Title: Gradient Sensing in Yeast
Speaker: Tim Elston (University of North Carolina, Chapel Hill)
Abstract: Yeast cells are able to direct growth toward gradients of mating pheromone (chemotropism). During chemotropism, the site of new cell growth is determined by a patch of polarity factors that wanders around the cell cortex. Interestingly, yeast also polarize their receptors in response to pheromone, but the benefit of such polarization was unknown. Mathematical modeling suggests a novel mechanism for gradient sensing in which active receptors and associated G proteins lag behind the polarity patch and act as an effective drag on patch movement. Because the strength of this effective drag is proportional to the local pheromone concentration, the location of the polarity patch, and hence cell growth, tend to align with the pheromone gradient. Consistent with model predictions, the polarity patch is trailed by a G protein-rich domain, and this polarized distribution of G proteins is required to constrain patch wandering. Our findings explain why receptor polarization is beneficial, and illuminate a novel mechanism for gradient tracking.
Seminar URL: http://mbi.osu.edu/programs/mbi-colloquium/
