Microtubule Organization in Plant Cytokinesis

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Intellectual Merit. Plant cells employ a cytoskeletal microtubule (MT)-based apparatus called the phragmoplast to execute cytokinesis during cell division. In the phragmoplast, MTs polymerize toward the division site and are organized perpendicularly to the division plane. Vesicles are transported along these MTs and fuse to give rise to a new cell wall/plate. Concomitant with cell plate assembly, the phragmoplast MT array expands outward toward the parental membrane. Although this process is superficially well described, very little mechanistic detail is known on how it occurs. In this project, the research team aims to understand how phragmoplast MTs are assembled and reorganized during cytokinesis, and will use Arabidopsis thaliana as a model system. The work is focused on revealing an interactive protein network that acts in the phragmoplast midzone, including participation of spindle checkpoint proteins, MT crosslinkers, and kinesin motor proteins. Planned experiments will combine high-resolution live cell imaging, biochemical proteomics, and mutation analyses. Novelty here lies in development of a paradigm-shifting model for phragmoplast expansion, for which the PI has solid preliminary data support.Broader Impact. The phragmoplast mechanism first appeared in advanced green algae and is considered to be an evolutionary landmark associated with the development of land plants. Details of its working mechanism are considered critical to understand plant evolution. Besides sharing knowledge of diverse mechanisms of cytokinesis with cell biology students, the PI will actively recruit undergraduates to participate in the designed experiments. The students will not only receive hands-on laboratory training in biochemistry, cell biology, and genetics, they will also build competitiveness through bench research, and oral and written presentations of their discoveries. The importance of the basic plant biology research will be advocated to local high school students to spark their interest in biology and encourage them to seek science-oriented careers.