MSGID: 1:317/3 6274a4d6   
   PID: hpt/lnx 1.9.0-cur 2019-01-08   
   TID: hpt/lnx 1.9.0-cur 2019-01-08   
    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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