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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.
2010 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 the expression of genes coding for 21 NRs showed that seven NRs E75, hormone receptor 3 (HR3),ecdysone receptor (EcR), ultraspiracle (USP), seven-up (SVP), FTZ transcription factor 1 (FTZ-F1) and hormone receptor 4 (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 hormone receptor 96 (HR96), hormone receptor 51 (HR51), hormone receptor 38 (HR38), hormone receptor 39 (HR39), Tailless (Tll), Dissatisfaction (Dsf) and Knirps-like is required for successful embryogenesis. The knock-down in the expression of genes coding for three other NRs (E78, hepatocyte nuclear factor 4, HNF4 and Eagle) partially blocked embryogenesis.
This study showed that at least 17 out of the 21 NRs identified in T. castaneum play key roles in female reproduction and embryogenesis.
Several nuclear receptors are identified as those required for reproduction and embryo genesis. These receptors could be used as target sites to develop new insecticides.
Xu J, Tan A, Palli S.R. (2010) The function of nuclear receptors in regulation of female reproduction and embryogenesis in the red flour beetle, Tribolium castaneum. J Insect Physiol. 56:1471-80.
Zhu,F., Parthasarathy,R., Bai, H., Woithe, K., Kaussmann,M., Nauen,R., Harrison,D.A. and Palli, S.R. (2010) A brain-specific cytochrome P450 responsible for the majority of deltamethrin resistance in the QTC279 strain of Tribolium castaneum. Proc Natl Acad Sci U S A 107:8557-62.