Ecdysteroids

Michael E. Adams

University of California, Riverside

The ecdysteroids are steroid hormones that, in combination with juvenile hormones, program gene expression appropriate for each stage of insect development. Beginning at embryogenesis, ecdysteroid levels rise transiently during each stage to initiate molting. Depending on the level of juvenile hormone, elevated ecdysteroids mobilize nuclear receptors of several types that bind directly to DNA to either promote or suppress gene expression. During the adult stage of some insects, ecdysteroids play important roles in reproduction, principally in the development of gametes.

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