Accurate decoding of spatial chemical landscapes is critical for many cell functions. Eukaryotic ... more Accurate decoding of spatial chemical landscapes is critical for many cell functions. Eukaryotic cells decode local chemical gradients to orient growth or movement in productive directions. Recent work on yeast model systems, whose gradient sensing pathways display much less complexity than those in animal cells, has suggested new paradigms for how these very small cells successfully exploit information in noisy and dynamic pheromone gradients to identify their mates. Pheromone receptors regulate a polarity circuit centered on the conserved Rho-family GTPase, Cdc42. The polarity circuit contains both positive and negative feedback pathways, allowing spontaneous symmetry breaking and also polarity site disassembly and relocation. Cdc42 orients the actin cytoskeleton, leading to focused vesicle traffic that promotes movement of the polarity site and also reshapes the cortical distribution of receptors at the cell surface. In this article, we review the advances from work on yeasts and...
Budding yeast use pheromones to select a single mating partner in crowded environments. This arti... more Budding yeast use pheromones to select a single mating partner in crowded environments. This article shows that cells assemble mobile polarity sites that both sense and secrete pheromone, enabling a search strategy whereby encounters between the polarity sites of partner cells trigger commitment.
Cells dynamically orient their direction of growth or movement by moving a polarity site that def... more Cells dynamically orient their direction of growth or movement by moving a polarity site that defines the front. A bottom-up computational model is used to explore the mechanism of movement. Assumptions inspired by findings in the yeast system show that vesicle traffic directed to the polarity site would suffice to produce realistic movement.
How small eukaryotic cells can interpret dynamic, noisy, and spatially complex chemical gradients... more How small eukaryotic cells can interpret dynamic, noisy, and spatially complex chemical gradients to orient growth or movement is poorly understood. We address this question using Saccharomyces cerevisiae, where cells orient polarity up pheromone gradients during mating. Initial orientation is often incorrect, but polarity sites then move around the cortex in a search for partners. We find that this movement is biased by local pheromone gradients across the polarity site: that is, movement of the polarity site is chemotactic. A bottom-up computational model recapitulates this biased movement. The model reveals how even though pheromone-bound receptors do not mimic the shape of external pheromone gradients, nonlinear and stochastic effects combine to generate effective gradient tracking. This mechanism for gradient tracking may be applicable to any cell that searches for a target in a complex chemical landscape.
Accurate decoding of spatial chemical landscapes is critical for many cell functions. Eukaryotic ... more Accurate decoding of spatial chemical landscapes is critical for many cell functions. Eukaryotic cells decode local chemical gradients to orient growth or movement in productive directions. Recent work on yeast model systems, whose gradient sensing pathways display much less complexity than those in animal cells, has suggested new paradigms for how these very small cells successfully exploit information in noisy and dynamic pheromone gradients to identify their mates. Pheromone receptors regulate a polarity circuit centered on the conserved Rho-family GTPase, Cdc42. The polarity circuit contains both positive and negative feedback pathways, allowing spontaneous symmetry breaking and also polarity site disassembly and relocation. Cdc42 orients the actin cytoskeleton, leading to focused vesicle traffic that promotes movement of the polarity site and also reshapes the cortical distribution of receptors at the cell surface. In this article, we review the advances from work on yeasts and...
Budding yeast use pheromones to select a single mating partner in crowded environments. This arti... more Budding yeast use pheromones to select a single mating partner in crowded environments. This article shows that cells assemble mobile polarity sites that both sense and secrete pheromone, enabling a search strategy whereby encounters between the polarity sites of partner cells trigger commitment.
Cells dynamically orient their direction of growth or movement by moving a polarity site that def... more Cells dynamically orient their direction of growth or movement by moving a polarity site that defines the front. A bottom-up computational model is used to explore the mechanism of movement. Assumptions inspired by findings in the yeast system show that vesicle traffic directed to the polarity site would suffice to produce realistic movement.
How small eukaryotic cells can interpret dynamic, noisy, and spatially complex chemical gradients... more How small eukaryotic cells can interpret dynamic, noisy, and spatially complex chemical gradients to orient growth or movement is poorly understood. We address this question using Saccharomyces cerevisiae, where cells orient polarity up pheromone gradients during mating. Initial orientation is often incorrect, but polarity sites then move around the cortex in a search for partners. We find that this movement is biased by local pheromone gradients across the polarity site: that is, movement of the polarity site is chemotactic. A bottom-up computational model recapitulates this biased movement. The model reveals how even though pheromone-bound receptors do not mimic the shape of external pheromone gradients, nonlinear and stochastic effects combine to generate effective gradient tracking. This mechanism for gradient tracking may be applicable to any cell that searches for a target in a complex chemical landscape.
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Papers by Debraj Ghose