Title: Cytokinesis: plant cells do it differently
Presenter: Prof. Bo Liu
University: Department of Plant Biology, University of California at Davis
Time: 15:30-17:00, March 28, 2013
Venue: Room A203, Institute of Microbiology, Chinese Academy of Sciences
Abstract: Plant cytokinesis is mechanistically different from that in animals and fungi. In fact, the cytokinetic apparatus phragmoplast is an evolutionary landmark that is shared by advanced green algae and plants. It contains a bipolar microtubule framework with microtubule plus ends facing the cell division site. The phragmoplast microtubule array expands centrifugally toward the cell periphery while the cell plate is built by fusions of Golgi-derived vesicles delivered toward microtubule plus ends by microtubule-based motors. Upon the completion of anaphase, microtubules in the spindle midzone have their polarities sorted out to assume a bipolar configuration. Segments near their plus ends are cross-linked by proteins like MAP65-3. Once cytokinesis takes off, new microtubules are polymerized at the peripheral edge of the phragmoplast. As critical regulators of microtubule nucleation and organization, the g-tubulin complex, the WD40 repeat protein NEDD1, and the augmin complex play critical roles in the nucleation of new microtubules and organization of the array. Newly polymerized microtubules are captured by MAP65-3 toward their plus ends near the division site in order to be stabilized. The motor Kinesin-12 ensures that microtubule plus ends are correctly positioned near the division site. Based on results obtained us and others, we present a modular model depicting the assembly of the phragmoplast microtubule array by mini-phragmoplasts units.