DIF, A DORSAL-RELATED GENE THAT MEDIATES AN IMMUNE-RESPONSE IN DROSOPHILA

There are striking parallels between the regulation of gene expression along the dorsoventral (DV) axis of Drosophila embryos and lymphoid-r estricted expression in the mammalian immune system. Both depend on re gulatory factors containing rel domains (dorsal and NF-kappaB) that ar e controlled at the level of nuclear transport. A novel Rel-containing gene in Drosophila, Dif (dorsal-related immunity factor), provides a potential link between these seemingly disparate processes. Although D if maps close to dorsal, it does not appear to participate in DV patte rning, but instead mediates an immune response in Drosophila larvae. D if is normally localized in the cytoplasm of the larval fat body, but quickly accumulates in the nucleus upon bacterial infection or injury. Evidence is presented that once in the nucleus, Dif binds to kappaB-l ike sequence motifs present in promoter regions of immunity genes. The se results suggest that mammalian and insect immunity share a common e volutionary origin.