Dr. Quatrano 96-04672 Zygotes of the brown alga Fucus provide a model system to study the basic mechanisms involved in the generation of zygotic/cell asymmetry and the partitioning of localized cytoplasmic components to the resulting daughter cells. Large, single-celled zygotes synchronously develop a polar axis in culture that can be experimentally oriented by imposed gradients such as unilateral light. Such cells present an ideal system to study how a polar axis is established and how a cell directionally transports cytoplasmic material to a site defined by an extracellular vector. Dr. Quatrano now knows that secretion of these targeted vesicles into the extracellular matrix (ECM) is required to stabilize the molecular asymmetry established by the external vector, and believes that this also have evidence that secreted material into the ECM may signal information to the cytoplasm to initiate polar growth and to orient the plane of cell division. The role of targeted secretion, resulting in an asymmetry of the macromolecules present in the zygotic ECM of Fucus, now provides an exciting paradigm to apply to other polar cells for the study of extracellular positional information during development. Using the Fucus system he will pursue answers to the following questions: What are the cellular cues and sequences in MRNA that are responsible for the localization of specific transcripts in the developing Fucus embryo? What are the roles of small GTP-binding proteins and septins in the development of cell polarity and the orientation of cell division in the Fucus zygote? What are the similarities between the molecules and processes that establish polarity in Fucus and those operative in higher plants, yeast, insects, and vertebrates?
