Endogenous β-Galactosidase Activity in the Larval, Pupal, and Adult Stages of the Fruit Fly, Drosophila melanogaster, Indicates Need for Caution in lacZ Fusion-Gene Studies

摘要

β-galactosidase activity is known to exist in Drosophila melanogaster, but a detailed analysis of the tissue-specific patterns of activity has not previously been reported. Such an analysis is of particular interest because Drosophila is commonly used for making transformants that carry fusion genes in which the E. coli β-galactosidase gene, lacZ, is used as a reporter gene. When these transformants are analyzed for β-galactosidase activity by using chromogen X-gal staining, the method does not distinguish true fusion-gene activity from endogenous β-galac-tosidase activity or from the β-galactosidase activity of bacterial contaminants. Therefore, detailed maps of endogenous β-galactosidase activity in this organism would help to prevent errors in data interpretation and would indicate which stages were most appropriate for experiments with the lacZ transformants. We have constructed such maps by applying X-gal staining methods to serial frozen sections and whole mounts of larval, prepupal, pupal, and adult stages of D. melanogaster reared under axe-nic conditions. Results showed endogenous β-galactosidase activity in a variety of organs including the larval intestine, spiracles, lymph glands, cellular epidermis, and eye-antenna imaginal discs; the pupal cellular epidermis, lymph glands, imaginal tissues, fat body, and spiracle; and the adult pericardial cells, thoracic nephrocytes, ven-triculus, and reproductive system. The good correlation between staining and metamorphic remodeling and phagocytic activity indicates that endogenous β-galactosidase is physiologically interesting.