Peking University, China
FAX: (303) 735-0770
University of Colorado
MCD Biology, 347 UCB,
Boulder, CO 80309-0347
In response to nutrient starvation, yeast cells enter a quiescent state. This state is defined by a marked increase in the viscosity of the cell cytoplasm, a phenomenon we term cell-freezing . Cell-freezing is a novel phenomenon discovered only recently through measurements of the viscoelastic properties of the cytoplasm of fission yeast cells. It occurs as a response to carbon starvation and leads to a dramatic immobilization of all visible sub-cellular structures, which suggests that the preservation of the internal organization of the cell in this quiescent state is its main biological function.
Recently we found evidence that the transition of viscosity of the cell cytoplasm could be reliably reproduced by starving cells of glucose and that septins might be involved. Septins were known to form fibers in vitro and following this idea, we hypothesis that a dense and homogeneous network will be formed by septins when the cell enters the starvation state and that this network is sufficiently fine to immobilize all major cell components. Moreover, it should be possible to visualize septin polymers and their interaction with cell organelles by 3-Dimension (3D) Cryo-Electron Microscopy (EM).
My project will focus on 1) Confirming the cell-freezing in starved fission yeast cells by light microscopy (LM); 2) Observing sub-cellular structure differences by EM (plastic embedding sample); 3) Observing septins fibers in vivo by Cryo-EM and Cryo-Electron Tomography (ET).
By comparing starved and unstarved yeast cells, I will resolve the proposed cytoplasmic fiber network and other structural changes that seem typical for starvation; by comparing wild type and septin mutant yeast cells, I will demonstrate the role of septins in cell-freezing .
University of Colorado, MCDB, 347 UCB, Boulder, CO 80309-0347