REU: Closing the Gap between the Genotype and Phenotype by Elucidating Cellular Dynamics of Endosperm Development

Flowering plant seeds consist of the embryo, endosperm, and seed coat. In the model plant Arabidopsis thaliana, as in many crop plants such as soybean, rice, and maize, the embryo-nourishing endosperm undergoes unique development: nuclear division without cytokinesis, generating a coenocyte followed by cellularization. The duration of the coenocytic endosperm development is strongly associated with the final seed size; however, it is still not clear what cellular dynamics occur during this unique coenocytic endosperm development, what exactly is controlled in the endosperm by identified factors that determine the timing of cellularization, and how it all affects the subsequent seed development. This project aims to increase our understanding of the relationship between the endosperm genotypes and the subsequent seed phenotypes by revealing detailed coenocytic endosperm developmental dynamics. To accomplish this goal, we have established a time-lapse livecell imaging system to visualize Arabidopsis endosperm development. Our imaging showed the novel dynamics of filamentous actin (F-actin) and nuclei movement in the coenocytic endosperm. Furthermore, manipulations of F-actin itself and F-actin regulators in the early-phase coenocytic endosperm caused changes the final seed size. Investigating further how F-actin participates in coenocytic endosperm development as well as what cellular and molecular changes occur in previously identified genetic and epigenetic factors will provide a massing link between the endosperm genotypes and the seed phenotypes, contributing to a comprehensive understanding of seed development. Understanding early-phase coenocytic endosperm development is also important not only for insight into plant cellular biology, but also from an agricultural perspective to increase yields with larger crop seeds.