Insect renal tubules constitute a cell-autonomous immune system that protects the organism against bacterial infection.
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.
McGettigan
J
J
Division of Molecular Genetics, Institute of Biomedical and Life Sciences, University of Glasgow, Glasgow G12 8QQ, UK.
McLennan
R K J
RK
Broderick
K E
KE
Kean
L
L
Allan
A K
AK
Cabrero
P
P
Regulski
M R
MR
Pollock
V P
VP
Gould
G W
GW
Davies
S-A
SA
Dow
J A T
JA
D000818:Animals; D029721:Drosophila Proteins; D004331:Drosophila melanogaster / Q000276:immunology*; D004926:Escherichia coli / Q000276:immunology; D015870:Gene Expression / Q000276:immunology; D019476:Insect Proteins / Q000378:metabolism; D008070:Lipopolysaccharides; D008317:Malpighian Tubules / Q000276:immunology*; D009252:NADPH Dehydrogenase / Q000378:metabolism; D009569:Nitric Oxide / Q000502:physiology; D019001:Nitric Oxide Synthase / Q000378:metabolism; D015398:Signal Transduction; D013997:Time Factors
C054756:DptA protein, Drosophila; D029721:Drosophila Proteins; D019476:Insect Proteins; D008070:Lipopolysaccharides; D009569:Nitric Oxide; D019001:Nitric Oxide Synthase; D009252:NADPH Dehydrogenase