BNMC Seminar:  Biological and imaging approaches to understanding plant cell growth

Adrienne Roeder

With the increasing focus on biofuels derived from cellulose in the plant cell walls, understanding how plant cells regulate their growth and division becomes critical.  Plant cells are locked into position by their cell walls, which essentially glue the cells together so that they cannot slide past one another.  Consequently, the growth of neighboring cells must be closely coordinated.  This raises the question of how cells of different sizes can form adjacent to one another.  An extreme example occurs in the Arabidopsis sepal where giant cells that can stretch half the length of the sepal form next to much smaller cells.

To determine how giant cells form, we are currently imaging living sepals over time and tracking the cells as they develop.  To process the images, Michael C. Burl at JPL has developed a segmentation program that extracts the 3D surfaces of the nuclei. One of the first observations we have made is that the giant cells have enlarged nuclei suggesting that they have undergone endoreduplication, a specialized cell cycle in which the DNA is replicated, but the cell does not divide.  Endoreduplication is common in plants and insects, and also occurs in a few mammalian cell types.  The endoreduplication of giant cells suggests that these large cells can form next to their smaller neighbors because they stop dividing earlier and continue to expand at the same rate as their neighbors, which remain small by continuing to divide.  Recent work suggests that a signaling pathway is involved in giant cell development.  The function of the giant cells is currently unclear, but they are not present in a canola, broccoli, or Capsella, which are plants related to Arabidopsis, suggesting that they arose recently in evolution.

About the speaker

Adrienne Roeder is a Postdoctoral Scholar in Biology in the Meyerowitz lab at Caltech.  She received a Helen Hay Whitney Postdoctoral Fellowship to investigate the development of giant cells.  Adrienne has been involved in research on plant development since she was an undergraduate at Stanford where she investigated the first asymmetric division of the Arabidopsis zygote.  Her interest in computational approaches also dates back to Stanford where she minored in Mathematical and Computational Sciences.  Adrienne learned molecular genetic approaches to plant development in her graduate studies at UCSD where she studied the differentiation of the tissues in the Arabidopsis fruit.  Her graduate work was funded by a Howard Hughes Medical Institute predoctoral fellowship.  Currently she is bringing her biological and computational interests back together by participating in the Computable Plant project (http://www.computableplant.org/).