BERN.1 Thursday, Jan. 5 How Does Juvenile Hormone Regulate Insect Metamorphosis and Reproduction? RIDDIFORD, Lynn M.; Janelia Farm Research Campus, HHMI email@example.com
Juvenile hormone (JH) both prevents the switching actions of ecdysone that are necessary for metamorphosis and regulates reproductive maturation in the adult. In holometabolous insect larvae, JH prevents the appearance of the ecdysone-induced, pupal-specific transcription factor Broad during the molts. As growth is completed, JH declines and a small surge of ecdysone initiates metamorphosis and the appearance of Broad. During the prepupal period JH again appears to prevent premature adult development of imaginal discs and the optic lobe of the brain in response to the prepupal peak of ecdysone. Allatectomy (CAX; removal of the corpora allata that produces JH) or loss of the JH receptor Methoprene-tolerant (Met) (a basic helix-loop-helix, Pas domain protein) causes precocious metamorphosis in most insects. In Drosophila allatectomy causes death at the time of pupation which is mimicked only by the loss of both Met and a closely related protein Germ cells expressed (Gce). Loss of only Met mimics some of the CAX phenotype, namely precocious adult maturation of the optic lobe. Expression of Met RNAi in various neurons showed that JH acts on the photoreceptors to prevent premature differentiation caused by ecdysone. In Drosophila adult females JH regulates the timing of the onset of mating receptivity as well as egg maturation. Genetic allatectomy during adult development caused a delay in the onset of receptivity that was prevented by application of JH at eclosion. The loss of Met causes a similar delay. Expression of Met RNAi in brain neurons known to be involved in female receptivity delayed the onset of receptivity, suggesting that JH acts via Met to promote the maturation of these neurons. Thus, in the regulation of both metamorphosis and reproduction, JH acts primarily via Met.