Team:iBowu-China/Description
In agriculture, chemical pesticides treatment is the most widely used solution to control plant diseases, but there are disadvantages in the highly toxicity and non-degradation. Even worse, long-term use of chemical pesticides results in human health hazards and local ecosystem damage. Recently, the less toxic, more specific and more effective method, biopesticide, has been developed. Traditional biopesticides utilize organisms (fungi, bacteria, insect viruses, etc.) or plant metabolites (pheromone, auxin, naphthaleneacetic acid, 2,4-D, etc.)[1]. In addition, with the rapid development of the transgenic technology, more attention is paid on genetically engineered bacteria to prevent and control agricultural diseases. However, this powerful tool ‘genetically modified organisms’ is limited in agricultural practice due to their biosafety risks.
The cell-free system is developed as an enabling platform for the construction and optimization of metabolic pathways and genetic circuits without a living cell, and this system can help to address the challenges about bio-safety problems[2]. This may provide us with an innovative idea to use the design of the gene circuits and apply it in syn-bio approaches in the field of bio-control of both individuals and multiple crop diseases.
To put our idea into practice, we designed the ‘Bio-Control of Soft Rot’ project.
Proposal of Core Issues
Potato (Solanum tuberosum) is a globally important high-yield crop that produces nutrient-rich tubers. This non-grain crop is the third most important food crop, after wheat and rice, and it is grown in more than 150 countries and regions around the world[3]. One of the major threats to potato production is soft rot disease caused by bacteria Erwinia Carotovora, which secrets enzymes capable of breaking down the cell wall components, causing histiocytic destruction of the affected crops. This disease generally occurs during cultivation, harvesting or transportation and storage of farm produce, resulting in considerable yield reduction, poor quality of produce, and economic loss.
Different approaches to soft rot disease control have been developed and applied. Physical methods improved the management and selection of healthy potato tubers prior to culture, transportation or storage. However, these measures are expensive, time consuming and failed to eradicate vascular pathogenic bacteria[4][5]. Several chemical strategies based on a massive use of chemical pesticides are efficiently, however, they are limited due to the damage to the solid and disturbance to the local ecosystem, health hazards, as well as the development of herbicide resistance.
| Sterilization Principle | Advantages | Disadvantages | |
|---|---|---|---|
| Bacillus subtilis | 1. After seed dressing or rooting, Bacillus subtilis can colonize and multiply sites in plant organs to protect crop roots from pathogen infection. 2. When colonizing and breeding Bacillus subtilis, Bacillus subtilis can produce bactericidal substances such as lipopeptides and proteins, thereby killing plant pathogenic bacteria and achieving disease prevention effects. |
1. It is non-toxic and harmless to humans and animals, does not pollute the environment, and is safe for crops. 2. It can produce a variety of antibiotics and enzymes, with broad-spectrum antibacterial activity and strong resistance to stress. 3. Bacillus subtilis is also capable of secreting active substances that promote crop growth, increasing crop immunity, increasing yield, and regulating growth of crops. |
1. The product has a short shelf life, slow effect, a single object, and is susceptible to the natural environment. 2. The transfer of the multi-enzyme system into the foreign plasmid is unstable and thus makes it difficult to use it as an expression system. |
| Chlorobromoisocyanuric acid | 1. When chlorobromoisocyanuric acid is sprayed, hypobromous acid (HOBr) and hypochlorous acid (HOCL) are released. The activity of hypobromous acid is four times that of hypochlorous acid. It has strong ability to kill bacteria and fungi. 2. The formation of triazinedione (DHT) and triazine (ADHL) by the release of hypobromous acid by systemic conduction, with strong viricidal effect 3. In addition, because the starting materials are rich in potassium salts and trace elements, it can promote the growth of crops. |
1. Can kill a variety of bacteria, algae, fungi and germs. 2. Chemically stable, easy to store and transport 3. Safe, simple, low dosage and good sterilization effect |
1. Long duration 2. Harmful to the environment 3. Low toxicity, moderate stimulation of the eyes |
