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United States Department of Agriculture

Agricultural Research Service

Research Project: MASS PRODUCTION OF BIOLOGICAL CONTROL AGENTS

Location: Biological Control of Pests Research Unit

Title: Saliva of Lygus lineolaris digests double stranded ribonucleic acids

Authors
item Allen, Margaret
item Walker Iii, William -

Submitted to: Journal of Insect Physiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: December 21, 2011
Publication Date: March 2, 2012
Citation: Allen, M.L., Walker III, W.B. 2012. Saliva of Lygus lineolaris digests double stranded ribonucleic acids. Journal of Insect Physiology. 58:391-396.

Interpretive Summary: Some of the newest strategies in insect pest control involve incorporating lethal gene products into crop plants. These gene products, called double stranded ribonucleic acids (dsRNA), would be used to kill insects by interrupting specific gene functions. This research shows that the saliva of the tarnished plant bug, Lygus lineolaris, can degrade these gene products. Thus the dsRNAs are not likely to kill tarnished plant bugs when they eat it. Saliva was collected by squeezing adult insects and collecting exuded saliva from individual mouthparts and by dissecting adult salivary glands and extracting them. Additionally, insects were allowed to feed on tiny packets that contained a drop of dsRNA solution. In all cases, the saliva digested the dsRNA, but was unable to digest samples of the same gene sequence in its DNA form.

Technical Abstract: The prospects for development of highly specific pesticides based on double stranded ribonucleic acid have been a recent focus of scientific research. Creative applications have been proposed and demonstrated. However, not all insects are sensitive to double stranded RNA (dsRNA) gene knockdown effects; applications in the order Lepidoptera, for example, have met with varied success. Gene knockdown has been demonstrated in several species in the order Hemiptera. In our laboratory, knockdown experiments relied on microinjection of dsRNA into the hemocoel of the tarnished plant bug, Lygus lineolaris. Subsequent experiments delivering dsRNA to insects by feeding were repeatedly unsuccessful in demonstrating knockdown, and a hypothesis was formulated that the dsRNA was digested and degraded by the insect prior to contact with the insect cells. Exposure of dsRNA to insect saliva, insect salivary glands, and insect hemolymph was compared with commercial RNAase III. The saliva of L. lineolaris was found to rapidly digest double stranded RNA. RNAase inhibitor did not affect the activity but heat treatment slowed enzymatic activity.

Last Modified: 9/10/2014
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