Research Accomplishment Reports 2010

Molecular Analysis of Juvenile Hormone Action in the Red Flour Beetle, Tribolium cataneum

S.R. Palli
Department of Entomology

 

Non-Technical Summary

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. We propose to study mechanism of JH action in regulation of vitellogenin gene expression in the fat body.

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. 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 JH analogs are being used for pest management, but some pests 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 agriculture by developing gene switches for various applications such as regulated expression of transgenes in crop plants.

2010 Project Description

Studies on hormonal regulation of reproduction in beetles showed that juvenile hormone (JH) and ecdysteroids play key roles in the regulation of female reproduction in the red flour beetle, Tribolium castaneum. JH regulates vitellogenin (Vg) synthesis in the fat body and ecdysteroids regulate oocyte maturation in the beetle ovaries. These two hormones cross-talk to control egg production when plenty of food is available. Under starved conditions, reproduction processes are shut down and all the resources are diverted towards survival mechanisms.

2010 Impact

These studies lay a solid foundation for future studies on molecular mechanisms on hormonal regulation of reproduction in beetles. These studies also contribute towards development of insecticides that target insect reproductive processes.

2010 Publications

Parthasarathy R, Sheng Z, Sun Z, Palli S.R (2010) Ecdysteroid regulation of ovarian growth and oocyte maturation in the red flour beetle, Tribolium castaneum Insect Biochem. Mol. Biol. 40:429-439.

Parthasarathy, R., Sun, Z., Bai, H., Palli, S.R., (2010). Juvenile hormone regulation of vitellogenin synthesis in the red flour beetle, Tribolium castaneum. Insect Biochem. Mol. Biol. 40:405-14.