Affiliation: Center for Plant Cell Biology, University of California, Riverside, CA 92521, USA.
Dr. Rasmussen's research summary
My lab investigates the underlying molecular mechanisms by which plant cells divide and subsequent influence of those divisions on development. We use a combination of cell biology, and chemical, reverse and forward genetics to elucidate the role of proteins that promote proper division plane orientation in several plant systems.
Summary of invited talk
Cell division is essential for the growth of any organism. One aspect of cell division that plays a critical role in proliferation and development in multicellular organisms is the location of the division axis. Proper establishment of the division axis or plane significantly contributes to the plant body organization. In order to determine how much cell geometry alone predicts division plane orientation, we used a mathematical modeling approach. Probabilistic division plane predictions of cells were made based on century-old observations of symmetric plant division: the daughter cells will have equal volume, and the dividing cell wall is a local surface area minimum. Many land plant cells form a preprophase band (PPB) composed of microtubules and other proteins that accurately predicts the future location of the new cell wall. We directly compared the mathematically predicted divisions to the location of the PPB. The PPB mostly overlapped with one of the possible types of purely geometrically predicted divisions. Discrepancies in PPB location compared to the predicted division occurred when the neighboring cell had a cell wall or PPB directly adjacent to the division site. The PPB location shifted to avoid creating a “four-way-junction”. Avoidance of four-way-junctions, in which nearby cell edges do not align at right angles, is a long recognized structural feature in overall patterning of plant cells. Finally, we use the predicted divisions to determine the relative contribution that cell geometry has in regulating specific division plane choices during maize leaf development. At a population level, the division predictions based only on cell geometry are not sufficient to describe the actual divisions observed during certain stages of maize leaf development suggesting other factors, such as mechanical signals might play an important role in division plane orientation.