Functional complementation of the malvolio mutation in the taste pathway of Drosophila melanogaster by the human natural resistance-associated macrophage protein I (Nramp-1)

The malvolio (mvl) gene of Drosophila melanogaster encodes a protein with a high degree of homology to natural resistance-associated macrophage protei ns (Nramps). This family of integral membrane proteins, many of which appea r to function as cation transporters, is remarkably conserved in several ph ylogenetically distinct species. In Drosophila melanogaster, the protein Mv l is expressed in macrophages and in differentiated neurons; loss-of-functi on mutations lead to defects in gustatory behaviour. The human Nramp-1 prot ein was expressed in Drosophila melanogaster using the hsp70 promoter. Over expression in normal animals does not lead to any alterations in their beha viour or physiology. In mutants, however, ubiquitous expression of human Nr amp-1 can totally rescue the taste defect. This finding that Nramp-1 can co mplement the taste defect in mvl mutants provides a potent means of exploit ing behavioural genetics to dissect the function of Nramp-1 and to identify other molecules involved with this transport system.