Drosophila melanogaster Acetyl-CoA-Carboxylase Sustains a Fatty Acid–Dependent Remote Signal to Waterproof the Respiratory System

Abstract

Fatty acid (FA) metabolism plays a central role in body homeostasis and related diseases. Thus, FA metabolic enzymes are attractive targets for drug therapy. Mouse studies on Acetyl-coenzymeA-carboxylase (ACC), the rate-limiting enzyme for FA synthesis, have highlighted its homeostatic role in liver and adipose tissue. We took advantage of the powerful genetics of Drosophila melanogaster to investigate the role of the unique Drosophila ACC homologue in the fat body and the oenocytes. The fat body accomplishes hepatic and storage functions, whereas the oenocytes are proposed to produce the cuticular lipids and to contribute to the hepatic function. RNA–interfering disruption of ACC in the fat body does not affect viability but does result in a dramatic reduction in triglyceride storage and a concurrent increase in glycogen accumulation. These metabolic perturbations further highlight the role of triglyceride and glycogen storage in controlling circulatory sugar levels, thereby validating Drosophila as a relevant model to explore the tissue-specific function of FA metabolic enzymes. In contrast, ACC disruption in the oenocytes through RNA–interference or tissue-targeted mutation induces lethality, as does oenocyte ablation. Surprisingly, this lethality is associated with a failure in the watertightness of the spiracles—the organs controlling the entry of air into the trachea. At the cellular level, we have observed that, in defective spiracles, lipids fail to transfer from the spiracular gland to the point of air entry. This phenotype is caused by disrupted synthesis of a putative very-long-chain-FA (VLCFA) within the oenocytes, which ultimately results in a lethal anoxic issue. Preventing liquid entry into respiratory systems is a universal issue for air-breathing animals. Here, we have shown that, in Drosophila, this process is controlled by a putative VLCFA produced within the oenocytes.

Flexible origin of hydrocarbon/pheromone precursors in Drosophila melanogaster

“…The interfering-RNA (RNAi) fl y lines provided from Fly Stocks of the National Institute of Genetics (NIG-FLY) or the Vienna Drosophila Resource Center (VDRC) ( 22 ) ( 23 ). Lipophorin receptor (LpR)1/2 defi ciency was generated as previously described ( 23 ) using the PBac[PB]c02106 and P[XP]d10508 elements ( 24 ).…”

“…Lipid (Nile Red) and nuclear (TO-PRO-3-iodide) staining was performed as previously described ( 23 ). Cuticles were mounted in DABCO and examined using a Nikon (TE-2000-U) confocal microscope.…”

Forward and feedback regulation of cyclic steroid production in Drosophila melanogaster

“…For immunostaining, ten to 20 ring glands were examined at each time point. FRT-mediated mitotic recombination and flip-out clones were generated as previously described (Parvy et al, 2005(Parvy et al, , 2012. Larvae raised at 25°C were heat shocked for 1 h at 37°C at early L1 stage or L2/L3 transition.…”

“…Reverse transcription and quantitative PCR were performed as previously described (Parvy et al, 2012) using two independent groups of 20 larvae for each time point.…”

The closed spiracle phase of discontinuous gas exchange predicts diving duration in the grasshopper, Paracinema tricolor

“…hairs). Indeed, spiracle water-tightness is critical to the survival of submersion in Drosophila larvae (Parvy et al, 2012), despite their low metabolic requirements and small size, which theoretically should enable sufficient diffusion of respiratory gases from their respiratory system.…”