Coordination of membrane and microtubule dynamics during cytokinesis in Arabidopsis thaliana

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Primary plant cell walls are laid down between anaphase and telophase in a transient membrane compartment referred to as the cell plate. The transport of vesicles to the cell plate is driven by a plant-specific array of microtubules and actin filaments, the phragmoplast. To avoid bisecting the nucleus, cytokinesis needs to be coordinated with the cell cycle in space and in time. A crucial question that arises is how membrane and cytoskeletal dynamics are coordinated and how they are regulated by cell cycle cues. In a genetic dissection of cytokinesis, we found that mutants in which cell plate biogenesis is impaired have defects in phragmoplast microtubule dynamics. We also found that the Sec1/Munc18 (SM) protein KEULE, involved in membrane fusion, is required for the reorganization of phragmoplast microtubules. We propose to further characterize membrane and microtubule organization and dynamics in a large collection of cytokinesis-defective mutants via antibody stains and live imaging, as well as electron and focused ion beam microscopy on cryofixed, freeze substituted samples. We then propose to test the hypothesis that KEULE interacts with microtubules, with microtubule-associated proteins, with motors and with the anaphase promoting complex. This would provide a model for how membrane fusion events are coordinated with microtubule dynamics and cell cycle progression cues in the context of plant cytokinesis.