There has been a continuous demand for the development of insect control methods that are target-specific. Juvenile hormone (JH) and ecdysteroids (20-hydroxyecdysone, 20E is the most active form) are the major hormones that regulate development and reproduction in insects. Since these hormones are not present in vertebrates, they represent attractive targets for the development of insect control methods. Hindering this effort is the lack of understanding of the molecular basis of JH action. During the current grant period, seven proteins that are components of multi-protein complexes involved in JH signal transduction and its cross-talk with 20E were identified. Ligand binding studies performed using labeled JH showed that none of these proteins bind to JH with high affinity. While these proteins are likely involved in JH action and its cross-talk with 20E, none of them are JH receptors. Search for a better system to study JH action without interference from ecdysteroids discovered JH regulation of reproduction in Tribolium castaneum, an ideal system to study JH action without interference from ecdysteroids. In this insect, JH without the interference from ecdysteroids regulates vitellogenin gene expression in the fat body and vitellogenin uptake by the oocytes. These two systems provide a unique opportunity to study both genomic (fat body) and non-genomic (ovary) actions of JH in the same insect at the same time. Therefore, the renewal application proposes to study mechanism of JH action in regulation of vitellogenin gene expression in the fat body and vitellogenin uptake into the oocytes with a major goal of identifying receptors, transcription factors and protein modifiers critical for JH signal transduction. Completion of whole genome sequencing, availability of microarrays, functioning of systemic RNA interference (RNAi) and excellent response to JH and its analogs make T. castaneum an excellent model system for studies on JH action. In the first specific aim, microarray, RNAi, qRT-PCR, electrophoretic mobility shift assays and ligand-binding assays will be employed to identify and characterize receptors, transcription factors and protein modifiers involved in JH regulation of vitellogenin gene expression. In the second specific aim, a panel of in vivo, cell culture and in vitro assays will be used to determine whether any of the 51 G- protein-coupled receptors indentified in T. castaneum as those required for egg production and embryogenesis are activated by JH to regulate vitellogenin uptake into the oocytes. JH analogs are being used for mosquito control, but some mosquitoes are already developing resistance to these analogs. The results from these studies will aid in understanding the mode of action of JH analogs, thus facilitating their judicious use. The genes identified will be useful to develop screening assays to identify new insect disease vector control agents. The receptors identified can also be used in medicine by developing gene switches for various applications such as gene therapy, tissue engineering and therapeutic protein production.

Public Health Relevance

Insect juvenile hormone analogs are being used for mosquito control, but some mosquitoes are already developing resistance to these analogs. The results from these studies will aid in understanding the mode of action of JH analogs, thus facilitating their judicious use. The genes identified will be useful to develop screening assays to identify new insect disease vector control agents and for developing gene switches useful for various applications such as gene therapy, tissue engineering and therapeutic protein production.

Agency
National Institute of Health (NIH)
Institute
National Institute of General Medical Sciences (NIGMS)
Type
Research Project (R01)
Project #
5R01GM070559-08
Application #
8215724
Study Section
Vector Biology Study Section (VB)
Program Officer
Chin, Jean
Project Start
2005-02-01
Project End
2014-01-31
Budget Start
2012-02-01
Budget End
2013-01-31
Support Year
8
Fiscal Year
2012
Total Cost
$206,415
Indirect Cost
$57,915
Name
University of Kentucky
Department
Zoology
Type
Schools of Earth Sciences/Natur
DUNS #
939017877
City
Lexington
State
KY
Country
United States
Zip Code
40506
Shukla, Jayendra Nath; Palli, Subba Reddy (2014) Production of all female progeny: evidence for the presence of the male sex determination factor on the Y chromosome. J Exp Biol 217:1653-5
Xu, Jingjing; Sheng, Zhentao; Palli, Subba Reddy (2013) Juvenile hormone and insulin regulate trehalose homeostasis in the red flour beetle, Tribolium castaneum. PLoS Genet 9:e1003535
Shukla, Jayendra Nath; Palli, Subba Reddy (2013) Tribolium castaneum Transformer-2 regulates sex determination and development in both males and females. Insect Biochem Mol Biol 43:1125-32
Sheng, Zhentao; Xu, Jingjing; Bai, Hua et al. (2011) Juvenile hormone regulates vitellogenin gene expression through insulin-like peptide signaling pathway in the red flour beetle, Tribolium castaneum. J Biol Chem 286:41924-36
Parthasarathy, R; Palli, Subba R (2011) Molecular analysis of nutritional and hormonal regulation of female reproduction in the red flour beetle, Tribolium castaneum. Insect Biochem Mol Biol 41:294-305
Zhang, Zhaolin; Xu, Jingjing; Sheng, Zhentao et al. (2011) Steroid receptor co-activator is required for juvenile hormone signal transduction through a bHLH-PAS transcription factor, methoprene tolerant. J Biol Chem 286:8437-47
Bai, Hua; Zhu, Fang; Shah, Kapil et al. (2011) Large-scale RNAi screen of G protein-coupled receptors involved in larval growth, molting and metamorphosis in the red flour beetle. BMC Genomics 12:388
Parthasarathy, R; Sheng, Zhentao; Sun, Zhiyuan et al. (2010) Ecdysteroid regulation of ovarian growth and oocyte maturation in the red flour beetle, Tribolium castaneum. Insect Biochem Mol Biol 40:429-39
Parthasarathy, R; Sun, Zhiyuan; Bai, Hua et al. (2010) Juvenile hormone regulation of vitellogenin synthesis in the red flour beetle, Tribolium castaneum. Insect Biochem Mol Biol 40:405-14
Bai, Hua; Palli, Subba R (2010) Functional characterization of bursicon receptor and genome-wide analysis for identification of genes affected by bursicon receptor RNAi. Dev Biol 344:248-58

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