Overview
In 2017, Lanzhou iGEM Team aims to develop a nontoxic, eco-friendly and without resistance problem Bio-pesticides through synthetic biology. Here is our safety control.
Safe Project Design
1. Using dsRNA directly
Through carefully thought, we decided to use dsRNA directly in verifying macro-experiments rather than bacterium with a suicide system.
Take the future application into consideration, genetically modified crops are currently the best approach once a plant can express the dsRNA in the appropriate tissue at the proper dose. Nevertheless, it is unlikely that all crops will be replaced by dsRNA transgenic plants. Thus, a topical, non-transgenic RNAi approach maybe more practical because it does not genetically alter the crops, which can be developed more rapidly to meet industry needs and can be completed in a shorter amount time.
Furthermore, we have done a domestic transgenic questionnaire. In recent years, the restrictions are severe for genetically modified foods (GMF) in China. Not only public opinion but cognition degree of the public at present is hindering the development of GMF. Many people think that if they eat GMF, their gene information will be modified as same or will bring some potential harm. So the majority don’t accept GMF. But RNAi (one gene silencing mechanism generated by dsRNA etc.) is a new measure to improve crops character such as insect pest injury resistance, and it don’t modify plant’s genome, which maybe more acceptable for the public.
For further safety, as a kind of soil pollutant, E.coli are not suitable in living in the soil. And bacterium will easily undergo horizontal gene transfer, which will increase RNAi off-target possibility towards non-target organisms. In contrast, dsRNA is much safer, which will gradually degrade within two months under the normal circumstance.
2. Steer clear of the potential RNAi off-target risk as much as possibleM
Exogenous gene silence is directly guided by small interfering RNA (siRNA) through the sequence complementarity. But the phenomenon they match with non-target gene and induce silence, called RNAi off-target. This happening mostly is owing to the wide range of gene homology in organisms, but there still have a small rate (around 10%) of off-target. Because the length of siRNA is only 19~21nt, it means that it has 1/419 to 1/421 probability for a 19~21nt mRNA to be identical with siRNA well-designed.
On the whole ,the sequence complementarity between siRNA and non-target organism is smaller, the off target rate is lower.
So we took some measures to steer clear of the RNAi off-target as much as possible. At first, we selected c4 weeds because most of crops are 3c and the metabolism of them has great difference. Second, we used NCBI blast and Mega software, selecting target sequence with over 99% specificity to avoid the possible sequence homology in non-target organisms.
Safe Measures
In order to ensure the safety of the project, our team paid great attention to requirements of iGEM policy and we never performed any dangerous experiments in daily bench work or faced any unusual safety issues. The bench work followed some basic regulations as below:
- Everyone must wear lab coat, rubber gloves, trousers and shoes before entering the laboratory.
- All involved participants needed to understand the experiment completely, make sure team members can complete the experiment independently.
- Food was not allowed to appear in the lab.
- Any steps involving potential release of live microorganisms were performed in a bio-safety cabinet.
- All liquid and solid waste potentially containing living organism was sterilized.
Safe Shipment
Our DNA parts submitted are all safe because they encode non-hazardous proteins such as pectinase, celluse, and functional nucleus acids. The DNA parts were safely confined within PCR tubes as the Parts Registry requires.
Reference
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