Associate Professor University of Kentucky Lexington, Kentucky
Fertilization involves dynamic cellular processes including gamete nuclear migration. The cytoskeleton generates the mechanical force required to move the gamete nuclei for karyogamy. In most animals, microtubules, organized by centrosomes, play the primary role in gamete nuclear migration. By contrast, flowering plants have lost the genes fundamental to centrosome formation and have evolved actin filament (F- actin) based sperm nuclear migration systems. F-actin mesh is generated around the plasma membrane and moves toward the nucleus in the female gamete cell. This F-actin inward movement is already established prior to plasmogamy and not only F-actin itself but also its movement is essential to sperm nuclear migration. ROP, WAVE/SCAR, formins, and the class XI myosin, are involved in the dynamic F-actin inward movement in Arabidopsis; however, the mechanism of how these factors coordinate to generate such an orchestrated F-actin movement remains largely unknown. Using confocal microscopy live-cell imaging with a combination of pharmacological and genetic approaches, we identified a novel system controlling F-actin dynamics and sperm nuclear migration. I will discuss our recent findings about the cellular mechanism that controls the critical step between plasmogamy and karyogamy in double fertilization.