title: A living vector field reveals constraints on galactose network induction in yeast.
abstract: When a cell encounters a new environment, its transcriptional response can be constrained by its history. For example, yeast cells in galactose induce GAL genes with a speed and unanimity that depends on previous nutrient conditions. Cellular memory of long-term glucose exposure delays GAL induction and makes it highly variable with in a cell population, while other nutrient histories lead to rapid, uniform responses. To investigate how cell-level gene expression dynamics produce population-level phenotypes, we built living vector fields from thousands of single-cell time courses of the proteins Gal3p and Gal1p as cells switched to galactose from various nutrient histories. We show that, after sustained glucose exposure, the lack of these GAL transducers leads to induction delays that are long but also variable; that cellular resources constrain induction; and that bimodally distributed expression levels arise from lineage selection-a subpopulation of cells induces more quickly and outcompetes the rest. Our results illuminate cellular memory in this important model system and illustrate how resources and randomness interact to shape the response of a population to a new environment.
authors.affiliation: Section of Ecology, Behavior, and Evolution, Division of Biological Sciences, University of California, San Diego La Jolla, CA, USA.
authors.forename: Sarah R
authors.initials: SR
authors.lastname: Stockwell
authors.affiliation: Section of Ecology, Behavior, and Evolution, Division of Biological Sciences, University of California, San Diego La Jolla, CA, USA sarifkin@ucsd.edu.
authors.forename: Scott A
authors.identifier: 0000-0001-8476-3256
authors.initials: SA
authors.lastname: Rifkin
mesh_terms: D005686:Galactokinase / Q000235:genetics*; D005690:Galactose / Q000378:metabolism*; D015966:Gene Expression Regulation, Fungal; D053263:Gene Regulatory Networks; D009876:Operon; D010641:Phenotype; D012441:Saccharomyces cerevisiae / Q000235:genetics / Q000254:growth & development*; D029701:Saccharomyces cerevisiae Proteins / Q000235:genetics*; D059010:Single-Cell Analysis; D014157:Transcription Factors / Q000235:genetics*
chemical_list: C099289:Gal3 protein, S cerevisiae; D029701:Saccharomyces cerevisiae Proteins; D014157:Transcription Factors; C524219:GAL1 protein, S cerevisiae; D005686:Galactokinase; D005690:Galactose
keywords: dynamics; galactose; gene expression; single‐cell; yeast