specific neurons modulates survival to starvation/desiccation stress [26], so neuropeptides implicated in fluid homeostasis have been identified. We show here that capaR is a canonical GPCR, expressed specifically in the key homeostatic tissue in the fly. This single GPCR directly modulates fluid homeostasis in the whole animal via its ligands, Drm-capa- 1 and -2, and we identify mammalian NMU as a putative functional homolog of these capa peptides. Supporting Information Figure S1 Validation of capaR RNA interference knock- down. (A) Q-PCR analysis confirmed a 65% decrease in capaR mRNA levels in the whole fly compared to control flies. Data are expressed as 1025 ng of capaR mRNA 6 SEM, N = 3. (TIFF) Figure S2 Tubule mRNA expression of GRK-1 and GRK- 2 under capa-1 stimulation. Wild-type (Canton-S) tubules were excised, incubated in Schneider’s medium for 3 h as controls, or treated with 1027 M (final concentration) of capa-1 in Schneider’s for 3 h. Samples were prepared for Q-PCR to assess GRK-1 or GRK-2 expression levels in control and capa-1-treated tubules (shaded bars). Data were normalized against the rp49 standard, and expressed as ng GRK-1 or GRK-2 mRNA 6 SEM, N = 3. (TIFF) References 1. Dow JAT (2011) eLS. 2. Gilleard JS, Woods DJ, Dow JA (2005) Model-organism genomics in veterinary parasite drug-discovery. Trends Parasitol 21: 302–305. 3. Kean L, Cazenave W, Costes L, Broderick KE, Graham S, et al. (2002) Two nitridergic peptides are encoded by the gene capability in Drosophila melanogaster. Am J Physiol Regul Integr Comp Physiol 282: R1297–1307. 4. Beyenbach KW, Skaer H, Dow JA (2010) The developmental, molecular, and transport biology of Malpighian tubules. Annu Rev Entomol 55: 351–374. 5. Terhzaz S, Cabrero P, Chintapalli VR, Davies SA, Dow JA (2009) Mislocalization of mitochondria and compromised renal function and oxidative stress resistance in Drosophila SesB mutants. Physiol Genomics. 6. 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Ramsay D, Kellett E, McVey M, Rees S, Milligan G (2002) Homo- and hetero- oligomeric interactions between G-protein-coupled receptors in living cells PLoS ONE | www.plosone.org 12 January 2012 | Volume 7 | Issue 1 | e29897