Ascaroside Expression in Caenorhabditis elegans Is Strongly Dependent on Diet and Developmental Stage

Abstract

BackgroundThe ascarosides form a family of small molecules that have been isolated from cultures of the nematode Caenorhabditis elegans. They are often referred to as “dauer pheromones” because most of them induce formation of long-lived and highly stress resistant dauer larvae. More recent studies have shown that ascarosides serve additional functions as social signals and mating pheromones. Thus, ascarosides have multiple functions. Until now, it has been generally assumed that ascarosides are constitutively expressed during nematode development.Methodology/Principal FindingsCultures of C. elegans were developmentally synchronized on controlled diets. Ascarosides released into the media, as well as stored internally, were quantified by LC/MS. We found that ascaroside biosynthesis and release were strongly dependent on developmental stage and diet. The male attracting pheromone was verified to be a blend of at least four ascarosides, and peak production of the two most potent mating pheromone components, ascr#3 and asc#8 immediately preceded or coincided with the temporal window for mating. The concentration of ascr#2 increased under starvation conditions and peaked during dauer formation, strongly supporting ascr#2 as the main population density signal (dauer pheromone). After dauer formation, ascaroside production largely ceased and dauer larvae did not release any ascarosides. These findings show that both total ascaroside production and the relative proportions of individual ascarosides strongly correlate with these compounds' stage-specific biological functions.Conclusions/SignificanceAscaroside expression changes with development and environmental conditions. This is consistent with multiple functions of these signaling molecules. Knowledge of such differential regulation will make it possible to associate ascaroside production to gene expression profiles (transcript, protein or enzyme activity) and help to determine genetic pathways that control ascaroside biosynthesis. In conjunction with findings from previous studies, our results show that the pheromone system of C. elegans mimics that of insects in many ways, suggesting that pheromone signaling in C. elegans may exhibit functional homology also at the sensory level. In addition, our results provide a strong foundation for future behavioral modeling studies.

Sex-specific mating pheromones in the nematode Panagrellus redivivus

“…3). Unlike C. elegans males, which show a bell-shaped concentration-dependent response (3,5) to different mixtures of ascr#2, ascr#3, ascr#4 (3), and ascr#8 (4) (Fig. 1), P. redivivus males responded robustly to ascr#1 as a single component, and the response did not decrease with increasing concentrations of attractant.…”

“…Males and females were both attracted to the flow-through and 50% methanol (MeOH) fractions, but they did not respond to the 90% fraction. Based on previous studies with C. elegans, the flow-through fraction contains many common metabolites, such as amino acids and sugars (18,19); some of these metabolites are attractive to nematodes (20), whereas the 50% MeOH fraction is enriched in ascarosides (3,5,21). We, therefore, focused our attention on the 50% MeOH fraction, which was further fractionated using ion exchange solid-phase extraction.…”

“…We have previously shown that hermaphroditic C. elegans produces a diversity of ascarosides (7,14) and that mixtures of ascr#2, ascr#3, ascr#4, and ascr#8 can synergistically act as male-specific attractants at very low concentrations (3)(4)(5). However, hermaphrodite-specific attraction to males has not been reported in C. elegans.…”

“…(1). Recent studies have shown that a family of small-molecule signals, the ascarosides, control sexual attraction (2)(3)(4)(5), aggregation (6,7), olfactory plasticity (8), dauer formation (9)(10)(11)(12), and dispersal (13) in the model organism Caenorhabditis elegans. Ascarosides ( Fig.…”

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

“…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).…”