Innervation of the ring gland ofDrosophila melanogaster

Abstract

In insects, peptidergic neurons of the central nervous system regulate the synthesis of the main developmental hormones. Neuropeptides involved in this neuroendocrine cascade have been identified in lepidopterans and dictyopterans. Since these organisms are not suitable for genetic research, we identified peptidergic brain neurons innervating the ring gland in Drosophila melanogaster. In larvae of Drosophila, ecdysteroids and juvenile hormones are produced by the ring gland, which is composed of the prothoracic gland, the corpus allatum, and the corpora cardiaca. Using the GAL4 enhancer trap system, we mapped those neurons of the central nervous system that innervate the ring gland. Eleven groups of neurosecretory neurons and their target tissues were identified. Five neurons of the lateral protocerebrum directly innervate the prothoracic gland or corpus allatum cells of the ring gland and are believed to regulate ecdysteroid and juvenile hormone titers. Axons of the circadian pacemaker neurons project onto dendritic fields of these five neurons. This connection might be the neuronal substrate of the circadian rhythms of molting and metamorphosis in Drosophila. Most of the neurons presented here have not been described before. The enhancer trap lines labeling them will be valuable tools for the analysis of neuronal as well as genetic regulation in insect development.

Development of an optimized synthetic Notch receptor as an in vivo cell–cell contact sensor

“…Slit-Gal4 also leads to strong ligand expression in the fly prothoracic gland and activated synNQ in the corpus allatum. Importantly, consistent with previous results (36), neurons that send axons into the ring gland can be clearly visualized after a longer exposure (Fig. 4G).…”

Regulation of insect steroid hormone biosynthesis by innervating peptidergic neurons

“…Although the importance of PG innervation has been well documented (13)(14)(15)(16)(17)(18), to our knowledge, this study is the first report on the molecular basis for neural regulation of ecdysteroidogenesis.…”

“…We show that BRFa peptides are produced in the CNS neurons that suppress PG activity by direct innervation. Although the importance of the PG-innervating neurons in the control of ecdysteroidogenesis has been well documented (13)(14)(15)(16)(17)(18), studies revealing molecular basis of the PG regulation have been restricted to hormonal substances throughout the last century (1). To our knowledge, this study is the first report of peptides controlling ecdysteroidogenesis by direct innervation, which may shed light on the regulatory mechanisms of insect development.…”

The neuroendocrine system of invertebrates: a developmental and evolutionary perspective

“…The majority of NSCs are found in the dorso-medial protocerebrum, the so-called pars intercerebralis (PI) and pars lateralis (PL; Pipa 1978, Raabe 1989, Schooneveld 1998, Veelaert et al 1998, Siegmund & Korge 2001. These NSCs project their axons toward a set of endocrine glands, the corpora cardiaca (CC) and corpora allata (CA; Fig.…”