Diverse small-molecule signals have been shown to regulate almost every aspect of C. elegans biology, including ascarosides, the polyketide nemamide, or the male-produced developmental accelerator nacq#11-3. Here we present evidence for another class of C. elegans signaling molecules, the modular glucosides. We initially discovered the modular glucosides when comparing the metabolomes of wildtype C. elegans and
glo-1 mutants, which lack lysosome-related organelles. When analyzing
glo-1 worms, we found that they are deficient in the production of almost all modular ascaroside pheromones (e.g. the dispersal signal osas#9 and the aggregation signal icas#3)4,5. Unexpectedly, we detected another, much larger family of compounds whose biosynthesis was also abolished in
glo-1 worms. Follow-up analyses via MS and NMR spectroscopy revealed that these
glo-1-dependent compounds represent a large class of novel modular metabolites that are derived from a glucose scaffold decorated with building blocks from amino acid, nucleoside, and fatty-acid metabolism. Analogous to the biosynthesis of modular ascarosides, enzymes of the carboxylesterase (CEST) family play a central role in the assembly of the modular glucosides6. Furthermore, biosynthesis of modular glucosides via CEST enzymes is evolutionarily conserved, similar to that of ascaroside pheromones5,7. Given their highly specific enzymatic assembly, we hypothesize that modular glucosides serve important biological functions. Notably, modular glucosides are primarily retained in the worm body, in contrast to ascarosides, which are primarily excreted, suggesting that the modular glucosides serve as intra-organismal signaling molecules. 1 Schroeder, F. C. Modular assembly of primary metabolic building blocks: a chemical language in C. elegans. Chem Biol 22, 7-16, (2015). 2 Shou, Q. Y. et al. A hybrid polyketide-nonribosomal peptide in nematodes that promotes larval survival. Nature Chemical Biology 12, 770-772, (2016). 3 Ludewig, A. H. et al. An excreted small molecule promotes C. elegans reproductive development and aging. Nature Chemical Biology 15, 838-845, (2019). 4 Srinivasan, J. et al. A Modular Library of Small Molecule Signals Regulates Social Behaviors in Caenorhabditis elegans. Plos Biol 10, (2012). 5 Artyukhin, A. B. et al. Succinylated Octopamine Ascarosides and a New Pathway of Biogenic Amine Metabolism in Caenorhabditis elegans. J Biol Chem 288, 18778-18783, (2013). 6 Le, H. H. et al. Modular metabolite assembly in Caenorhabditis elegans depends on carboxylesterases and formation of lysosome-related organelles. Elife 9, (2020). 7 von Reuss, S. H. et al. Comparative Metabolomics Reveals Biogenesis of Ascarosides, a Modular Library of Small-Molecule Signals in C. elegans. Journal of the American Chemical Society 134, 1817-1824, (2012).