Microfluorometer assay to measure the expression of beta-galactosidase andgreen fluorescent protein reporter genes in single Drosophila flies

beta -galactosidase and green fluorescent protein (GFP) are among the most commonly used reporter genes to monitor gene expression in various organism s including Drosophila melanogaster. Their expression is usually detected i n a qualitative way by direct microscopic observations of cells, tissues, o r whale animals. To measure in vivo the inducibility of two antimicrobial p eptide genes expressed during the Drosophila innate immune response, we hav e adapted two reporter gene systems based on the beta -galactosidase enzyma tic activity and GFP. We have designed a 96-well microplate fluorometric as say sensitive enough to quantify the expression of both reporter genes in s ingle flies. The assay has enabled us to process efficiently and rapidly a large number of individual mutant flies generated during an ethylmethane su lfonate saturation mutagenesis of the Drosophila genome. This method may be used in any screen that requires the quantification of reporter gene activ ity in individual insects.