Graduate student University of Kentucky Lexington, Kentucky
Body of Abstract: In Arabidopsis thaliana, the early-stage endosperm undergoes unique coenocytic development and rapidly expands, which drives seed growth. This coenocyte or the liquid endosperm generates turgor pressure which is the guiding force for expansion just like other plant cells. However, the question still remains, what is the molecular mechanism that regulates turgor pressure inside the coenocytic endosperm. Here, we combine the molecular and biophysics studies to answer the question. We show that changing the F-actin dynamics of the coenocytic endosperm can cause differences in growth and development and ultimately affecting the final seed size. The overexpression of the actin gene specifically during coenocytic endosperm development (OX-ACTIN) makes larger seeds, whereas the overexpression of the dominant negative form of the actin gene (DN-ACTIN) makes smaller seeds. We measured seed stiffness of these lines and found differences among the control, OX-ACTIN, and DN-ACTIN lines. Our results indicate that F-actin dynamics in coenocytic endosperm not only help in the nuclear organization in the multinuclear endosperm, but they also regulate the seed stiffness which is linked with the turgor pressure of the endosperm. The relationship between F-actin dynamics and turgor pressure provides us with insights into the unique developmental mechanism of endosperm and new opportunities for increasing seed size which is important for food security.