Resolving the spatial dynamics of single cell circadian regulatory networks

Project Summary/Abstract Physiological and metabolic health relies on the circadian alignment of biological processes with the environment. Since the first documented study of circadian rhythms in the 18th century using a plant system, model organisms have been critical for defining the transcriptional mechanism of the oscillator and revealing the importance of the clock on fitness. Most of this work is based on whole organism or organ level studies leaving many mechanistic questions about how cell specific gene regulation leads to coordination of cellular clocks and a concerted physiological response. We know that gene regulatory networks are effective at modeling gene expression dynamics but resolving cell-type specific networks with time resolution remains a significant challenge. To delineate regulatory connections across cell-types, a single cell view is needed to develop network models that reflect the true cell state rather than the variation among groups of cells or tissues. Only with these cell specific networks can we begin to develop testable hypotheses about what regulatory variation underlies physiological responses. This proposal describes a research strategy that leverages the genetic and molecular power of the plant model system Arabidopsis thaliana and the latest single cell technologies to 1) Identify the cell-types with distinct oscillators and their underlying regulatory networks, 2) Dissect how cell-type specific circadian regulatory networks maintain a synchronized physiological response, and 3) Perturb cell-type specific circadian gene regulatory networks and evaluate their physiological consequences. Over the next five years, our goals are to delineate single cell circadian gene regulatory networks across an entire organ with spatial resolution. Our Arabidopsis model system will be used to dissect how distinct cell type specific circadian regulation controls a physiological response. Through perturbations to tissue specific gene regulatory networks we will gain a better understanding of how cellular gene programming is coordinated. Our long-term goal is to develop Arabidopsis into a model for understanding how cell specific gene regulatory networks influence inter-tissue communication. This research will generate valuable insight into how we interpret the influence of circadian gene regulatory variation on human health and the application of targeted therapies.