Sterols as dietary markers forDrosophila melanogaster

Abstract

26During cold acclimation fruit flies switch their feeding from yeast to plant food, however there 27 are no robust markers to monitor it in the wild. Drosophila melanogaster is a sterol auxotroph 28 and relies on dietary sterols to produce lipid membranes, lipoproteins and molting hormones. 29 We employed shotgun lipidomics to quantify eight major food sterols in total extracts of heads, 30 female and male genital tracts of adult flies. We found that their sterol composition is dynamic 31 and reflective of flies diet in an organ-specific manner. Season-dependent changes observed in 32 the organs of wild-living flies suggested that the molar ratio between yeast (ergosterol, 33 zymosterol) and plant (sitosterol, stigmasterol) sterols is a quantifiable, generic and 34 unequivocal marker of their feeding behavior, including cold acclimation. It provides 35 technically simpler and more contrast readout compared to the full lipidome analysis and is 36 suitable for ecological and environmental population-based studies. 37 38 39 3 40 Introduction 41 42 Drosophila melanogaster (Dm) is an established model to study dietary and environmental 43 impact on lipid homeostasis and development [1]. Although in the wild Dm is believed to feed 44 on yeasts grown on rotten fruits and plants, it can also develop on a variety of foods, including 45 an artificially delipidated diet supplemented with sterols [2]. Dm lacks Δ-6 and Δ-5 desaturases 46 [3] and can only produce short-to medium-chain fatty acids comprising not more than one 47 double bond [4]. However, Dm also makes use of dietary lipids with polyunsaturated fatty acid 48 moieties (e.g. unsaturated triacylglycerols from plant oil) and incorporate them into its own 49 lipids [5,6]. Manipulating the composition of laboratory diets helps to produce larvae and adult 50 flies with a varying degree of unsaturation of their glycero-and glycerophospholipids and study 51 their impact on metabolism and physiology. However, changes in lipids unsaturation span 52 many lipid classes in a tissue-dependent manner and therefore a snapshot of the full-lipidome 53 profile could hardly serve as a robust marker of shifting dietary preference. 54 Like other arthropods, Drosophila is a sterol auxotroph: it exclusively relies on dietary 55 sterols to build biological membranes, lipoproteins, and to produce molting hormones [7]. Each 56 common dietary component supplies flies with unique sterols: a commonly used yeast food 57 (YF) is enriched in ergosterol (Erg); plant food (PF) contains phytosterols e.g. sitosterol (Sit), 58 campesterol (Cam) or stigmasterol (Sti), while animal components supply cholesterol (Cho) 59 (Figure 1). We hypothesized that, in comparison to the full lipidome composition, sterol 60 composition could be a more specific dietary marker supporting ecological and nutritional 61 studies also in wild-living animals. 62Our recent study showed that switching from yeast to plant diet increased flies survival 63 at low temperatures by preserving the fluidity of their biological...

Dietary polyunsaturated fatty acids affect volume and metabolism of Drosophila melanogaster sperm

“…Our work linking dietary lipids and male fertility is likely to have relevance beyond mere mechanistic explorations in the laboratory environment. A recent study (Knittelfelder et al, 2019) showed that adult D. melanogaster altered their dietary preferences in the wild and that the dietary lipids of adult flies altered the lipid signature in the membrane within one to two weeks. Because D. melanogaster males continuously produce sperm and because we show diet-based differences in sperm production, it is likely that seasonal changes in food preference identified by Knittelfelder et al (2019) will translate into seasonal changes in sperm production.…”

“…Their recipe and composition are given in Tables S1 and S2. Briefly, PF contained four times more lipids overall than YF, and its fatty acids are longer and more unsaturated and contains phytosterols such as sitosterol, campesterol or stigmasterol, whereas YF contains fungal sterols, such as ergosterol (Table S2) (Carvalho et al, 2012;Knittelfelder et al, 2019). The diets are nearly isocaloric at 800 kcal/L (Table S1) and reflect natural differences between growth on fresh fruit in the early season (PF), and the yeasts and other fungi associated with rotten fruit in later season (YF) (Brankatschk et al, 2018;Knittelfelder et al, 2019).…”

“…First, dietary lipids comprise sterols, which are the main building blocks for biological membranes and lipoproteins (Liu & Huang 2013) and affect their fluidity (Connor et al, 1998;Juan & Bayard, 1995;Carvalho et al, 2012;Brankatschk et al, 2018). Since animals, plants and fungi have very different sterols and because different sterols affect membrane properties differently (Czub & Baginski, 2006;Grosjean, Mongrand, Beney, Simon-Plas, & Gerbeau-Pissot, 2015), diet generally affects membrane composition and fluidity (Brankatschk et al, 2018;Carvalho et al, 2012) but also the fatty acid (FA) profile of sperm and the reproductive tract (Safarinejad, 2011;Comhaire et al, 2000;Knittelfelder et al, 2019). Therefore, the sperm membrane fluidity can reasonably be expected to be affected by dietary lipids in both vertebrates and invertebrates.…”

“…For example, D. melanogaster lacks desaturating enzymes and so can only synthesize saturated FA or MUFA (Shen et al, 2010). Unsaturated FA are taken up from dietary plant material, whereas fungal FA are also generally more saturated (Carvalho et al, 2012;Brankatschk et al, 2018;Knittelfelder et al, 2019).…”

“…Here, we employed a protocol of dietary lipid manipulation in D. melanogaster that previously has been shown to alter membrane composition, membrane properties as well as female reproduction and survival (Carvalho et al, 2012;Brankatschk et al, 2018;Knittelfelder et al, 2019). We reared D. melanogaster males on a diet that contained either few or many PUFA and either plant-or fungus-based sterols.…”