A Modular Library of Small Molecule Signals Regulates Social Behaviors in Caenorhabditis elegans
Figure 1
Identification of indole ascarosides as daf-22-dependent metabolites.
(A) Chemical structures of important ascarosides [7]. (B) Schematic representation of Differential Analysis via 2D-NMR spectroscopy (DANS). Comparison of wild-type NMR spectra with daf-22 mutant NMR spectra enabled detection of spectroscopic signals that may represent daf-22-dependent signaling molecules. (C) Small section of the actual wild-type and daf-22 NMR spectra used for DANS. Signals of indole carboxylic acid are present in both spectra (green box), whereas another indole-derived signal (red box) is only present in the wild-type, but not the daf-22 spectrum. (D) HPLC-MS-based comparison of the wild-type and daf-22 metabolomes. Ion chromatograms obtained for wild-type show peaks for the molecular ions of five different indole ascarosides which are absent from the daf-22 chromatograms. (E) Structures of identified indole ascarosides. (F) Structures of additional non-indole ascarosides identified in this study. (G) Relative amounts of indole ascarosides icas#3 and icas#9 and non-indole ascarosides ascr#3 and ascr#9 secreted by C. elegans N2 grown in liquid culture, as determined by HPLC-MS analyses of media extracts (normalized to concentration of ascr#3; n = 5, ±SEM). For mass spectrometric quantification of indole and non-indole ascarosides, standard mixtures of authentic reference compounds were used.