Part:BBa_K2904054

aTc inducible sfGFP regulated by modular Adda riboswitch containing Tuner E

Design

Background of 2019 OUC-China's project——RiboLego

Due to context-dependent performance and limited dynamic range, the widespread application of riboswitches is currently restricted. By replacing its original ORF with a new one, the structure of an aptamer domain can be subtly disrupted, resulting in a loss of ligand response. So riboswitch is still not be considered as a ‘plug and play' device. To tackle these problems, our project focuses on a standardized design principle to be used for modular and tunable riboswitch. The modular riboswitch we defined consists of the original riboswitch, Stabilizer and Tuner. Stabilizer can protect the structure of riboswitch from damage while Tuner can reduce the expression probability of fusion protein and make improvement of riboswitch function.

The construction of this part

This part was used to validate our design principle of modular riboswitch. We employed activating Adda riboswitch, which can regulate the expression of adenosine deaminase by binding 2-aminopurine in Vibrio vulnificus.The first 150bp of adenosine deaminase was chosen as Stabilizer of Adda riboswitch because our docking matrix suggested that a normal riboswitch structure would be observed when using this length of Stabilizer. We used sfGFPas the reporter gene to reflect output of our system. Besides, Tuner E was inserted between Stabilizer and sfGFP. The modular Adda riboswitch containing the original riboswitch, Stabilizer and Tuner E was under control of the tetracycline promoter, which was induced by aTc.

Result

We did three kinds of experiments to help us confirm the function of modular Adda riboswitch containing Tuner A.

The result by confocal microscopy

For the sake of functional test, other 2 circuits are set, Adda-sfGFP and Adda-Stabilizer-sfGFP, which also were under control of the same promoter. By Confocal Microscopy Leica TCS SP8, it’s obvious that no fluorescence could be observed when the adenine riboswitch had sfGFP introduced directly. The direct fusion of sfGFP to Stabilizer yielded very clear inclusion bodies, manifested as distinct spots present at one pole of the cell which are formed by misfolded insoluble proteins. By comparison, the modular Adda riboswitch yielded soluble working protein since Tuner has the ability to insulation the target gene from Stabilizer.

The result by microplate reader

The qualitative experiment is not enough to analyze the modular Adda riboswitch. So we tested our system by microplate reader, which is used to reflect the intensity of sfGFP changing over time. The following chart shows the dynamic curve measured every two hours. It can prove that the modular Adda riboswitch can restore the structure of riboswitch and control the downstream gene expression during the whole cultivation period.

Figure 1: The results of modular Adda riboswitch containing Tuner E by microplate reader.

Summary

This year, we achieved a rational design principle of modular riboswitch. Many Tuners was utilized for tunable and efficient gene regulation.
[http://2019.igem.org/Team:OUC-China/Model The method we used to design different Tuners is on this page!]
The results demonstrate that these Tuners are capable of shifting and tuning the induction response of modular Adda riboswitches. Sequence and Features BBa_K2904054
SequenceAndFeatures Not understood