Tuning the Yeast MAPK Pathway for Yeast-Based Biosensors

MAP Kinase pathways are ubiquitous signal transduction motifs in eukaryotes. As such, they are a promising tool for engineered signaling applications such as yeast-based biosensors (YBBs). By finely tuning the pathway components, a designer can control many aspects of the output signal including sensitivity, basal output, fold activation, dynamic range, ultrasensitivity, signal amplification, and inter- and intra-cellular variability (noise.) However, our ability to design signalling pathways remains hampered by our lack of understanding of the pathway’s many tunable components. Although much qualitative work has explored various aspects of signal transduction and feedback regulation, there is a disappointing dearth of quantitative studies. Those quantitative studies that do exist frequently focus on only one aspect of the pathway output rather than fully characterizing the signal. Available data characterizes each pathway component individually, and there has been little attempt to determine the effects of combining pathway modifications. This study uses CRISPR to produce specific modifications in the yeast mating pheromone MAPK pathway, both individually and in combination. The many aspects of the transcriptional output of the pathway are then quantitatively characterized. This work enhances our understanding of MAPK pathway motifs that may be found in other eukaryotes, and improves our ability to predictively design signal pathways with user-defined output characteristics.