Targeted Metabolomics Reveals a Male Pheromone and Sex-Specific Ascaroside Biosynthesis in Caenorhabditis elegans

Abstract

In the model organism Caenorhabditis elegans, a class of small molecule signals called ascarosides regulate development, mating and social behaviors. Ascaroside production has been studied in the predominant sex, the hermaphrodite, but not in males, which account for less than 1% of wild-type worms grown under typical laboratory conditions. Using HPLC-MS-based targeted metabolomics, we show that males also produce ascarosides and that their ascaroside profile differs markedly from that of hermaphrodites. Whereas hermaphrodite ascaroside profiles are dominated by ascr#3, containing an α,β-unsaturated fatty acid, males predominantly produce the corresponding dihydro-derivative ascr#10. This small structural modification profoundly affects signaling properties: hermaphrodites are retained by attomole-amounts of male-produced ascr#10, whereas hermaphrodite-produced ascr#3 repels hermaphrodites and attracts males. Male production of ascr#10 is population density-dependent, indicating sensory regulation of ascaroside biosynthesis. Analysis of gene expression data supports a model in which sex-specific regulation of peroxisomal β-oxidation produces functionally different ascaroside profiles.

Contrasting responses within a single neuron class enable sex-specific attraction in Caenorhabditis elegans

“…Further, both males and females could produce different levels of the same pheromone, as seen in mice (7), making some threshold selection mechanism necessary. In fact, we now have evidence that male C. elegans also produce some ascr#3 at a lower concentration (21).…”

“…Chemical analyses of hermaphrodite secretions by mass spectroscopy and 2D NMR spectroscopy have discovered a novel family of small molecules called ascarosides (21)(22)(23), which serve diverse biological functions (24). Certain ascarosides secreted by hermaphrodites are attractive exclusively to males, which exhibit strong concentration preferences (23).…”

Genetic mapping of variation in dauer larvae development in growing populations of Caenorhabditis elegans

“…Dauer pheromone, a complex mix of structurally related ascarosides (Jeong et al, 2005;Butcher et al, 2007;Pungaliya et al, 2009;Park et al, 2012), is used by C. elegans to assess population density, with these ascarosides also acting to regulate aggregation, mate recognition and dispersal (Srinivasan et al, 2008;Harvey, 2009;Pungaliya et al, 2009;Izrayelit et al, 2012;Jang et al, 2012). Although there is an extensive and detailed understanding of the genetic pathways that specify dauer and non-dauer larval development in C. elegans (see Hu (2007) for a review), the ecology of the species is still poorly understood.…”

Acyl-CoA oxidase complexes control the chemical message produced by Caenorhabditis elegans

“…Dauers have a thickened cuticle, do not feed, derive energy from fat stores, and up-regulate stress-resistance pathways (6). Certain ascarosides also influence behaviors, including male attraction to hermaphrodites, hermaphrodite attraction to males, avoidance, and aggregation (7)(8)(9)(10)(11)(12). C. elegans senses the ascarosides using several classes of G protein-coupled receptors (GPCRs), which are expressed in specific chemosensory neurons (13,14).…”

“…Ascaroside production has been shown to be influenced by a variety of factors, including developmental stage (21), temperature (3,19), and sex (8), although interpretation of these results is often complicated by the fact that they were obtained by changing multiple variables at the same time (21) or by using longterm, mixed-larval stage cultures (3,19). Starvation has been suggested to increase the ratio of asc-ΔC9 to asc-ωC3 in longterm, mixed-stage cultures (11).…”