DESCRIPTION (provided by applicant): The fundamental basis for the generation of cellular diversity in all organisms is the asymmetric deployment of structural and regulatory proteins to the cell poles prior to cell division and the consequent differential readout of the genome in the two daughter cells. The bacterium Caulobacter crescentus provides an elegant system in which to decipher the complete molecular circuitry that controls the asymmetry that underlies cell differentiation. As Caulobacter moves through its cell cycle, cell differentiation is accompanied by the polar localization of distinct complements of phospho-signaling proteins. The goals of our research program turn on three important questions: 1- How does a polar matrix nanodomain function to dynamically re-wire polar phosphosignaling pathways to drive cell differentiation and asymmetric cell division? We are approaching this question through reconstitution of the polar environment using liposomes and microfabricated solid substrates, three dimensional superresolution imaging modalities and single molecule tracking in living cells, and the creation of optogenetic mutants that enable instantaneous light-induced reconfiguration of the cell pole composition, thereby allowing us to directly observe the consequences of re-wiring a spatially-restricted signaling cascade in a living cell. 2- How do cell-type specific signaling pathways beget cell type-specific gene expression? We are defining the exquisite complexity of the complete genetic circuitry that uses both transcriptional and translation control to drive cell cyce progression culminating in daughter cells of different cell fate. 3- How does chromosome organization, replication and segregation along the long axis of the cell serve as a timer of cell cycle-regulated transcription using epigenetic mechanisms? Our goal is to integrate these spatiotemporal regulatory paradigms to establish the logic that is applicable to the dissection of asymmetry in all living systems.