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Eicosanoids: Exploiting Insect Immunity to Improve Biological Control Programs
Biological Control of Insects Research Laboratory, USDA Agricultural Research Service, 1503 S. Providence Rd., Columbia, MO 65203, USA
Department of Chemistry, Creighton University, Omaha, NE 68178, USA
Department of Biological Sciences, Northern Illinois University, DeKalb, IL 60115, USA
* Author to whom correspondence should be addressed.
Received: 15 March 2012; in revised form: 24 April 2012 / Accepted: 9 May 2012 / Published: 16 May 2012
Abstract: Insects, like all invertebrates, express robust innate, but not adaptive, immune reactions to infection and invasion. Insect immunity is usually resolved into three major components. The integument serves as a physical barrier to infections. Within the hemocoel, the circulating hemocytes are the temporal first line of defense, responsible for clearing the majority of infecting bacterial cells from circulation. Specific cellular defenses include phagocytosis, microaggregation of hemocytes with adhering bacteria, nodulation and encapsulation. Infections also stimulate the humoral component of immunity, which involves the induced expression of genes encoding antimicrobial peptides and activation of prophenoloxidase. These peptides appear in the hemolymph of challenged insects 6–12 hours after the challenge. Prostaglandins and other eicosanoids are crucial mediators of innate immune responses. Eicosanoid biosynthesis is stimulated by infection in insects. Inhibition of eicosanoid biosynthesis lethally renders experimental insects unable to clear bacterial infection from hemolymph. Eicosanoids mediate specific cell actions, including phagocytosis, microaggregation, nodulation, hemocyte migration, hemocyte spreading and the release of prophenoloxidase from oenocytoids. Some invaders have evolved mechanisms to suppress insect immunity; a few of them suppress immunity by targeting the first step in the eicosanoid biosynthesis pathways, the enzyme phospholipase A2. We proposed research designed to cripple insect immunity as a technology to improve biological control of insects. We used dsRNA to silence insect genes encoding phospholipase A2, and thereby inhibited the nodulation reaction to infection. The purpose of this article is to place our view of applying dsRNA technologies into the context of eicosanoid actions in insect immunity. The long-term significance of research in this area lies in developing new pest management technologies to contribute to food security in a world with a rapidly growing human population.
Keywords: biological control; insect immunity; signal transduction; eicosanoids; prostaglandins; phospholipase A2
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Cite This Article
MDPI and ACS Style
Stanley, D.; Haas, E.; Miller, J. Eicosanoids: Exploiting Insect Immunity to Improve Biological Control Programs. Insects 2012, 3, 492-510.
Stanley D, Haas E, Miller J. Eicosanoids: Exploiting Insect Immunity to Improve Biological Control Programs. Insects. 2012; 3(2):492-510.
Stanley, David; Haas, Eric; Miller, Jon. 2012. "Eicosanoids: Exploiting Insect Immunity to Improve Biological Control Programs." Insects 3, no. 2: 492-510.