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Functional Genomics Studies on Nuclear Receptors: Target Sites for Insecticide Development and Resistance Management
Department of Entomology
A number of insect pests are developing resistance against insecticides. There is a need to discover new insecticides as well as to understand resistance development by insect pests. A combination of post-genomic technologies (RNA interference, polymerase chain reaction and microarray analysis) will be used to determine the function of Nuclear receptors in the red flour beetle, Tribolium castaneum. We will determine protein:protein interactions of these NRs in two-hybrid assay in beetle cell line and develop reporter assays that can be used to screen for agonists and antagonists of NRs. We will also determine the role of select NRs (TcHR96, TcHNF4 and TcRXR) in development of resistance against insecticides by performing RNAi and microarray analysis in T. castaneum strain that showed resistance against synthetic pyrethroids (Pyr-R) in comparison with the susceptible Lab-S strain.
2009 Project Description
Nineteen canonical and two Knirps-like family nuclear receptors (NRs) were identified in the genome of Tribolium castaneum. The current study was conducted to determine the function of these NRs in regulation of female reproduction and embryogenesis.
RNA interference (RNAi)-aided knock-down in expression of genes coding for all 21 NRs showed that seven NRs E75, HR3, EcR, USP, SVP, TcFTZ-F1 and HR4 are required for successful vitellogenesis and oogenesis. Knocking down the expression of genes coding for these seven NRs affected egg production by reducing the levels of vitellogenin mRNAs as well as by affecting the oocyte maturation. Expression of seven additional NRs HR96, HR51, HR38, HR39, Tailless (Tll), Dsf and Knirps-like is required for successful embryogenesis. The knock-down in expression of genes coding for three other NRs (E78, HNF4 and Eagle) partially blocked embryogenesis.
This study showed that at least 15 out of the 21 NRs identified in T. castaneum play key roles in female reproduction and embryogenesis.
Identified NRs can serve as good target sites for developing new and more potent environmentally-friendly insecticides. These NR target sites can also be used to discover chemicals that can be used to decrease or slow down resistance development against currently used insecticides.
Garry N.H., Hill R.J., DedosS.G., Swevers L., Iatrou K. Tan A., Parthasarathy R., Bai H., Zhang Z. and Palli S.R. (2008) Applications of RNA interference in ecdysone research. In: Ecdysone, structures and functions G. Smaghhe (ed). Springer Science, PP203-225.
R. Banerjee, Palli, S. R. and Nag, A. (2008) Pest management biotechnology. In: Text book of agriculture biotechnology. Eds. Nag, A. PHL Learning Private Ltd.