Prothoracicotropic Hormone: A Role in the Adult Insect (2008)

Undergraduate: Chelsea Snyder

Faculty Advisor: Lawrence Gilbert
Department: Biology

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With over a million known species, insects employ a variety of successful developmental and survival strategies. One of these strategies, insect metamorphosis, is controlled by a unique endocrine system. Manduca sexta, the tobacco hornworm, has provided much insight on the functioning of this novel system. In this insect, prothoracicotropic hormone (PTTH), a brain hormone, stimulates the prothoracic glands to secrete ecdysone. Ecdysone, also known as the “molting hormone”, controls insect metamorphosis through a series of molts until maturity. In the mid to late-pupal stage, the prothoracic glands undergo programmed cell death because ecdysone is not needed for molting in adulthood. However, a pilot study suggested that PTTH is found in the brains of adult and near-adult Manduca sexta. The question then is: does PTTH have a new, undefined role in the adult insect, or is it merely left over from earlier stages? In vitro experiments exploring this question have shown that PTTH present during adult life is functional in stimulating larval prothoracic glands to secrete ecdysone, and does so in the same manner as earlier forms of PTTH. Experiments also reveal that PTTH may have a role in insect reproduction by changing protein activity and protein synthesis.