Location: Biological Control of Insects Research2012 Annual Report
1a. Objectives (from AD-416):
Objective 1. Use established procedures to obtain basic understanding of eicosanoid-mediated immune signaling in pest (squash bug, Anasa tristis) and beneficial (spined soldier bug, Podisus maculiventris) insect species. Objective 2. Generate new knowledge for future deployment of dsRNA to silence genes involved in immune signaling, particularly eicosanoid-mediated signaling, in a pest insect (squash bug, Anasa tristis) and test for species specificity using a beneficial insect (spined soldier bug, Podisus maculiventris).
1b. Approach (from AD-416):
1) Determine the influence of infection on PLA2 activity in immune tissues from squash bugs and spined soldier bugs; 2) Characterize and determine the influence of infection on prostaglandin production in immune tissues from squash bugs and spined soldier bugs; 3) Test the idea that prostaglandins and other eicosanoids mediate cellular reactions to infection; 4) Design dsRNA to silence genes involved in immune signaling; and 5) Determine the influence of dsRNA on immune signaling in intact squash bugs.
3. Progress Report:
For Objective 1a we characterized an enzyme responsible for signaling infections in a lepidopteran pest, the tobacco budworm. This work demonstrated the presence of a gene for the enzyme in the pest insect and showed the basic properties of the enzyme, such as the temperature range required for enzyme activity. This prepares the groundwork for more detailed research aimed to silence expression of the enzyme and thereby cripple the ability of pest insects to respond to natural infections and some biopesticides. For Objective 2a we completed the design of tools to silence expression of an enzyme responsible for signaling infections in a lepidopteran pest and other critical components of immune signaling in squash bugs. These tools will be deployed to cripple the ability of pest insects to respond to natural infections and some biopesticides.
1. Discovery of prophylactic immunity in insects. Insect developmental hormones are attractive targets for developing novel insect pest control technologies, however, they have not been fully exploited because the actions of these hormones are not sufficiently understood. ARS researchers in Columbia, Missouri, working in an international collaborative team, discovered a new biological role for one of the developmental hormones. Specifically, a developmental hormone mediates expression of insect immunity during molting. This is the first example of natural prophylactic immunity because expression of immunity is a developmental process, not caused by an infection. This finding reveals a new target scientists will use to develop novel technologies to improve biological control of insect pests. Ultimately, this research will benefit crop producers and consumers by reducing the insecticide load in the environment.
2. Discovery of immune signaling mechanism. Biological control is based on the idea that direct application of insect-specific pathogens and parasites can reduce pest insect populations and the economic damage due to pest insects, and offers a potentially powerful alternative to classical chemical insecticides. The problem, however, is the efficiency of beneficial organisms in biological control programs is limited by the insect’s immune defenses. One approach to improving the efficiency of biocontrol agents would be to disable insect immune reactions to viral, bacterial, fungal and parasitic infections. With this goal, ARS researchers in Columbia, Missouri, working in an international collaborative team, identified previously unknown biochemical signals responsible for stimulating insect defenses to infection. This discovery shows new, specific targets that will be useful to scientists working to develop new biological control technologies. The ensuing improved biological control methods will benefit a wide range of agricultural producers and consumers by supporting the long-term sustainability of agriculture.
3. Developing genetic insect control technologies. Challenges to long-term use of classical insecticides in agriculture include the development of insect resistance to insecticides and environmental concerns with chemical usage. Insect pests consume or destroy about 15% of the world’s human food production, which is driving research to invent and develop new insect pest management technologies. Recent advances in basic knowledge of insect genetics provide the basis for new pest control strategies. ARS scientists, working in a collaborative international team, introduced and expressed a specific gene in the Asian corn borer. This result demonstrates the viability of a new approach for the genetic control of Asian corn borers and related pests of corn. This research benefits producers and consumers through the development of new tools for economically and environmentally sustainable agriculture.
Srikanth, K., Park, J., Stanley, D.W., Kim, Y. 2011. Plasmatocyte spreading peptide influences hemocyte behavior via eicosanoids. Archives of Insect Biochemistry and Physiology. 78:145-160.