Drosophila as a model system for antibacterial peptides.

As a defence against bacteria, infected insects synthesize cecropins and a large number of other bactericidal proteins and peptides. To understand this response and its possible relationship with similar systems in mammals, we need to characterize the induced components and how they act, as well as how this antibacterial response is initiated. To study the molecular basis for this response we cloned the genes for cecropins and other bactericidal peptides from Drosophila, 14 genes in total. The cecropin genes were selected as convenient markers for the immune response because they are strongly induced by different microbial substances. In contrast the lysozyme gene family is constitutively expressed in the digestive tract. We have developed an inducible blood cell line from Drosophila for studying the immune response in vitro. Using this system we are now investigating the function of membrane proteins and signal pathways in the transcriptional activation of immune genes in Drosophila.