2012 SURF: Genetic Regulation of Responses to Hormones

Genetic Regulation of Diverse Responses to Steroid Hormones 

Mentor: Dr. Dave Champlin, Biology Department

All animals have a species-specific size range.  In insects, the lower limit is controlled by the “minimum viable weight” (MVW). Prior to reaching MVW, the larval endocrine system lacks the capability to undergo metamorphosis. Recently, the Champlin Lab at USM has demonstrated that MVW is the result of a dramatic transition in the hormonal control of growth. In the tobacco hornworm, Manduca sexta, metamorphosis is initiated 20 hours into the final larval feeding period. A critical element of this status can be transferred between larvae by transplantation of the prothoracic gland (PG). The primary function of the PG is the synthesis of the steroid hormone, ecdysteroid.

Steroid hormones function by entering target cells and regulating gene expression. Ecdysteroid is a steroid hormone that regulates molting and metamorphosis and it is synthesized by the PG. Our research project examined whether ecdysteroid hormone affected the PG through a feedback loop. We used Polymerase chain reaction (PCR) to analyze the expression of several genes in the PG whose expression in other tissues is sensitive to ecdysteroid.

Insect metamorphosis is an important model for understanding nutrient-dependent hormonal regulation of animal growth. In addition, hormones that regulate insect metamorphosis are the targets of several important insecticides. Consequently, studies with Manduca sexta have relevance not only for human dietary health but also controlling agricultural pests and insect-borne diseases.

Start Slideshow

Response to Hormones 1: Manduca sexta Tobacco hornworm caterpillars are fast-growing larvae. View Full-Size	Response to Hormones 2: Dissection Prothoracic glands were removed from hornworms under dissecting microscope. View Full-Size
Response to Hormones 3: PCR PCR was performed using a thermal cycler and heat to amplify DNA. View Full-Size	Response to Hormones 4: Electrophoresis PCR results were analyzed by agarose gel electrophoresis and electrical current. View Full-Size
Response to Hormones 5: Broad Gene Quantitative PCR was used to analyze onset of Br (Broad) gene expression. View Full-Size	Response to Hormones 6: Results DNA Primer Gel results were recorded and reported. View Full-Size