Nicole King, UC Berkeley
Joint EEB/MolBio Seminar | TITLE: Choanoflagellates, interkingdom signaling, and the building blocks of animal origins
Audience: Open to Public
Location: 003 Lewis Thomas Lab
Date/Time: 02/11/09 at 12:20 pm - 02/11/09 at 1:20 pm
A light reception is available at 12 noon.
Abstract: The evolution of animals from their single celled ancestors represents one of the major transitions in life's history. While the environmental context of animal origins has been well studied, little is known about the roles of genome evolution and interspecies interactions in the transition to multicellularity. Choanoflagellates, a group of colony forming and unicellular eukaryotes, represent the closest living relatives of animals and provide direct insights into animal origins and ancestral features of animal biology. The genome of the choanoflagellate Monosiga brevicollis reveals that cell-cell signaling and adhesion genes (including receptor tyrosine kinases and cadherins) evolved in the pre-metazoan era, predating the origin of multicellularity. Remarkably, the choanoflagellate genome contains all of the components of the tyrosine kinase signaling pathway and more tyrosine kinase genes (126) than the human genome. Choanoflagellates use tyrosine kinase signaling to interpret nutrient availability in their extracellular environment, highlighting a potentially ancient linkage between cell signaling genes and environmental sensing. In addition, choanoflagellates contain an abundance of cadherins, two of which localize to the choanoflagellate feeding collar, where evidence is building that they are used for bacterial prey recognition or capture. Finally, we find that the induction of colony development in the choanoflagellate Proterospongia sp. requires a chemical signal from the bacterial prey species Algoriphagus. This inter-kingdom signaling interaction is specific and experimentally tractable, promising to provide mechanistic insights into the regulation of eukaryotic morphogenesis by bacteria.
Category: EEB 522 Colloquium