Institut de Zoologie, Université de Fribourg, 1700 Fribourg, Switzerland,
Using the enhancer trap technique we isolated a P[Gal4] insertion line (GH 298) which shows a specific expression pattern in local interneurons (LocI) of the adult antennal lobe of Drosophila melanogaster. LacZ expression is first seen in third instar larva. A few presumptive interneurons in the ventral ganglion and cell bodies associated with the terminal and/or dorsal organs are labeled. From 24 hours after puparium formation on, cells belonging to the suboesophageal ganglion are stained. However, no larval or pupal expression in antennal LocI has been seen both by tau and lacZ reporter gene expression. From ablation studies, using hydroxyurea, we know that LocI are already formed in the larval antennal lobe earlier than 72 hours after larval hatching. Activity of the enhancer in LocI may thus be confined to the adult stage. The insertion is localized in 99F on the right arm of the third chromosome. By plasmid rescue we obtained a 12 kb genomic fragment adjacent to the insertion site of the P element. Screening of an adult head cDNA library with the genomic DNA led to the isolation of 15 related clones. Partial sequences obtained from two representative cDNAs do not overlap with any known gene and have not yet shown a significant homology. We will present further data on the molecular organization of the gene.