REU: Collaborative Research: How Do Plants Control Sperm Nuclear Migration For Successful Fertilization? (47.074)

Gamete nuclear migration is a dynamic and fundamental cellular process for successful fertilization in both animals and plants. Most animals and early diverging land plants, such as ferns, control gamete nuclear migration by microtubules. However, flowering plants have evolved a novel system where actin filaments (F-actin) play the essential role in sperm nuclear migration. Prior to fertilization, female gametes generate constant movement of an F-actin meshwork from the plasma membrane periphery towards the center of the cell, where the nucleus is located. Upon sperm nucleus release into the female gamete, the sperm nucleus migrates along with this F-actin meshwork inward movement, for karyogamy. The membrane-anchored Rac/Rop small GTPase and a unique ARP2/3-independent WAVE/SCAR pathway are essential for the Factin meshwork movement and sperm nuclear migration in the central cell, one of the two female gametes in flowering plants. Myosins and formins also play roles in F-actin dynamics for fertilization; however, the mechanism of how these factors and pathways coordinate to precisely control F-actin dynamics and sperm nuclear migration in flowering plants remains largely unknown. By combining real-time live-cell imaging and computational simulations through the collaboration of plant molecular biology lab (Kawashima, University of Kentucky) and computer simulation lab (Abel, University of Tennessee, Knoxville) dissections of the molecular and cellular mechanisms that control F-actin meshwork movement in the female gamete for sperm nuclear migration will be carried out in the flowering plant, Arabidopsis thaliana.