Team:NCTU Formosa/introduction

Our program is to design “Pathway Commander”, which is just like its name, is able to direct a pathway’s going. The goal is to control a pathway to stop at any intermediate state. In traditional pathway design, one circuit will express itself all to the end, unable to stop at any state involved. However, with our “RNA Thermometer”, which is temperature-controlled, the pathway can be easily controlled at specific temperature. The circuit we design can stop at any intermediate state we want and accumulate intermediate products, and then continue to express if the condition is changed. Even branched circuit can also be created.

We design three examples to demonstrate our idea, which are Carotenoid pathway, Volacein pathway and Butanol pathway.

In Carotenoid pathway, we can stop the pathway at three states. In every state, it can turn to the next state after accumulate enough intermediates. For instance, when the temperature is below 37℃, E-coli synthesizes enzyme CrtE,CrtB and CrtI, which catalyze the precursors into pigment-Lycopen, and the red color is displayed. Later, when the temperature rises to 37℃, E-coli synthesizes CrtZ which catalyzes accumulative Lycopen into β-carotene, which is orange. Finally, we raise the temperature up to 42℃ and E-coli synthesize CrtY which catalyzes β-carotene into Zeaxanthin, and the yellow color show up in the end.

In Volacein pathway, we bear the same idea in mind controlling the pathway with branches. Intermediate PVA can turn into Deoxychromoviridans or Protoviolaceinic acid regulated by different temperature. The Protoviolaceinic acid will turn into volacein eventually and then two branches are created.

Last and the most important, in Butanol pathway, we use low-temperature-induced pathway because our product will easily vapor in high temperature, and the specific enzyme involved has better activity at 30℃. We know that butanol is fatal to E-coli if the amount is too much. Now, we can exploit our “Pathway Commander” idea to the fullest in this situation. First, intermediate products accumulate until enough quantity to be bio-fuel and then we lower the temperature to induce the enzyme which catalyzes precursors into butanol. Of course, the Ecoli dies due to butanol of high concentration, and there won’t be environmental issue and get enough butanol to produce bio-fuel!