Part:BBa_K2904051
aTc inducible sfGFP regulated by modular Adda riboswitch containing Tuner B
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 B was inserted between Stabilizer and sfGFP. The modular Adda riboswitch containing the original riboswitch, Stabilizer and Tuner B was under control of the tetracycline promoter, which was induced by aTc.
Result
In order to verify the factionality of this part, 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 containing Tuner B can restore the structure of riboswitch and control the downstream gene expression during the whole cultivation period.
Summary
This year, we achieved a rational design principle of modular riboswitch. Many Tuners was utilized for tunable and efficient gene regulation. To verify the functionality of different Tuners, we engineered different modular Adda riboswitches including Tuner A to E respectively. All circuits selected sfGFP as the target gene. Using different Tuners, muti-level regulation can be achieved.
[http://2019.igem.org/Team:OUC-China/Model The method we used to design different Tuners is on this page!]
First, microplate reader was used to measure the fluorescence intensity of sfGFP. Data is shown for each construct until steady state is reached (at least two consecutive subsequent data points do not increase fluorescence). The results demonstrate that these Tuners are capable of shifting and tuning the induction response of modular Adda riboswitches.
Then we also tested our modular Adda riboswitches by flow cytometer. The figure below shows the measured expression distributions at the same induction for modular Adda riboswitch with different Tuners.
By all the experiments mentioned before, we proved that Tuners work as expectations successfully. They are expected to serve as a powerful and tunable tool of riboswitch for future iGEM teams based on their demand.
If you are interested in the other parts we designed, you can click modular riboswitches containing Tuner A,Tuner C,Tuner D,Tuner Eand Tuner S.
Sequence and Features
- 10COMPATIBLE WITH RFC[10]
- 12COMPATIBLE WITH RFC[12]
- 21INCOMPATIBLE WITH RFC[21]Illegal XhoI site found at 1
- 23COMPATIBLE WITH RFC[23]
- 25COMPATIBLE WITH RFC[25]
- 1000INCOMPATIBLE WITH RFC[1000]Illegal SapI.rc site found at 410
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