Nematodes are one of the most numerous and diverse multicellular organisms on earth. They have a profound impact on human health, agriculture, and economy. Like many other organisms, they synthesize and use small molecules to communicate within and between their species. In Caenorhabditis elegans, ascarosides have been found to control dauer formation (Butcher, et al., 2007), mating (Srinivasan, et al., 2008), aggregation (Macosko, et al., 2009), and olfaction (Yamada, et al., 2010). Pristionchus pacificus is a useful satellite organism for comparative studies with C. elegans (Hong & Sommer, 2006). We are developing a bioassay for gender specific chemotaxis (e.g. mating behavior) in P. pacificus for activity-guided fractionation of the mating cue. The mating assays are complicated by aggregation behavior in males under some conditions. We are trying to understand the chemical and environmental factors that control these different behaviors. Several behaviors, including aggregation may be mediated or enhanced by chemical cues on the cuticle surface of the nematodes. Therefore, we are trying to develop an alternative approach to chemical ecology studies in nematodes using matrix-assisted laser desorption/ionization (MALDI) mass spectrometric imaging (MSI) (Garrett & Yost, 2006). This technique could potentially not only allow us to detect metabolites on the surface of nematodes, but also visualize the spatial distribution of these small molecules. Using a combination of MALDI MSI and principal component analysis (PCA), we can compare nematodes of different species and find differences in mass spectral profiles resulting from gender, developmental stage, strain or species. We are currently examining C. elegans strain N2 (a standard wild-type) and C. elegans
daf-22 (dauer-defective mutants). Daf-22 mutants are unable to produce short chain ascarosides such as the dauer pheromones common in the N2 strain. Once this technique is developed by the use of C. elegans, we will begin to analyze the surface molecules of P. pacificus nematodes. Bibliography: Yamada, K., et al. (2010). Science, 329 (5999), 1647-1650. Butcher, R. et al. (2007). Nature Chemical Biology, 3 (7), 420-422. Garrett, T., & Yost, R. (2006). Analytical Chemistry, 78, 2465-2469. Hong, R., & Sommer, R. (2006). BioEssays, 28, 651-659. Macosko, E., et al. (2009). Nature (458), 1171-1175. Srinivasan, J., et al. (2008). Nature, 1115-18.