| Streptomycin sulfate | Streptomycin sulfate is an aminoglycoside antibiotic drug. Streptomycin sulfate has a strong antibacterial effect on Mycobacterium tuberculosis and has strong antibacterial activity against many Gram-negative bacilli. | This product is effective for all kinds of skin tuberculosis, inhibits the proliferation of Mycobacterium tuberculosis and the production of toxins. It has a bactericidal effect at high concentrations (>0.4 μg/mL). | Streptomycin sulfate is less harmful to the kidneys |
| Thiobacillus | 1. It has special effects in controlling bacterial diseases of crops. 2. Sterilization mechanism, both the unique control effect of thiazole groups on bacteria, and the excellent control effect of copper ions on fungi and bacteria. |
1. It has excellent control effect on rice disease, base rot and cabbage soft rot, cucumber leaf spot, citrus canker and scab, and is also excellent for other fungal diseases such as banana leaf spot and watermelon blight. Control effect. 2. Novel structure, advanced dosage form, good internal absorption and low toxicity |
Toxicity |
| Amber | 1. A commonly used organic copper mixed fungicide 2. It has protective bactericidal effect and is suitable for controlling bacterial diseases. 3. The copper ion exchanges with the cation on the surface of the pathogen membrane to coagulate the protein on the cell membrane of the pathogen, and some copper ions penetrate into the pathogen of the human pathogen to bind with certain enzymes, affecting its activity. |
1. Amber bactericidal copper has a wide spectrum of sterilization 2. Protective sterilization |
1. Low toxicity to the human body 2. Stimulating plant growth |
| Copper Ammonia | 1. Compounds synthesized by glycine and copper complex | 1.Copper ammonia is a broad-spectrum fungicide. 2.Contains a variety of trace elements. Can promote crop growth 3.It can promote the deep roots of plants, increase chlorophyll content, enhance photosynthesis and drought resistance. 4.Significant increase in production |
1. Unstable under acidic conditions 2. Low toxicity to humans and animals |
| Copper Hydroxide | Its bactericidal action mainly relies on copper ions, which are absorbed by the germinated spores. When a certain concentration is reached, the spore cells can be killed, thereby playing a bactericidal effect, but this effect is limited to preventing spore germination, that is, only protection effect. | 1. The drug has excellent suspension and dispersibility, is resistant to rain, and has a long-lasting effect and is easy to use. 2. No phytotoxicity at the recommended dosage, it is one of the copper preparations to replace Bordeaux mixture |
Toxic to human body and the environment |
| *Bacillus Subtilis | 1. After seed dressing or rooting, Bacillus subtilis can colonize and multiply sites in plant organs to protect crop roots from pathogen infection. 2. When colonizing and breeding Bacillus subtilis, Bacillus subtilis can produce bactericidal substances such as lipopeptides and proteins, thereby killing plant pathogenic bacteria and achieving disease prevention effects. |
1. It is non-toxic and harmless to humans and animals, does not pollute the environment, and is safe for crops. 2. It can produce a variety of antibiotics and enzymes, with broad-spectrum antibacterial activity and strong resistance to stress. 3. Bacillus subtilis is also capable of secreting active substances that promote crop growth, increasing crop immunity, increasing yield, and regulating growth of crops. |
1. The product has a short shelf life, slow effect, a single object, and is susceptible to the natural environment. 2. The transfer of the multi-enzyme system into the foreign plasmid is unstable and thus makes it difficult to use it as an expression system. |
This chart shows that farmers nowadays mainly used chemical pesticides with severe impacts on the water pollution and soil pollution[4]. The remains of the chemical pesticides will stay in the soil or water, which may impose potential threats to people’s health. Therefore, we come up with the idea that by capitalizing on synthetic biology means, we can produce a harmless and effective pesticide.
We plan to develop an easier toolkit, based on cell-free system which can detect and prevent the occurrence of soft rot. Therefore, we designed two kinds of gene circuits in order to detect and prevent the disease. One’s function is to detect N-(3-oxohexanoyl)-L-homoserine lactone (OHHL,quorum sensing signal molecular of E.carotovora) [6,7,8,9]; the other is to express the hydrolase AiiA and the antibacterial peptides which could degrade OHHL and generally kill bacteria separately[7,10,11,12]. The gene circuits coupling with cell-free expression system are lyophilized on paper and can be used with rehydration.
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2. Pardee K, Green A, Ferrante T, et al. Paper-Based Synthetic Gene Networks[J]. Cell, 2014, 159(4):940-954.
3. Taylor , Andrew. Soft Rot Diseases of Potatoes[J]. Agriculture and Food, 2018. https://www.agric.wa.gov.au/potatoes/soft-rot-diseases-potatoes.
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