IP Endocrinology

Control of juvenile hormone synthesis by the corpus allatum

N.A. Granger 1 , R. Rybczynski 2 & L.I. Gilbert 2

1 Dept. of Cell Biology and Anatomy, CB #7090; 2 Dept. of Biology, CB #3280, Univ. of North Carolina, Chapel Hill, NC 27599, USA

Changes in the hemolymph titer of juvenile hormone (JH), which regulates growth, development, and reproduction in insects, are precisely controlled by various physiological and biochemical processes. Of these, regulation of synthesis is generally considered the most important, and both neuropeptides, termed allatotropins (stimulatory) and allatostatins (inhibitory), and neurotransmitters have been demonstrated to modulate JH synthesis by the corpora allata (CA). The one allatotropin that has been isolated and sequenced (from Manduca sexta: Mas-AT) appears to be a functional moiety in other Lepidoptera as well. Mas-AT can either directly affect the CA in these other species or oppose the action of the Manduca sexta allatostatin (Mas-AS), although it has no effect on Manduca larval CA. The apparently ubiquitous nature of Mas-AT is thus similar to that of the allatostatin of Diploptera punctata (Dip-AS), 13 different forms of which exist in this species, each with a similar C-terminus (Y/F-X-F-G-L/I-NH2). More than 30 different peptides belonging to this allatostatin family have been identified in a number of different insect species, as well as in Crustacea. Mas-AS bears no homology to the YXFGLamide family of allatostatins but inhibits JH biosynthesis reversibly in Manduca and other Lepidoptera. Mas-AT has functions other than the stimulation of JH production, much as the YXFGLamide allatostatins have been found to have other physiological roles. Similarly, neurotransmitters have been shown to affect JH synthesis in both Manduca and Diploptera (dopamine and octopamine, respectively), mimicking effects of the neuropeptides. In Diploptera, octopamine inhibits JH biosynthesis, while in Manduca larvae, dopamine either stimulates or inhibits, depending on the developmental stage. The interactions between and among allatostatins, allatotropins, and neurotransmitters are fertile but unexplored territory, and should lead to studies of the control of their titers, their receptors, and downstream events controlled via the ligand-receptor interactions; studies of degradative mechanisms and receptors for the YXFGLamide allatostatins have already begun. The stage is also set for the investigation of the possible control of JH biosynthesis by ecdysteroids at the genomic level. Both ecdysteroid receptor protein (EcR) and ultraspiracle protein (USP), which together form the heterodimeric ecdysteroid receptor, are expressed in the CA of Manduca, and there is preliminary evidence that 20-hydroxyecdysone affects the expression of dopamine receptors in Manduca larval CA.

Index terms: allatotropins, allatostatins, neurotransmitters, ecdysteroid receptor

Copyright: The copyrights of this original work belong to the authors (see right-most box in title table). This abstract appeared in Session 18 – REPRODUCTION AND DEVELOPMENT Symposium and Poster Session, ABSTRACT BOOK II – XXI-International Congress of Entomology, Brazil, August 20-26, 2000.