Plant Synthetic Biology: Design, Quantification and Amplification of a Cell Type Specific Synthetic Genetic Circuit in Arabidopsis

Synthetic biologists can utilize plants as platforms to create photosynthetically driven and self-sustainable genetic circuits. Furthermore, there are many downstream applications for rationally designed plants. Although plants are excellent platforms, issues and unpredictability arise from the innate complexity of multicellularity and its underlying genetic regulation. The ability to quantitatively control gene expression within specific cell types can address some issues arising from multicellularity. In our research, we have developed a genetic circuit with the ability to induce and quantitatively control expression in Arabidopsis thaliana root epidermal cells. Our circuit design uses an externally applied ligand that activates a computationally designed transcriptional response driven by a tissue specific promoter to control output (GFP expression). In addition, we engineered a circuit that adds a positive feedback motif to amplify the system. To quantify the behaviors of these circuits we developed a Matlab program to remove autofluorescence from optical sections captured on a spinning disk confocal micrscope. The program subsequently defines a region of interest, and computes the mean log pixel intensity of the GFP signal within the region. We will present results describing our data to date and on-going work showing this genetic circuit is highly specific for the cell type (root epidermis), fully controllable with the external ligand, and capable of amplification with the positive feedback circuit. The concepts and components of these circuits can be implemented in future designs to engineer and produce plants with more predictable behavior affording the operator greater control.