LAUSR

Since it was first postulated by Wigglesworth in 1934, juvenile hormone (JH) is considered a status quo hormone in insects because it prevents metamorphosis that is initiated by the molting hormone 20‐hydroxyecdysone (20E). During the last decade, significant advances have been made regarding JH signaling. First, the bHLH‐PAS transcription factor Met/Gce was identified as the JH intracellular receptor. In the presence of JH, with the assistance of Hsp83, and through physical association with a bHLH‐PAS transcriptional co‐activator, Met/Gce enters the nucleus and binds to E‐box‐like motifs in promoter regions of JH primary‐response genes for inducing gene expression. Second, the zinc finger transcription factor Kr‐h1 was identified as the anti‐metamorphic factor which transduces JH signaling. Via Kr‐h1 binding sites, Kr‐h1 represses expression of 20E primary‐response genes (i.e. Br, E93 and E75) to prevent 20E‐induced metamorphosis. Third, through the intracellular signaling, JH promotes different aspects of female reproduction. Nevertheless, this action varies greatly from species to species. Last, a hypothetical JH membrane receptor has been predicted to be either a GPCR or a tyrosine kinase receptor. In future, it will be a great challenge to understand how the JH intracellular receptor Met/Gce and the yet unidentified JH membrane receptor coordinate to regulate metamorphosis and reproduction in insects.