Revision as of 20:18, 19 October 2016

T7Promoter+RBS+Sf1a+linker+snowdrop-lectin+linker+6X His-Tag

Introduction:

Figure 1.T7promoter+RBS+Sf1a+linker+snowdrop-lectin+linker+6xhistag

       By ligating the IPTG induced promoter T7 (BBa_ I712074), strong ribosome binding site (BBa_B0034), Sf1a, linker, snowdrop lectin (BBa K1974020) and the 6xHistag (BBa_ K1223006), we can express Sf1a, the toxin by IPTG induction
       This year we create a revolutionary system that integrates biological pesticides, automatic detector, sprinkler, and IoT. We made a database that contains most of the spider toxins and selected the target toxins by programming. U2-segestritoxin-Sf1a is coded for the venom of a spider, Hadronyche versuta.
       It is under the control of the strong T7 promoter. Snowdrop-lectin acts as a carrier that could transport the toxin to insect’s nervous system, hemolymph and can improve the oral activity. A 6xHistag is added for further protein purification.
       According to reference, snowdrop-lectin is resistant to high temperature and would not be degraded by digestive juice. The species-specificity is based on the toxin, and the snowdrop lectin is the role of the carrier.

Mechanism of Sf1a:

      According to reference, U2-segestritoxin-Sf1a has a structure called ICK(inhibitor cysteine knot).^[1] This kind of structure contains three disulfide bonds and beta-sheet. With this structure, U2-segestritoxin-Sf1a can resist the high temperature, acid-base solution and the digest juice of insect gut. U2-segestritoxin-Sf1a can bind on insect voltage-gated Calcium channels (CaV1) in the central nervous system, making it paralyze and die eventually.

Figure 3. Mechanism: In the alimentary canal, lectin binds to gut epithelial glycoproteins, and crosses the epithelium cell by endocytosis and exocytosis, and transported into haemolymph.

Features of Sf1a

1. Non-toxic: U2-segestritoxin-Sf1a is non-toxic to mammals and Hymenoptera (bees). Since the structure of the target ion channel is different, U2-segestritoxin-Sf1a does not harm mammals and bees. So it is safe to use it as a biological pesticide.

2. Biodegradable: U2-segestritoxin-Sf1a is a polypeptide so it must degrade over time. After degradation, the toxin will become nutrition in the soil.

3. Species-specific: According to reference, U2-segestritoxin-Sf1a has specificity to Lepidopteran (moths), Dipteran (flies) and Orthopteran (grasshoppers).

4. Eco-friendly: Compare with chemical pesticides, U2-segestritoxin-Sf1a will not remain in soil and water so that it will not pollute the environment and won’t harm the ecosystem.

       Together, using U2-segestritoxin-Sf1a is totally an environmentally friendly way for solving harmful insect problems by using this ion channel inhibitor as a biological pesticide.

Target insect:

Figure 4.

Experiment

1. Cloning :
After assembling the DNA sequences from the basic parts, we recombined each T7 Promoter+B0034+Sf1a+ linker + snowdrop -lectin +linker+ 6xhistag+ linker +6xHistag gene to pSB1C3 backbones and conducted a PCR experiment to check the size of each part. The DNA sequence length of these parts is around 500-700 bp. In this PCR experiment, the toxin product's size should be near at 800-1000 bp.Proved that we successfully ligated the toxin sequence onto an ideal backbone.

Figure 5.

2. Expressing:
E.coli(DE3) express the protein and form the disulfide in the cytoplasm. We sonicated the bacteria and purified the protein by 6xHis-tag behind the toxin using Nickel resin column.

3. Analysis:
We do the Bradford analysis to get the protein concentration.

Figure 6.

Figure 7.

4.Modeling:
According to reference, the energy of Ultraviolet will break the disulfide bonds and the toxicity is also decreased. To take the parameter into consideration for our automatic system, we modeled the degradation rate of the protein and modify the program in our device.

5. Device:
We designed a device that contains detector, sprinkler, and integrated hardware with users by APP through IoT talk. We use infrared detector to detect the number of the pest and predict what time to spray the farmland. Furthermore, other detectors like temperature, humidity, lamination, pressure of carbon dioxide and on also install in our device. At the same time, the APP would contact the users that all the information about the farmland and spray biological pesticides automatically. This device can make farmers control the farmland remotely.

Results

       Pantide-expressed E. coli Rosetta gami strain and diluted it with the three concentration.We applied the sample onto the leaf disks and put five cutworms into the separate cabinets for feeding assays. The positive control in the experiment was to apply Bacillus thuringiensis, which is the most widely-used bioinsecticide. We preserved all the result of the remained leaves sealing with the glass paper and calculated the ratio of the remained area on the leaves. The collected data were analyzed by t – test. Here are the feeding assay results.

Figure6.Below are leaves with of Negative control ( DDwater ), Positive control ( Bacillus thuringiensis bacteria ), Sf1a+linker+His-Tag, Sf1a+linker+snowdrop-lectin+linker+His-Tag

Figure7.Below are leaves with of Negative control ( DDwater ), Positive control ( Bacillus thuringiensis bacteria ), Sf1a+linker+snowdrop-lectin+linker+His-Tag,

Sequence and Features