McGettigan, J., McLennan, R.K., Broderick, K.E., Kean, L., Allan, A.K., Cabrero, P., Regulski, M.R., Pollock, V.P., Gould, G.W., Davies, S.A., Dow, J.A. (2005). Insect renal tubules constitute a cell-autonomous immune system that protects the organism against bacterial infection.  Insect Biochem. Mol. Biol. 35(7): 741--754.

FBrf0187746

Research paper

Innate immunity is a widespread and important defence against microbial attack, which in insects is thought to originate mainly in the fat body. Here we demonstrate that the fluid-transporting Malpighian (renal) tubule of Drosophila melanogaster constitutes an autonomous immune-sensing tissue utilising the nitric oxide (NO) signalling pathway. Reverse transcriptase PCR (RT-PCR) shows that tubules express those genes encoding components of the Imd pathway. Furthermore, isolated tubules bind and respond to lipopolysaccharide (LPS), by upregulating anti-microbial peptide (diptericin) gene expression and increased bacterial killing. Excised, LPS-challenged tubules, as well as tubules from LPS-infected flies, display increased NO synthase (NOS) activity upon immune challenge. Targetted expression of a Drosophila NOS (dNOS) transgene to only principal cells of the tubule main segment using the GAL4/UAS system increases diptericin expression. In live flies, such targetted over-expression of dNOS to tubule principal cells confers increased survival of the whole animal upon E. coli challenge. Thus, we describe a novel role of Malpighian tubules in immune sensing and insect survival.