53:	Functional differentiation of regions of the body plan of Acetabularia acetabulum.

Authors:	Serikawa, Kyle(A)Richmond, Christina(A)Michelangelo, von Dassow(A)Odell, Garrett(A)Mandoli, Dina, F.(A)
Affiliations:	(A): University of Washington, Depts of Botany & Zoology
Presenter:	Mandoli, Dina F., mandoli@u.washington.edu

Acetabularia acetabulum is a good organism for studying regional differentiation of body parts in the absence of cellularization during growth and morphogenesis. First, time lapse stills and videos of plants coated with carbon particles were used to determine regions where wall extension occurred, i.e. to define the equivalent of the "meristems" on this organism. Growth occurs by a combination of localized growth at the tip and of more diffuse growth between the whorls, in the "interwhorl" regions of the vegetative stalk and at the stalk junction on reproductive plants. NIH Image and Mathematica were used to generate a map of the stresses on the stalk apex assuming that the sole force on the cell wall is turgor pressure. Second, we used fluorescent dyes to see which portions of the body plan are active in taking up substances, such as B-vitamins, from the surrounding seawater. Dye-loaded individuals were grafted to unloaded plants so that dye movement could be monitored while alterations or breaches in the body plan healed. Finally, we cloned carbonic anhydrase, a metabolic gene, to see if its mRNA is temporally and spatially localized during development of the body plan. CA is an adult gene not present in juvenile phase in this species. Temporal and spatial localization of a homeobox gene from this species may be presented as time permits. Supported by REU NSF (MVD) and HHMI Undergraduate awards (CR & MVD) and by NSF #96-30618 (DFM) and NSF postdoctoral grant in Biosciences related to the environment.