1 Bela Keshan

Insect molting and metamorphosis are regulated by two major insect hormones, the juvenile hormone (JH) and ecdysteroids. Ecdysteroids initiate the molting process, whereas JH dictates the character of a molt. At the critical period of ecdysteroid rise, the presence or absence of JH directs larval-larval molting or metamorphosis. Ecdysteroid after binding with its receptor activates the expression of many downstream genes such as E75 and broad, also known as transcription factors. JH modulates the ecdysteroid action by altering the expression of these downstream genes. E75A has been found to play a crucial role in maintaining the “status-quo” function of JH during larval development, whereas E75C seems to be primarily involved in pupal-adult transition. The broad gene has been found to be a pupal specifying gene and thus plays a key role in pupal developmental program. The modulation of expression of these ecdysteroid induced transcription factors by JH indicates that JH plays a critical role in directing ecdysteroid signaling, although the modulation effect depends on the developmental status of the insect.