Team:NTHU Taiwan/Description
Inspiration
About Past Thermal Sensitive Systems
The thermal-regulated expression system has been successfully used for the production of many recombinant proteins and peptides. When NTHU_Taiwan looked into the general thermal-sensitive promoters, we found these promoters have much in common.
- Lots of them display low expression at regular temperatures but can be induced by heat or cold exposure.
- Most thermal-sensitive promoters can be activated only in a specific narrow range of temperatures.
If we wanted to use those general promoters to detect temperature variations and subsequently regulate the expression of the downstream gene, the characteristic mentioned above sets a limitation. Many experiments based on these promoters focuses on the temperature that will cause a sudden rise in activation, for instance, the phage ƛ promoter that has often been used by previous iGEM teams, is fully repressed at 28°C to 30°C and is activated at about 42°C. But our team wishes to have a promoter that can sense continuous temperature change and reacts accordingly.
Another issue past temperature promoters have is that the temperature range of promoter-activation is between 35°C-45°C. It is apparently inadequate for systems which target a higher or lower range of temperature.
Herein, NTHU_Taiwan brings forth our engineered E.coli, Tunable-Temperature-Sensitive-System (TTSS). It’s the “artificial thermal sensitive promoter” designed to fit any temperature range you want and respond to temperature change continuously.
A Customizable and Continuously Thermal-Sensitive Promoter
Our team aims at constructing a system that has the following characteristics:
- Being capable to respond to any range of temperature we want.
- Being capable of continually responding to temperature change.
Therefore, we got rid of the inherent temperature-sensitive promoter systems and combined two compartments to reconstruct an “artificial” temperature-sensitive promoter system. In our system, TTSS, we fuse the temperature-sensitive lipase and fatty acid sensitive promoters system. Now, we can arbitrarily choose lipases with different optimal temperature ranges so that our system can be applied to different environments, as long as the lipase doesn't denature. Choosing various lipase system to cooperate with different fatty acid sensitive promoters, we can present a continuously thermal-sensitive promoter that can sense many temperature ranges and make a response, thus achieving customization.
Description
After researching, we found that agricultural over-fertilization poses a great danger to both the environment and plants, which threatens and brings limitations to the development of the industry. Likewise, the phenomenon prevails in Taiwanese agriculture which inspired us to develop a new fertilizing method, which we call “FarFarmIA” bacteria.
Based on a temperature-sensitive system, our TTSS looked into the details of plant growth to seek a solution to over-fertilization.
Overview of current Situation
According to our reference, nowadays, conventional fertilizer tends to adopt "single-dose application" policy. The releasing rate of fertilizer is far higher than the amount the plants actually need.
Harm to the plants
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Photo by Laura Rivera on Unsplash
Environmental pollutions
Photo by Micaela Parente on Unsplas
Threat to human health
Photo by Dragon Pan on Unsplash
How can we help?
We found that when plants are growing, the way they absorb, utilize, and even the elements they need changes constantly. However, among all the factors, temperature is shown to influence all these changes. Our references point out that in most cases, as the temperature rises gradually, the rate of nutrient absorption increases correspondingly.
For example, in temperate climate zones, the uptake rate of nitrite and ammonium increases as temperatures rise from 12℃ to 23℃ in Fuji apples and Ryegrass. Many reactions, besides nutrient absorption rate, such as stem elongation, root length, and the morphology of leaves and flowers, of tomatoes, also vary greatly on temperature. For instance, the most suitable temperature for germination of tomatoes is 28-30 ° C.
Temperature plays an important role in plant growth. To confirm our thoughts, we had an interview with an aged farmer. He opened a gate and lead us to take a glimpse into agriculture nowadays. ( Details in Human/Human Practices)
After our conversation, we found out that farmers have no spare time to monitor farm conditions and fertilize accordingly all the time, though they approved the importance of it. Therefore, we decided to use our TTSS system as well as IOT systems ( Details in Hareware/Overeview) to help.
In conclusion, to grow crops better in agriculture, and to prevent over-fertilization, we believe that the TTSS system can definitely help to make the release rate of fertilizer fit the curve of absorption rate of plants.
Temperature-Sensitive Operator system:Farfarmia
Our system can help detect the temperature change in the environment, and subsequently, release different amounts of fertilizer (which is nitrogen-based in our project) to the crops. For example, when it is summer and temperature is high (around 30\degc), our FarFarmIA can release more fertilizer to the plant, and when the temperature is lower (below 15\degc), vice versa.
Can Our design Hit the Point?
After coming up with this idea, our team surprisingly found a product from a big fertilizer selling company in America, Essential Smart Nitrogen (ESN), which backed up our design. The off-the-shelf fertilizer from ESN Inc. also tries to address over-fertilization and also proposed a solution based on temperature change. Different from us, ESN’s fertilizer granules are coated with special polymers where the pore size is proportional to ambient temperature. Therefore, different amounts of nutrients will be eluted through the pores as temperature changes.
However, we think that the modification of polymers is technically difficult and expensive, making ESN hard to tailor fertilizer release rate for a specific crop.
On the whole, our TTSS can be completely customized and designed to be sensitive to any temperature range because our system can be simply modified by changing the compartment (lipase and promoter), which can be viewed in detail in design. With varying combination of enzyme activity and transcription rate, designing matching curves for all kinds of plants can be more approachable than traditional chemical fertilizer and ESN. Our system may also be used to produce any substance that can be coded into the gene, making it usable not only for agriculture, but also for other purposes.
References
- Relationships between Root Temperature and the Transport of Ammonium and Nitrate Ions by Italian and Perenal Ryegrass(Lolium multiflorum and Lolium perenne) Agricultural Research Council, Letcombe Laboratory, Wantage OX12 9JT England
- Soil temperature and plant growth stage influence nitrogen uptake and amino acid concentration of apple during early spring growth. Shuting Dong, Carolyn F. Scagel, +2 authors Paul T. RygiewiczPublished in Tree physiology 2001
- Production of recombinant proteins in E. coli by the heat inducible expression system based on the phage lambda pL and/or pR promoters Norma A Valdez-Cruz1 , Luis Caspeta1 , Néstor O Pérez2 , Octavio T Ramírez1 , Mauricio A Trujillo-Roldán
- REPOILA, F.; GOTTESMAN, S. Temperature sensing by the dsrA promoter. Journal of bacteriology, 2003, 185.22: 6609-6614
- VALDEZ-CRUZ, Norma A., et al. Production of recombinant proteins in E. coli by the heat inducible expression system based on the phage lambda pL and/or pR promoters. Microbial cell factories, 2010, 9.1: 18.
- iGEM 2009_Imperial College London, Part:BBa_K200011
- GOLDEN, Bobby, et al. Nitrogen release from environmentally smart nitrogen fertilizer as influenced by soil series, temperature, moisture, and incubation method. Communications in soil science and plant analysis, 2011, 42.15: 1809-1824.
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