Ecdysone-initiated developmental changes in wing epidermis RNA polymerase activity during the adult development of the oak silkmoth, Antheraea pernyi

Abstract

RNA polymerase activity of Antheraea pernyi wings has been measured during pupal-adult development and correlated with the circulating ecdysone (molting hormone) titer. The hormone concentration, which was determined by radioimmunoassay and gas chromatography, persisted at a low level in pupae placed at low temperature. 2 days after transfer of the animals to room temperature and photoperiodic conditions conducive to adult development, the ecdysone titer increased rapidly, and decreased gradually thereafter to the end of adult development. Upon transfer to environmental conditions where adult development occurs, both RNA polymerase I and II activity increased. A second phase of enzyme stimulation coincided with the rise in ecdysone titer; however, the two classes of enzyme activity did not develop synchronously. Removal of the pupal brain prevented both the increase in ecdysone titer and the concomitant rise in polymerase activity, but did not interfere with the initial enhancement of enzyme activity after the pupae were transferred to room temperature. These and other observations suggest that resumption of normal metabolic activity at room temperature is mediated by a low ecdysone titer but that adult development is elicited by a greatly elevated hormone titer.