Team:Harvard

The goal of this project is to genetically engineer a photointerconvertible system of optical communication in the yeast Saccharomyces cerevisiae. To build such a pathway we combine a light-detecting component and a light-emitting component within the framework of the yeast two-hybrid system. Light detection occurs at the phytochrome PhyB, a plant photoreceptor sensitive to both red and infrared light. When treated with red light in the presence of the small molecule phycocyanobilin (PCB), PhyB binds to the protein PIF3, causing a conformational change that promotes the expression of the gene firefly luciferase. When subsequently treated with infrared light, the phytochrome reverts to its inactive conformation, halting the production of the gene. Light emission results from the luciferase-catalyzed oxidation of the pigment luciferin and can be tuned to emit in the same wavelength range as the phytochrome’s absorption spectrum. It is necessary to supplement the system with PCB, either exogenously or by directly integrating the PCB biosynthetic pathway, normally found in lower plants and cyanobacteria, into the yeast genome. One proof-of-concept application of such a system is a light-switchable display, or “cellular blackboard,” wherein a red laser pointer functions as the writing utensil and an infrared lamp as the eraser. Another potential application is a system of optical communication among a population of S. cerevisiae, not unlike fiberoptics. Using red light as a means of communication, yeast populations can be induced to perform tasks such as mating and interacting with other species of organisms.