Biotechnology for control of crop pest insects and insect vectors of human diseases

Summary

Control of pest insects is necessary for the production of crops and the reduction of human diseases transmitted by insects. Controlling pest insects has become more difficult due to emerging insect resistance to chemical pesticides and the introduction of invasive insect species. The insecticidal proteins of Bacillus thuringiensis (Bt) provide an alternative to chemical pesticides by their deployment in crop plants and biopesticides. Our basic research on how Bacillus thuringiensis (Bt) kills pest insects is relevant to both agricultural pest insects and insects that vector human disease. This research is being translated into novel methods for enhanced insect control that are in commercial development.

Situation

Insects that damage crops and vector diseases threaten human food security and human health. We rely on chemical pesticides and products based on biotechnology as essential tools for pest insect control. Since almost no new insecticides have been become available in the recent past, there is an increased reliance on biotechnology-based solutions for pest insect control. Corn and cotton engineered to produce insecticidal Bacillus thuringiensis (Bt) Cry proteins has greatly reduced the number of chemical pesticide applications. While managing the threat of insects becoming resistant to Bt Cry proteins has mostly been successful, the emergence of corn rootworm, Fall armyworm and possibly cotton bollworm resistant to Bt crops is a serious threat to the long-term usage of this in the United States and globally. Insects such as mosquitoes that vector human disease are often controlled by the same chemical pesticides used against crop pests. Innovative strategies and tools are needed to address insect control needs now and in the future. We need to inform students and the broader public about the impact insect pests have on crops and human disease and effectively communicate how innovative technologies can address this situation.

Response

Tarnished Plant Bugs, Lygus lineolaris, have emerged as major global crop pests. This group of bugs in the Order Hemiptera has piercing – sucking mouth parts, stylets that puncture plant cells and remove cellular contents. These species are cosmopolitan pests of high value crops. During the early bud and bloom stage, feeding by these insects causes bud and flower loss reducing yield on stone fruits, and a number of agricultural crops including cotton. Recently, the structure of Cry51Aa was solved by a collaboration with the Adang laboratory. A bioassay method was developed and Cry51Aa was shown to have some toxicity to third instar Lygus nymphs. Global climate change and acquired resistance to insecticides are threats to world food security. Drosophila suzukii, a devastating invasive pest in many parts of the world, causes substantial economic losses to fruit production industries, forcing farmers to apply broad-spectrum insecticides frequently. This could lead to the development of insecticide resistance. In a collaborative project with Dr. Ash Sial we determined the median lethal concentration values of zeta-cypermethrin, spinosad, and malathion insecticides against D. suzukii colonies established from Clarke and Pierce county Georgia. We identified a high number of differentially expressed genes that are likely involved in detoxification and reduced cuticular penetration, especially in the Pierce population flies thus highlighting molecular mechanisms underlying the higher tolerance of Pierce population flies to pesticides. Mosquitoes vector major human diseases including malaria, dengue and Zika viruses and West Nile virus. Research investigated the action of the insecticidal toxins of Bacillus thuringiensis (Bt) and Lysinibacillus sphaericus (Lsph) against larvae of mosquito species. Because the Lysph bacterium is highly toxic to Culex mosquitoes that vector West Nile virus and lymphatic filiarisis it has been widely used as a biopesticide against Culex larvae. Control of Culex is especially important in the Recife Brazil as the region is endemic for lymphatic filiarisis; unfortunately, incidences of Culex resistance to Lysph are reported in this region. To address this problem, a collaboration with researchers at FIOCRUZ was initiated to investigate strategies for improving Lysph activity against Culex mosquitoes. Lectures on human diseases transmitted by insects were integrated into undergraduate biotechnology classes. Students learned about disease agents such as protozoa that cause malaria and Zika virus. They were presented examples of how biotechnology is used to discover therapeutics, synthesize therapeutics and develop antibody-based biologics. Students were introduced to the latest technologies for manipulating insects that vector disease. The regulation of new insect technologies by governmental agencies is discussed as are the ethics related to insect genetic technologies.

Impact

Spotted wing drosophila, Drosophila suzukii, responded to chemical pesticides in our experiments by increasing expression of specific proteins, notably cuticular proteins a results suggesting that attention be directed at the role of cuticular proteins in pesticide resistance. With emerging resistance to pyrethroids reported for this pest, it is urgent that attention be directed at mechanisms of resistance and the application of this information to detection of incipient resistance for early intervention. The larval stage of pest insects remains an attractive target for use of insecticidal proteins derived from Bt and other insect pathogens. The results from a decade of research on Bt mosquitocidal Cry proteins were summarized in a published review. In the past few years, a new category of insecticidal proteins has become more important. These proteins fold differently from most Bt Cry proteins and they are called the Beta pore-forming toxins. Cry51Aa, which is active against beetle and Lygus larvae was shown to be a Beta pore-forming toxin. Similarly, the binary toxins of the mosquitocidal bacterium Lysinibacillus sphaericus are Beta-pore forming toxins. Our research yielded insights into how this group of toxins functions to kill pest insects. It is our long term goal to apply this information to designing novel proteins for insect control. Hundreds of undergraduates were educated about the role of insects in emerging and orphan human diseases. They were taught to understand the impact of such diseases in an increasingly global society. Students learned about innovative technologies for developing therapeutics and managing pest insects in the context of global human challenges. The impact is that these individuals are more aware that new technologies are needed to better human food security and human health and they need to be involved as citizen scientists.

State Issue

Plant Production

Details

• Year: 2016
• Geographic Scope: International
• County: Clarke
• Program Areas:
  • Agriculture & Natural Resources