Spatiotemporal Dynamics of Gradient Sensing and Polarization in Yeast

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  • March 22, 2019
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  • Jin, Meng
    • Affiliation: School of Medicine, Department of Biochemistry and Biophysics
Abstract
  • Cells are able to interpret different kinds of spatial information. Characterizing the spatiotemporal dynamics in signal transduction is essential to understand how a cell process information from its environment. Here, we quantitatively studied the gradient sensing and polarization in budding yeast Saccharomyces cerevisiae, using mathematical modeling and time-lapse microscopy. In the gradient sensing, we found that yeast cells can dynamically remodel local pheromone gradient and achieve better gradient sensing by secreting Bar1, a protease that degrades [alpha]-factor. Altering the local environment also avoids non-productive cell-cell interactions. During the polarity establishment without spatial cues, imaging with high spatiotemporal resolution revealed oscillation in the initial clustering of polarity factors, suggesting the presence of a negative feedback loop that disperses the factors. Mathematical modeling including an additional negative feedback reproduced similar dynamics and predicted that negative feedback would confer robustness to the polarity circuit, and make the kinetics of competition between polarity clusters relatively insensitive to the concentrations of polarity factors. These predictions were confirmed experimentally. Lastly, to understand how scaffold protein processes the spatial information of pheromone, we presented preliminary results for characterizing the kinetics of pheromone induced Ste5 membrane recruitment using time-lapse fluorescent imaging and single cell tracking.
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  • ... in partial fulfillment of the requirements for the degree of Doctorate of Philosophy in the Department of Biochemistry and Biophysics, School of Medicine.
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  • Elston, Timothy
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