to grow from a seed, cells need to divide numerous times.

Daughter cells can each take on different tasks and sometimes vary
in size. How plants determine the plane of cell division in this
process, known as mitosis, is being researched byProf. Dr. Ralf Reski
and Dr. Elena Kozgunova from the University of Freiburg in a joint
effort with Prof.Dr. Gohta Goshima fromNagoya University. Working with Physcomitrella -- a moss plant, they have now identified how the mitotic apparatus is localized in the plant cell: "Using moss cells we were able
to observe an unexpected process that is important for the position
of the cell division site in plants. The process could be far more
similar to animal cell division than previously thought," Reski from
the cluster of excellence CIBSS comments on the results of the study,
which has appeared in the journal Nature Communications.


==========================================================================
When cells divide, microtubules -- a dynamic network of protein filaments
- - form a mitotic spindle that draws the chromosomes apart and arranges
them into two daughter cells. Here, plants and animals differ: once
the spindle is formed, it remains in the same place in plant cells. In
animal cells, the spindle moves during cell division. The cells divide
where it comes to rest.

The unusual thing about moss cells is that in the process of mitosis they
do not form a belt of microtubules and actin filaments, both elements of
the cytoskeleton. Until now it was thought that this 'preprophase band'
(PPB) determines where the spindles form and where they are localized
in plants. "But why is the mitotic spindle static in moss cells like
in other plants even though there is no preprophase band?" wondered
Kozgunova, lead author of the study and holder of a Humboldt-Bayer
research fellowship in Reski's laboratory.

Mobile spindles previously unknown in plants To solve this puzzle,
the team delved into the molecular biology box of tricks: they modified spreading earthmoss (Physcomitrella) plants, removing five genes.

The researchers knew that they resemble the animal gene of a molecule
that is significant in mitosis: the protein TPX2 takes part in mitotic
spindle assembly in animals.

Under the microscope the researchers observed mitosis in moss plants
without the TPX2 genes. They were startled to find that in these cells
the spindles now moved during cell division in leafy shoots known as gametophores. "Spindle movement had never been documented before in
plant cells," explains Kozgunova.

Such cells divided irregularly, and as the plant developed, it led to malformations.

Tug-of-war in the cytoskeleton The researchers now proceeded to influence
the actin skeleton of the cells and showed that actin filaments move
the mitotic spindle: "It's a kind of tug-of- war between microtubules
and actin that positions the mitotic spindle in the cell. It appears to
be similar to the processes in animal cells," reports Reski. Likewise,
actin filaments are important for spindle transport in animal cells. These findings are helping researchers to identify which signals determine
the fate of cells as they develop. They hope that this will improve understanding of plant growth and eventually our ability to influence it.

The recordings of the cell division were produced in the Life Imaging
Centre, a central facility of the Cluster of Excellence CIBSS --
Centre for Integrative Biological Signalling Studies at the University
of Freiburg.


========================================================================== Story Source: Materials provided by University_of_Freiburg. Note:
Content may be edited for style and length.


========================================================================== Journal Reference:
1. Elena Kozgunova, Mari W. Yoshida, Ralf Reski, Gohta Goshima. Spindle
motility skews division site determination during asymmetric cell
division in Physcomitrella. Nature Communications, 2022; 13 (1)
DOI: 10.1038/s41467-022-30239-1 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2022/05/220505150343.htm

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