Utilizing microfluidics to investigate temporal gene expression in saccharomyces cerevisia

Recent technological advances in molecular biology techniques and gene expression assays have provided the tools necessary to monitor both native and synthetic biological systems with high temporal resolution. The yeast S. cerevisiae has long served as a workhorse for eukaryotic cell biology and has proven to be an educational model for the study of complex cellular processes such as aging, cancer progression, and the development of genetic disease. The ease with which we can manipulate the yeast genome makes it particularly conducive to gene expression studies, as fluorescent protein fusions can provide a read-out of native protein production in vivo. A novel microfluidic device developed by our lab allows for single-cell dynamical measurements over long time periods, and thus enables the collection of valuable statistics for studying the development of biological processes within a population of cells. Here, we utilize our device to investigate the temporal transcription program of the enzymes involved in the galactose utilization network in yeast. Motivated by a recent E. coli study, which discovered that the production of enzymes involved in amino acid biosynthesis is precisely timed in order to optimize metabolic efficiency, we employ S. cerevisiae as a model to investigate whether a similar phenomenon exists in more complex organisms. Utilizing a gravity-driven media switch on our device, we can alternate between inducing and non-inducing medium and monitor the precise timing of production of the three key galactose enzymes. We present multi-color fluorescence trajectories, representing the in vivo enzyme production of individual cells, and we compare the three trajectories to investigate their temporal expression program. Our data presents a novel property of eukaryotic gene expression and highlights the potential of single-cell fluorescence microscopy to shed light on complex biological processes