Plant viruses seriously affect the yield and quality of crops, such as corn chlorotic mottle virus, wheat streak mosaic virus, potato Y virus, etc., which cause global economic losses of more than 60 billion US dollars every year and seriously threaten food security.
Plant viruses have a wide range of transmission routes and scopes. It can be parasitic in plant cells, and can also be transmitted by insects, pollen or seeds in nature; some plant viruses can enter the coelenterate of insects, making them capable of spreading viruses throughout their lives. The current prevention and control of plant viruses mainly relies on chemical pesticides. Unlike plant diseases caused by other pathogens (such as pests and fungi), the attack characteristics of viruses reduce the targeting and effectiveness of traditional chemical pesticides, which usually require repeated applications. On the other hand, the mutation of the virus forces the use of larger doses of chemical pesticides, endangering ecology and food safety. Therefore, the development of highly efficient and targeted new antiviral pesticides is imminent.
At present, the application of nanotechnology in the field of agriculture has become a new focus of international research. It is shown that a chiral nanoparticle (3 nm Cu1.96S) can quickly enter plant cells through the stomata of leaves, accurately identify the subunit of the capsid protein of tobacco mosaic virus, kill tobacco mosaic virus efficiently, and block tobacco mosaic virus on Infestation of crops.
The “nano” pesticides currently on the market mean the “formulation scale” of pharmaceutical molecules, and their mechanism of action is no different from that of chemical pesticides. In contrast, the chiral nanoparticles studied in this study kill viruses by specifically destroying the virus coat protein without producing drug resistance or residue. It is a new type of green pesticide.
The research comes from the cooperation of Jiangnan University Xu Chuanlai and Professor Kuang Hua’s team with the University of Michigan, the Federal University of San Carlos in Brazil, the University of Illinois, and the Tobacco Research Institute of the Chinese Academy of Agricultural Sciences.
Non-reactive nanoparticles have biological effect in the life system
Chirality is a three-dimensional concept, which refers to the property that the mirror image of an object cannot completely overlap with itself, just like the left hand and right hand are mirror images of each other and cannot be superimposed. In 2001, three scientists who used chiral catalysts to produce chiral drugs were awarded the Nobel Prize in Chemistry. Today, chiral synthesis has become an important research field in the 21st century and is widely used in life sciences.
Before the development of chiral pesticides against plant viruses, Xu Chuanlai’s research team has been mainly developing nano-biological materials for human viral infections, and at the same time developing immunoassay methods based on antibody labeling. Antibody labeling is carried out during the visual analysis process. The team It took the lead in discovering the excellent detection performance of chiral plasma materials, and developed a series of immunological rapid detection test strips, kits, affinity chromatography columns, immunomagnetic beads, etc., which are widely used in the detection of risk factors in food, agricultural products, and the environment. Daily monitoring.
Considering the nanoscale characteristics of biomacromolecules and the stereoselectivity in recognition, the team then developed chiral nanoparticles that match the domains of biomolecules to regulate life processes. In 2018, the research team developed a CdTe chiral material comparable to restriction enzymes, and in 2021 developed a chiral copper sulfide nanomaterial that specifically kills hepatitis B virus.
”Preliminary work has proved that the structure of inorganic chiral nanomaterials can be like natural proteases, which can accurately recognize specific sites of biomolecules; it can also degrade Aβ amyloid under the action of light, and alleviate Alzheimer’s disease.” Chuan Xu Introduction, the clinical application of chiral nanomedicine is very long, “so we hope to push chiral nanotechnology to another field—sustainable agriculture.” Using inorganic salts required for plant growth itself as raw materials, the development of targeted nano Pesticides, which are friendly to the environment and crops, may bring transformative ideas to the research and development of pesticides.
Tobacco mosaic virus (TMV) is the first plant virus discovered by humans. It is easy to spread and stable in performance. It infects a variety of important economic crops and can survive the winter on a variety of plants, seriously affecting crop yield and quality. Therefore, the team used TMV as an object to carry out the synthesis of chiral nanomaterials.
