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ARS Home » Midwest Area » Columbia, Missouri » Biological Control of Insects Research » Research » Publications at this Location » Publication #333319

Research Project: Insect Biotechnology Products for Pest Control and Emerging Needs in Agriculture

Location: Biological Control of Insects Research

Title: Relish2 mediates bursicon homodimer-induced prophylactic immunity in the mosquito Aedes aegypti

item ZHANG, HONGWEI - University Of Missouri System
item DONG, SHENGZHANG - University Of Missouri System
item CHEN, XI - University Of Missouri System
item Stanley, David
item BEERNTSEN, BRENDA - University Of Missouri System
item FENG, QILI - South China Normal University
item SONG, QISHENG - University Of Missouri

Submitted to: Scientific Reports
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/20/2017
Publication Date: 2/22/2017
Citation: Zhang, H., Dong, S., Chen, X., Stanley, D.W., Beerntsen, B., Feng, Q., Song, Q. 2017. Relish2 mediates bursicon homodimer-induced prophylactic immunity in the mosquito Aedes aegypti. Scientific Reports. 7:43163.

Interpretive Summary: Chemical insecticides are effective pest insect management tools, however, negative effects, including environmental contamination and insect resistance to the insecticides attend use of these products. These negative effects drive research into alternative insect management technologies such as biological control based on deploying insect pathogenic microbes, known as microbial control. The problem with microbial insect control is insects have very powerful immune responses to pathogenic microbes, which reduces the efficacy of these microbes. We address this problem with research designed to understand and limit insect immunity. In this paper we report on insect prophylactic immunity that is expressed while insects shed their old cuticles, to be replaced with new ones. Insect prophylactic immunity is a new concept which may be expressed in several different ways. It represents a new, researchable target that may be exploited to increase the effectiveness of microbial biocontrol of insect pests. This new finding will be used by scientists working to suppress insect immune systems and will ultimately benefit growers and consumers of vegetable and other food crops.

Technical Abstract: Bursicon is a neuropeptide hormone consisting of two cystine-knot proteins (burs a and burs ß), responsible for cuticle tanning and other developmental processes in insects. Recent studies show that each bursicon subunit forms homodimers that induce prophylactic immunity in Drosophila melanogaster. Here, we investigated the hypothesis that bursicon homodimers act in prophylactic immunity in insects, and possibly arthropods, generally, using the mosquito, Aedes aegypti. We found that burs a and burs ß are expressed in larvae, pupae and the first few hours after adult emergence. Treating newly emerged D. melanogaster and Ae. aegypti adults with recombinant bursicon proteins led to cuticle tanning in both species. Treating larvae and adults with these proteins led to up-regulation of five anti-microbial peptide (AMP) genes. The induced AMPs effectively suppressed the growth of bacteria in vitro. RNAi knock-down of the transcriptional factor Relish2 abolished the influence of recombinant bursicon homodimers on AMP production. We infer the bursicon homodimers induce expression of AMP genes via Relish2 in Ae. aegypti, as prophylactic immunity to protect mosquitoes during the vulnerable stages of each molt. Extending the D. melanogaster finding to another insect species supports our hypothesis.