Understanding insect endocrine systems: molecular approaches

Molecular approaches have led to spectacular improvement of our knowledge o f insect endocrinology. The present review focuses on two major classes of insect lipidic hormones, ecdysteroids and juvenile hormones. Although the e cdysteroid biosynthetic pathway is not yet fully elucidated, several new st eps have been recently characterized, and molecular studies of biosynthetic enzymes are now beginning. It is expected that, thanks to suitable biologi cal models (e.g., ecdysteroid-defective mutants of Drosophila), the entire biosynthetic pathway will be elucidated in the near future. The understandi ng of the ecdysteroid mode of action has benefited from studies with Drosop hila and major developments relate to the cascades of gene activation and t he molecular basis for the stage- and tissue-specificity of hormonal effect s. The biosynthetic pathway of juvenile hormones is fully known, but molecu lar studies of enzymes are still in their infancy, and there is some contro versy about the nature of juvenile hormone receptors. Within the forthcomin g years, molecular tools will allow to characterize all the enzymes involve d in hormone biosynthesis and then to analyze the fine regulation of hormon e titers. They will also allow comparative studies aimed at investigating t he presence of related molecules (hormone biosynthetic enzymes and receptor s) among other Invertebrates (Arthropods and non-Arthropods), and thus to p ropose evolutionary scenarios for their endocrine systems.