The outer shell of TMV is a helical tubular structure formed by 2130 protein subunits. The diameter of the inner tube is about 4nm, and the genetic material single-stranded RNA is inside. According to this structural feature and scale, we modified the structure of the previous copper sulfide nanoparticles to make them smaller, and also designed the ‘chirality’. The 3nm copper sulfide nanoparticles can better enter the inner pores of the TMV virus, and are stably bound in the pores by binding to specific sites of protein subunits. The binding force between right-handed nanoparticles and TMV protein subunits is 20 times stronger than that of left-handed nanoparticles.
Efficient and specific binding to viruses or animals for analysis, agriculture, medicine, and pharmaceuticals should be widely used
The targets of chemical pesticides are usually some biological targets of pathogens, and these targets often exist in some important physiological functions (such as nerve conduction) and signal pathways. Under the selection pressure of pesticides, pathogens “evade” the “death threat” of these targets through mutation, and the pesticides will become ineffective. The unique mechanism of chiral nanoparticles to kill viruses will not induce pathogen resistance and have better biological safety.
In this work, with D-penicillamine as the surface ligand, chiral 3nm Cu1.96S nanoparticles specifically recognize the Q99ANPTTA105 site in the viral protein capsid, and the site selectivity of chiral nanoparticles makes this The “tailor-made” nanoparticles have a specific binding force of 1 0 7L/M to TMV, which can efficiently and specifically kill TMV virus under sunlight (the affinity with other virus capsids is 3000 times lower~ 10,000 times). With the help of sunlight, the peptide bond between the 101st asparagine (Asp, Q) and the 102nd proline (Pro, P) of the capsid protein is broken, resulting in the cleavage of the viral capsid, which is equivalent to Destroying the physical barrier of the virus exposes and then degrades the nucleic acid in the hole; this killing effect is not aimed at the physiological metabolic pathway of the virus, so it does not induce virus mutation, nor does it give any chance for the mutated virus to escape.
Further studies have confirmed that by spraying TMV-infected crops with the particle aqueous solution (1 μM, 5 mL/plant), more than 95% of the virus can be eliminated within 3 days, and the efficiency is significantly higher than that of all current chemical pesticides against plant viruses. It enters plant cells through the stomata of plant leaves to play a virus-killing role. During this process, monovalent copper is oxidized to divalent copper ions, which are quickly absorbed by plants and have a high utilization rate. The concentration of copper used in pesticide application is much lower than the basic copper content in the soil and plants themselves. The research team further verified that pesticide application has no change in the copper content in crops or soil by monitoring the roots, stems, leaves and soil of crops. The chiral nano-pesticide is expected to be a green and safe new type of pesticide, which will find a new direction for the application of chiral nano-materials.
”Next, we plan to popularize and apply it.” In this regard, Xu Chuanlai said that larger-scale field trials are needed to monitor issues such as dosage and spraying intervals. Although its efficiency is far better than that of traditional pesticides under experimental conditions, in practice, the occurrence of TMV around the target farmland should be considered to determine the drug concentration for effective crop protection; and to observe its effects on different Solanaceae plants and plants in different growth stages Effect. For other plant viruses, due to the limitation of biosafety, the team has not conducted extensive research. “Experiments on plant viruses involve biosafety issues, and must cooperate with qualified institutions such as the National Academy of Agricultural Sciences.” Chiral nanomaterials target
killing The work of destroying TMV has opened up new horizons. “We found that the interaction of all living systems depends on unique structures and spatial conformations. We develop nanomaterials that match their conformations and scales, which provides a basic strategy for us to carry out life regulation at a more complex level in the future.” In addition, regarding the application level, Xu Chuanlai believes that the life cycle of nanoparticles must be considered – how they function, how they are excreted from animals and plants, and whether they affect ecological security.
According to the surface receptors of human intestinal epithelial cells and intestinal microorganisms, the team used trace elements as materials to design chiral nanoparticles with specific affinity, which is expected to regulate intestinal homeostasis and improve body health and immunity.