Chapter Four - The Juvenile Hormone Receptor and Molecular Mechanisms of Juvenile Hormone Action

Abstract

Juvenile hormone (JH) is a critical regulator of insect development and physiology, widely known for its ability to delay metamorphosis. The mechanisms underlying the action of JH have been poorly understood, partly as a result of difficulties identifying the JH receptor. However, the last few years have seen a rapid expansion of knowledge surrounding JH signalling. Ultraspiracle (USP), a nuclear receptor that was once considered as a possible receptor to JH, instead appears to function as a receptor to the JH precursor methyl farnesoate. The bHLH–PAS protein Methoprene-tolerant (Met) has now emerged as the principal receptor for JH, involved in regulating multiple JH-dependent pathways including the antimetamorphic function of JH. Structural analyses are beginning to elucidate the mechanistic basis of JH reception by Met. Simultaneously, studies of JH target genes are providing an explanation as to how JH to carries out diverse regulatory functions and crosstalk with other signalling pathways, with Met operating through direct gene activation and the use of multiple interacting partners. In this chapter, we provide an overview of efforts to characterize JH signalling through the identification and characterization of the JH receptor and describe the significant advances that have been achieved in recent years.