Hormonal control of insect epidermal cell commitment in vitro.

Abstract

DEPENDING on the hormonal milieu, the insect epidermal cell can express one of several differentiated states manifest by the type of cuticle it secretes. In the Lepidoptera, as long as the juvenile hormone (JH) titre is high, the epidermis secretes larval cuticle periodically in response to ecdysone. When the JH litre declines at the end of larval life1, ecdysone causes the secretion of pupal cuticle. In the tobacco hornworm, Manduca sexta, two distinct releases of ecdysone are necessary for this metamorphosis2,3. The first triggers the cessation of feeding and causes the epidermal cells to switch from a commitment to make larval cuticle to one for pupal cuticle4. After this time JH can no longer prevent pupal differentiation. The second ecdysone release begins 2 d later and causes pupal cuticle synthesis. Consequently, during the time of the first release it is possible to study the events which occur to alter the cellular commitment unhindered by those events involved in the expression of this commitment. I report the hormonal manipulation of this cellular commitment in an in vitro system.