Collaborative Research: Harnessing plant hormone receptors for the rapid design of genetic circuits controlled by user-specified ligands

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Organisms across the tree of life can sense features of their environments and respond to them. For example, plants grow in the direction of light, and bacteria swim toward nutrient sources. An organism’s ability to sense and respond is a core biological function undergirded by molecular machinery that recognizes specific signals and then triggers responses, such as changes in the organism’s growth, development, or movement. In this project, a team of engineers and biologists work together to develop new biological functions by engineering a sense-response module taken from plants. This sensor is unique because it can be used as a simple switch for turning other proteins on and off at will and can be reprogrammed to recognize diverse chemicals. This project develops sensors for pharmaceuticals and dietary molecules and then uses these new sensors to design synthetic ‘sentinel cells’ that can easily indicate the presence of many different molecules. For example, the project designs cells that turn different colors depending on to which pharmaceutical they are exposed. To do this, the team is reprograming a plant sensor to recognize new molecules and then physically link the new sensors to a bacterial enzyme that regulates gene expression. This union enables bacteria to turn different colors in response to input signals. The project supports the training of students in STEM careers and the research findings are integrated into a discovery-based lab associated with an introductory laboratory course.This project enables the rapid construction of single and multi-channel genetic circuits controlled by user-specified molecules. This capacity is enabled by building a platform for the rapid construction of programmable chemically inducible RNA polymerases (ChIRPs). To do this, computational design, mutagenesis, and genetic selections are used to reprogram the ligand-binding specificity of a novel plant-derived chemical-induced dimerization module that is used to regulate the activity of split T7 RNA polymerase. In parallel, a new set of orthogonal T7 variants that recognize novel promoters are developed and converted into ChIRPs to deliver multi-input/multi-output chemical-regulated circuitry. These efforts open a vast range of new ligand-controlled biotechnologies and allow investigators to design complex genetic circuits controlled by the best specific ligands for target applications.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.