Freie Universität Berlin, Institut für Genetik Arnimallee 7, 14195 Berlin,
The larval ring gland of Diptera is composed of the prothoracic gland, the corpora allata and the corpora cardiaca. As a link between neuronal and hormonal system, the ring gland is essentially involved in various developmental processes. It is, for example, the site of production and release of the developmental hormones ecdysone and juvenile hormone. The synthesis and the function of these hormones in Drosophila are known, but there is a lack of information about the control of the ring gland itself.
Peptidergic neurons of the brain are supposed to play a significant role in regulating ring gland function. Antibodies against peptide hormones from Manduca sexta and Bombyx mori indicate the presence of allatotropic, allatostatic and prothoracicotropic hormones in the brain of Drosophila. Brain neurons producing these hormones are assumed to innervate the ring gland through the nervi corporis cardiaci.
The initial goal of our work is to plot a map of the neuronal connections between the larval brain and the ring gland. For this purpose we performed an enhancer trap screen using the GAL4 system with tau-lacZ as reporter gene. Axons labeled by the tau-lacZ fusion-protein can be visualized histochemically.
More than 500 new enhancer trap lines were generated and screened for axonal stainig in the nervi corpora cardiaca. 14 lines were selected for further analysis, because they show reporter gene expression in identifiable neurons or groups of neurons projecting to the ring gland. Nine other lines show specific expression in parts of the ring gland.
Green fluorescent protein and antibody staining of reporter gene products, transmitters and peptide hormones are used to further charakterize the cells defined by the selected enhancer trap lines.