Research Accomplishment Reports 2009

Molecular Analysis of Pest Development and Resistance to Insecticides

S. R. Palli
Department of Entomology

 

Non-Technical Summary

Identification of genes that are involved in the functioning of these hormones will help in developing environmentally friendly pest-management methods We propose to identify critical genes that are involved in pest development and use them for designing better pest management tools and gene switches.

2009 Project Description

We investigated the mechanisms of JHA action in red flour beetle, Tribolium castaneum, belonging to the order Coleoptera. We cloned Juvenile hormone esterase gene from Aedes aegypti. We identified broad from Tribolium castaneum. Broad (br), a transcription factor containing the Broad-Tramtrack-Bric-a-brac (BTB) and zinc finger domains was shown to mediate 20-hydroxyecdysone (20E) action and pupal development in Drosophila melanogaster and Manduca sexta. We determined the key roles of br during larval-pupal metamorphosis using RNA interference (RNAi) in a coleopteran insect, Tribolium castaneum. Using DNA affinity column, we purified proteins that bind to the Juvenile hormone response element. Mass spectrometric analysis identified five DNA/RNA binding proteins.

We studied hormonal regulation of mosquito larval and pupal development. Biochemical mode of action and differential activity of new ecdysone agonists against Mosquitoes and Moths were studied. We used ecdysone receptor-based assays to screen for new more potent ecdysteroid analogs and identified new ecdysteroid analog that works very well in mosquitoes.

We prepared a Heliothis virescens embryonic library at 50-70% development stage. Analysis of about 200 clones showed 100% inserts with an average insert size of 1.5-4.5 kb. We sequenced 200 clones and all of them showed inserts with open reading frames (ORF). Comparing these ORF sequences with the sequences in the GenBank showed similarity with tubulin, C3H1 zinc finger, thymidylate synthase, RNA helizase, neurotactin, glyceroldehyde phosphate dehydrogenase, nitrate extrusion protein and Riken.

2009 Impact

The long-term goals of this research are to understand the molecular basis of hormone action and use this information for development of environmentally-friendly pest management methods. The information and materials generated during these studies can be used to

(a) understand the mode of action of existing hormone analogs,

(b) develop target-site based screening assays to discover new, more potent, species-specific, environmentally benign hormone analogs,

(c) interfere with insect development by over or under expressing critical genes involved in JH action through recombinant microorganisms, transgenic insects or transgenic plants and

(d) develop gene switches for controlling the expression of transgenes in plants, animals and human beings.