Ga14 in the Drosophila female germline

The modular Ga14 system has proven to be an extremely useful tool for condi tional gene expression in Drosophila. One limitation has been the inability of the system to work in the female germline. A modified Ga14 system that works throughout oogenesis is presented here. To achieve germline expressio n, it was critical to change the basal promoter and 3'-UTR in the Ga14-resp onsive expression vector (generating UASp). Basal promoters and heterologou s 3'-UTRs are often considered neutral, but as shown here, can endow qualit ative tissue-specificity to a chimeric transcript. The modified Ga14 system was used to investigate the role of the Drosophila FGF homologue branchles s, ligand for the FGF receptor breathless, in border cell migration. FGF si gnaling guides tracheal cell migration in the embryo. However, misexpressio n of branchless in the ovary had no effect on border cell migration. Thus b order cells and tracheal cells appear to be guided differently. (C) 1998 El sevier Science Ireland Ltd. All rights reserved.