Part 1: Understanding cell shape: Big insights from little plants: Polarized cell growth in plants depends on the assembly and disassembly of actin filaments.
Part 2: Using reverse genetics to dissect the formin gene family: Formins promote nucleation and elongation of actin filaments and are required for polarized cell growth.
Part 3: Myosin and actin steer plant cell division: Plants have only two classes of myosins; myosin VIII and XI. Myosin VIII is required for proper location of the cell division plate.
Magdalena Bezanilla’s lab is interested in understanding what determines cell shape at the molecular level. In Part 1 of her talk, Bezanilla explains why the moss, Physcomitrella patens, is an excellent model system to address this question. P. patens grows quickly and entire plants can be vegetatively regenerated from single cells. The genome is sequenced and its cells undergo efficient homologous recombination- the only plant known to do this! In the filamentous tissue that establishes the plant, cells at the tips grow in a polarized manner as flexible cell wall material is incorporated and then pushed out by turgor pressure. To study the role of actin in determining cell shape, Bezanilla’s lab used a live-cell actin binding probe to label actin and imaged cell growth with fluorescence microscopy. They showed that polarized growth depended on the rapid disassembly and assembly of actin filaments; processes regulated by actin binding proteins.